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NASA Contractor Report 165839 19820018589 Develop, Delllonstrate, and Verify Large Area COlllposite Structural Bondirlg With Polyilllide Adhesives Bashir D. Bhombal Donald H. Wykes Keith C. Hong Arnold A. Stenersen Rockwell International Downey, CA 90241 Contract NAS 1 .. 15843 May 1982 NI\S/\ National Aeronautics and Space Administration Langley Research Center Hampton. Virginia 23665 111111111111111111111111111111111111111111111 NF01350 https://ntrs.nasa.gov/search.jsp?R=19820018589 2020-03-12T03:28:10+00:00Z

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Page 1: Develop, Delllonstrate, and Verify Large Area COlllposite ... · Verify Large Area COlllposite Structural Bondirlg With Polyilllide Adhesives Bashir D. Bhombal Donald H. Wykes Keith

NASA Contractor Report 165839

NASA~CR~165839 19820018589

Develop, Delllonstrate, and Verify Large Area COlllposite Structural Bondirlg With Polyilllide Adhesives

Bashir D. Bhombal Donald H. Wykes Keith C. Hong Arnold A. Stenersen Rockwell International Downey, CA 90241

Contract NAS 1 .. 15843 May 1982

NI\S/\ National Aeronautics and Space Administration

Langley Research Center Hampton. Virginia 23665

111111111111111111111111111111111111111111111 NF01350

https://ntrs.nasa.gov/search.jsp?R=19820018589 2020-03-12T03:28:10+00:00Z

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NASA Contractor Report 165839

Develop, Detnonstrate, and Verify Large Area Cotnp()site Structural Bonding With Polyirnide Adhesives

Bashir D. Bhomhal Donald H. Wykes Keith C. Hong Arnold A. Stenersen Rockwell International Downey, CA 90241

Contract NAS 1 .. 15843 May 1982

NI\SI\ National Aeronautics and Space Administration

Langley Research Center Hampton Virginia 23665

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FOREWARD

This is the final report on an effort to develop, demonstrate, and verify

large area composite structural bonding with polyimide adhesive. This

program was conducted by the Advanced Manufacturing Technology of Space

Transportation and Systems Group of Rockwell International, under Contract

NASl-15843, for. the Materials Division of NASA's Langley Research Center,

Hampton, Virginia. Robert M. Baucom was the NASA Technical Monitor.

The Program Manager during the Process Development phase was Arnold A.

Stenersen. Donald He Wykes assumed program management responsibilities

of Technology Demonstrator Segment and final report phases of the Contract.

Bashir D. Bhombal was the Technical Project Manager.

The following Rockwell personnel were principal contributors to this program.

J. D. Leahy Materials Technology

R. L. Crabb Materials Technology

D. W. Houston Chemical Testing

R. L. Long Specification Development

S. R. Graves Advanced System

iii

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SECTIO~

1.0

2.0

3.0

CONTENTS

INTRODUCTION. • • • • lit • • • • • • • •

SCREENING OF ADHESIVE SYSTEMS •

2. I Selection Criteria for the Adhesives . . . 2.2 Industry Survey •• . . · . . ... . . . 2.3 Polyimide Resin Chemistry

Condensation vs. Addition Type PI Resins •

2.5 Adhesive Screening Tests • •

2.6 Lap Shear Test • • • • • • . . . . . 2.7 Flatwise Tensile Test

2.8 Climbing Drum Peel Test. . . . 2.9 Glass Transition Temperature •

2.10 Out-Time Study. · . . .

2

2

2

t" .)

6

7

B

2. II Mid-Plane Bonded Large Area Panels • 9

2.12 Evaluation of Primers and Surface Treatments. 9

2. 13 Selection of Three Adhesive Systems

PROCESS DEVELOPMENT . . . . . . . . . . . . . . 3.1

3.2

3.3

3.5

Celion/PMR-15 and Celion/LaRC-160 Adherends ••

Surface Treatment Study.

Primer Evaluation · . . . . . . . . . . . Processing of Adhesive • . . . Process for Mid-Plane Bonding Large Area • Panels

v

9

10

10

11

1 I

12

12

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SECTION

4.0

5.0

6.0

7.0

CONTENTS

3.6 Process for Bonding Honeycomb Sandwich Panels.

3.7 Core-Coating of Paste Adhesives •••••

3.8 Aging Stability of Selected Adhesives ••

3.9 Out-time of Selected Adhesives •

3. JO Effect of Water Immersion on Lap Shear · , · . 3. 11 Final Selection of Adhesives · . . QUALIFICATION OF SELECTED ADHESIVES

4. 1

4.2

4.3

4.4

4.5

Process for Fabrication of Honeycomb Sandwich. Panels

Process for Mid-Plane Bonding Large Area Panels

· . Effect of Bond-Line Thickness on Lap Shear • • Strength

Effect of Out-Time on Filleting Properties • • of LaRC-I3

Evaluation of Catalysts to Reduce Cure • • • • Temperature

SUMMARY • • • • • • . . . . . . TECHNOLOGY DEMONSTRATOR SEGMENT • •

FABRICATION OF STRUCTURAL TEST ASSEMBLY · . . · · · · 7. 1 Prepreg Tape . · • 7.2 Leading Edge Cover Panel . . . . · · · · 7.2. 1 Skin . . • . . . • . . · · • · 7.2.2 Closeout Channel · · · • 7.2.3 Assembly of Leading Edge - Bonding Tool.

7.2.4 Prefit of Details

vi

PAGE NO.

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13

14

14

15

15

15

15

16

16

16

17

17

19

20

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CONTENTS

SECTION

7.2.5 Cleaning and Priming of Details •••••

7.2.6 Assembly of Details on Tool. • • • • • • • •• 26

7.3 Stability Rib 27

7.3.1 Stability Rib Sandwich Panel. • 27

7.3.2 Pi Cap Element . . . . . . .. " . . . . . . . . 28

7.3.3 Bonding of Closeout Channel and Pi Cap to Web. 28 Sandwich Panel

7.4 Lower and Upper Cover Panels. 29

7.4.1 Honeycomb Core 29

7.4.2 Skin ••• 29

7.4.3 Close-Out Edge Member • 30

7.4.4 Honeycomb Sandwich Assembly. 30

8.0 DEMONSTRATOR SEGMENT TEST PROGRAM 31

8. 1 Test Approach 32

8.2 Test Constraints. . .. . . . 32

8.3 Technology Demonstrator Segment NASTRAN Model. 32

8.4 Room Temperature and 5330 K Mechanical Tests 33

8.5 400 Cycle Simulated Fatigue Test. • 34

8.6 Thermal Cycling Test 34

8.7 Acoustic Fatigue Test • 35

8.8 Internal Pressure Test 3,5

8.9 Summary • . . . 36

DOCUMENTATION • . . . . . . . . . . . . . . 37

APPENDIX A • . . . . . . . . . . . . . . . . . . 115

vii

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FIGURE

2

3

4

5

6

7

8

9

10

1 1

12

13

14

15

16

ILLUSTRATIONS

LARC-13 Monomer Reactants ••••• . . . LARC-13 Polyimide Reaction Sequence

Adhesive Prepreg Mill • • • • • • • • •

Reaction Scheme of NR150B2G Adhesive . . . . . . . Flatwise Tensile Test Specimen • • •

Flatwise Tensile Test Specimen After Testing •••

Climbing Drum Peel Test Apparatus • • • • • •

C-Scan of 76 x 46 cm (30"x 18") Panel. 8 Ply, Unidirectional

C-Scan of 76 x 46 cm (31" x 18") Panel of Celion/ • PMR-15 Composite Panel. 8-ply, Unidirectional

C-Scan of Honeycomb Sandwich Panel with FM34B-18 Adhesive

C-Scan of Honeycomb Sandwich Panel with LARC-13 •••• Adhesive

Comparison of Primers for Bonding Celion 6000/PMR-15 •• Panels with LARC-13

C-Scan of 30.5 by 30.5 cm (12 x 12 in.) Mid-Plane Bonded Panel with LARC-13 Adhesive on Style 104 carrier

. . .

C-Scan of 30.5 cm (12 x 12 in.), Mid-Plane Bonded ••• Panel with M-LARC-13E Adhesive on Style 104 Carrier

C-Scan of 30.5 cm by 30.5 cm (12 x 12 in.) Mid-Plane Bonded Panel with FM34B-18 Adhesive on Style 104 Carrier

CUre Cycle for the Fabrication of Honeycomb Sandwich Panels with LARC-13 M-LARC-13E and FM34B-18 Adheives

ix

. .

PAGE NO.

39

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

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FIGURE

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

ILLUSTRATIONS

Technology Demonstrator Segment Completed Structure •

Staging Lay-up for Flat Laminates •

Autoclave Cure for Flat Laminates • . . . . . . . . . "u" Channel Lay-up Mold . . . . . . . . . . . . Staging Lay-up for "u" Shape Laminate • . . . . Curing Lay-up for "u" Shape Laminate . . . . . . . Alternate curing Lay-up for "u" Shape Laminate

Curing Lay-up for Honeycomb Sandwich Panel •• . . . . Cure Cycle for Cover Panels • • • • • • • • • •

Tool Configuration for Stability Rib Close-out. Channel

. . . Curved "pi" Joint Element Design . . . . . . . . . . Cure Cycle for Skins . . . . . Oven Post Cure Cycle for Skins ••••

C-Scan of 76.2 cm x 157.5 cm (30" x 62" Skin for Leading. Edge

Skin for the Leading Edge • • • • • • • • • •

Vacuum Forming of the Close-out Channels

Leading Edge Panel Bonding Jig. . . Leading Edge Bonding Assembly-Cross Section View. •

Leading Edge Cover Panel on Bonding Jig •

Leading Edge/Cover Panel

Primer Being Applied on Rib Web for Bonding of "U". Channel

x

. .

PAGE NO.

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

7 1

72

73

74

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FIGURE

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

ILLUSTRATIONS

Primer Being Applied to the Inner Section "U" Channel

"U" Channel Being Inserted to Web Sandwich Panel • • . . . "U" Channel Complete for Bonding. • • . . " . . . . . Drilling Fixture for Bonding Close-out Channel and Pi. • • Cap to Web Sandwich Panel

CloBe up View of Forward Section of the Fixture ••

GrlPI Composite Body Flap Technology Demonstrator •• Segment (TDS)

GriP! Technology Verification TDS (All Bonded Structure) •

Demonstrator Segment Test Concept Constraints ••••

Technology Demonstrator Segment NASTRAN Model •••

R.T. Mechanical Load Test . . . . . . . . . . . . . . . ~

Typical Cover Panel Stress Contours . . . . . . . . . High Temperature Mechanical Load Test. • . . . . . . Simulated Fatigue Test • . . . . . . . . . . . Thermal Cycle Test • • • • • • • • • . . . . . . . . . Acoustic Fatigue Test . . . . . . . . . . . . . . . . Internal Pressure Test • . . , . . . . . . . . . .

xi

PAGE NO.

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

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TABLE

2

3

4

5

6

7

8

9

10

11

12

13

14

IS

16

TABLES

Lap-Shear Strength of Polyimide Adhesives • • • • •

Flatwise Tensile Strength of Polyimide Adhesives

Climbing Drum Peel Strength of Polyimide Adhesives •••

Glass Transition Temperature of Polyimide Adhesives

Effect of Out-Time on Lap-Shear Strength of Polyimide • Adhesives

Effect of Out-Time in Humid Environment of Lap-Shear Strength

Comparison of Primers for Bonding Celion 6000/PMR-15 Panels with LARC-13 Adhesive

Comparison of Surface Treatment for Bonding Calion/ PMR-15 Laminates with LARC-13 Adhesives

Comparison of Polyimide Adhesives • • • • • • • • • • •

Comparison of FM34B-18, LARC-13 and LARC-13E Adhesives-

Properties of Celion 6000/PMR-15 Prepreg and Cured •• -Laminates

Flatwise Tensile Strength of FM34B-18 LARC-13 and ••• M-LARC-13E Adhesives

Lap-Shear Strength of LARC-13 Adhesive Prepared by •• Anhydride and Ester Methods

Short Beam Shear Strength of LARC-13 and FM34B-18 •••

Slotted Shear Strength of Test Specimens from Mid- •• Plane Bonded ·30.5 by 30.5 em Panels

Aging Stability of Polyimide Adhesives Wrapped in • • • Aluminum Foil

xiii

PAGE NO.

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

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TABLE

17

18

19

20

21

22

23

TABLES

Aging Stability of Polyimide Adhesives Not Wrapped •••• in Aluminum Foil

Aging Stability of Selected Adhesives . . . . . . . Effect of Water Immersion on Lap-Shear Strength of •

LARC-13 and FM34B-18

Effect of Bondline Thickness on Lap-Shear Strength •

Out of Refrigeration Effect of Filleting Properties. of LARC-13

Use of Catalyst in LARC-13 to Reduce Cure Temperature •

Orbiter Body Flap/Demo Segment Stress Comparison

xiv

PAGE NO.

107

]08

109

110

111

112

113

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1.0 INTRODUCTION

Contract NASI-15843 is a NASA La.RC Program under Project CASTS

(Composites for Advanced Space Transportation Systems). This project

was established to develop and demonstrate the technology required to

produce graphite/polyimide structural components with operational capa­

bility at 5890 K (6000F).

The CASTS project includes several current research contracts to

develop and demonstrate processes for fabricating graphite/polyimide com­

posites materials and nondestructive inspection (NDI) of structures. The

fabrication of structural elements in these studies includes flat laminates,

honeycomb panels, skin stringer panels and chopped fiber moldings. These

elements are a.ssembled and joined primarily by adhesive bonding. Techniques

for assembling and bonding the structural elements into a completed structure

were developed in this program.

The objective of this contractual study program was to develop pro­

cesses for joining large area structural subcomponents by bonding with

polyimide adhesives, to verify the reliability of the adhesive bonds by

mechanical and nondestructive testing and to demonstrate the quality of

the large area bonding technique by fabrication of a large completed stru­

cture. The original plan to fabricate a box beam as a demonstration com­

ponent was changed to the fabrication of components for a deliverable struc­

tural test assembly representative of the Space Shuttle aft body flap.

Identification of commercial products in this report is to adequately

describe the materials and does not constitute official endorsement, express­

ed or implified, of such products or manufacturers by the National Aero­

nautics and Space Administration.

The NASA "A" standard to ultrasonic evaluation of composites referenced

on p. 10 is a sensitivity level that is utilized at NASA as an indication

1

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of high quality, voidfree composites. Rockwell used the NASA "A" standard

as a point of reference only in this report since this standard is not

universal in the art.

2.0 SCREENING OF ADHESIVE SYSTEMS

2.1 S~lection Criteria for Adhesives

The criteria used in selecting adhesive systems suitable for

(I) bonding large area Celion graphite reinforced PMR-15 polyimide

laminates; and (2) fabricating large area honeycomb and skin/stringer

panels with Celion 6000/PMR-15 or Celion 6000/LARC-160 face sheets

were:

o Commercial availability

o Existing data base

o Processability

Resin processability

Processability of supported film adhesive (adhesive

prepreg)

Processing and cure of primer and adhesive 5890 K (600oF)

and 1.379 MPa (200 psi) nominal upper processing limits).

o Handleability

o Stability under normal storage conditions

o Filleting capability

o Low areal weight

o Mechanical properties

Lap shear strength

Climbing drum peel strength

Flatwise tension strength

o Ability to form low porosity bond lines in mid-plane bonded

panels.

2.2 Industry Survey

2

An industry survey was made to assess the status of development

of polyimide adhesive with operational capability at 5890

K (600oF).

The data obtained in this survey indicated that the LARC-13 adhesive,

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developed by NASA-LARe, was the most promising polyimide adhesive avail­

able for large area bonding. Other potential polyimide adhesives with

operational capability at 5890 K (6000 F) included several systems based

on dUPont's NR-150B2 polyimide resins, the FM34B-18 adhesive and

adhesive systems based on the PMR-15 and LARC-160 polyimide resins.

The FM34B-18 adhesive is commercially available from American Cyanamid

Company both in paste and scrim-supported film form. The NR-150

polyimide resins are available in solution form at resin solids con­

centrations of about SO percent. The LARC-13, LARC-160, and PMR-15

polyimide resins are produced from monomer reactants. Most of these

monomer reactants are readily available from several commercial sup­

pliers.

For production of scrim-supported film adhesives, based on these

polyimide resin systems, a hot-melt process and a solvent evaporation

process had been evaluated at Rockwell. The hot-melt process was found

to be the most suitable of these methods in regard to production rate,

film quality, film uniformity, and reproducibility. As a result of

the industry survey, the hot-melt polyimide adhesive systems listed

below were selected for initial screening.

o FM34B-18

o LARC-13

o Mod LARC-13

o Mod LARC~ 13

o NR-lS0B2

o PMR-15

o Mod PMR-15

American Cyanamide Company

NASA Process

Use of methyl and ethyl esters of BTDA and

NA used in place of anhydrides, and flex­

ibilizers such as silicon and rubber materials.

Use of amine substitutes by replacing part or

all of 3,3' MDA compared with the armomatic

diemines such as 4,4' MDA and 3,3' and 4,4'

DADS (Diamino di Sulphone).

Linear and cross-linked systems duPont

NASA formulation prepared by Rockwell

Use of amine substitutes by replacing part or

all of 3,3' MDA compared with other aromatic

drainides such as 4,4' MDA and 3,3' and 4,4'

DADS.

3

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o LARC-160

o Mod LARC-160

NASA formulation, prepared by Rockwell

Use of flexibilizers such as silicon and

rubber materials.

2.3 Polyimide Resin Chemistry

4

The LARC-13 addition-type polyimide polymer is formed by reactions

of benzophenone tetracarboxylic dianhydride (BTDA), nadic anhydride

(NA), and 3;3'-methylenedianiline (3,3'MDA). This polymer also can

be formed by reacting the methyl or ethyl esters of BTDA and NA with

3,3'-MDA. The chemical structures of these monomer reactants are

shown in Figure I.

When the anhydrides, BTDA and NA are used, the sequence of the

polymer reactions generally is reported to take place in a simplified

manner as shown in Figure 2. At first, 3,3'-MDA reacts with PMDA

nadic groups. These reactions are followed by the imidization inter­

mediate. This imidization reaction is generally carried out on

staging of the adhesive prepreg at normal pressure and temperatures

from 422oK(300oF) to 4490 K (350°F). On application of higher tempera­

tures, S330 K (500°F) to S890 K (600°F), and increased pressure, addition­

type reactions occur at the norbornene groups. These addition-type

reactions, reverse Diels-Alder reactions, result in chain extension

and cross-linking.

When the methyl esters of pMDA and NA are used in place of the

anhydrides, these esters at first react with 3,3'-MDA to form amide

acid and methanol. These reactions are followed by imidization, chain

extension, and cross-linking reactions, as shown in Figure 2.

The PMR-IS and LARC-J60 resins are similar to LARC-J3 in chem-

ical structure and polymer reactions. Several other polyimide resins

evaluated also contained PMDA, and NA as monomer reactants along with

different aromatic diamines such as diaminodiphenyl sulfone (DADS).

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Initially, the LARC-13, LARC-160 and PMR-15 resins used for the

polyimide adhesives were processed with methyl esters of BTDA and

NA and an aromatic diamine used as monomer reactants. Later the

anhydrides, BTDA, and NA were used as monomer reactant,s with armomatic

diamines.

The methyl esters of BTDA and NA were prepared by refluxing a

mixture of these andydrides with methanol for two hours. The aromatic

amine then was added in several portions and mixed for one-half hour.

Filler and other additives then were added and mixed at room tempera­

ture.

The adhesive prepreg, or film adhesive was processed on a labor­

atory scale with use of a coating device as shown in Figure 3. Glass

fabrics were used as carrier materials for the film adhesives.

2.4 ,Condensation vs. Addition Type P.I. Resins

The PMR-15 and LARC-160 resins are similar to LARC-13 in chem­

ical structure and polymer reactions. Several other polyimide resins

evaluated also contained PMDA and NA as monomer reactants along with

different aromatic diamines such as diaminodiphenyl sulfone (DADS).

The NR-150B2G and NR-056X polyimide resins are condensation

type polyimide systems structured as shown in Figure 4. The poly­

mers are formed by reacting 4,4' (Hexafloroisopropy lidene)-bis

(phthalic acide) ("6F tetra acid) with 4,4' phenylene diamine and

3,3' -phenylene diamine. Water is split off as a condensation product.

The PMR-15 (II) on the other hand can be classified as an

addition type resin. It contains 4,4' (Hexafloroisopropy lidene)-

bis (phthalicacide) and phenylenediamine, as does NR1S0-B2G but in

addition, it contains NA and end-capper. The reaction sequence for

this monomer reaction is similar to that of LARC-13. At first amic

acids is formed which on heating to a temperature such as 4500

K (350o

F)

5

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is converted into a po1yimide prepo1ymer. On further heating at

higher temperature. such as 5890

K (600oF) and application of pressure

such as 100 psi, chain extension and cross-linking takes place at the

norbornene groups as for LARC-13. The chain extension and cross-link­

ing reactions are addition type reactions by which no condensation

products are formed. Therefore, the PMR-15 (II) resin solution also

should be suitable for large area bonding.

2.5 Adhesive Screening Tests

6

The tests used for screening of the selected po1yimide adhesives

are shown below. The initial tests included a lap shear test (Table

1) and a flatwise tensile test (Table 2) at R.T. and 5890 K (600°F)

and a climbing drum peel test (Table 3) at R.T. The glass transition

temperature (Tg). the storage stability or out-time, and ability to

form low porosity, large area bonded also were evaluated for the most

promising adhesives.

Lap-shear strength at R.T.

and 5890K (600°F)

F1atwise tensile strength

o ° at R.T. and 589 K (600 F)

Glass transition temperature

Tg.

12.7 mm (0.5 in.) overlap specimen

of unidirectional, 8 ply, 1.02 to

1.115 mm (0.040 to 0.045 inch) thick

composite laminates; Fed. spec.

MMM-132A.

5.1 by 5.1 cm (2 by 2 in.) sandwich

panels of HRH 327-3/16-4 T = 1.27

(0.5) honeycomb with 8 ply composite

face-sheet MIL-A-25463A.

6.25 mm diameter 1.02. to 1.14 mm

(0.040 to 0.045 in.) thick adhesive

panels.

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Storage stability of adhesive

film prior to use (out-time)

by lap-shear tests.

12.77 mm (0.5 in.) overlap spE~cimen

of unidirectional, 8 ply, 1.02 to

1.14 mm (0.040 to 0.045 inch) thick

composite laminates. Fed Spec.

MMM-132A.

Ability to form low poro.sity 15.2 by 1.52 cm (6 by 6 in.) com-

bond lines in Mid-plane bondedposite panels and steel panels,

panels. T = 0.12 (0.5).

2.6 La}, Shear, Test

The adhesive systems screened for lap-shear strength to Celion/

PMR-15 laminates and the test data obtained are shown in Table I.

A unidirectional, 8 ply laminate of Celion 6000/PMR-15 composite of

1.02 to 1.14 mm (0.040 to 0.045 inch) thickness was selected for this

test to provide strain compatibility (equal strain under a given load)

with one inch wide titanium adherends. (Titanium finger panels, 25.4

mm wide and 1.27 mm thick (I inch wide and 0.050 inch thick), of 6AL-

4V titanium, had been used in several research and development pro­

grams at Rockwell for evaluations of polyimide adhesives for use in

the Space Shuttle). The selected thickness of the Celion/PMR-15

composite was obtained from the following relationship:

Acomp x Ecomp :: ATi x ETi

Acomp :: ATi x ETi

Ecomp

Acomp = ( I x 0.05) (15 x J06)

18 x 106

Acomp = 0.042

x T = 0.042

'I~ = .042 :: 1.07 mm

7

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Where

Acomp = (I x T) = Cross sectional area of one inch wide

composite lap shear specimen.

ATi = ( I x 0.05) = Cross sectional area of one inch wide by

0.05" thick titanium lap shear specimen.

Ecomp = 18 x 106 = Modulus of Celion/PMR-15 composite.

ETi = 15 x 106 = Modulus of 6AL4V titanium.

T = Thickness of one inch wide Celion/PMR-15 composite.

2.7 Flatwise Tension Test

A series of adhesives that appeared promising in the lap-shear

test were evaluated further by a flatwise tensile test (Table 2)

using test specimens as illustrated in Figure 5 and 6.

2.8 Climbing Drum Peel Test

A climbing drum peel test, according to specification MIL-A-

2546A, Figure 7 was selected as a measure of the peel strength of

the polyimide adhesives. This test was used primarily to provide

data for design and handleability of honeycomb sandwich components

to be fabricated. The target value set for the climbing drum peel

test of the polymide adhesives was 900 g/cm width (5 in. lb/in.) at

R.T. (Table 3).

2.9 Glass Transition Temperature

Measurements of the glass transition Tg. were made for a series

of adhesives using a Dupont 941 TMA-900TA analyzer. The adhesive

samples were fabricated into laminates of about 1.14 mm (0.045 in.)

thickness. The samples were cured for two hours at 5890 K (600oF)

and postcured for ten hours at 5890 K (600oF). The test data is

shown in Table 4.

2.10 Out~Time StudX

A series of six adhesives were evaluated for storage stability

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over an II-day period. The relative humidity during this period

varied between 6 and 40 percent and the temperature varied between

291 and 2990 K (65 and 80°F). The test data obtained as shown in

Table 5 shows that the lap-shear strength of the six adhesives was

not affected by exposure to this dry environment. A similar study

was conducted when the relative humidity in the storage area was 40

90 percent. The lap shear data obtained as shown in Table 6 shows

that the strength values of FM34B-18 adhesive are significantly

reduced after the three and seven days out-time periods. In com­

parison, the lap-shear properties of the LARC-13 and M-LARC-13

adhesives were not detrimentally affected by these exposures. The

results show that exposure of the FM34B-18 to a humid environment

must be avoided prior to application.

2.11 Mid-Plane Bonded Large Area Pan!.!.:!

Several of the selected polyimide adhesives that looked prom­

ising by the lap-shear climbing drum peel and the flatwise tensile

tests were screened for ability to produce low porosity bond-line

in mid-plane bonded panels. The dimensions of the panels used were

t.52 by 15.2 cm (6 by 6 in.). The porosity in the bond-line was

inspected by ultrasonic c-scanning, using the NASA "A" sensitivity

standard.

2.12 Evaluation of Primers and Surface Treatments

The primers evaluated in the initial experiment consisted of an

alcohol/diglyme solution of condensation and addition type polyimide

adhesive. The use of primers resulted in increased bond strength,

apparently because their polymer chains are linear, more flexible,

and tougher than the cross-linked addition type polymers. The

result is increased load carrying capacity; as shown in Table 7 and

Table 8.

2.13 Selection of Three Polyimide Adhesive Sxstems

Table 9 shows a comparison of availability and physical prop­

erties for six of the most promising adhesive systems. Based on

this data, the following three adhesive systems were selected for

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further study and evaluation:

LARC-13 - Produced by NASA process

Modified LARC-13 - Partial substitution. of 3,3' MDAwith

4,4' MDA

FM34B-18 - American Cyanamid Company

A more in-depth comparison of the three selected systems is shown in

Table 10.

The laminate surface treatment selected was light abrading follow­

ed by a diglyme wash. BR34B-18 was chosen as the laminate primer

through lap shear tests as shown in Table 7.

3.0 PROCESS DEVELOPMENT

3.1 Celion/PMR-IS and Celion/LARC-160 Adherend

10

All of the Celion/PMR-IS test panels used for evaluation of the

polyimide adhesives were fabricated using procedures developed in

Contract NASI-ISI83 (Design, Fabrication, and Test of Graphite Poly­

imide Structural Elements and Specimens).

The composite materials fabricated for the lap shear tests were

unidirectional eight-ply panels of Celion 6K/PMR-IS prepreg tape.

The prepreg tape was furnished by U.S. Polymeric and Fiberite Corp­

oration.

The quality control tests used for these lap shear panels in­

cluded specific gravity, fiber volume, fiber weight, and void fraction.

The test data obtained for a series of 76.2 by 4S.7 cm (30 by 18 in.)

panels, fabricated for this test, are shown in Table II. These panels

also were inspected by ultrasonic c-scanning. The c-scan recordings

show that all of the panels met the NASA "A" sensitivity standard with

few detectable defects as indicated for the panels in Figures 8 and

9.

The flatwise tensile tests panels were fabricated using eight­

ply prepreg with symmetrical (0, +4S, -45, 90)s construction. The

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test data for these panels are included in Table 12. The c-scans

of these panels also met the NASA "A" sensitivity standard as

illustrated in Figure 10 and 11.

Two composite panels used for the climbing drum peel tests were

fabricated using two plies of Celion 6K/PMR-15 in a (O,90-degree)

lay-up constructions. The cured thicknesses of these laminates were

about 0.2 rom (O.OOS in.). A four-ply laminate of symmetrical con­

struction (0, ! 45, 90) of Celion 3K/LARC-160 tape also was fab­

ricated for this test. After cure the two ply laminates curled up

into a cylindrical form while the symmetrical laminates retained

their flat shape.

3.2 Surface Treatment Studz

A series of seven surface treatments were evaluated by lap

shear tests for bonding Celion 6000/PMR-15 composite laminates:

with LARC-13 adhesive. The BR34B-18 material was used as primer for

all adherends in this study. The surface treatments used and the

test results obtained are shown in Table 8. The highest bond

strength values were obtained with light grit blasting folloWE~d by

a diglyme wipe.

3.3 Primer Evaluation

The standard lap shear test used for screening of the adhesives

was used for evaluation of a series of primers. The BR34B-18 primer,

used in all of the screening tests, was used for comparison. Table

7 shows the primer systems evaluated and the test results obtained

at RT and 5890 K (600°F). A bar chart for comparison of the test

values is shown in Figure 12.

The data shows that the highest bond strength values at RT

were obtained with the linear polyimide primers, BR34B-18, NR-150B2,

and 050X, respectively. At 5890 K (6000 F), the highest bond values

were obtained with NR-150B2, PMR-15E, and BR34B-18 primers, respect­

ively. Since BR34B-18 was among the best primers evaluated and is

11

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12

a comercially available product; it was selected for use.

3.4 Processing of Adhesive

The LARC-13 adhesive can be produced either by the standard

anhydride method developed by NASA or by an ester method. In the

anhydride method, the amine component, 3.3' MDA, is first dissolved

in the DMF solvent. Then the anhydride components, BTDA and NA, are

added gradually to the amine solution and stirred until they are

dissolved.

By the ester method; the BTDA and NA components are first con­

verted in methyl or ethyl esters. Then the amine component is added

and mixed until it is dissolved.

A study to evaluate and compare the safety and economics of

these methods was conducted both at Hexcel and Rockwell. Hexcel

found the ester method to have the following advantages over the

anhydride method for large scale production: (1) better control of

the advancement of the resin mix, (2) a shorter mixing period, and

(3) less toxic solvents. Therefore, tests were conducted to compare

the lap shear strength of the LARC-13 adhesive prepared by the two

processes. The results in Table 13 show that there is not sig­

nificant difference in lap shear strength resulting from the two

processing methods. The only advantage observed for the anhydride

process was slightly better flow of the adhesive in cure.

3.5 Process for Mid-Plane Bonding Large Area Panels

Processes for mid-plane bonding 30.5 by 30.5 em (12 by 12 inch)

composite panels were developed. The porosity in the bond lines

was examined by c-scanning, using NASA standard "A" sensitivity.

Void free or near void free bond lines were obtained using several

bonding me~hods for LARC-13 and M-LARC-13E film adhesives with style

112 carrier. The simplest of these processes had the following cure

cycle:

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1 • Pull full vacuum and apply 100 psi pressure

2. Heat to 6000 F at 50 F/min.

3. Cure at 6000 F for 1 hour

4. Cool to 1500 F before r.eleasing pressure and vaCUum

The c-scans obtained for the LARC-13 and M-LARC-13E adhesives

with thi.s cure cycle, Figures 13 and 14, show practically void free

bond lines. The best c-scans obtained in mid-plane bonded 30.5 by

30.5 cm (12 by 12 inch) composite panel with FM34B-18 is shown in

Figure 15.

A study of shear beam and slotted shear was done, which was

prepared from mid-plane bonded panels. They are shown in Tables

14 and 15.

3.6 Process for Bondins Honeycomb Sandwich Panels

The use of scrim-supported film adhesive resulted in good

filleting and high flatwise tensile strength values for each of the

three selected adhesives with the porous HRH 327-3/16-4 core, as

shown in Table 12. In this process, the core and the Celion 6000/

PMR-15 face sheets were at first cleaned and primed with the 13R34B-18

primer. Then a layer of the adhesive film, having an areal weight

of 293 g/m2 (0.06 lb/sq. ft.), was applied on each side of the core,

permitting the panel to be cured in one operation. A suitable cure

cycle for the FM34B-18, LARC-13 and the M-LARC-13E adhesive is

shown in Figure 16. In this cUre cycle, a maximum pressure of

2.75MPa (40 psi) and a maximum temperature of 5890 K (600oF) were used.

The application of lower pressures around 1.72 MPa (25 psi) produced

good panels while the use of 3.45 MPa (50 psi) pressure resulted

in slight damage to the honeycomb core.

3.7 Core Coating of Paste Adhesives

The pl.rpose of applying the polyimide paste adhesive by a core­

coating process is to optimize distribution of the adhesive at the

core-face sheet interface, thereby reducing the required adhesive

weight. This process requires proper surface tension and thixotropic

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14

properties for the adhesive. To evaluate the core-coating ability

of the LARC-13 and M-LARC-13E adhesives, (FM34B-18 was available

as a supported film only) experiments were conducted with rubber

paint rollers and a laboratory coater. It was apparent that the

surface tension and the viscosity of the adhesives were too low to

produce sufficient quantity and uniform distribution of the adhesives

in one application, as required for an automated core-coating process.

However, good distribution of the adhesives was obtained using a

rubber paint roller and three or four layers of the adhesive.

3.8 Aging Stability of Selected Adhes.ives

A study was undertaken to evaluate the aging stability of

LARC-13 and FM34B-18 adhesives. Honeycomb sandwich panels were

fabricated and flatwise tensile specimens 5.08 em (2") x 5.08 em

(2") were machined. Half of these specimens were wrapped in alumi­

num foil and aged at 5890 K at (600oF) for 125 hours in an air circu­

lating oven. The other half of the specimens were exposed directly

to the hot air stream in the oven. It was observed that the flat­

wise tensile strength decreased on aging, but the decrease was much

smaller for the specimens wrapped in aluminum foil than for those

subjected directly to the air stream. The results are shown in

Table 16 and 17.

An evaluation of the physical properties of the three adhesives

was continued with an aging study of lap shear specimens at 5890 K

(600oF) using Celion 6000/PMR-15 adherends. The test data obtained

after exposure of the lap shear specimens in an air circulating oven

at this temperature is shown in Table 18. The values for the three

adhesives were reduced significantly by exposure at 5890 K (600oF)

for periods of 125 and 250 hours. However, the lap shear specimens

failed partly in the laminates, indicating that the aging stability

of the adh~sives is as good as that of the laminates.

3.9 Out-Time of the Selected Adhesives

An out-time study was made of the FM34B-18, LARC-13, and the

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M-LARC-13E adhesives for periods up to II days in a very dry atmos­

phere (6-40 percent RH). The effect of this storage environment was

evaluated, using lap shear tests with Celion 6000/PMR-15 adherends.

None of the three adhesives were significantly affected by storage

in the dry atmosphere prior to the bonding operation. To determine

effects of out-time exposure in a humid environment, a similar study

was conducted during the month of December, when the relative

humidity in the storage area was 40 - 90 percent. The lap shear

data obtained (Table 6) shows that strength values of the FM34B-18

adhesive are significantly reduced after the three and seven day

out-time periods. In comparison. the lap shear strength properties

of the LARC-13 andM-LARC-13E adhesives were not detrimentally

affected by these exposures. The results show that exposure of the

FM34B-18 adhesives to a humid environment must be avoided prior to

application.

3.10 Effect of Water Immersion or Lap-Shear Strength

The data in Table 19 shows that the lap-shear strength of

LARC-13 and FM34B-18 adhesives are only slightly affected by water

immersion at RT for 7 days.

3.11 Final Selection of Adhesives

The selection of an adhesive for fabrication of a structural

test assembly was made by a comparison of 14 factors as sho~~ in

Table 10 for the FM34B-18, LARC-13 and the M-LARC-13 adhesives.

These factors included commercial availability, material cost,

out-time, tack and drape, filleting, tooling and processing cost,

mechanical and adhesive properties. Each factor was given a

significance rating of I, 2, or 3. By this comparison, the LARC-13

adhesive had the highest point rating and was selected for qual­

ification tests.

4.0 QUALIFICATION OF SELECTED ADHESIVES

4.1 Process for Fabrication of Honeycomb Sandwich Panels

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A method for fabrication of honeycomb sandwich panels with the

LARC-13 adhesive was developed. The materials to be used for .the

fabrication of honeycomb sandwich panels are HRH 3/16-4 core of

1.27 cms (0.5") thickness and eight plies of Celion 6000/PMR-15 or

Celion 6000/LARC-160.

4.2 Process for Mid-Plane Bonding Large Area Panels

Composite laminates of Celion 6000/PMR-15 or Celion 6000/LARC-160

were used for fabrication of mid-plane bonded panels.

The 30.5 cms (12") x 30.5 ems (12") mid-plane bonded panel fab­

ricated with LARC-13 and FM34B-18 adhesives were c-scanned as shown in

Figure 13 and IS and subsequently cut into slotted shear and short

beam shear specimens to evaluate bond properties. Test results are

shown in Tables 14 and 15.

4.3 Effect of Bond Line Thickness on Lap-Shear ,Strength

Several lap shear specimens with varying numbers of LARC-13

adhesive layers 0.034 gm/cm2 (0.07 Ibs/ft2 per layer) were fabricated.

These specimens were subjected to destructive testing after the bond

line thickness had been determined. It was concluded from the data

obtained, as shown in Table 20 that the lap-shear strength decreases

as the bond-line thickness increases. These lower bond strength

values, with increased bond-line thickness, is apparently due to high

porosity in the thick bond lines.

4.4 Effect of Out-Time on Filleting Properties of LARC-13

16

A study to observe the effects of out of refrigerator time vs

filleting was completed. A series of 17.8xll.4xl.27 cms (7"x4i"xi")

thick sandwich panels were bonded with a single batch of LaRC-J3

adhesive that was exposed to normal atmospheric temperature for up to

8 days. 2"x2" flatwise tensile specimens were cut from each panel

and tested at R.T. and 5890 K (600oF) after measuring fillet thickness.

Results of these tests are shown in Table 21. It is concluded through

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the data obtained that the adhesive LaRC-13 is not significantly

affected and there is no remarkable difference in filleting as well.

4.5 Evaluation of Catalxst

A study to evaluate catalysts to reduce the required cure tem­

perature for LARC-13 adhesive was undertaken. Initial studies, (with

organic peroxides like USP-138 which is a new cyclic peroxyketal

recommended for broad high temperature applications as a polymeri­

zation catalyst and cross linking agent and Experox-IO which is

tertiery butyl perbenzoate recommended for the same reasons from

WITCO chemicals), showed promising results when the adhesive was

cured at 5330 K while maintaining the same 5890 K (600oF) post oven

cure cycle. Preliminary specimen tests resulted in lap-shear

strength in excess of 13.6MPa (2000 psi). Catalyst used is in the

amount of 2% by weight.

Further work indicated that if the cure temperature is reduced

to as low as SOSoK (4S0oF), poor bonding results and the laminates

debond while being post cured. Therefore, based on the study and

the data shown in Table 22, it was concluded that by using a catalyst

we can reduce the cure temperature at S330 K (SOOoF) and still main­

tain the lap-shear strength above 13.6MPa (2000 psi).

Thus, our initial efforts with catalized product indicated that

a drastic change from the conventional LARC-13 cure temperature of

589°K (600°F) to below 5330 K (500°F) could not be made by the addi­

tion of the organic peroxide and still achieve adequate cure. From

this evidence, it was concluded that the material cannot be cured as

are current aerospace grade epoxies.

5.0 SUMMARY

During the course of this program, a series of polyimide adhe­

sives were screened for mechanical and physical properties and for

processibility in fabrication of large mid-plane bonded panels and

honeycomb sandwich panels. The mid-plane bonded panels were fabri-

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18

cated using Celion 6000/PMR-15, composite sheets and honeycomb panels

of HRH 327 3/16-4 core with face-sheets of Celion 6000/PMR-15. From

a series of 41 adhesive formulations, the LaRC-13, FM34B-18; and a

modified LaRC-13 adhesive designated as M-LaRC-13E were selected for

process evaluation studies. On the basis of the data obtained during

these studies as shown in Table 10, LaRC-13 adhesive was rated as the

best of the three adhesives in terms of availability, cost, process­

ability, properties and ability to produce void free large area

( 12"x 12") midplane bonds.

An evaluation also was made of surface treatment and primers

for the graphite/polyimide adhesives to be used in bonding studies.

The selected surface treatment consisted of light-abrading with

Behr-Tex pads followed by diglyme wash. One selected primer was

BR34B-18. Processes also were developed for fabrication of honey­

comb sandwich panels of very good quality for the LaRC-13, M-LaRC-13E,

and the FM34B-18 adhesives. The good quality was evidenced by rup­

ture in the honeycomb core rather than in the honeycomb face sheet

bands on flatwise tensile strength testing.

In future studies on polyimide adhesives, it is recommended

that the following areas be addressed:

o Polyimide adhesives investigated to date tend to be brittle

and fail in peel mode more readily than lower temperature,

higher strength epoxy systems. To overcome this disadvantage,

plasticiers must be studied to determine if a more flexible

PI adhesive can be produced with improved peel strength,

increased handleability, and minimum effect on lap shear

and other adhesive qualities.

o A low cost substitute for 3,3' MDA should be located and

evaluated to study the overall affect on adhesive cost,

mechanical properties, and processing characteristics.

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6.0 TECHNOLOGY DEMONSTRATOR SEGMENT

The initial intent of this task was to fabricate a represent­

ative demonstration component of the Space Shuttle aft body flap.

It was intended that the component design would incorporate all

developed processes and structural configurations to demonstrate

manufacturing feasibility of graphite/LARC-160 to full-scale

structures.

The requirement "to fabricate a representative demonstration

component' was later changed "to fabricate a representative struc­

tural test component". This structural test component has been

given the designation of Technology Demonstrator Segment (TDS). The

completed TDS, ready for installation of instrumentation for ground

testing, is shown in Figure 17.

In changing from a demonstration to a structural test component,

the complexity of the task changed correspondingly: All aspects of

design, tooling, NDI, fabrication, and assembly became more critical.

To implement this change, the scope of Contract NASI-15843 (Develop,

Demonstrate, and Verify Large Area Composite Structural Bond with

Polyimide Adhesive) was amended to fabricate the cover panels, ribs,

and leading edge covers of the TDS. Fabrication of the remaining

TDS components and final assembly was accomplished under Contract

NAS1-15371, Development and Demonstration of Manufacturing Processes

for Fabricating Graphite/LARC-160 Polyimide Structural Elements.

Design details of the TDS test component as shown in Appendix

drawings, all fabricated elements of the TDS i.e., solid laminate

structures, laminate skins. and bonded honeycomb panels were non­

destructively inspected to assure that high quality structure within

the state-of-the-art was fabricated. Typical NDI records for the

TDS are included in the report to indicate the high quality of the

laminates and sandwich assemblies produced.

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7.0 FABRICATION OF STRUCTURAL TEST ASSEMBLY

7.1 Prepreg Tape

Unidirectional prepreg tape used in fabrication of all details

was supplied by U. S. Polymeric, Inc., Santa Ana, California. The

tape consisted of 3000 graphite fiber filaments in the basic tows

impregnated with high temperature polyimide resin. The filaments

were high modulus (typical 234 GPa or 34 x J06 psi) and high

strength (typical 2.758 MFa or 400 x 103 psi) PAN-based carboni

graphite fibers manufactured by Celanese, Inc. (under the trade name

of Celion 3000) and sized with polyimide resin NRI50-B2, had a

typical fiber density of 1.76 g/cm3 (0.064 Ib/in3). The polyimide

resin (originally developed by NASA-Langley Research Center with

designation LARC-160) was prepared via addition-type reaction or

reverse Diel-Alder reaction and had a upper operating temperature

limit of 5890 K (6000 F).

The composite tape was stored inside sealed bag at 2550 K (OoF)

in a freezer until it was ready to be used. The sealed bag was

removed from freezer and thawed to room temperature before opening

. to avoid any deposit of moisture on the tape. They were inspected

visually to examine overall quality, such as drape, tack, amount of

tow splice, fibers collimation, uniformity of resin on the tape and

thickness of tape. The nominal cured ply thickness was 0.0064 cm

<0.0025"). The supplier provided samples of resin and fiber for

reference. Several feet of the tape from each roll underwent quality

control tests to confirm the reported properties from supplier. The

cover consisted of three major components, honeycomb core, upper and

lower skins, and forward and aft closeout edge members as shown on

Appendix A drawings.

7.2 Leading Edge Cover Panel

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7.2.1 Skin

Prepreg tape was removed from freezer and allowed to thaw to

room temperature before any work would start. It was cut according

to its specific orientation with aid of templates. The lay up was

done with great care and once i.t was completed the skins were weighed

and arranged under vacuum bag as shown in Figure 18. It was imidized

following the cycle below:

I. Apply 5.1 cm (2") Hg vacuum and maintain throughout the cycle.

2. Raise temperature to 4910 K (425°F) at a rate of 2.20 K (4°F)

per minute.

3. Stage the skin at 4910 K (425°F) for 30 minutes.

4. Cool to 3380 K (150°F) before removing the part from oven.

After imidization, the laminate was weighed and examined "isually

to determine any abnormali ty being committed to further work. The

staged laminates were prepared as in Figure 19 to be autoclave cured

with the following cycle (Figure 28):

I. Apply full vacuum and 1.4 MPa (200 psi) autoclave pressure

and maintain throughout cure.

2. Raise temperature to 5190 K (475°F) at a rate of 4°F per

minute.

3. Hold 5140 K (466°F) for 42 minutes.

4. Increase temperature to 6020 K (625°F) at a rate of 4°F

per minute.

5. Hold at 602°K (625°F) for 2 hours and 45 minutes.

6. Lower temperature to 4220 K (300°F at a rate of 20 K (3.70 F)

per minute.

7. Below 4130 K (284°F), cooling rate may be increased to 4.SoK

(8°F) per minute.

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8. Release autoclave pressure at 338°K (IS00 F) and remove part

from autoclave.

The curing temperature of 6020 K (62SoF) has substantially de­

creased the post cure time. The cured laminate was free standing post

cured in the oven at S890 K (600oF) for 2 hours. The heating and cool­

ing rate for this process were not closely monitored. The heating

rate was at 2.SoK (SoF) to 4.SoK (8°F) per minute and cooling rate

varied even more. After the assembly was completed, the skin was post

cured for an additional 4 hours (Figure 29). Several parameters were

used to assess the condition of the skins after autoclave cure. These

included total resin loss, fiber volume (calculated through several

methods), skin thickness, skin final weight, glass transition tempera­

ture (Tg) and overall cosmetic appearance. A computer program was

developed earlier to relate most of these variables.

Ultrasonic transmission c-scan tests were performed as part of

quality control effort on skins and all other assemblies in the cured

and post-cured conditions. Established,NASA-LARC "A" sensitivity

standard specimens were used as a control in setting equipment sen­

sitivity for quality verification. This particular nondestructive

testing has been a very useful and time-saving method to detect any

voids or delaminations. C-scan recording of both skins were made

and no defects were detected. One of the recordings is shown in

Figure 30.

Because of its unsymmetrical orientation, the skins curled up

after autoclave cure (Figure 31). These skins were thin (0.031 cm

Or 0.021 inch) and very fragile; to minimize damage during handling

for ultrasonic c-scanning and clearing for water-broken surface,

aluminum picture frame was designed and fabricated to the correct 'size

to hold skin stretched out and lay flat.

7.2.2 Closeout Channel

22

. Same material for the fabrication of skins was used to fabricate

the closeout channels. These are closeout "U" shape edge members on

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the honeycomb sandwich cover assemblies. One of the cover panels

will be mechanically fastened to the final body flap segment. A

16-ply internal doubler was incorporated to one of the flanges.

The difference in thickness on both flanges required a specially

designed tool for layup, staging and curing. The layup was a time­

consuming and tedious process. Four plies of prepreg tapes were laid

up, debulked and consolidated under full vacuum at room temperature

for 2 hours, then vacUUm formed onto the tool (on the tape that was

already laid up) at room temperature, heat was applied to facilitate

the transfer. Layup 0 f more than 4-ply debulked tape would make the

vacuum form difficult and increase the formation of fiber twisting

and wrinkle. Transparent vacuum bagging material was used to provide

maximum visibility (Figure 32).

The arrangement for staging and curing these channels are shown

in Figures 21 and 22. respectively. For staging, autoclave cure and

post cure, same cycles as those for the skins were used on closeout

channels. During the bagging for autoclave cure, the channel should

be placed on the correct side on the layup die as the flanges had

different thickness; wrinkles could be introduced very easily and

more care should be exercised to avoid, or at least to minimize,

any wrinkles.

Several modifications in the staging cycle were needed to obtain

void free and targeted-fiber-volume or targeted-thickness channels.

These are primarily higher staging temperature (up to 497°K or 4350 F),

longer staging time (up to 1-1/2 hour) and different numbers of

bleeder/breather or combination of these.

Because of unbalanced channel design (thicker on one leg) it:

assumed the expected moderately bowed condition when removed from

mold lay-up die (LUD). This bow caused some difficulty during next

assembly bonding. In a production mode either the part or the tool

should be revised to produce a straight part at ambient temperature.

Cured channels were submitted for c-scan inspection and con'­

firmed to be void free before trimming was done.

23

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7.2.3 Assembly of Leading Edge - Bonding Tool

Because of its favorable thermal expansion coefficient, stain­

less steel was used for fabrication of the hinged cover bonding tool.

The tool was roll formed to the desired curvature as close as possible.

However, it was not stiff enough and two additional flat stainless

steel sheets were bolted to the inside of the curved sheet to avoid

rocking and stabilize the bonding tool. Two L-shape steel angle

members were fastened to the bonding tool along its length to protect

the sandwich assembly from crushing during bonding operation. The

angle members were located so that no additional positioning on the

width was needed. The completed bonding tool was sprayed with a thin

coat releasing agent FREKOTE-33, the agent was dried in the oven at

3660 K (2000 F) minimum for 30 minutes or more (Figure 33).

7.2.4 Prefit of Details

The relatively small value of radius over of radius over core

thickness ratio of sandwich panel indicated a potential difficulty

in fitting the core to the curvature of "the tool. A plain core seg­

ment was forced to follow the contour of the bonding tool with vac-

24

"uum bag pressure employed at room temperature. A vacuum level of

approximately 500 mm Hg (20 inches) was sufficient to have the core

fitting nicely to the tool, but upon removing the vacuum bag pressure,

the core sprang back to its original shape. Another approach was

tried. A segment of this 1.91 em (0.75 inch) thick core was heated

in oven (free standing) at 5890 K (6000 F) for about an hour. Immedi­

ately following its removal from the oven, the core was tied down to

the bonding tool by heat-sensitive shrink tape and dead weight for

about 30 minutes. However, once the tapes were removed, the core

again returned to its flat shape. Preforming this cured honeycomb

core to the bonding tool before assembly for sandwich panel bonding

was impossible.

In order to determine the exact contour of cured panels fab­

ricated from this tool and at the same time develop the bonding

process, several smaller sandwich panels were fabricated at different

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locations on the bonding tool. The arrangement for the autoclave

bonding was similar to that shown in Figure 34. Three of these small

panels were fabricated and the exact number of 0.0076 cm (0.0030 inch)

porous separators and 0.013 cm (0.005 inch) non-porous separators to

be used as tooling shims to make panel fit the stability rib fr()nt

curved segment better was determined.

7.2.5 Cleaning and Priming of Details

Some sort of surface treatment of the bonding areas must be

carried out to achieve optimum strength.

For skin and closeout channel bonding surface, heavy duty

"Behrtex" type scrubbing pad and "Comet" cleaning agent were used

to remOVE~ all grease and other contaminants. Parts were rinsed with

deionized water to check the waterbreak condition. Then they were

dried in oven at 394°K (250°F) for about 30 minutes and the details

were ready to be primed and bonded.

The honeycomb core used for the fabrication of hinged covers

were supplied by Hexcel Corporation. It was HRH-327 high tempera­

ture glass-fabric reinforced polyimide honeycomb core with 0.47 cm

(3/16 inch) cell size, 1.91 cm (0.75 inch) thickness and 0.048 g/cc

(3 Ib/ft3)density. This core did not need to be degreased. Methyl

ethyl ketone was sprayed into core cells to remove dUst and any

contaminants.

The liquid paste adhesive counterpart of FM34B-18 film adhesive,

BR34B-18, was used for priming all bonding surfaces. This primer has

an aluminum-powder filled adhesive with 90% solid content. (Alu­

minum powder + organic polymer). It was diluted into 35% solid con­

tent with ketone/alcohol thinner, this diluted primer was sprayed

on skins and closeout channels. A thin coat of 25.4 cm or 0.001 inch

thick prime~ solution on the surface was sufficient. Roller was used

to apply a thicker coat of primer solution onto the cores. The

primer was air dried at room temperature for 30 minutes and oven

dried at 366°K (2000 F) for 2 hours.

25

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7.2.6 Assembly of petails On Tool

26

Up to 5 plies of 0.0076 cm (0.0030 inch) 3TLL porous teflon­

coated glass fabric separator were used on the bonding tool at

different locations. The separators were stacked with different

width and length to avoid any sudden change on tool surfaces; up to

3 plies of thicker 0.013 cm (0.005 inch) 5TB non-porous teflon­

coated glass fabric separators were used for the same purpose of

shimming. One ply of 5TB separator was used to cover the entire

bonding tool for the panel assembly.

The adhesive used for the bonding was supplied by American

Cyanamid Company_ It was scrim-cloth-carrier polyimide adhesive

FM34B-18, aerial density 0.04 g/cm2 (0.09 Ib/ft2). In order to

achieve the desired ribbon direction on the core, 3 pieces of core

were spliced together with FM34B-IS. The splicing adhesive was

cured together with the sandwich panel assembly.

As mentioned earlier the cores would not form to the contour

of the bonding tool. Great care and effort were needed to ensure

that the cores were positioned correctly. After the cores were in

their proper positions, several openings existed between cores and

the closeout channels. Beads and stacks of FM34B-18 adhesive were

used to fill up and bridge these areas.

One layer of FM34B-18 adhesive was put on top and bottom of

the cores to be bonded to the skins. The top skin was covered

with one layer of porous separator and stainless steel caul plate

to obtain smooth outer surface. The lay-up die (with straight sides)

of the closeout channels were used to avoid channel crushing and

maintain proper alignment. Pieces of wood wrapped with teflon were

taped down to bonding tool to protect sides of sandwich panel. The

whole assembly was arranged as shown in Figure 34 and cured in

autoclave with the following cycle (Figure 25).

I. Apply full vacuum and 17.6 KPa (25 psi) autoclave pressure

and maintain throughout cure cycle.

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2. Raise temperature to 4630 K (3750 F) at a rate of 2.SoK

(SoF) per minute.

3. Cure adhesive at 456°K (3620 F for 2 hours.

4. Cool to 33SoK (1500 F) at a rate of 20 K (3.7°F) per

minute before releasing autoclave pressure.

The assembly was free standing oven post cured with the same cycle

as the skins and closeout channels.

The leading edge cover was visually inspected for its bonding

quality. Adhesive filleting on the honeycomb core cell wall in··

dicated good flow was achieved and good quality bonding was expected.

The cover had uniform thickness and retained its curved configuration

(Figure 35 and 36). It was checked against the stability ribs and

some change on the contour would give a better fit (Figure 36).

During the fabrication on the second leading edge cover, two

additional plies of STB separators were put on the straight portion

of the bonding tool on top of the shimming that was used for the

first cover panel. The fabrication procedure for the second cover

. was identical to the first one. With this extra shimming, the second

hinged cover fitted the stability ribs better and was used as the

bonded, lower hinged cover of TDS. The first cover was used as the

bolted, upper hinged cover.

7.3 STABILITY RIB , W'

The stability ribs have honeycomb sandwich panel webs with

secondard bonded pi shaped closeout out channels top and bottom

completing the "I" beam configuration. A "u" channel closed out

the front edge with a Pi shaped channel at rear.

7 .3.1 Stability Rib Sa:n,d:vich Panel

The skins for these ribs were rather thin, the nominal thickness

was 0.020 cm (O.OOS") and had unsymmetrical ply orientation of

(90, ~ 45). All skins were fabricated as in section 7.2.1.

27

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7.3.2

7.3.3

28

The honeycomb core was the same material as used in leading edge

panels except they were 1.27 cm (0.50") thick and no splicing was

needed to obtain the desired ribbon direction. The panel was bonded

as in section 7.2.6.

The front U shape closeout channels were fabricated from woven

fabric broadgoods, Thornell 300/LARC 160. The nominal thickness of

cured laminate was 0.018 cm (0.007"). The channel was laid up on

the tooling shown in Figure 26 and held in place by heat-sensitive

plastic tapes, the channels were staged and cured with cycles used

in section 7.2.1.

Undiluted 80% solid BR34B-18 primer was used in place of

adhesive FM34B-18 for bonding of closeout channels to stability ribs,

a thick coat of primer was applied on the bonding surface using a

paint brush.

Pi Cap Element

The configuration of the Pi joints is shown in Figure 27,

special tooling had been designed and machinEd for the fabrication

of these joints. These joints were autoclave cured with cycle

similar to those described in section 7.2.1 except that lower cure

temperature of 5600 K (5500 F) was used to prevent degradation to the

silicone rubber tool details. To obtain the desired 6250 F Tg the

Pi joints were subsequently post cured in an oven for four (4) hours.

Bonding of Closeout Channel and pi Cap to Web Sandwich Panel

All faying surface of the web sandwich panel, closeout channel

and Pi cap were cleaned and oven dried with the same procedure as

above. Similar priming process used in Section 7.2.5 for leading

edge cover was carried out. The flanges of Pi cap were clamped

down to an aluminum tool that would increase the width of center

opening to ease the fitting of Pi cap on web panel.

For the forward closeout channel to web bonding area, FM34B-18

film adhesive was not used because it was so tacky that installing

the channel to web would produce non-uniform bond line. Undiluted

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80% primer solution of BR34B-18 was applied by paint brush to all

areas (Figures 37 and 38). The channel was installed relatively

easy (Figures 39 and 40). After FM34B-18 adhesive was wrapped on

the upper and lower bonding areas on the web, additional undiluted

primer solution was brushed on. This lubricated the entire arE~as.

Graphite pin passing through both pi cap and web after the assembly

was posi.tioned and indexed in the drilling fixture which was :~hown

in Figures 41 and 42. This fixture was modified to allow to be used

as bondi.ng fixture for stability rib assembly fabrication.

NDI technique was performed to verify bonding quality.

7.4 Lo;wer and Upper C.o,ver Peane

l1s

7.4.1 Honeycomb Cor,e

High temperature glass-fabric reinforcedpo1yimide honeycomb

core HRH-327 (supplied by Hexce1 Corp.) was used-cell size 0.47 cm

(3/16"), thickness 1.91 em (0.75"), density 0.048 g/cc (3 1b/ft3).

Several pieces of honeycomb core were spliced together with high

temperature polyimide adhesive (FM34B-18) to obtain the size required

in the ribbon direction. The splice lines added a mere 45 gm to the

total weight of 3.9Kg of full size honeycomb core.

The aft edge of the spliced core was recessed to fit the outer

skin spar recess joggle.

7.4.2 Skin -The skin for cover panel was laid up, staged and cured following

the same procedure used in fabricating skin leading edge cover in

Section 7.2.1. During autoclave cure, a stainless steel metal strip

was placed under the aft edge of laminate to mold into the skin to

form a joggle of 0.051 cm (0.020") thick; this would allow for the

flush fit of the rear spar to cover panels.

29

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7.4.3 Closeout Edge Member

A typical edge member layup die (LUD) is shown in Figure 20.

These molds were made of aluminum. For production use steel would

be more appropriate considering the 6020 K (6250 F) cure temperature.

Eight ply 0.051 cm (0.020" thick) forward and aft channels

were laid up and bagged as shown in Figure 21, (for oven staging).

The staging cycle was similar to the one used for cover skins. The

staged channels were prepared as in Figure 22 and autoclave cured

using c9ver skins cure cycle. They underwent similar post cure and

NDI procedures.

In order to get a completely wrinkle-free outer surface on the

channels, a different bagging system was used as shown in Figure 23.

The high-temperature-resistant silicone rubber bag improved the

cosmetics quality of channels due to its wiping action as vacuum

was applied. One pair of forward and aft channels were fabricated

using this preferred method.

7.4.4 J:ion,eycomb S~ndwich Asse1ll;bly

30

To achieve optimum bonding strength the faying surfaces of

skins, core, and fore and aft edge members were cleaned and primed

following the procedure used in section 7.2.5. All the detail parts

were assembled without adhesive and a vinyl impression check was

carried out in the autoclave under 25 psi autoclave pressure and

full vacuum at 4220 K (3000 F) for 30 minutes. The impression check

verified fit up of details.

The detail parts were assembled with the same po1yimide adhesive

used for leading edge cover fabrication and autoclave cured under the

same cycle used in Section 7.2.6. The cover was a large flat honey­

comb sandwich panel and no bonding fixture other than a modified

picture frame was used as arm around the whole panel. After cure

NDI ultrasonic c-scanning was also used to check bonding quality~

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8.0 DEMONSTRATOR SEGMENT TEST PROGRAM .. -

A preliminary test program has been defined for the graphite/

polyimide body flap Technology Demonstrator Segment (TDS) shown in

Figure 43. The test objective is to verify the structural adequacy

of a typical composite body flap section to sustain acoustic, mechan­

ical, and thermal load cycles representative of 100 Space Shuttle

missions. The proposed TDS test program is outlined below and in­

volves mechanical testing at room temperature and S330 K (SOOoF) and

thermal cycling and acoustic testing under overall sound pressure

level (OASPL), resources permitting, The S330 K (SOOoF) maximum

temperature is based on Orbiter entry and Terminal Area Energy

Management (TAEM) environment. The fabrication of a large, all

bonded graphite/polyimide structure is advanced state-of-the-art,

and as a result the integrity of the major bonded joints is open to

question. Loading conditions have been determined to subject these

joints to stress levels equivalent to the compos:i.te body flap stress

levels. The TDS will also be subjected to internal pressure to test

the adhesive bonds in flatwise tension.

The TDS is stiffness. rather than strength, due to the structure/

TPS deflection requirements. Therefore, failure under mechanical

loads is not anticipated. Due to the location of the body flap

relative to the Orbiter main engines, acoustic fatigue is the pre­

dicted failure mode;

The primary purpose for testing the TDS is to develop confidence

in the structural capabilities of graphite/polyimide. The confidence

is high that a static test will verify the reliability of the NASTRAN

model and other TDS static analysis techniques. The confidence level

associated with the thermal models is relatively high. However, the

confidenc·e in the acoustic model is low, and acoustic fatigue is the

predicted failure mode. These relative confidence levels are illus­

trated in Figure 44. If the TDS can survive all of the tests, the

confidence level in GR/Pi structure will be high, and the all bonded

GR/pi structure technology will be verified.

31

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8. 1 Test Approach

The body flap is loaded and supported through four-hinge ribs.

However. lack of a hinge rib on the TDS precludes actual body flap

loads. Test conditions to adequately simulate the stress state in

the region of the body flap stability ribs were input to theTDS

NASTRAN model for several loading and support conditions. The tech­

nology demonstration segment test approach is outlined below:

MECHANICAL LOAD TEST

o Simulated Load at Room Temperature (RT) and 5330 K

(5000 F).

o 400 Cycle Simulated Fatigue 5330 K (5000 F)

o Internal Pressure at RT

THERMAL CYCLING TEST

o 100 Cycles (222K and 5890 F) for 100 missions

ACOUSTIC FATIGUE TEST

o 165 dB OASPL for 34 Minutes (lift Off)

o 161.5 dB OASPL for 38 Minutes (Aerodynamic)

0157 dB OASPL for 60 Minutes (Aero/Shock)

8.2 Test Constraints

Test constraints for the TDS are summarized in Figure 45.

Acoustic test constraints require attachment to all three stability

ribs. Thermal test constraints make application of distributed loads

at elevated temperature complex. Mechanical test constraints require

the TDS to be contilevered from the outer ribs, while loading is to

be applied at the trailing edge. Funding constraints preclude spec­

trum fatigue and thermal cycling tests.

8.3 Technology Demonstrator Segment NASTRAN Model

32

The TDS NASTRAN model was used to define the loading .condition

for the mechanical load test and is presented in Figure 46. The

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374 node model was extracted from the 1000+ node body flap model.

The cover panels are represented by QUAD 1 sandwich elements which

model the honeycomb core and laminate face-sheets. The spars and

ribs are modeled by SHEAR panels stabilized by ROD elements. Spar

and rib caps are represented by offset BAR elements.

8.4 Room Temperature an~5330K M~chanical Load Tests

Lack of a hinge rib (through which the body flap is loaded

and supported) on the Technology Demonstration Segment makes appli­

cation of actual body flap loads impossible. The objective of the

mechanical load test is to simulate the body flap stress state and

verify the structural adequacy of the TDS to sustain Orbiter static

stress levels. A combination of supports and loads that would re­

produce the stress state in thd vicinity of the body flap stability

ribs were determined from several test conditions input to the TDS

NASTRAN model. Test program loading support concept is described

in the following paragraph.

As shown in Figure 47. the TDS is cantilever supported at the

outer ribs, has the middle rib displaced to stress the front spar,

and has concentrated loads at the trailing edge. These concen­

trated loads do not require the attachment of a special loading

fixture. A TDS/body flap cover panel stress contour comparison

is presented in Figure 48 and the stress levels in the caps, webs,

and cover panels are compared in Table 23. The stress state of

the load concepts adequately compare with the body flap stress

state. The stability rib web shear, and stability rib cap com­

pressive stress are somewhat larger than the body flap stress

levels, but a large factor of safety is still apparent.

The loads applied at the rear spar cause a twisting downward

moment, and flex the rear spar. These loads simulate the ultimate

stress levels, and will also be applied at 5330K as shown in

Figure 49.

33

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8.5 400 Cycle Simulated Fatigue Test

The objective of the fatigue test is to verify the TDS struc­

tural integrity to sustain mechanical loads simulating 100 missions.

Because of the high cost, spectrum loads will not be applied. In­

stead four lifetimes (400 cycles) of limit loads will be applied

(R = + 0.10) at 5330 K (Figure 50). Spectrum loads would have only

a few cycles approaching limit loads, making the test condition more

severe than an actual service environment. Due to test fixture

limitations, however, load reversals will not be applied.

8.6 Thermal Cycling Test

34

The body flap is subjected to a thermal environment with a

temperature range from 2220 K (_600 F) to 5890 K (6000 F). The maximum ~

applied mechanical loads occur at body flap temperatures between

1660 K and 5330K, with maximum temperature 5890 K (6000 F) resulting

from heat soak back after the orbiter is on the ground. The objectives

of the thermal cycling test are: (1) verification of the TDS struc­

ture under 125 thermal load cycles, and (2) verification of the

analytically predicted thermal strains.

The selected thermal cycle is shown in Figure 51. The cycle

represents the temperatures and thermal gradients obtained during

an abort-once-around (AOA) thermal trajectory for the upper 5890 K

(6000 F) temperatures, and the cold temperatures 1660 K (-160.80 F)

are from a severe cold on orbit mission. The structure would not

be subjected to these extremes on a single mission.

The baseline aluminum body flap was not tested under thermal

cycling. However, some of the body flap joints and other components

were subjected to thermal cycling. The components were exposed to

a temperature range of 1990 K (101.40 F) to 4490 K (348.SoF) for ISO

cycles. The baseline graphite/epoxy OMS Pods were subjected to 400

mechanical load cycles and 100 thermal cycles (1660 K to 4490 K) to

simulate 100 space missions. It therefore appears that a similar

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test program is required for the composite body flap structure.

8.7 Acoustic Fatigue Te~t

Due to the location of the body flap relative to the orbiter

main engines, acoustic fatigue is potential failure mode. The TDS

should be exposed to acoustically induced random vibration simulating

overall sound pressure levels as high as 165 dB anticipated du:ring

Space Shuttle Vehicle (SSV) ascent. The objectives of the acoustic

test are as follows: verify the primary structure acoustic fatigue

life (100 Space Shuttle missions). demonstrate the integrity of

selected regions of the direct· .. bond TPS. and verify the analytically

predicted cover panel RMS strain and frequency.

ThE! body flap acoustic environment is shown in Figure 52.

Upon successful completion of the mechanical and thermal cycling

tests, the TDS will be modified for acoustic test_ funding permitting.

Modifications will include adding direct-bond fibrous reflects the

composite insulation (FReI) tiles, and closing out the TDS open

bays. Testing is to be conducted by NASA.

8.8 Internal. Pressure Test

The TDS may be tested under internal pressure (approximately

.02 MPa (3 psi» to assess the integrity of the major adhesive bonds

by placing them in flatwise tension. The TDS torque box would be

filled with styrofoam to reduce danger due to the pressure. The

test article would be sealed by replacing the front spar access

panels with metal panels equipped with pressure seals and fittings.

The front spar attachment "T" members were designed for shear

loads. Concern has been expressed over the integrity of these

members under internal pressure loads (see Figure 53). Analytical

models predict failure at .03 MPa (5 psi), but confidence in the

analysis is low. It is recommended that this test be conducted

last, predicated on successful completion of a subelement test.

35

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36

8.9 Summary

The test objective is to verify the structural adequacy of

a typical composite body flap section to sustain acoustic, mechan­

ical, and thermal load cycles representative of 100 Space Shuttle

missions. The lack of a hinge rib on the TDS precludes actual

body flap loads, therefore, loading conditions to simulate the

body flap stress state were determined by using a NASTRAN model of

the TDS.

Since it would be very difficult to perform mechanical and

thermal cycling simultaneously, an alternate method is suggested:

First, perform the mechanical testing; Second, perform the thermal

cycling and acoustic testing; and finally, the mechanical test

could be performed again to assess the structural degradation

from the previous testing. It is assumed that the acoustic test­

ing would take place in a NASA facility -- JSC.

Because the TDS is stiffness rather than strength critical,

failure under mechanical loads is not anticipated. However, due to

the extreme sonic environment (165 dB OASPL), acoustic fatigue is

a significant failure mode. The body flap must also be able to

withstand the Orbiter thermal environment 166°K to 589°K (-160 to

6000 F for 100 space missions.

The TDS design was updated to provide for cantilever support

during testing. The stability rib caps were beefed up in the lead­

ing edge area, and potting and inserts were added to the bolt holes.

When testing is complete, analytical predictions for stress

levels, deflections, and acoustic fatigue will be correlated with

test data. The analytical models for the GR/Pi Orbiter Body Flap

can then be updated.

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DOCUMENTATION

1. AS-EMR-SO-053, "Technology Demonstration Segment NASTRAN Model", dated

April 14, 1980.

2. AS-EMR-80-052, "GR/pI Technology Demonstration Segment Design Update",

dated April 14, 1980.

3. AS-EMR-SO-,On, "Technology Demonstration Segment Test Definition",

dated May 2, 1980.

4. SSV80-22, "GR/pI Technology Demonstration Segment Test Concepts:,

dated April 14, 19S0.

5. AS-EMR-80··164, "Composite Body Flap Segment Test Program", dated

September 2, 1980.

37

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This Page Intentionally Left Blank

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0 0 0 H 0

" " " I " O'C:O-C~C'O ... c c, H2N -0- ~ -0-NH2 IO:g:O

" " H " 0 0 0

BTOA ~~ NA

BENZOPHENONE 3,3' ·METHYLENE 5·NORBORNENE TETRACARBOXYLIC OIANILINE 2·3-OICARBOXYLIC ACID ANHYDRIDE

ACID ANHYDRIDE

0 0 0 H 0

" , , ,

" HO-C:o'C"():C -OH H2N -o-~-o-NH2 IO:C- OH H3COC C - OCH3 C-OCH3 , " H " 0 0 0

.!!TDE 3,3' ·MDA 1!!.

DIMETHYL ESTER 3,3' ·METHYLENE METHYL ESTER OF OF 3,3', 4,4'· DIANILINE 5·NORBORNENE BENZOPHENONE 2·3 ·DICARBOXYLIC TETRACARBOXYLIC ACID ACID

Figure 1. LARC 13 Monomer Reactants

A .. PRESSURE

MONOMER REACTANTS

AMIDE ACID

POLYIMIDE

'/

0 f 0 0 OJ 0(3 II II II " II

~ c..... c c c.... ,e THERMALLY ~- N"O"CH2"QTN~:or IOC~, N1O""CH2-o- N,~ CROSS LINKED

o 0 0 n 0

Figure 2. LARC 13 Po1yimide Reaction Sequence

39

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Figure 3. Adhesive Prepreg Mill

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o CF3 0 II I n

HO-C C C-OH

Ho-clOrc~PC-OH II II o 0

+

HEAT 4,4' ·PHENYLENE DIAMINE SOLVENT

9- NH2

NH2 3,3' ·PHENYLENE DIAMINE

4,4' ·(HEXAFLUOROISOPROPYLIDENE) • BIS(PHTALIC ACID)

Figure 4. Reaction Scheme of NR150B2G

41

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Figure 5. Flatwise Tensile Test Specimen

42

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Figure 6. Flatwise Tensile Test Specimen After Testing

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44

LOADING BAR

BOLT HOLE

A ~~ ,<»1 • 1 ~

E._ STRAP

CLAMP 8

SECTION A-A

(1.995-2.005) 5.067-5.092

I---+-- (1 • 50!,0 . 01) 3.8!,0.03

CLAMP A

r i PLUS (0.500+0.005) 1.27+0.01

COUNTER-- . -WEIGHT

DIMENSIONS IN INCHES. NOT COMPLETELY DIMENSIONED r i • RADIUS OF DRUM TO MID-DEPTH OF SPECIMEN FACING r • RADIUS OF MID-DEPTH OF STRAP o

Figure 7. Climbing Drum Peel Test Apparatus

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Figure 8. C-Scan of 76 x 46 cm (30" x 18") Panel of Celion 6000/PMR-15 Composite Panel, 8 Ply, Unidirectional

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Figure 9. C-Scan of 76 x 46 cm (30" x 18") Panel of Celion 6000/PMR-15 Composite Panel, 8 Ply, Unidirectional

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NASA STANDARD 'WI SENSITIVITY

Figure 10. C-Scan of Honeycomb Sandwich Panel With FM34B-18 Adhesive

47

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NASA STANDARD "A" SENSITIVITY

Figure 11. C-Scan of Honeycomb Sandwich Panel With LARC 13 Adhesive

48

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::c I-~ z w a:: l-V)

a:: « w ::c V)

Q. « ..J

PS I MPa 1 8

2500 r-

15

2000 r-

1500 I-10

1000 I-

5

500 l-

CJ - RT

r-- ~ 589°K (600°F) ~

r--I- ,...-

I"""'"" ., ,.....

~

~

~ ~ ~ ~ P')c

~ P')c ~ ~ I>c)< ~ ~

~ >< ~ ~ X< x >Y »« ~ ><x" >< x;< ~ ~ ><x" - X<

~ >« "- >0- X)< >xX 0x »c >0- X)< X<x >0- >« »c >xX X'X >< ~ X)< X<x >0. >0 >< >xX ~ -h ~ >< ><>< »« ~ X" »< xx >xX Y>< ~ -h X" ~ )eX >xX >0- >0c X" X'>< Yx )c>< ><x Y>< >0- X< X'>< Yx >-y >x< ><x Y>< >0c ~ >9 >0c Yx X)< »« ><x Y>< '10< X< yy. ~ ><;t- X)< »c ~ X< Yx >Y ><y. »c X<x '10< X" >Y

Y>< X)< XX< »c ~ >0c X< ><x" -- X<x ~ ~ >0c X)< ><;t- »c '10< X" >Y D0c ><;t-

~ )0 ><y X" >Y D0c >y ;0 ><y .;x >« ><x" Y>< ;0 Yx D0c ~ Y>< >y ~ X< X" X< :>c:>< X< X< ~ X)' :>0< )c:>< :? y. ~ ~ X" )

~ y X)' :>:>< ~ ~ Y)c ) ) >y ~ :>>c ~ >< Y) :xy. ~ »>< ~ )< ~ >c Y> ~ ~ 'I >c t>? >- t>? ~ Y> ~ ~ ~

)c t>? Y) DY< >y 'I Y. t>? ~ ~ D<)< ~> 'I )c )c

BR34B-18 LARC-13 LARC-160 PMR-15E NR-150B2 052X 050X AI1130L

Figure 12. Comparison of Primers For Bonding Ce1ion 6000/PMR-15 Panels With LARe 13 Adhesive

r--

~ >c >0 >0< Yx ~ ~ ~ ~ »c -h X" X"

X< Y>< ~ ><>c >c>< ><>c

»c>< »c>< .~ ~ »c>< ~ ~ >xc >xc

AI830

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HBS-S6. NASA STANDARD "A" SENSITIVITY

Figure 13. C-Sean of 30.5 by 30.5 em (12 x 12 in.) Mid-Plane Bonded Panel With LARC 13 Adhesive on Style 104 Carrier

50

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MBS-4B. NASA STANDARD "A" SENSITIVITY

Figure 14. C-Sean of 30.5 em by 30.5 em (12 x 12 in.), Mid-Plane Bonded Panel With M-LARC-13E Adhesive on Style 104 Carrier

51

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MBS-16 NASA STANDARD "A" SENSITIVITY

Figure 15. C-Sean of 30.5 em by 30.5 em (12 x 12 in.) Mid-Plane Bonded Panel With FM 34B-18 Adhesive on Style 104 Carrier

52

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Figure 16. Cure Cycle for the Fabrication of Honeycomb Sandwich Panels with FM34B-18 LARC-13 and M-LARC-13E

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A810828 F-3C

Figure 17. Technology Demonstrator Segment Completed Structure

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2" WIDE KAPTON TAPE

GS43

KAPTON FILM

~~~~~~~~~~~~~~~~~~~~~120 G~SS CLOTH

------ , .. PERFORATED KAPTON

--f I .. ____ ...... LA ..... V-_U .... P_T ... O __ B .. E _I.M .... I D ... I ... Z_E .. D ____ ..... I > 3TLL POROUS SEPARATOR

- - - - - -- - - --s ___ 5TB NON-POROUS

~~~==========================================1~~ SEPARATOR STAGING TOOL

Figure 18. Oven Imidization For Flat Lamir~te

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PICTURE FRAME

BOLT

A-Boo SEALANT

./ KAPTON FILM

,-----------------------------------~ ______________________________________ f~120 GLASS CLOTH

I=--=-~-:~~:--=--=-Z)3TLL POROUS SEPARATOR

-----------------------YS/ KAPTON FILM

CURl NG TOOL

Figure 19. Autoclave Cure For Flat Laminate

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A810430 A-8e

Figure 20. "u" Channel Lay-Up Mold

57

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KAPTON FILM

STAGING TOOL

NOTE: TOOL SECTION HAS BEEN COATED WITH FREKOTE 33 OR SIMILAR TYPE OF RELEASING AGENT.

58

Figure 21. Staging Lay-Up For "u" Shape Laminate (In Oven)

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A-SOO SEALANT

GS:-43 SEALANT

Figure 22.

KAPTON ENVELOPE BAG

120 GLASS CLOTH

- 3TLL POROUS SEPARATOR

(KAPTON ENVELOPE BAG)

Curing Lay-Up For "u" Shape Laminate (End View)

59

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SILICONE RUBBER BAG (BEFORE VACUUM DRAWN)

A-Boo SEALANT

CUR ING TOOL

SILICONE RUBBER BAG (AFTER VACUUM DRAWN)

120 GLASS CLOTH

~ 3TLL POROUS SEPARATOR

MECHANICAL FASTENER (CLAMP OR RING)

Figure 23. Alternate Curing Lay-Up For "U" Shape Laminate

60

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WRIGHTON 8400

GS-43 SEALANT

________________ 1162 GLASS CLOTH

~THIN CAUL PLATE

Pl-----------~V ............. 3TLL POROUS ________ ~ SEPARATOR

~====-~I=!~.:I =H=O=NE=Y=CO=M=B===PA=N=EL==~I ~ :..... ~ (PICTURE FRAME WITH

l DOUBLE BACK TAPE

~-------------------------------------------TOOL

5TB NON-POROUS SEPARATOR

Figure 24. Curing Lay-Up For Honeycomb Sandwich Panel

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LLI a: ~

589

533

~ 478 LLI 0.. ~ LLI I-

LLI 422 a: ~ u

366

311 (100)

CURE TIME (HOURS)

Figure 25. Cure Cycle For Cover Panels

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11.359 r-- (4.427 11

)----..

-~-

Figure 26. Tool Configuration For Stability Rib Closeout Channel

31.8 (12.5")

63

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~ 10.16R (19.911 + 0.025R)

+(4.00R) ,(7 .839 ~.010R)

2.54 11.00)

(.25)TI~", ____ ------ (49.18)------------i-It-.. -

6.35 0.64 --, 124.92 r A

lip III ANGLE

0.175 CM (0.069)

"PI" CHANNEL 90 0 PLY DIRECTION

J--l.349-+.010 I ( .531) -.000

+ 0.292CM (1.25) (0.115) ~.18 0.475R (0.187R)

~~~~~.-l t.:-~ (3. 00 )I __ "':---_ .. ~I' lip I" CAP

90 0 PLY DIRECTION 7.62 SECTION A-A 00 FILLET, 2 PlCS

(2.50)

I LA 10.16R (4.00R) 2 PLCS.

.f- I .. (12.06) 30.63

Figure 27. Curved "PI" Joint Element Design 8879-00250-007 (and -011)

!ill

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UJ 533 a:::: :::> .-;i! UJ 0.. 478 x: UJ .-UJ a:::: B 422

366

311

(600) P

(500)

(400)

(300)

(200)

(100)

I:': ,,;n ' !'~: m: !::~ [::i ::i Ii:: iii: ,~;:i mi:::::: m: ';: 1::.m'T,:t;:',- " ,,: ,: J/I:I':::;:" WL :T I::; In" , , I;:::",',::::' ;:,,' , ':"I"H" ":';i1i:+:it;;i';;,;H>:'l::,;;,,',,';;':::; :';: i\;d,:·:i:L: i:; ::', . :' I":: , ,: ::': i:; l::T'J;;' :;!H:;;::

hir ::: I!!H ll!i!jfljjil'i[1: i;. , ~;i ':1 ,:::: U gil:: lii~ ,Hi ' iii' .ji;; I,::: i:ll h ' Ii; llEi 1:1 UiP miilWllH::: ~:, ii: g:, g: :1:./!:;:I"::: : I::: ,':' i> I , !n:I,,::!':: .:;:T:: ,H I:",

.~ g: ::: :,", ::;ii,;:: ,ii' iii!;';l:: :::;-:: .. , I:::: ::i; " , , 'iTi!:UiI!!li:i; iii, '!: j~E'ijiJ!!r:: Ill' ,;',,1: :\i!ididEIT ;:' I::: • !:li m .' :l: H, rit::'!:::l:H, 'Il! :i:

TEMPERATURE 'I'::

. !:::'

. I:;;:

:iii ;': , [::;: IE

,PF",:I::,I',: .. +,:

bi m , Ii!!: !iHi ,: ,liE H ' lilHHT;;:;:, • ,;\': ' :' : IIItHII iHlIlIllla: 1'1' HHIIIU; 11111 ,,:: '"''

1 2 3 4 5 6 7 8 9

CURE TIME - HOURS

Figure 28. Cure Cycle For Skins

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'" '"

u.! rr. ::::> I-

~ u.! 0... ::E: u.! I-

OK

589

533

478

422

366

311

• of

~ (GOO)

(SOOf

(400~ • (300)- •

R' , ' (200)

(100

. '-t .

II •

2 3 4 5 6 7 8 9 10 11 12

POST CURE TIME-HOURS

Figure 29. Oven Post Cure Cycle For Skins

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Figure 30. C-Sean of 76.2 em by 157.5 em (30" x 62") Skin For Leading Edge

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g; A801023 G-7

Figure 31. Skin For the Leading Edge

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A810430 A-7C

Figure 32. Vacuum Forming of the Close-Out Channels

69

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-...J o

A810918 G-IC

Figure 33. Leading Edge Panel Bonding Jig

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STAINLESS

120 GLASS CLOTH

WRIGHTON 8400 VAC PAK

STEEL CAUL PLATE

3 TLL POROUS SEPARATOR

LEADING EDGE PANEL

CLOSE-OUT CHANNEL

SEALANT

Figure 34. Leading Edge Bonding Assembly-Cross Sectional View

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A810803 A-22C

Figure 35. Leading Edge Cover Panel on Bonding Tool

72

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A810803 A-19C

Figure 36. Leading Edge Cover Panel

73

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A810420 C-2

Figure 37. Primer Being Applied on Rib Web For Bonding "U" Channel

74

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A810420 C-3

Figure 38. Primer Being Applied to the Inner Sec tion of "U" Channel

7S

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A810420 C-4

Figure 39. "U" Channel Being Inserted to Web Sandwich Panel

76

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A810420 C-S

Figure 40. "U" Channel Complete For Bonding

77

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A810126 F-IO

Figure 41. Drilling Fixture For Close-Out Channel & Pi Cap to Web Sandwich Panel

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A810126 F-8

Figure 42. Close-Up View of Forward Section of the Fixture

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00 0

COVER PANELS TDS CONFIGURATION

(HONEYCOMB SANDWICH) • THREE STABILITY RIBS • NO HINGE RIB

LEADING·EDGE ACCESS PANEL • NO TRAILING EDGE

TDS OBJECTIVE • CONFIRM GRIPI COMPOSITE

TECHNOLOGY

~

HINGE RIB ">-• '~H OUTBOARD SEGMENT

STABILITY I!IBS LHINBDARD

HINGE RIB SEGMENT FRONT SPAR WEB RH INBOARD

/ ~EGMENT < PLANE OF TORQUE BOX LEADING·EDGE SYMMETRY ~~ '-.... FAIRING RH OUTBOARD ./ ~ •• ~ SEGMENT

LEADING EDGE ~

BODY FLAP ....... ~PLANEOF

SYMMETRY

TDS STATUS • PRELIMINARY DESIGN COMPLETED OCT 1980 • FABRICATION DEVELOPMENT

- TOOLING INITIATED FEB 1980 - COMPONENT FAB INITIATED APRIL 1980

• FABRICATION - COMPLETION AUGUST 1981

Figure 43. GRIp! Composite Body Flap Technology Demonstrator Segment (TDS)

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CONFIDENCE

THERMAL STRUCTURAL

ANALYSIS

PREDICTED FAILURE MODE

ACOUSTIC FATIGUE

ANALYSIS

Figure 44. GRip! Technology Verification (TDS - All Bonded Structure)

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00 N

DEMONSTRATION SEGMENT

BODY FLAP

COVER PANELS (HONEYCOMB SANDWICH)

• MECHANICAL TEST CONSTf~AlfH

-LACK OF UlNGE RIB PRECLUDES ACTUAL BOllY FLAP LOAllS

-CAN SIMULATE LOCAL STRESS fIELDS

• THERMAL TEST CONSTRAINT

- APPLICATION Of DISTRIBUTED LOADS AT EL(VATED TEMPERATURE (~5000f) 528°K COMPLEX

- TlIERMAL & LOAD CYCLING RESOURCE R£QUIHLHlNTS ARE HIGH

• ACOUSTIC TEST CONSTRAINT

-LACK OF IUNG( RIB REQUIRES DEMO SEGMUn TO UE SUPPORTED ON SlAIHllTY RIB

-TEST FACILITY AVAILABILITY LIMITED

Figure 45. Demonstrator Segment Test Concept Constraints

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00 w

TUREE STABILITY

374 NODES ---

NASTRAN BODY FLAP MODEL

1000 NODES ..

END RIB

FORWARD SPAR

TRAJlIN(i EDGE

Figure 46. Technology Demonstrator Segment - NASTRAN MODEL

STABILITY RIBS

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APPLIED AT ROOM TEMPERATURE

(2520 LB) 1145 KG

255 KG (560 LB)

1018 KG (2240 LB)

ANCHOR (TEST Fl XTURE)

TEST OBJECTIVES

-SIMULATE BODY FLAP STRESS STATE & VERIFY GRIPI STRUCTURAL INTEGRITY UNDER ORBITER ULTIMATE STATIC STRESS LEVELS

-VERIFY ANALYTICALLY PREDICTED STRAIN LEVELS

TEST CONSTRAINTS

- LACK OF A HINGE RIB PRECLUDES ACTUAL BODY FLAP LOADS -- LOCAL STRESS FIELDS IN THE VICINITY OF THE BODY FLAP STABILITY RIBS SIMULATED

APPROACH

- LOADING CONDITIONS DEFINED TO REPRODUCE THE BODY FLAP STRESS LEVELS AS DETERMINED FROM TDS NASTRAN MODEL

-APPLY CONCENTRATED LOADS AT TDS TRAILING EDGE

-DISPLACE CENTER SUPPORT -CANTILEVER FROM OUTER RIBS

LEADING EDGE

Figure 47. R. T. Mechanical Load Test

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00 VI

.. . ... 0::: X

*STAB IL lTV RIB **HINGE RIB

----------- ----------------,

TECHNOLOGY DE~10NSTRAT I ON SEGMENT

• DEFINE LOAD CONCEPTS TO SIMULATE STRESS FIELD BETWEEN BODY FLAP STABiLiTY RiBS

Figure 48. Typical Cover Panel Stress Contours

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255 KG (560 LB)

1018 KG (2240 LB)

(2520 LB) 1145 KG

I 1510 KG (3324 LB)

TEST OBJ ECTI VES

• SIMULATE BODY FLAP STRESS STATE & VERIFY GR/PI STRUCTURAL INTEGRITY UNDER ORBITER ULTIMATE STATIC STRESS LEVELS AT (500°F) 528° K

• VERIFY ANALYTICALLY PREDICTED THERMAL & MECHANICAL STRAINS

TEST CONSTRAINTS

• LACK OF A HINGE RIB PRECLUDES ACTUAL BODY FLAP LOADS

APPROACH

-STRESS FIELD IN THE VICINITY OF THE BODY FLAP STABILITY RIBS SIMULATED

• LOADING CONOITIONS DEFINED TO REPRODUCE THE BODY FLAP STRESS LEVELS AS DETERMINED FROM TDS NASTRAN MODEL

• APPLY CONCENTRATED LOADS AT THE TRAILING EDGE

• DISPLACE CENTER SUPPORT AT LEADING EDGE

• CANTILEVER SUPPORT FROM OUTER RIBS AT' LEADING EDGE

• APPLY 528°K (500°F) TO THE LOWER COVER & 444°K (340°F) TO THE UPPER COVER. INTERNAL TEMPERATURE WILL BE 485°K (41S0F)

Figure 49. High Temperature Mechanical Load Test

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400 CYCLES OF LIMiT LOAD APPLIED AT 528°K (500°F)

727 KG

c t- C ZO 161-'

~t-161-o..~

-'

(1800 LB) 818 KG .

181 KG (400 LB) I (1600 LB) t

100

R = (0.10) 0.25

10

ANCHOR (TEST Ff XTU"E)

NUMBER OF CYCLES 400

... TEST OBJECTIVtS

• VERIFY Tbs STftUCTUAAl INTEGRITY TO SUSTAIN MECHANICAL LOADS SIMULATING 100 MISSIONS

• DEVELOP CONFIDENCE IN ALL-BONDED STRUCTURE SUBJECTED TO A HIGH-TEMP SIMULATED FATIGUE ENVIRONMENT

APPROACH

o APPLY 4 LIFETIMES (400 CYCLES) OF R = (+0.10) 0.25

o MAINTAIN UPPER COVER AT 528°K (50QoF), LOWER COVER AT 444°K (340°F) FOR INDUCED THERMAL STRESSES

RATIONALE

o 400 LIMIT CYCLES AT 528 8 K (500°F) IS HIGHER LOADING CONDITION THAN SPECTRUM LOADS WOULD APPLY

~ Figure 50. Simulated Fatigue Test

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00

00 SELECTED THERMAL CYCLE OK of 589 600

533 500

478 400

422 300

-589°i< (600°F) -.

~ I~ - --~£8~

--- -- r'\ - - r-- - . - -533°K (500 0 F)-t .~ --\ -,-- ---------

1--

~ - . ·-1---1----

~ I- - - -11 -- ·-I/l - - ,-11'1 i- - ,

1- - - I--

ILl a::

366 ::J 200 I-

~~ ,I-\-LOWER COYE~ FACE" SH-EE! .~ _\

I-- - r-- \- - 1-:\

~ ILl a... x:

311 ILl

100 I-

'" 1\1\. \ -

255 0 \ I\. _\ -'-\ ,

"\ 200 -100 \ \ , -\

..... " I. ........

"0 0.2

I 1-,-I-- J I 1-/- - -1

I II I-

--7- 1-

1\ "\

-- \-\ , -

'" -

~ - Vi I\. !.dr"'" -- -

UPPER COVER PANEL (0)

I~ -:---:f-I- -'" " -UPPER COYER FACE SHEET -L

" - £. - --,- -..I

~ - 1-- ..... - - ---..I ./ ,/

k!: ".. .... t-

0.4 0.6 0.8 TIME (~OURS)

Figure 51. Thermal Cycle Test

--

1.0

t- LOWER COYER PANEL (0)

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00 \0

ACOUSTICALLY DRIVEN AREAS (LIFT-OFF CRITICAL)

153 .dB

157 dB

• PANEL FLUTTER ISSUE

~ SONIC FATIGUE ISSUE

[g BASIC STRENGTH AREA

• 165 dB OASPL FOR 34 MINUTES (LIFT-OFF) • 161.5 dB OASPL FOR 38 MINUTES (AERODYNAMIC) • 157 dB OASPl FOR 60 MINUTES (AEROSHOCK)

160 dJJ 163 dB

164 dB

165 dB

BODY FLAP SIZED TO ACCOUNT FOR SONIC FATIGUE

• BODY FLAP IS SUBJECTED TO 165 dB SOUND PRESSURE LEVELS

• ACOUSTIC FATIGUE IS THE PREDICTED FAILURE MODE

• TEST IS PROPOSED TO BE CONDUCTED AT NASA/JSC

Figure 52. Acoustic Fatigue Test

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\0 o

FILL TORQUE BOX WITH STYRQFOAM TO REDUCE DANGER DUE TO PRESSURE

REPLACE FRONT SPAR ACCESS PANELS WITH METAL PANELS EQUIPPED WITH PRESSURE SEALS & FITTINGS

COYER PANEL (BONDED)

CRITICAL ~ AREA

P

, ..

LEADINl1 EDGE ACCESS PANEL (BOLTED) \

. .,

rt I , I I I

" "TEE"

I t __ !"\

~- FRONT SPAR '. rd- .---WEB (BOLTED) ~I-, . I­I-

• I NTERNAL PRESSURE MAY DAMAGE FRON SPAR "T"

• PRESSURIZE TO APPROXIMATELY 0.02 MPa (3.0 PSI) • MAX LOAD ON "T" AT 0.02 MPa (3 PS I) = (20 LB/IN.) 3579 GMS/CM

• PREDICTED FAILURE AT 5 PSI

• LITTLE CONFIDENCE IN ANALYSIS

• SUBELEMENT TEST REQUIRED

• RECOMMEND TEST BE DEFERRED PENDING SUBELEMENT TEST

Figure 53. Internal Pressure Test

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Table 1. Lap-Shear Strength of Polyimide Adhesives

AVerage Lap Shear Strength, NPa (psi)

Type Mode of 58yOK M,)J" uf Adhesive Scrim Basic P.1. Resin Sy.stc·m In Failur .. (bOO°F) Failur~

FH34-1B No. I 104 FM34B-IB 19.3 (2800) 80/;L 20;.C 11.9 (J 730) - 100%C FM34-18 No. 2 104 FM34B-IB lS.1 (2190) - 100%C 11.6 (1680) - 100% LARC 13A No. 1 104 LARC 13 NASA process 19.6 (2BSO) 35%L 6S%C lS.6 (2260) 10%L 90%C LARC 13A No. 2 104 l.ARC 13 NASA process, DNF 17 .7 (2450) 40%L 60%C 12.7 (1B45) - 100%C LARC 13A 108 LARC 13 NASA process, DM!' 16.6 (2410) 40%L 60%C 13.0 (lBBO) - 100%C LARC 13A 112 LARC 13 NASA process, DM!' lS.4 (2240) 30%L 70%C 12.S (1BI0) - 100%C LARC BE 104 LARC 13 ester, diglyme* 19.2 (27BO) 40%L 60%C IS.2 (2200) 20%L 80/.C I.ARC BE 108 LARC 13 ester, diglyme 17.1 (2480) 2S%L 7S%C 12.7 (1840) 50%L 95%C LARC 13E 112 !.ARC J3 ester, diglyme 17.1 (2480) SO%L SO%C 12.7 (1840) 10%L 90%C 17-51:: 104 BTDE/NE, 3,3'/4,4' - ~WA~100/0 lS.4 (2240) 80%L 20%C 12.B (1860 ) 15%L 8S%C 17-6E 104 BTDE/NE, 3,3'/4,4' - MDA~BO/20 17 .4 (2S30) 30%L 70%C lS.4 (2240) 9S%L 5i.:C 17-7E 104 BTDE/NE, 3,3'/4.4' - MDA~60/40 IS.B (2300) 20%L 80%C 13.2 (19 20) S%L 9S%C 17-8E 104 BTDE/NE, 3,3'/4,4' - }UlA=40/60 lS.7 (2270) 70%L 30%C lS.7 (22BO) 100%L -17-9E 104 BTDE/NE, 3,3'/4,4' - }WA=20/BO 14.2 (2060) 100%L - 14.6 (2120) 100%L -17-10E 104 BTDE/NE, 3,3'/4,4' - MDA=0/100 16.4 (2380) 30%L BO%C 14.1 (2140) 30%L 70%C 18-6 104 BTDE/NE, 3,3'/4,4' - MDA=25/75 17.1 (2480) 95%L 5%C 16.0 (2330) - 100%C 1B-6A 104 BTDE/NE, 3,3'/4,4' - HDA=25/75 16.0 (23 2S) 90%L 1O;;C 15.8 (2290) - 100%C 1B-6B 104 BTDE/NE, 3,3'/4,4' - }IDA=25/7S lS.5 (2250) 30%L 70/;C 11.6 (16BO) 30%L 70%C 18-6C 104 BTDE/NE, 3,3'/4,4' - HDA=25/75 lS.3 (2220) 95%L 5%C lS.0 (2185) 60%L 40%C 21-5 104 BTDE/NE,H,M' - phenylenediamine 12.0 (1750) 30%L 70%C 13.7 (1990) 60%L 40%C IB-l 112 BTDE/NE, DADS, DMF 12.3 (1790) - 100%C lS.2 (2200) - 100%e 18-2 112 BTDE/NE, DADS/4, 4' - NDA 13.S (1960) - 100%C 11.4 (1660) - 100%C IB-3 104 BTUE/NE, DADS/3,3' - MDA 11.4 (1660) - 100%C 18-4 104 BTDE/NE, DADS, 4,4' - MDA 13.4 (1940) 10%1. 90%C 14.2 (2070) - 100%C 15-1 104 BTDA/NA, DADS, om' 9.9 (1430) lO%L 90%C 15-2 104 BTDA/NA, DADS, diglyme B.9 (1260) - 100%C lS0-1 104 OS6X (NR-1S0B2) 17/0 (2470) 20%L 80%C 13.S (1970) - 100,;C 150-2 No. 1 104 050X (NR-lS0B2) 12.S (1820) - 100%C 12.8 (lB60) - 100%C lS0-2 No. 2 108 050X (NR-1S0B2) 13.5 (1910) 25%L 75%C 12.7 (lB50) 30%1. 70%C 150-3 No. 1 104 OS2X (NR-1S0B2) 15.B (2300) 10%L 90%C 15.2 (2200) 10%L 90%C 150-3 No. 2 lOB 052X (NR-150E2) 15.B (2290) 30%L 70i;C 14.3 (2080) 30%L 70%C 150-4 104 051X (NR-150B2) 15.B (2300) 20%L BO%C 12.7 (1840) 15%L 85%C IB-IB 104 PMR-15. diglyme 16.9 (2450) 70%L 30%C 14.6 (2120) 40%L 60%C 20-1 104 PHR-15, tackifier, dlglyme 14.1 (2050) 30%L 70%C 15.5 (2250) 30%L 70%C 17-11B 104 PHR-15, NR-150B2, UHF 12.7 (1B40) 50%L 95%C 12.1 (1750) - 100%C 17-11C 104 PHR-15, AI-1l30L, DHF 11.2 (1625) - 100%C B.O (1160) - 100%C 1B-12C 104 LARC 160*, dig1yme 12.3 (1790) - 100%C 12.0 (1745) - 100%C 18-8 104 LARC 160, DADS, tackifier 15.2 (2210) 60%L 40%C 15.2 (2200) SO%L SO%e

diglynte 18-12B 104 tARC 160, AI325 17.0 ( 2460) - 100/.C J3 .9 (2020) - 100%C IB-1211 104 tARC 1 bO, A1ll301. 11.4 (J650) - IOOZC 7.7 (J 260) - 100%C 21-4 104 LARC 160,4,4' - HilA, dlglyme 13 .8 (ZOOO) 501;i. 95%C j() .0 (j 560) lOO:tc -

Unidirectional eight-ply laminates Average vf four tests; all adhesives cured two hour>: at 58yOK (600 0 n and 0.6895 MPa (100 psi} pressure plus 10 hours at 5;l9°K (600 0 n All aJherends primed with BR34B-18 after light abrading and diglyme wipe L: Failure in composite laminate, C: Cohesive fa i lure in bond line

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\0 N

Table 2 - Flatwise Tensile Strength of Polyimide Adhesives

Flatwise Tensile Fillet, mm (in.) Strength, MFa (psi) (1)

Base Polyimide 5890 K (600°F) Adhesive/Scrim Resin System Top Bottom RT

FM34B-18/104 FM-34 3.0 (0.12) 1.2 (0.05) ].93 (280) 2.34 (340)

LARC- ] 3A/ 104 (Hexcel) LARC-13A 0.50(0.02) 0.50(0.02) 2.51 (365) 2.07 (300)

LARC-13E/112 (Hexcel) LARC-13E 0.50(0.02) 0.50(0.02) 1.86 (270) 2.48 (215)

21-1/104 PMR-15 207 (0.11) 0.50(0.02) 2.72 (395) 2.96 (430)

21-4/ ]04 MOD. LARC-] 60 ] .5 (0.06) 1.2 (0.05) 2.90 (420) 2.31 (335)

]8-6/104 MOD. LARC-13 2.5 (0.10) 0.50(0.02) 2.48 (360) 2.41 (350) 3,3'/4,4'-MDA

18-7/104 MOD. LARC-13 3.8 (0.15) 300 (0012) 2e58 (375) 2.55 (370) 3,3'/4,4'-MDA

18-4/104 BTDE/NE/DADS 3.8 (0.15) 0.7 (0.03) 2.44 (355) 2.44 (355)

18-2/104 BTDE/NE/DADS 1.2 (0.05) 0025(0.0]) 1.72 (250) 1093 (280)

18-12C/I04 LARC-160 3.3 (0013) 2.54(0.10) 2.0 (295) 1.86 (270)

150-3/104 NR-150B(052X) 0.38(0.015) 0.25(0001) 1051 (220) -150-2/104 NR-150B(050X) 3.8 (0.15) 002 (0.0)) 1.37 (200) -

(1) Average of three tests. All adhesive cured (in autoclave) for two hours at 5890K (600°F) under full vacuum and 0.1724 MFa (25 psi) pressure and postcured for 10 hours at 5890 K (600°F) and normal pressure.

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Table 3 - Climbing Drum Peel Strength of Polyimide Adhesives

Adhesive Peel Strength at RT(I)

Form No. Resin System g/cm Width in. lb/in.

FM34B-18 FM34 630

LARC-13A LARC-13, anhydride process 756

LARC-13E LAR,C-13, ester process 486

18-12C MOdified LARC-160 90

17-6E MOd. LARC-13. 3.3'/4.4'MDA=80/20 594

17-9E MOd. LARC-13. 3.3~4.4'MDA==20/80 360

17-10E MOd. LARC-13. 3.3'/4.4'MDA=0/100 486

18-6B MOd. LARC-13. 3,3~4,4'MDA=25/75 594

18-4 BTDE/NE.DADS,4,4'MDA 300

(I) HRH' 327-3/16-4 honeycomb core. Celion~OOO/PMR-15 face sheets in

two-ply (0,90) construction

3.5

4.2

2.7

0.5

3.3

2.0

2.7

3.3

1.7

Test specimens, 30.5 em (12 in.) long and 7.6 cm (3 in.) wide, were

tested according to Spec. MIL-A-25463A.

The average skin load was 11.24 Kg (25 lb)

93

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94

Table 4. Glass Transition Temperature of Polyimide Adhesives(l)

Adhesive Glass Transition

Form No. Resin System Temperature, Tg, oK (OF) (1)

FM34B-lS FM34B-18 Not measurable

LARC-13 on 112 glass IARC-13 588°K (599°F) scrim NASA Process

l8-6A Mod LARC-13 639°K (690°F) amine substitute

lS-6B Mod LARC-13 629°K (672°F) amine substitute

l7-11B PMR-15 modified 60SoK (634°F) with NR-lSOB2

17-11C PMR-15 modified with Not measurable AI l130L

l8-12J Mod LARC-13 62SoK (671°F) amine substitute

IS-12K Mod LARC-13 59SoK (617°F) amine substitute

(l)Tg measured on a duPont 941 TMA-900TA analyzer at a heating rate of 5°K (9°F) per min. The expansion probe used had a 0.25 cm (O.l-inch) diameter. The adhesives cured for two hours at 5S9°K (600°F) under 0.6895 MFa (100 psi) pressure and postcured for ten hours and 589°K (600°F) under normal pressure.

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Table 5. Effect of Out Time in Dry Environment on Lap-Shear Strength

Adhesive

FM34B-18

LARC-13A/104

LARC-13E/104

18-6A (MOD. LARC··13E)

lS-6C

OUt-Time Days

1 5

11

1 5

11

1 5

11

1 5

11

1 5

11

Lap Shear Strength (2) , MPa (psi)

RT

19.3 (2800) 18.4 (2670) 15.9 (2320)

16.6 (2415) 16.6 (2350) 14.7 (2130)

16.0 (2335) 15.7 (2250) 11. 7 (1706)

14.2 (2050) 16.2 (2360) 15.1 (2200)

15.0 (2185) 13.6 (1980) 15.2 (2210)

11.9 (1730) 15.6 (2270) 15.3 (2225)

12.7 (1845) 1~.3 (2085) 14.5 (2100)

14.3 (2080)

14.3 (2075)

13.9 (2010) 16.0 (2330) 13.6 (1980)

15.3 (2225) 13.4 (1950) 15.6 (2270)

(1) Storage condition: 6-40% RH, 291-299°K (65-80 0 F) Adherends: Celion 6000/PMR-15, eight-ply, unidirectional Primer: BR34B-18

(2) Surfaee treatment: light abrading, diglyrnewipe Cure: Two hours at 589°K (6000 F) and 0.6895 MPa (100 psi) pressure Postcure: 10 hours at 589°K, (600o

F) normal pressure

95

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Table 6

EFFECT OF OUT-TIME IN HUMID ENVIRONMENT ON LAP SHEAR STRENGTH

Lap Shear Strength, MPa (psi) (1)

Out-Time Mode of (2 Adhesive Days RT Failure (%) 5890K (6000F)

Hode of (2) Failure (%)

FM34B";18

LARC-l3

o 3 7

o 3 7

15.8 (2300) 11.4 (1660) 11. 7 (1700)

15.0 (2175) 16.1 (2340) 15.0 (2190)

L40, C60 LIS, C85 L5, C95

L20, C80 L90, CI0 L30, C70

l3.4 (1950) 12.2 (1770) 11.2 (1620)

13.2 (1910) 16.1 (2330) 14.8 (2140)

L40, C60 LI0, C90 L45, C55

LIS, C8S L80, C20 L50, C50

M-LARC-l3E o 3 7

14.1 (2055) 16.1 (2195) 14.2 (2080)

LIS, C85 L30, C70 L55, C45

12.3 (1790) 1l.8 (1710) 14.0 (2030)

L30, C70 L50, C50 L60, C40

96

(1) Environment: 40-90% RH, 288-294 (60 - 70°F)

Adherends: Ce1ion 6000/PMR-15, 8-p1y, unidirectional

Surface Treatment: Light abrading, dig1yme wipe

Primer: BR 34B-18

(2) Hode of Failure: L - Laminate failure, C - Cohesive failure in adhesive

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Table 7 - Comparison of Primers for Bonding Celion 6000/PMR-l5 Panels with LARC-13 Adhesive

Primer Lap Shear Strength MPa (psi) _. __ .. _-----

Form No. Batch No. RT 600°F

BR34B-18 B-673 16.6 (2410) 12.9 (1880)

LARC-13A 8-23-1 14.3 (2085) 11.1 (1623)

LARC-160 8-23-2 14.6 (212S) 11.7 (1705)

PMR-1SE 8-23-3 13.7 (1995) 14.8 (2,150)

NR1S0-B2 8-23-4 IS.3 (223S) 12.9 (1880)

052X 8-23-5 13.5 (1970) 9.6 (1400)

050X 8-23-6 15.6 (2265) 121 (1760)

AI Il30L 8-23-7 13.9 (2030) 11.9 (172S)

AI 830 8-23-8 13.5 (1960) 11.9 (1740)

Adherends: Celion 6000/PMR-·15 composites; eight-ply, unidirectional construction

Adhesive: LARC-13 (NASA process) with style 108 scrim Surface Treatment: Light abrading (Behr Tex) diglyme wipe Average of three or four test specimens Cure: Two hours at 589°K (600°F) and 0.6895 MPa (100 psi)

pressure + 10 hours at 5890 K (600°F) under normal pressure

97

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\0 00

Table 8 - Comparison of Surface Treatments for Bonding Celion/PMR-15 Laminates with LARC-13 Adhesive

Surface Bond Line Test Lap Shear Treatment mm (mils) Temperature Strength, MPa

Behr Tex 0.15 (6) RT 20.3 (2950) MEK 589K ( 600°F) 9.4 (1360)

NMP 0.15 (6) RT 17 .9 (2600) 589K (600°F) 15.6 (2260)

MEK 0.19 (8) RT 14.9 (2160) 589K (600°F) 13.4 (1950)

Grit blasting, 0.15 (6) RT 20.5 (2970) diglyme 589K (600°F) 19~3 (2800)

Alkaline 0.15 (6) RT 16.7 (2430) etch 589K (600°F) 15.9 (2310)

Acid etch 0.15 (6) RT 13.6 (2010) 589K (600°F) 15.0 (2180)

Grit blasting, 0.15 (6) RT 17 .6 (2550) (sand)-MEK 589K (600°F) 19.8 (2870)

Adherends: Celion/PMR-15 composite laminates, eight-Plr' unidirectional Cure: 2 hours at 5890 K (600°F) and 0.6895 MPa (100 psi pressure Postcure: Ten hours at 5890 K (60QoF) and normal pressure

Mode (psi) of Failure

laminate cohesive

laminate cohesive

cohesive cohesive

laminate laminate

cohesive cohesive

cohesive cohesive

laminate laminate

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Table 9 - Comparison Availabilities and Properties of Po1yimide Adhesives

Ava llabi 11 ties LARC-13 Mod. LARC-13 Mod. PMR-15 and Properties FM34B-18 NASA Process 18-6 20-1

Commercially available Yes No No No Production methOd Yes Yes Yes

developed or under development

Can be supplied by Yes Yes Yes Hexcel on request

Resin processability Fair Good Good Hot melt processability Good Good Good Tack and drape Good Good Good Good Flow on cure Good Good Good Good Filleting ability Good Good Good Good

Lap shear strength 1 Composite-to-composite( ) toTa (psi), RT 15.1-19.3 17.7-19.6 19.2 (2780) 15.3 (2225)

(2190-2800) (2450-2850) 589°K (600°F) 11.6-11.9 12.7 ..... 15.6 15.2 (2200) ,

13.9 (2010) (1680-1730) (1845-2260)

F1atwise tensile strength(l) MFa (psi), RT 1.93 (280) 2.52 (365) 2.48 (360) 2.92 (395)

589°K (600°F) 2.34 (340) 2.07 (300) 2.41 (350) 2.96 (430)

Climbing drum peel strength at RT, '1.1 cm width (2) (in.lb/in.) 630 (3.5) 756 (4.2) 59!, (3.]) 360 (2.0) Glass transition temp., Not 315 (599Op) 366 (6900 F) -

(Tg)OC Measurable Ability to form low porosity Poor Good Good (;ood

large area bonds

(1) Adherends: Ce1ion 6000/PMR-15 composite laminates, eight-ply unidirectional Primer: BR34B-18; surface treatment: light ahrading, dig1yme wipe

(2) Adherends: Celion 6000/PMR-15 composite, two-ply (0.90) construction Primer: BR34B-18; surface treatment: light abrading, diglyme wipe

Mod. LARC-160 NR-150B 18-8 150-3

No No Yes No

Yes I No

Good Good Poor Good Fair Good Fair Good Poor

15.2 (2210) 16.9 (2450)

15.2 (2200)

2.03 (295) 1. 52 (220) 1.86 (270) -

90 (0.5) i -- , -

Good 1 Poor

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I-' o o

I.

2.

1.

4.

5.

6.

7.

8.

9.

10.

u. 12.

13.

14 ..

el) (2)

Table 10 - Comparison of PM 34B-18, LARC-13 and LARC-13E Adhesives

- -FM348-1H J.ARC-Il M-LAltC- I )E

. 'ACTOa RATING PTS. -~~. 1.2)' 1U\'l'INC ~f .. (iY

-W'lNG l·T~. fi£ ~-Commercial Availability V. Good 1 2 6 Good 2 2 4 Good 2

Hatedal Coat High 2 2 " lIigh 2 2 4 lIigh 2

Out-TiM Fair I 2 2 V.Good 1 2 6 V.Good 3

Tack and Orape Good 2 2 " Good 2 2 " Good 2

,illetiDI Good 2 1 6 Good 2 2 " Good 2

Too1iaa , .roc.aaiD8 Coat Excel. " 1 12 Fair I 1 1 Fair I

Ability to provide void-free Poor 0 1 0 V.Good 3 3 9 V.Good 1 1arle araa boDda. add-plane bo_iDI

• Ability to provide larae area Fair I 3 3 V.Good 1 1 9 V.Good 1 booded Hie .andwich panela

Lap shear atrenath vs. over- Fair I 3 3 V.Good 3 3 9 V.Good 3 lap shear area

Load-carryin8 capacity in Poor 0 1 0 V.Good 1 1 9 V.Good 3 shear of aid-plane bonded panela

Peel streogth (climbing drum) 1-'air I 2 2 Fair 1 2 2 Fair 1

Ftatviae tensile Str. Hlc Good 2 1 6 Good 2 3 6 Good 2 core to GrlPi composite

ASiDS .tability @5890 K(600oF) Fair I 3 3 Fair 1 3 3 Fair 1

Amount of Industry Experience V.Good 3 :J 9 Good 2 J I) Fair 1 S.,. : Significance Factor -_. __ h. __ . __ ._._. ___________ 1--____ ._

TOt'ALS 6 I 78 T: Total

S.L \~)

2 4

2 4

2 6

2 4

2 " 1 3

1 9

1 9

1 9

3 9

'l 2 .. 3 6

J 3

3 3

15

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.... o ....

Panel No.

Prepreg Lot No.

Supplier

Prepreg Physical Properties

1. Fiber areal weight, g/m2

2. Resin solids (%)

3. Calculated thickness per ply, mm (mils)

Composite Physical Properties

1. Specific gravity

2. Fiber volume (%)

3. Void fraction (%)

4. Cured thickness mm (miles)

5. Weight loss on cure (%)

6. Tg OK (OF)

7. C-scan transmission (%)

Table 11. Properties of Ce1ion 6000/PMR-15 Prepreg and Cured Laminates

CPSU-A1 CPSU-A2 CPSU-A3 CPSU-A4 CPSU-A5 CPSU-A6 CPSU-A17 CPSU-A1S CPSU-A19 CPSU-A20 CPSU-A21 CPSU-A22 CP8U-A23 CP8U-A24

2W4474 2W4474 2W4474 2W4474 2W4474 2W4474 CO-0l5 CO-015 CO-015 CO-015 CO-015 CO-015 CO-015 CO-015

USP USP USP USP USP USP Fiberite Fiberite Fiberite Fiberite Fiberite Fiberite Fiberite Fiberite

14S.5 148.5 148.5 14S.5 14S.5 14S.5 156.2 156.2 156.2 156.2 156.2 156.2 156.2 156.2

36.5 36.5 36.5 36.5 36.5 36.5 33.S 33.S 33.S 33.S 33.S 33.S 33.S 33.S

0.127(5) 0.127(5) 0.127(5) 0.127(5) 0.127(5) 0.127 (5) 0.127(5) 0.127(5) 0.127(5) 0.127(5) 0.127(5) 0.127(5) 0.127(5) 0.127(5)

1.5S 1.59 1.59 1.56 1.59 1.59 1.5S loSS 1.5S 1.57 1.59 1.60 1.60 1.60

61.6 63.3 63.6 56.6 63.7 62.9 60.1 61.4 60.3 5S.1 64.3 64.S 64.5 65.4

0.4 0.2 0.3 0.3 0.3 0.0 -0.1 0.3 -0.1 0.0 0.5 -0.1 -0.2 0.1

1. 06 (42) 1.09(43) 1.06(42) 1.19(47) 1.09(43) 1.09(43) 1.14(45) 1.09(43) 1.06(42) 1. 09 (43) 1.43(45) 1.11(44) 1.09(43) 1.11(44)

17.S lS.0 17.9 17.S lS.2 13.0 12.7 12.0 12.0 12.7 11.9 11.S 13.2 13.6

6000K 599°K 5SSoK 5S7°K 599°K 592°K 615°K 616°K 615°K 611 0K 613°K 614°K 60SoK 613°K (620°F) (61S0F) (599°F) (597°F) (61S0F) (606°F) (647°F) (649°F) (64S0F) (640°F) (644°F) (645°F) (635°F) (643°F)

100 100 100 995 100 100 100 100 100 100 100 100 100 100

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TABLE 12 - FLATWISE TENSILE STRENGTH OF FM34B-18 LARC-13 AND M-LARC-13E ADHESIVES

Fillets, mm(in.) F1atwise Tensile Test Temp Strength

Adhesive/Scrim Top Bottom OK(oP) MPa(psi) (1)

FM34B-18/104 2.0 (0.10) . 1.0 (0.05) RT 3.17 (460)

2.0 (0.10) 1.0 (0 .. 05) 589 (600) 1.72 ( 250)

LARC-13/104 2.0 (0.10) 1.0 (0.05) RT 3.17 (460)

2.0 (0.10) 1.0 (0.05) 589 (600) 2.76 (400)

M-LARC-13E/l04 1.0 (0.05) 1.0 (0.05) RT 2.76 (400)

1.0 (0.05) 1.0 (0.05) 589 (600) 1.86 (270)

(1) Face Sheets: Ce1ion 6000/PMR-15, 8-p1y, crossp1ied construction

Primer: BR34B-18

Core: HRH327-3/16-4. T=0.5

(2) Core: Rupture in the honeycomb core

C: Cohesive failure in the adhesive

Mode of Failure (%) (2)

Core 5, C95

Core 20, C80

Core 10, C90

Core 50, C50

ClOO

Core 50, C50

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TABLE 13 - LAP SHEAR STRENGTH OF LARC-13 ADHESIVE PREPARED BY ANHYDRIDE AND ESTER METHODS

Mode of Test Temp.· Lap Shear Strength Method oK (OF) MPa (psi) Failure (%) (1)

Anhydride RT 17.4 (2525) L95, C5

Anhydride 5890 K (600°F) 16.6 (2410) L80, C20

Ester RT 16.9 (2445) L70, C30

Ester 5890 K (600°F) 18.3 (2660) L80, C20

(1) L: Laminate failure; C: cohesive failure in adhesive

Adherends: Celion 6000/PMR-15, eight-ply, unidirectional

Surface Treatment: Light abrading, diglyme wipe

Primer: BR34B-18

103

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I-' ~ Table 14 - Short Beam Shear Strength of LARC-13 and FM34B-18

SHORT BEAM STRENGTH -MPa(psi)

ADHESIVE TEMP 1 i 3 4 5 AVE

LARC-13/l08 R.T. 0.09(14.3) 0.09( 14.4) 0.10(15.5) 0.1005.9) 0.10(15.5) 0.10(15.1) 0.07 Lb/ft2

589 0 K 0.04(6.9) 0.04(6.7) 0.04(6.5) 0.04(6.4) 0.03(5.0) 0.04(6.3) (600°F) .

FM34B-18/104 R.T. 0.0903.0) 0.09(13.3) 0.07 Lb/ft2

0.09( 13 .5) 0.09(13.5) 0.0903.2) 0.09(13.3)

5890 K (600°F) 0.04(6.1) 0.04(6.3) 0.04(6.1) 0.04(6.1) 0.04(6.2) 0.04(6.2)

0) Adherends: Ce1ion 6000/PMR-15~ 8 Ply. unidirectional

Surface Treatment: Light Abrading~ dig1yme wipe

Primer: BR34B-18

Test Methods: MMM-A-132

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...... o \J1

Table 15. Slotted Shear Strength of Test Specimens From Mid-Plane Bonded 30.5 em (12".0 in.) by 30.5 em (12.0 in.) Panels

Ultimate Load Lap Shear Strength Adhesive Cm (in.) Test Tempo MPa (psi) MPa (psi)

. FM34B-18 1.27 (0.50) RT 109 275 3 08 (550)

5.18 (2000) 3.2 460 1.6 (230)

1027 (.50) 5890 K (600°F) 1055 225 3.1 (450) 5.18 (200) 504 770 2.7 (385)

LARC-13 1.27 (.50) RT 8.05 1170 16.1 2340 5018 (2.0) 19.6 2840 908 1420

1.27 (.50) 5890 K (600°F) 7.25 1055 14.5 2110 5.lS (2.0) I 1S.2 2640 9.1 1320

Adherends: Celion 6000/PMR-15, 8 ply, unidirectional

Surface Treatment: Light abrading, diglyme wipe

Primer: BR34B-18

Test Method: MMM-A-132

Mode of Failure

ClOO% ClOO%

ClOO% ClOO%

L40, C60 L50, C50

L35, C65 L35, C65

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Table 16. Aging (1) Stability of Polyimide Adhesives Wrapped in Aluminum Foil

FLATWISE TENSILE STRENGTH MPa (psi) ( 2)

R.T. 5890K(6000F) Adhes~ve 1 2 3 AVE 1 2 3 AVE

FM34B-18 1.41(203.8) 0.86025.0) 1.38( 200.0) 1.22(176.3) .95032.5) 0.97(140.0) 1.0(146.3) 0.97(139.6)

LARC-13 1.57(227.5) 1.59(2300) 1.17(170.0) 1.44(209.1) 1.10(160.0) 1.55(225.0) 0.88(127.0) 1.18(170.7)

(1) Specimens were aged for 125 Hr. at 589~ (600°F) ~n air circulated oven. All specimens were wrapped in aluminum foil.

(2) All adhesives cured in autoclave for two hours at 5890 K under full vacuum and 0.1724 MPa (40 psi) pressure and post cured for 10 hours at 5890K (600°F) free standing in oven.

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Table 17. Aging (1) Stability of Polyimide Adhesives Not Wrapped in Aluminum Foil

FLATWISE TENSILE STRENGTH, MPa (psi) (2) RT 5890 K (6000 F)

i

ADHESIVE 1 2 AVE 1 2 AVE

FM34B-18 0.70(102.5) 0.64(92.5) 0.67(97.5) 0.84(122.5 0.55(80.0) 0.69(101.2)

LARC-13 1.10(152.5) 1.38(200.0) 1. 24 (176 • 3 ) 1.34 (195.0) 1.26(182.5) 1.30(188.8)

(1) Specimens were aged for 125 hours at 589~ (600°F) in air circulated oven w All specimens were no t wrapped in aluminum fo il.

(2) All adhesives were cured in autoclave for two hours at 5890K (600°F) under full vacuum and 0.1724 MPa (40 psi) pressure and post cured for 10 hours at 5890K (6000F) free standing in oven.

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I-' 0 00

Table 18 - Aging Stability of Selected Adhesives at 5890K (600°F)

AGING LAP SHEAR STRENGTH, MPa (psi) (1)

PERIODS MODE OF MODE OF FAILURE ADHESIVE HOURS RT FAILURE AT RT(2) 5890K(6000F) AT 5890K (6000F(2)

FM34B-18/l04 0 15.5(2250) L20%, C80% 13.4(1945) L40%, C60% 0.06 lb/ft2 125 8.7(1255) L15, C85 7.9(1145) L5, C95

250 7. 7( l1l5) LlO, C90 8.1(l180) L15, C85

LARC-13/l08 0 14.0(2030) L70, C30 14.5(2100) L35, C65 0.07 lb/ft2 125 9.2(1330) L5, C95 8.3(1210) L5, C95

250 7.0(1020 L5, C95 8.1( l180) ClOO

M-LARC-13E~108 0 15.8(2295) L65. C35 12.7(1845) L25, C75 0.07 lb/ft 125 8.9(290) L15, C85 9.7(1400) LlO, C90

250 6.7(965) L20. C80 8.1(1180 ) LlO, C90

(1) Aging Environment: Lap shear specimens exposed directly to air current in circulating oven at 5890K( 600°F)

Adherends: Celion 6000/PMR-15, 8 ply, unidirectional

Surface Treatment: Light abrading, diglyme wipe

Primer: BR34B-18

(2) L: Laminate failure, C: Cohesive failure

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I-' o \0

Table 19 - Effect of Water Immersion on Lap Shear Strength of LARC-13 and FM34B-18Adhesives

TEST LAP SHEAR WATER-IMMERSION TEMP STRENGTH MODE OF

ADHESIVE PERIODS, DAYS °K(Op) MPa (psi) (1) FAILURE

FM34B-18!I04 0 RT 16.5 (2390) L80%, C20% 0.06 Ib/ft2 5890K (600°F) 1104 (1660) L5 , C95 .

7 RT 5890K (6000F) 12.2 (1770) L5 C95

LARC-13/108 0 RT 15.4 (2240) L25 C75 0.07 Ib/ft2 5890K (6000F) 14.9 2165 L5 C95

7 RT 14.4 (2095) L5, C95 5890K(6000F) 12.0 (1745) ClOO

I I (1) Adherends: Celion 6000/PMR-15

8-ply, unidirectional Surface Treatment: Light abrading, diglyme wipe Primer: BR34B-18

(2) Laminate failure, C-Cohesive failure

(2)

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Adhesive

LARC-13/l08

LARC-13 I 108

LARC-13 I 108

LARC-13/108

LARC,.... 13 I 108

LARC-13/108

LARC-13 I 108

LARC-13/108

LARC-13 I 108

LARC-13/108

LARC-13 I 108

LARC-13 I 108

LARC-13 I 108

LARC-13/108

LARC-13 I 108

LARC-13/108

No. of Layers

1

1

2

2

3

3

4

4

5

5

6

6

7

7

8

8

Table 20. Effect of Bondline Thickness on LaplShear Strength(l)

Test Temp.

oK (OF)

R.To 589°K (600°F)

R.T. . 589°K (600°F)

R.T. 589°K (6-()OOF)

R.T. 589°K (600°F)

R.T" 589°K (600°F)

RoTo 589°K (600°F)

R.T. 589°K (600°F)

R.T. 589°K (600°F)

Bond line Thickness

After Cure

0.0020

0.0015

0 0 0050

0.0040

0 0 0055

0.0050

0.008

0.008

0.010

0.011

0.012

0.012

Lap Shear Strength-PSI 1 Z 3;

i AVE

2590

2400

2790 I I

2300

2700

I 2600

2693

2433

2830 2880 3150 2955

2020 2550 2240 2270

2760 2630 2790 2725

1740 2580 1760 2026

2340 2870 2460 2556

1700 1740 1990 1810

2800 3280 3140 3073

1920 1910 1910 1913

2900 2530 1960 1796

1460 1560 1660 1560

1680 1350 1580 1536

1120 1250 980 1116

1590 1600 1530 1573

1340 1450 1300 1363

Mode of Failure % (2)

L95 C5

L75 C25

L95 C5

L50 C50

L90 C10

L5 C95

L85 CIS

L25 C75

L45 C55

L10 C90

L50 C50

LlO C90

L80 C20

LlO C90

L60 C40

L5 C95

(1) Adherend: Ce1ion 6000/PMR-15, 8 ply unidirectional Primer: BR-34B-18 Cure: 2 hours at 5890K (600°F) and 0.6895 MPa (100 psi) pressure, Postcure: 10 hours at 5890 K (600°F) and normal pressure.

(2) L: Laminate failure, C: Cohesive failure in the adhesive

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Table 2l. Out of Refrigeration Effect on Filleting Properties of LARC 13(2)

,

Test Fillet Flatwise Tensile Spec Out of Refr igera tion Temp. Thickness Strength (1) Mode of No. Time oK (OF) mm (Inch) MPa (psi) Failure

HCS104 1 Hl: • R.T. 0.8(0.035") 2 0 34(340) Core to Adhesive HCS104 1 n 589°K II 2.24 (326) II II II

(600°F) HCS105 2 Hrs. R.T. 0.70(0.030") 2.48(360) Core to Adhesive HCS105 " II 589°K II 2.20(320 II II II

(600°F) HCS106 8 Hrs. R.T~ 0.5(0.020") 4.06(590) Core to Adhesive HCS106 " II 589°K " 2.27(330) " " II

(600°F) HCSI09 8 Days R.T. 0.2(0.010") 3.37(490) Core to Adhesive HCS109 11 II 589°K II 2.58(375) II u !!

(600°F)

(1) Face-Sheets: Ce1ion 6000/PMR-15 8-p1y, crossp1ied Construction

Primer: BR34B-18

Core: HRH 327-3/16-4, T = 0.5

(2) LARC-13/108, 0.07 1b/ft2

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I-' I-' N

Table 22. Use of Catalyst in LARC 13 to Reduce Cure Temperature

ADHESIVE CURE TEST LAP SHEAR STRENGTH-PSI~~ MODE OF FAILURE TEl1P TEMP. I 2 "3 AVE %

LARC-J3( I) 5280 K e;oOoF) R.'l. I

2260 2320 2460 2346 L25 C75 5280 K (500°F) 600°F 2340 2040 2420 2266 L5 C95

LARC-13(1) 5050 K (450°F) R.Ta 1380 1530 1740 1550 L65 C35 600 F 830 1320 1600 1050 - CIOO"

LARC_I/ 2) 5280 K (500°F) R.T. 1980 1860 2160 2000 LIOO C-1 600°F 1640 1820 1840 1766 L20 cso I

. LARC-13(2) 5050 K (450°F) DID NOT GET CURED TOO RITTLE. PANEL SEPARATED

(I) Catalyst: USP-138, 2% by Weight

(2) Catalyst: Experox - 10, 2% by Weight

(3) Adherend: Celion/PMR-15, 8 Ply Unidirectional Primer: BR34B-18

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Table 23. Orbiter Body Flap/Demo Segment Stress Comparison

BODY FLAP (ULT}MPA (KSD LOAD CONCEPT NO. 8 MPA (KSI)

MAX MAX STRESS MIN STRESS MAX SHEAR

RT RT MAX MIN SHEAR STRESS STRESS STRESS

241 -73.0 STABILITY RIB CAP (35.0) (-10.6)

FRONT SPAR CAP 43.4 -48.2 (6.3) (-7.0)

REAR SPAR CAP 9.6 -31.7 (1.4) (-4.6)

STABILITY RIB WEB 37.9 (5.5)

FRONT SPAR WEB 43.4 (6.3)

REAR SPAR WEB 33.7 (4.9)

HIC COVER PANELS 91.7 -82.7 53.8 (13.3) (-12.0) ( 7.8)

r:... I-" \.oJ

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This Page Intentionally Left Blank

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APPENDIX A

This appendix contains the Engineering Design drawings which define the

TDS. The drawing list is as follows:

SS79-00249 2 Sheets

SS79-00250

SS79-00251 2 Sheets

SS79-00252

SS79-o0253 3 Sheets

Technology Demonstration Segment -Graphite/Polyimide, Shuttle Body Flap

Cover - Body Flap Segment

Rib-Stability Technology Demonstra­tion Segment, Graphite/Polyimide

Leading Edge Panels - Body Flap Segment

Spar Webs - Body Flap Segment

115

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--I 14 13 4 12 --11------, 10 ------, 9 I =h ___ a ._1 u ____ 7 6

<:. SvMMETRY

I I

. .

-'S~7'7-00,~OO4 , Z"lEQ'O / ,

/

SS79-C~3-002.

/

' 2 R£Q' 0 ,

/ / I' -' . i -

I ' I •• I

I ,. I. 1 ' .

r @ NEA~ !!oIOE. IqO~ ~~ :::J ,A HO\.E :OAR. :;10:: w .... ::. r:581C-3T-I3' ROI!>.!)-IOOZ-OOO~ MDIIA-loa, -1004 I!) PL...ACE,S

56 _I

• .i~.;~~~A~I~D~ F~~~~~ ~---=- -=.::::=:-.:-~ ==-~~-=---:----- ----- - ---=--:' -'~ RDI~3-IDOZ'OO:::::' Zo<;'1 : ... MDIIA-,OOI-1004 !l~ PLACEs-.

"'"0

,

~

_...:.~_-;;_;;;;;;;:;; _~ __ ~~_-='~:~'9f------t ---­I I I ,I I

II 9(aUA~ 5~

I 2. PLACES

I

.:.0,.---- -----

6 ECLlA.L 5PACE~ • !>T~E~ED

Sl79-OOZ.:l2--oQ

Q9

I x.=.!IOOQ

I"'~"'" V ~~r' r r5S1"OD' - I I / 3 R ~5I'OOI -'- \ I - oo~n

EQO I-~' J.. _ 1!tl IZP,Aa'S -

- I -, 6.9Z

<t 5'<'MMETRY

. ,

" I r=t=-t-t+1Hi+t--+-t4--H-lH-!..-' J -~ .. CT.'POSm I r .... 1

.t;~~~~~~~~~g~' ~I £~i' ~ SS7<rOOz::.=l-OO;:)

r---- ------,(, .5YWIl-~

1.50 ~ I ~~O~1J I I I ~--:

L~S79 .. DOZ;:)!l~ "cbo\ClPPOSITt 2. RECI' D '-='

~ SS79-ClOZ!IO-009

@) F IIJ N. A6.">D-t!>Lv

--~z="

lqo""'~ O/A HOLE POrnN5- PE" DEP.:.;n-MEf.l7 OClB _TR Z4Z~-4a54 ~,I~ HOLl''; '-S Ii:EQ ~

.-

5 ... 4 I

CO INSTAU. FASTE:NER.5 P!:~ MAOIOI,~ Q.A5S 1

® DRILL 9/J6 DIAMET"f:R HOLE AND 11--l'5TAL~ ~149-~770 - ',?E B INSERTS WITH PO-rrl1-lQ- COMPOUNI') PEP. DEP.4RTMENT 098 L."T'Q- Z4-:2.3- 4.Q 5L

@ OOND WITH MBD\.ZO-O~ - ......... ~ ADHESIVE S'CS'TEM '=J~E. '?E.~

"'D1.Dqa 1..1Q Z42.5-4C::.c...

~ UL -r;;rASONIC INSPE.C'T PER MTO!)C)I-DIO

G INSPECr.l.AM"-.lI:Cl1:M-',~ PEl=< 'L'TR Z433-44bz'

3

,

@ FAeRICA-re~Pl u.,....J,~"'--=:.s PER =OCE:!!5 SPECIFlCATlO1--J !\;\A::l1 ~·.e.33A. CU<'t: evt::LE S:JD'79-!!53 ~ s;::EClF1C PROC.:::S~ ;:>~ ::'/0<')8 L'TR 242.5-~

~ ~L ..... ' .. ;:;;m: ITA;~ 0 OO~ "l"l11~K CE:L.IDN esOOO/LA;:": 160 PEo< /,'IBOI30-I::>1.""

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Page 140: Develop, Delllonstrate, and Verify Large Area COlllposite ... · Verify Large Area COlllposite Structural Bondirlg With Polyilllide Adhesives Bashir D. Bhombal Donald H. Wykes Keith

1. R.port No

NASA CR 165839 T 2. Governmtnt ACCllSlon No. 3. Recipient's ~t.alog No

4 Tltl. and Subtltl. Develop, Demonstrate and Verify Large Area Composite

5. Repon Dlte

May 1982 Structural Bonding with Polyimide Adhesives.

7 Author(s)

Bashir D. Bhombal, Donald H. Wykes, Keith C. Hong, Arnold A. Stenersen

9 Performing Organization Name and Address

Rockwell International 12214 Lakewood Blvd. Downey, Ca. 90241

6. Performing OrganlZltlon Code

8 Performing Organization Repon No

10 Work Unit No

11 Contract or Grant No

NASI-15843 r.::-::----:---:~-----------------------1'3 Type of Repon and Period Covered

12 Sponsoring Agency Nam. and Address

National Aeronautics and Space Administration -Washington, D.C. 20546

Contractor Report 14 Sponsoring Agency Code

15 Supplementary Notes Langley Technical Monitor: Robert M. Baucom Final Report

16 Abstract

This program was conducted to develop and demonstrate processes for large area structural bonding with polyimide adhesives. The program consisted of two parts: Process Development for PI resin systems and fabrication of Demonstration components. Process development included establishing quality assurance of the basic PI adhesives, non-destructive inspection of fabricated components, developing processes for specific structural forms and qualification of processes through mechanical testing. In the second part of the program, demonstration components were fabricated using the processes developed in part one. The demonstration components consisted of adhesively bonded honeycomb sandwich cover panels, ribs, and leading edge covers of Celion graphite/LARC-160 polyimide laminates, and a Technology Demonstration Segment (TDS) representative of the Space Shuttle aft body flap.

17 Key Words (Suggested by Author(s)) 18 Distribution Stl,ement

Polyimide Resin Systems, Celion/LARC-160, Graphite/Polyimide Polyimide Adhesive Bonding Non-Destructive Inspection

19 Secunty oasslf (of thIS report)

Unclassified

20 Security elaUlf (of thIS PIli')

Unclassified

Unclassified - Unlimited

21 No of Pages

134 22 Price

H-305 For sale by the National Technical Information Service. Springfield. Virginia 22161

Page 141: Develop, Delllonstrate, and Verify Large Area COlllposite ... · Verify Large Area COlllposite Structural Bondirlg With Polyilllide Adhesives Bashir D. Bhombal Donald H. Wykes Keith

End of Document