uk stave work
DESCRIPTION
UK Stave Work. Contribution to Strip Staves Local Supports presentation at AUW. Scope. Co-curing (8 slides) - TJJ Classical Laminate Theory for co-cured face sheets CLT Calculations Manufacture & test of tokens & comparison with CLT calculations Surfaces of Co-cured Facesheets - PowerPoint PPT PresentationTRANSCRIPT
UK Stave Work
Contribution to Strip Staves Local Supports
presentation at AUW
LSWG Meeting - Strip Stave Local Supports 2
Scope• Co-curing (8 slides) - TJJ
– Classical Laminate Theory for co-cured face sheets• CLT Calculations• Manufacture & test of tokens & comparison with CLT calculations
– Surfaces of Co-cured Facesheets• Potted history (successes & failures)• Properties of co-cured stave surfaces
• Stave Assembly Tooling (3 slides) - TJJ– Tooling Design– Stavelet 6
• Glue film for honeycomb
• Locking Mechanisms (6 slides) - SY
• Plans for Sector Prototype (3 slides) – SY
• ABCN130 Stave FEA (3 slides) - GB09/11/2011
LSWG Meeting - Strip Stave Local Supports 3
Co-curing – initial trials• 7 electrical and 2 mechanical co-cures of full size tapes & 4 stavelet
size– Co-cured face sheets can be sucked onto vacuum jig, although residual
curvature difficult to control along edge.– In autoclave gluing edge of tape needs to be protected from glue creep with
tape. – Larger residual twist in electrical tapes (thicker aluminium)– Dimensional changes measured– Concerns over face sheet integrity– Concerns over surface ‘roughness’
Autoclave cures for full length stave
Press cures for full length stave
Autoclave cures for 0.5mm stavelet on CF Tooling
09/11/2011
LSWG Meeting - Strip Stave Local Supports 4
Ripples, Defects & De-laminations• Ripples in Plank 5 tapes seen after
few 10’s of thermal cycles– Issue with tape manufacture?
• Defects– Detailed investigations of used/unused
face sheets reveal large variety of surface ‘defects’
• De-laminations (within CF face sheet)– 125C/4h co-cured K13D2U/RS3 face
sheets (US tapes) – De-laminations after 1 hour at -45C– Focus on theoretical calculations / FEA
modelling of stresses in co-cured structures together with a prototyping plan for verification 09/11/2011
LSWG Meeting - Strip Stave Local Supports 5
Surface Defects• Likely that these are from the
process– CFRP face sheets are free from defects
• Process (based on US technique)– Abrade tape with Scotch-brite / ethanol– Bake out tape over night at 110C– Lay up 0/90 & compact for 30’– Add top 0 layer & compact for 30’– Remove tape from oven, allow to cool &
add to stack.– Add release ply, silicone rubber pad &
caul plate, compact for 1hr– Transfer to autoclave & cure at 120 deg C
for 3 hours; release autoclave pressure & allow autoclave to cool over night with vacuum pump on;
• Surface Profiles– Initial 2D measurements using needle-
probe• New sample better than plank 5 but
worse than plank 4 0 2.5 5 7.5 10 12.5 15 17.5-10.0
-7.5-5.0-2.50.02.55.07.5
10.0Plank 4Plank 5Co-cure #1
Position (mm)
Defle
ction
(mic
rons
)
09/11/2011
LSWG Meeting - Strip Stave Local Supports 6
Classical Laminate Theory Applied to Co-cured face sheet (120C cure)
• Model– Assume copper has little effect– Aluminium thickness = 0.05mm– Aluminium modulus = 69MPa
• Classical Laminate Theory– In general, the loads [N] and moments [M], expressed as column
vectors, acting on a laminate can be related to the strains () and mid-plane curvatures () through the matrix equation;
– [A],[B] and [D] are 3x3 matrices called the extensional, coupling and bending stiffness matrices respectively.
• Extensional matrix [A] relates the resultant in-plane forces to the in-plane strains
• Bending matrix [D] relates the resultant bending moments to the laminate curvatures.
• Coupling matrix [B] couples the resultant forces and moments to mid-plane strains and curvatures.
– Solving the matrix equations gives the strains () and mid-plane curvatures ()
– Curvature seen in non-zero kappa values
K13C2U/EX-1515(0 deg)
0.065mm
K13C2U/EX-1515(90 deg)0.065mm
K13C2U/EX-1515(0 deg)
0.065mm
Kapton0.05mm
Kapton0.05mm
Aluminium0.05mm
Kapton0.025mm
09/11/2011
LSWG Meeting - Strip Stave Local Supports 7
Experimental Measurements
• Plot of height vs x2(where x is the position along the length) will have a slope of /2.
– 0/90 K3.6 (5.8)– 0/90/0+tape K 9.2 (11.5)
• Measure strain on top and bottom surfaces of 0/90/0+tape laminate vs temperature and compare with prediction from CLT
0/90/00/90
0/90/0 + tape 90/0/90 + tape
0
0 0.001 0.002 0.003 0.004 0.0050
0.005
0.01
0.015
0.02
0.025
0.03
f(x) = − 1.77890529885669 x + 0.0106056935538004
f(x) = − 4.62335517315441 x + 0.0255515487368161
0/90/0 + tapeLinear (0/90/0 + tape)
x2 (m2)
Heig
ht (m
)
0 20 40 60 80 100 120 140-4000
-3000
-2000
-1000
0
1000
2000
3000
4000
5000
6000 Exp - topExp - bot -tomExp - diffCLT - topCLT - bot -tomCLT- diff
Temperature (deg C)
Stra
in (m
icro
-str
ain)
09/11/2011
LSWG Meeting - Strip Stave Local Supports 8
Effect of Aluminium Yield Strength• Use CLT to predict stresses for a given
temperature change
• Apply external moments to keep laminate flat & simulate sandwich construction
• Calculate using EXCEL– Split matrix summations into
constant part and aluminium modulus dependent part
– For a given temperature change• Use CLT to calculate stresses in each layer
with suitable external moments applied to keep laminate flat
• Sum to give total stress in aluminium layer
• Use aluminium stress and Ramberg-Osgood formula to calculate aluminium modulus for next temperature change
-120 -100 -80 -60 -40 -20 00
20
40
60
80
100
120Yield strength = 25MPaYield Strength = 50MPaYield Strength = 75MPaYield Strength = 100MPa
Temperature Difference (deg C)
Alum
iniu
m S
tres
s (M
Pa)
-120 -100 -80 -60 -40 -20 070%75%80%85%90%95%
100%105%110%
Yield strength = 25MPaYield Strength = 50MPaYield Strength = 75MPaYield Strength = 100MPaMeasurement
Temperature Difference (deg C)
Smal
ler C
urva
ture
rela
tive
to
E=69
MPa
09/11/2011
LSWG Meeting - Strip Stave Local Supports 9
Stresses in CF Layers vs. Al yield Strength
-200 -150 -100 -50 0-400
-320
Ply 1&3 (x) Stress vs Temperature
25
50
75
100
150
200
300
No Tape
Max. StressTemperature (deg C)
Stre
ss (M
Pa)
-200 -150 -100 -50 0-400
-320
Ply 2(x) Stress vs Temperature
25
50
75
100
150
200
300
No Tape
Max. StressTemperature (deg C)
Stre
ss (M
Pa)
-200 -150 -100 -50 00
20
40
60
Ply 1,2,3(y) Stress vs Temperature
255075100150200300No TapeMax. Stress
Temperature (deg C)
Stre
ss (M
Pa)
Unless the aluminium yield strength is very high, co-cured face sheets should be robust against thermal cycling down to operating temperature with a reasonable safety margin.
09/11/2011
LSWG Meeting - Strip Stave Local Supports 10
Co-curing Conclusions• Historically we’ve had mixed experience
– De-laminations• Some co-cures show signs of de-lamination – but not all
– Surface Defects• Some co-cures have very smooth surfaces – others do not
• Likely cause (of both!) is the lamination process– Take on-board expertise in US (LBNL September meeting) in
particular;• Bake-out of bus tape• Compactification during lay-up
– 1st sample looks encouraging
09/11/2011
LSWG Meeting - Strip Stave Local Supports 11
Stave Assembly Tooling• Programme to develop low(er) mass, more
stable stave assembly tooling– Start with CF sandwich version of stavelet
tooling to prove manufacturing techniques• 1.5mm CF skins on 7mm Nomex honeycomb• Embedded vacuum channel• FR4 vacuum channel network• ~ 380 2mm dia. vacuum holes
– Global flatness measured on CMM• 60% within +/- 10mictons
– Surface roughness measured using needle probe• Ra ~ 1.5microns
0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400 425 450 475 5000
25
50
75
100
125
150
+0.03mm09/11/2011
0 2.5 5 7.5 10 12.5 15 17.5-10
-7.5
-5
-2.5
0
2.5
5
7.5
10
Position (mm)
Disp
lace
men
t (m
icron
s)
LSWG Meeting - Strip Stave Local Supports 12
Stave Version• Combination of the 2nd
Liverpool stavelet jig and the requirements for the Oxford stave assembly tooling for individual components
• Parts in fabrication at Liverpool & Oxford
• Hope to complete by end of 2011
09/11/2011
LSWG Meeting - Strip Stave Local Supports 13
Stavelet 6• Conventional build +
– New tooling– 80C cure glue film for honeycomb (~ 60% area removed using pattern cutter)
09/11/2011
LSWG Meeting - Strip Stave Local Supports 1414
UK Locking Mechanism Update
The UK stave mounting design is based on the edge mounting and end insertion. Once inserted into position, the stave is fixed at the Z=0.0 position at two locations, and along the long edge at 5 locations. The fixing condition at the Z=0.0 is fully locked on one side and guided on the other, and those along the long edge are “locked” in a manner that when the mounting points are locked, the stave is pressed against a pre-determined datum faces that guarantees the azimuth and radial positions of the stave, but allows differential thermal movement between the stave and the cylinder in the Z-direction.
Previous locking mechanism
09/11/2011
LSWG Meeting - Strip Stave Local Supports 15
Motivation of new locking mechanism• The existing design works when stave tilting angle at 16 deg.
– Can not fit into the space envelope when the stave tilting angle at 10deg.
• Further improvement of the existing design from the following aspects:– Reduce the number of parts– Reduce the number of reference faces to avoid over constraint– Further improvement on end insertion – Fit into the space envelop at stave tilting angle of 10o.
Number of parts reduced from 6 to 3. Material volumes very similar.09/11/2011
LSWG Meeting - Strip Stave Local Supports 16
Locking and Reference Faces
Cam (retracted)
Over centre dimples
Guide Rail interface
Reference faces
Unlocked, typ gap 0.2
Locked, 0 gap
Reference faces
Reference faces
4
2
09/11/2011
End insertion and tooling conceptSlide in guide rails using features in mounting brackets to locate.
Rotate guide rails so that the rails + the mounting bracket corms a continuous channel. Secure by inserting rode (green)
Stave slides along channels via the locking points. When the stave is in the correct location, the stave is locked in Z, the cams are actuated and the guide rails removed.
Note: Guide rails are only used during insertion of the stave, and are fully withdrawn once insertion has finished.
LSWG Meeting - Strip Stave Local Supports 18
3D illustration09/11/2011
LSWG Meeting - Strip Stave Local Supports 19
Being supported at various rotational positions
09/11/2011
LSWG Meeting - Strip Stave Local Supports 20
Clearance within space envelope (for 10o stave tilt angle) including that for the rotation of the guide rails.
Space envelope
Innermost layer Geometry and Stave Envelope
09/11/2011
LSWG Meeting - Strip Stave Local Supports 21
Remarks• The new locking mechanism design fits into the revised space
envelope when the stave tilt angle is 10
• A prototype of the new locking mechanism has been made out of PEEK, and is working as expected.
• This new design allows end insertion to be carried out during installation as well as stave removal should this proves necessary after installation;
• Plan to build a stave sector prototype with 4 staves to demonstrate the end insertion and positioning of the locking mechanism. The design and construction of this setup is now underway and we aim to get this done by the early next year.
09/11/2011
LSWG Meeting - Strip Stave Local Supports 22
Stave Sector Prototype
Carbon Fibre sandwich sector base
some tooling balls will be fitted on various position on the sector for easy survey.
FEA carried out to check the interlink rigidity.
09/11/2011