nondestructive characterization and evaluation of adhesive ... · concept for implementation of ndt...

© Fraunhofer

Nondestructive Characterization and Evaluation of Adhesive Bondings

- R&D and Applications -

European Adhesive Engineer © [email protected] Fon +49 9302 / 3610Fraunhofer IZFP | Campus E3 1 | 66123 Saarbrücken, Germanywww.izfp.fraunhofer.de

Prof. Dr. Bernd Valeske

AIST Tsukuba, TIA-Fraunhofer Workshop, Oct. 5th 2017

© Fraunhofer

Tsukuba / JAPANOct 3rd – 5th 2017

[email protected] Fon +49 9302 / 3610

www.izfp.fraunhofer.de2

Fraunhofer IZFP : R&D for Applied Research

Fraunhofer Mission

New Business Models

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OUTLINE

Objectives and Philosophy (NDT Strategy)

Classical NDT for Defect Detection

Extended NDT (E-NDT) for Characterization ofAdhesive‘s & Adhesion Properties

Summary & Conclusions

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Nondestructive Monitoring & Testing throughout the complete Process Chain

Original Materials:joining components + surfaces + (bulk) adhesive

Bonding Process:application of adhesive,joining,curing

„Finalized“ Joint:(before delivery)

completely set-upand cured bonded joint

Pre-Process:integrity of all materials,residual stresses in joining materials, surface state ofsubstrates, viscosity of adhesive/ state of storage

In-Process:rheological properties, change of viscosity, application of adhesive(geometry, position, thickness of bondline), cavities, inclusionsunsufficient wetting, curing

Post-Process:cohesive / adhesive failure, „defects“ (delaminations, disbonds, pores, „weak bonds“)thickness & geometry ofbondline, degree offilling

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Adhesion

Cohesion

Microstructure

Molecularmobility

Geomety

Substrates

Properties

PoresInclusions

DelaminationsCorrosion

Cracks

Defects

In-service

& usage

Processing,

production

intrinsic stresses

, , t, T

Stresses/loads

chemical, physical,Perfor-

mance

Fields of application of non-destructive quality assurance

Classical NDT(Defect Detection)

Extended NDT(E-NDT)

Design

ProcessControl

aging, degradation

Monitoring

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Development

Approval

Production

Quality Control(SPC ↔ 100%)

OperationIn-Service Inspection,

Predictive Maintenance, Repair

ultrasonicsTHz, videoscopy …

Xray CTshearography ,thermography

thermal waveselectro-magneticfields and waves

elasticvibrations & waves

NDT physical interactions (absorption, reflection) of „signals“ withmaterial inhomogeneities („defects“) and appropriate 2D or 3D visualization

Fields of application of classical NDT (defect detection)

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OUTLINE





Classical NDT(Defect Detection)

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Specimens / master samples withrepresentative artificial defects („reference defects“)

Cap Profile

Flat Sandwich

o Xray CTo Thermographyo Air Coupled Ultrasound

Phased Array Ultrasoundo Shearographyo …

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cavitiesproper bonding

kissing bonds lack of adhesive restriction / retraction

NDT validation with more than 100 investigation programs

Different EP and PU adhesives (bond thickness: 1,5 … 3 mm)

Various material combinations: Steel, Aluminium, Glass, CFRP, GFRP, Polymers

500 mm

50 mm

top side

50 mm

bottom side~ 20 mm ~.50 mm

bondline

Specimen / master sample withrepresentative artificial defects („reference defects“)

wormholes

( 1 und 2mm)

bondline

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wormholesrestriction / retraction

of adhesive cavities, d 3,5 mm

restriction / retractionof adhesive

cavities, d 0,5 mm cavities, d 0,5 mm

squeezingexcesss adhesive

lack ofadhesive

squeezingexcesss adhesive

CFRP / EP / St

Xray CT

Air coupledultrasound

CFRP / EP / Al

NDT for post-process defect detection – Examples ofextensive validation and selection of best suitable inspection methodfor more than 30 material and adhesive combinations

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Air Coupled Ultrasound (contactless)

cavities

restriction ofadhesive

lack ofadhesive

wormholes

cavities

restriction ofadhesive

lack ofadhesive

wormholes

Kissing Bonddetection

unstressed state

sample under load

KissingBond

Bondline 2

Bondline 1

Bondline 1

Bondline 2

top views

Al / EP / St

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NDT for post-process defect detection – Examples ofextensive validation and selection of best suitable inspection methodfor more than 30 material and adhesive combinations

Thermography

Phased ArrayUltrasound

St / EP / GPRP

St / EP / CPRP

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Automated Evaluation (specific signal & image processing) automated detection of bond line + defects / suspicious RoI‘s

no defects defects & border artefacts defects

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Advanced Algorithms and NDT Analysis Software to automatically evaluate the statistics of defect indications specialized segmentation & blob analysis

Feature extraction andclassification of essential defect and bondline parameters

advanced signal& image processing

specialized featureextraction & analysis

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Input DataRaw Data byrobotizedThermographicInspection Output

Feature Extractionby Advanced Signal

Processing and Pattern Recognition

Bonding & Bondline Okay

Missing Adhesive, Debondg

Defect in Bondline(pores, wormholes…)

Advanced Algorithms and NDT Analysis Software to automatically evaluate the statistics of defect indications specialized segmentation & blob analysis

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Results of test program (exemplary)

Benchmark Results of Different NDT methods / Capability

Test program + NDT Capability Benchmark

Datasheets: Capability for quantitative defect detection

Kanäle

Anzahl Anzahl Anzahl Anzahl

Kanal 1 2 3 4 5 6 7 8 Kanal 1 2 3 4 5 6 7 8 Kanal 1 2 3 4 5 6 7 8 Kanal 1 2 3 4 5 6

Länge / mm 21,5 21,5 20,8 21,1 20 13,9 18,5 21,1 Länge / mm (21,5) (21,5) (20,8) (21,1) (20,0) (13,9) (18,5) (21,1) Länge 17,3 17,2 17,8 17,2 17,4 12,9 17,6 17,5 Länge ca. 20 ca. 20 ca. 20 ca. 20 ca. 20 ca. 20

Breite / mm 2,4 3,0 2,5 2,5 1,2 1,4 1,5 1,6 Breite / mm 2,4 3,0 2,5 2,5 1,2 1,4 1,5 1,6 Breite 2,4 2,4 2,3 2,4 1,6 2,3 1,6 1,6 Breite

Tiefenlage / mm 3,3 3,3 3,3 3,3 3,8 3,3 3,9 3,9 Tiefenlage / mm Tiefenlage Tiefenlage

Nachweis Nachweis Nachweis Nachweis

Styropor‐Einschlüsse

Anzahl Anzahl Anzahl Anzahl

Größe von: bis: Größe von: bis: Größe von: bis: Größe von: bis:

Tiefenlage von: bis: Tiefenlage Tiefenlage Tiefenlage


Klebnahtunterbrechung

Länge Länge Länge Länge


Klebnahtrückfall

Ausführung Ausführung Ausführung Ausführung

Rückfalltiefe 1 Rückfalltiefe 1 Rückfalltiefe 1 Rückfalltiefe 1

Bereichslänge 1 Bereichslänge 1 Bereichslänge 1 Bereichslänge 1

Rückfalltiefe 2 Rückfalltiefe 2 Rückfalltiefe 2 Rückfalltiefe 2

Bereichslänge 2 Bereichslänge 2 Bereichslänge 2 Bereichslänge 2

Fehlender

Flächenanteil

Fehlender

Flächenanteil

Fehlender

Flächenanteil

Fehlender

Flächenanteil


Werkstoffkombi 5 ‐ CFK auf Alu ‐ Probe P06 H‐AlKT‐CFPr‐2P‐01

FehlerRöntgen‐CT Radiographie Luft‐US

Verfahren

Thermografie

7 7 von 7 8 von 8

keine Aussage möglich (Transmission) keine Aussage möglich (Transmission)

100% 100% 100%

19 19

11 Anzeigen von 19 Einschlüssen (teilweise

Überdeckung/Überlagerung/Verschmelzung, 19

Einschlüsse nicht getrennt nachweisbar)

0,4 mm 2,9 mm 0,4 mm 2,9 mm 10,6 mm1,1 mm

2,1 mm 4,7 mm keine Aussage möglich (Transmission) keine Aussage möglich (Transmission)

100% 100% 85% (allerdings nicht einzeln nachweisbar)

46 mm 46 mm 46,5 mm

100% 100% 100%

zweiseitig zweiseitig zweiseitig

5 mm 5 mm 4,2 mm

ca. (438 + 666) mm²

134 mm 130 mm 132,7 mm

5 mm Abschattung Hutprofil 5,9 mm

6 von 8

keine Aussage möglich (integraler Wärmefluss)

80%

ca. 2

‐ ‐

nicht auswertbar

keine Aussage möglich (integraler Wärmefluss)

10%

ca. 40 mm

100%

einseitig

Anmerkung: Die Länge der Kanäle kann bei Radiographie nur unter

Zuhilfenahme der geometrischen Abmessungen der Probe

(Abschattungskanten) sowie Vorkenntnissen aus der Röntgen‐CT

exakt bestimmt werden. Daher stehen die Werte in Klammern.

Anmerkung: Das Vermessen von Merkmalen in thermographischen Aufnahmen stellt eine verfahrensbedingte

Schwierigkeit dar und ist derzeit auch kein qualifiziertes Verfahren zur Bestimmung von Fehlergrößen. Infolge des

lateralen Wärmeflusses kommt es zur "Verschmierung" von klaren Kanten, so dass die bestimmten Werte der

Merkmale oft deutlich von den wahren Fehlergrößen abweichen können (unscharfe Randausbildung). Es ist zu

beachten, dass aus prüfphysikalischen Randbedingungen, die Anzeigengröße der Merkmale nicht mit der wahren

Fehlergröße gleichzusetzen ist.

50%

nicht detektierbar

nicht detektierbar

ca. 9 mm

ca. 150 mm

ca. 1060 mm²

100% 100% 100%

161 mm Abschattung Hutprofil 143,7 mm

(540+700) mm² (430+???) mm²

Concept for implementation of NDT test set-ups

windshieldspare wheel

well

liftgate

roof

NDT supportedby robots

Sh

ea

rog

rap

hy

Th

erm

og

rap

hy

Air

-co

up

led

Ult

raso

nic

X-r

ay

-CT

Ph

oto

gra

ph

ic P

ictu

re

Rating matrix of defect detection

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R&D / Contract Research for the German Automotive Consortium

Validation of Prototypes

Analysis of capability for different NDT Technologies

System selection and specific development

NDT System prototypes

Reference Samples

spare wheel well

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Video clip: Spare wheel well (GFRP / PU / Al)

Video clip: Windshield (VSG / PU / St)

New:Fully automated non-destructive testing of real vehicle structures

Lab-Prototypes: NDT test set-up at real components

Long-term strategic R&D partnership

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OUTLINE




Summary & ConclusionsExtended NDT

(E-NDT)

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One Sided Access Nuclear Magnetic Resonance Technique (OSA-NMR)

NMR Inspect © NMR-Technique for components andmaterials inspection In-Process E-NDT

Resonance excitation of H1-Spins by suitablepulse sequencies

Informations concerning therelaxation behaviour in polymers(e.g. T2-relaxation time)

in the fluid state of adhesivesin the solid statein the visco-elastic state

Characterization of molecular dynamicsin polymer adhesives

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Comparison of different types of NMR for Imaging vs. NDT

“Classical“ NMR (lab method, MRI)

NMR one-sided access technique (NDT for components)IZFP

Magnet

Magnet

Spu

le

Spu

le

Spule

Magnet

MagnetMagnetic field B0

HF field B1

Measurement layer (sensitive volume)Total measurement areaTest “object”

Magnetic field B0

HF field B1

Measurement layer (sensitive volume)Total measurement areaTest object

coil

coil

coil

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Example: Curing of Araldit 2014 (2K EP) Process Control

Signal Ratio of Hahn-Echo / Solid-Echo („liquid / solid“ – dynamics)

3

5

7

9

11

13

15

0 50 100 150 200 250 300Aushärtungszeit, t A [min]

Spin

ech

o-S

ign

al,

SH

E u

nd

SS

E in

[V

]

1

1,5

2

2,5

3

3,5S

SE/S

HE in

[V

/V]

DSC: 52 % Aushärtung

curing time [min]

OSA-NMR In-Process NDT of Polymer Properties (Curing Process)

DSC: 52 % degree of cure

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OSA-NMR for characterization of adhesive curing

security glass (wind screen) bonded with 2-part PU onto

Al-Sheet or Polymer Plate

dimensions of samples: ~ 10 cm x 10 cm, thickness of bonding: ~ 3 mm

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OSA-NMR for monitoring the Curing in Adhesive Joints

appropriate mixing ratio (50:50)

excess of curing agent (70:30)

Adhesive Curing

curing time [min]0 min 300 min

pro

cess

ed

measu

rem

en

tsi

gn

al

[a.u

.]

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New Approach for Testing of the Bond Performance:Laser Bond Inspection / Laser Proof Testing

Laser Bond Inspection Ph.D. Bastien Ehrhart (in cooperation with Fraunhofer IFAM and CNRS-ENSMA, Poitiers)

testing principle: generationof small defects by LASER shock waves for weak bonds(strength below criticalthreshold value)

new approach forclassification of degrees ofbond quality (bond strength)

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Systematic correlation of critical LASER threshold values necessaryfor debonding (opening of weak bonds) compared to G1C - value

Examples for inspection of weak bonds in CFRP samples [source: Ph.D. Bastien Ehrhart, 2015]

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OUTLINE





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Nondestructive inspection of bond quality & bond performance needs both:

necessarily the detection of defects by classical NDTand

additionally the evaluation of adhesive‘s polymer properties (correct cure,degradation / aging), i.e. performance of adhesion E-NDT

In many cases: defect detection is sufficient for rejection of bad quality advanced NDT developments with automated evaluation / signal processing succesful validation of NDT methods, selection of best NDT technology

for a broad variety of material combinations and adhesives

New approaches for structural adhesive bonding or where „safe life“ design philosopy needs full evaluation of bond performance / nondestructivemonitoring of adhesive bonds in construction components & assemblies promising E-NDT methods

(e.g. OSA-NMR, upscaling of spectroscopic methods) sensing of bond strength e.g. by shock waves or advanced ultrasound

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Nondestructive Quality Control of Adhesive Bonding

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Acknowledgements

To all my colleagues at Fraunhofer IZFP for contributions inR&D works and in the recent projects

Dr. Bastien Ehrhart, and the corresponding partner institutions Fraunhofer IFAM, CNRS-ENSMA (Poitiers, France) and AIRBUS (Bremen, Germany)

To the research partners from industry over the last years, mainly the GERMAN Automotive OEMs (Porsche, AUDI, Volkswagen, BMW andDaimler /Mercedes-Benz)

To the European Commission for R&D Fundingmainly for the FP7-Project „ENCOMB“ and the CORNET-Project „ZeDeMAB“

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www.izfp.fraunhofer.de

Non-Destructive Monitoring of Adhesive Bonding

by Smart Sensors and NDE 4.0

Prof. Dr. Bernd [email protected] Fon +49 9302 / 3610Fraunhofer IZFP | Campus E3 1 | 66123 Saarbrücken, Germanywww.izfp.fraunhofer.de

nondestructive characterization and evaluation of adhesive ... · concept for implementation of ndt...

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