Adhesive Bond Process Qualification Protocols Development & Development of … · 2019-06-03 ·...

Adhesive Bond Process Qualification Protocols Development & Development of Roadmap for Bonded Structure Certification

Waruna Seneviratne, John Tomblin, and Upul Palliyaguru

2019Technical Review - (05/22/2019)

2

Adhesive Bond Process Qualification Protocols Development & Development of Roadmap for Bonded Structure Certification

• Principal Investigators & Researchers

• John Tomblin, PhD, and Waruna Seneviratne, PhD

• Upul Palliyaguru and Anushi Amaranayake

• FAA Technical Monitor

• Ahmet Oztekin

• Other FAA/CMH-17 Personnel Involved

• Larry Ilcewicz, PhD, Cindy Ashforth, and Curtis Davies,

• DoD & Industry Participation

• AFRL, Boeing, Bell Helicopter, Henkel, Honda Aircraft Co., Lockheed Martin, MMM, MTech Engineering Services, NAVAIR, Solvey Industries , Textron Aviation, Boom Aerospace

Adhesive Bond Process Qualification Protocols Development (Background)

• Aircraft companies tend to use bonded joins in their primary structure due to various time and cost savings. However, qualification of the bond process and certification of the bonded structure requires extensive amount of substantiation work.

• Due to the complexity and numerous variables seen in a bond system, locking on to a these parameters needs extensive exploration of all possible variations in the bond process. After locking onto this processes, effective and efficient methods for quality assurance needs to be implemented to qualify the bonding process.

• After the bond process qualification tasks are completed, bonded structure needs to be certified per the requirements of the safety agencies.

3

The Primary goal of this research program is to develop a road map for qualification activities of a bond system and support development of certification road map for bonded structures per the safety requirements through substantiation.

Substrate

Metal Composites

Surface Preparation

Degreasing Abrasion Chemical Treatment

Can be combined

Type

Primer

Bond Process Qualification[Critical Factors]

Surface PreparationMaterial & Process

Variability (Material Qualification)

Pre-Bond Surface Characterization

Adhesive

Material Batch Variability Process Variability History Quality

Paste Film

Mixing(for Paste)

Adhesive Application Bondline Thickness Control Cure Environment Effects of Defects

TgViscosity

Shelf lifeStorage lifeOuttime

TemperatureHumidityField Repair Conditions

Multiple Cure OptionsTooling CTE MismatchTemperature ControlsRamp Rate(s)Pressure

Application MethodOpen Time

(ex., Amine Blush)

Paste Film

Pre-Mixed Glass BeadsGlass Bead Mixing into

Adhesive Mix

Knit Random Mat

Unsupported

Application side(s)ApplicatorPreheat SubstratePreheat AdhesiveAdhesive Fillets

TolerancesVacuum or notMixing Technique

Scrim ClothMicro Beads Mixed into

Adhesive

X-Ray Photoelectron Spectroscopy

Fourier Transform IR Spectroscopy (FTIR)

Sessile Drop Contact Angle (CA)

Grit Blasting Hand Sanding Peel-Ply RemovalPlasma (Ionized Gas)

Treatment

Applicator Mix RatioMixing Technique

BPQ Critical Factors 2017 03 14.pdf

Adhesive Bond Process Qualification Protocols Development (Road Map)

4

Objective

Manufacture a bonded wing

structure

Preliminary Design Requirements/Knowledgebase of

the Bonded Structure1. General Size2. Mechanical property requirement

for Bonded Joints3. Environmental Envelope 4. Manufacturing Requirements5. Analysis of critical bonded joint

types seen in the structure6. Bondline thickness requirements

Preliminary Selection and Screening of Substrate and Adhesive Materials

1. Material allowable – (Material databases)2. Adhesive & Substrate compatibility assessment & Wettability assessment3. Selection of surface preparation methodology4. Adhesive processing parameters of a representative design.5. Conduct basic adhesive test methods at room temperature to validate the

parameters

Bond Process Qualification Plan and Protocol Development

1. Finalized Bond System2. Based on the parameters,

compose a test matrix to ensure quality assurance of surface preparation and processing parameters

3. Generation of quality assurance methodologies

Design and Preliminary Bond System Assessment


Bond Process Qualification and Protocol Generation

Structural Certification of Bonded Structure &

Maintenance

Structural Certification of Bonded Structure & Maintenance

1. Screening of bond system2. Long term durability3. Substrate & adhesive characterization4. Bonded joint characterization5. Durability & environmental scatter 6. Damage Tolerance and Crack growth

Maintenance1. Inspection methodology development 2. Inspection methodology for bond

strength degradation.3. Identification of inspection level and

frequency.

Adhesive Bond Process Qualification Protocols Development (Road Map)

5

Objective

Manufacture a bonded wing

structure

Preliminary Design Requirements/Knowledgebase of

the Bonded Structure1. General Size2. Mechanical property requirement

for Bonded Joints3. Environmental Envelope 4. Manufacturing Requirements5. Analysis of critical bonded joint

types seen in the structure6. Bondline thickness requirements

Preliminary Selection and Screening of Substrate and Adhesive Materials

1. Material allowable – (Material databases)2. Adhesive & Substrate compatibility assessment & Wettability assessment3. Selection of surface preparation methodology4. Adhesive processing parameters of a representative design.5. Conduct basic adhesive test methods at room temperature to validate the

parameters

Bond Process Qualification Plan and Protocol Development

1. Finalized Bond System2. Based on the parameters,

compose a test matrix to ensure quality assurance of surface preparation and processing parameters

3. Generation of quality assurance methodologies



Bond Process Qualification and Protocol Generation

Structural Certification of Bonded Structure &

Maintenance

Structural Certification of Bonded Structure & Maintenance

1. Screening of bond system2. Long term durability3. Substrate & adhesive characterization4. Bonded joint characterization5. Durability & environmental scatter 6. Damage Tolerance and Crack growth

Maintenance1. Inspection methodology development 2. Inspection methodology for bond

strength degradation.3. Identification of inspection level and

frequency.

Overview of the Presentation

• Preliminary screening and down-selection of adhesive-substrate combinations

• Critical parameters in the surface preparation

• Surface preparation methodology

• Quality assurance and handling of prepared substrates

• Critical parameters in the adhesive application and cure process

• Adhesive handling guidelines

• Mixing and application

• Bondline thickness control

• Bond process qualification protocols generation to asses the effect of varying the parameters

6

Preliminary Selection and Screening of Various Substrate and Adhesive Materials

• Selection of preliminary candidates for the adhesive and substrate materials

• Bond system parameter down-selection

• Surface preparation and adhesive processing

• Phase I – Facility and equipment limitations

• Preliminary design dimensions – a general idea of the size

• Facility processing equipment – Curing and pressure application

• Phase II – Material performance limitations and incompatibility issues

• Operational environmental envelope

• Physical - wettability of substrates and adhesive

• Thermal – CTE and Tg mismatch

• Mechanical – poor static and durability performance – failure mode based assessment

7

Pre

lim

ina

ry S

cre

en

ing

Act

ivit

ies

Substrate

Metal Composites

Surface Preparation


Can be combined

Type

Primer





Adhesive


Paste Film

Mixing(for Paste)


TgViscosity





(ex., Amine Blush)

Paste Film


Adhesive Mix

Knit Random Mat

Unsupported




Adhesive





Treatment


X


Bond Process Qualification Protocol GenerationQuality Assurance of Surface Preparation Methodologies

• Abrasion

• Hand Sanding

• Grit Blasting

• Peel Ply

• Atmospheric Plasma Treatment (ATP)

• Degreasing

• Chemical Treatments

• Corona Discharge

• Laser Ablation

8

Common Surface Preparation Methods(Metallic & Composite substrates)

• Pre-surface preparation checklist

• Quality control and process specification of substrates (cured)

• Ex. Mold release, surface finish (bag/tool)

• Quality control of equipment/tools used in surface preparation

• Material specifications

• Ex. Sand paper/sanding disks, peel ply, chemicals

• Operational settings of equipment

• Ex. – Sander types, speed, force, Plasma generator parameters

• Quality control and training of technicians involved in the process

• Quantification and assessment of variability in the hand sanding process

• Evaluation of surface preparation to bonding time limitation

• Effect of environmental exposure duration on surface free energy

• Quality check of the prepared substrates to ensure the integrity of the bond system.

• Development of surface preparation standards and quantification of the effects

Bond Process Qualification Protocol GenerationQuality Assurance Standard Development

• Surface Preparation

• Goal – Increase the surface free energy -> better wettability -> good bonds

• Method of verification -> Water contact angle measurement

• Quality check -> Water contact angle measurement comparison to a known standard

• Equipment used – Surface Analysts – BTG Labs

• Contact angle measurements validated with Goniometer results.

• Surface preparation quality assurance standard

• Utilizing different abrasion methods (pressures/grit size) – obtain a range of different surface free energies (contact angles)

• Fabricate bonded joint specimen and evaluate the bond strength

9

59o

65o

63o

64o

58o

62o

60o

63o

55o

62o

58o

60o

55o

62o

57o

59o

Surface Analyst Goniometer


0123456789

101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869

Point 1 Point 2 Point 3 Point 4 Point 5 Point 6 Point 7 Point 8 Point 9 Point 10 Point 11 Point 12 Point 13 Point 14 Point 15 Point 16

An

gle

[d

egre

es]


± 2 variation

0

1000

2000

3000

4000

5000

6000

7000

20 30 40 50 60 70 80 90 100

Bo

nd

Str

eng

th [

psi

]

Quality Assurance of Surface Preparation – FM300-2M

10

Substrate - T800/3900-2 Adhesive – FM300-2M

Surface Preparation – MultipleTest Method – D3165

Cohesion/First PlyHigh Adhesion/Low

CohesionAdhesion

51o

54o

55o

54o

53o

51o

52o

51o

63o

58o

58o

60o

59o

56o

59o

60o

57o

57o

58o

57o

59o

57o

57o

55o

56o

58o

55o

54o

53o

50o

53o

56o

Quality Assurance of Surface Preparation – EA9394

11

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

25 35 45 55 65 75 85 95

Bo

nd

Str

eng

th [

psi

]

Average Water Contact Angle [degrees]

Substrate - T800/3900-2 Adhesive – EA9394

Surface Preparation – MultipleTest Method – D3165

Cohesion/First Ply Adhesion

37 44 64 73 93

Environmental Exposure Effects of Prepared Substrates

12

25

30

35

40

45

50

55

60

65

0 200 400 600 800 1000 1200

Co

nta

ct A

ng

le [

deg

rees

]

Time [mins]

Substrate 1 Substrate 2

Substrate - T800/3900-2 Surface Preparation – Manual 120G

0

10

20

30

40

50

60

1 2 3 4 5

Co

nta

ct A

ng

le [

deg

rees

]

Technician

Surface Preparation - Hand Abrasion Technician Process Variation

13

Substrate - T650/5320-1Surface Preparation – Manual Abrasion 120G

51o

54o

55o

54o

53o

51o

52o

51o

63o

58o

58o

60o

59o

56o

59o

60o

57o

57o

58o

57o

59o

57o

57o

55o

56o

58o

55o

54o

53o

50o

53o

56o

Surface Preparation - Peel Ply Removal

14

• Initial assessment of peel plies

• Commonly used Nylon and Polyester peel ply was used for the study.

• Peel ply usage studies were performed to identify critical parameters

• Peel ply removal time frame and exposure duration

• A – Immediately before bonding

• B – Removed and surface exposed to 14 days.

• C – Immediately before bonding; exposed to for to 14 days.

• Mode I and Single Lap Shear Properties

• Post cure effects on peel ply prepared surfaces – Multiple Cure Cycles (MMC)

• FM300-2M – T800/3900-2 (Substrate and Adhesive combination)

• Cure Cycles

• Baseline Initial Cure – 350F for 2hrs with 85 psi pressure (Substrate Cure)

• MCC1 – 350F for 2 hrs.

• MCC2 – 350F for 2hrs (X2)

• Degree of Cure and Fiber Volume Fraction

• Mode I and Single Lap Shear Properties (in progress)

Material Code Style Finish Thickness [in] Description

Nylon

40000 56180 60 0.0075 – 0.0085 Natural

41661 56137 60 0.0065 – 0.0075 Natural

51789 52006 60 0.0045 – 0.0055 Natural

52008 56115 60 0.004 – 0.005 Natural

Polyester

60001 60001 60 0.005 – 0.006 Natural

60002 56030 60 0.005 – 0.006 Natural

60004 56111 60 0.0045 – 0.0055 Natural

60005 56210 60 0.006 – 0.007 Natural

60005 56210 65 0.006 – 0.007 Very Low Porosity

Peel Ply Thickness Adhesive Test Method

MEK MEK wipe only

120G Hand sanding with 120 grit

A Peel ply removal immediately before bonding

B Peel ply removed, surface exposed for 14 days

C Peel ply intact, substrate exposed for 14 days

PP-MCC1 Peel ply intact, one post cure thermal cycle

PPR-MCC1 Peel ply removed, one post cure thermal cycle

PP-MCC2 Peel ply intact, two post cure thermal cycles

PPR-MCC2 Peel ply removed, two post cure thermal cycles

MEK MEK wipe


PAA PAA + BR 127 primer

AC130.2 AC130-2 + BR 6747-1 primer

Al Aluminum 2024

Ny

EA9394

FM300-2M

D1002

D3167

EA9394

FM300-2M

D3165

D5528

Nylon peel ply

Poly Polyester peel ply

T1

T800 T800H/3900-2 unitape

Substrate Surface Preparation Peel Ply Surface Prep

100

% A

dh

100

% A

dh

100

% A

dh

54%

LF

T, 4

6%

Co

h

74%

LF

T, 2

6%

Co

h

43%

LF

T, 5

7% C

oh

0

10

20

30

40

50

60

70

80

90

0

1000

2000

3000

4000

5000

6000

7000

Ny-

T1-

A

Ny-

T1-

B

Ny-

T1-

C

Po

ly-T

1-A

Po

ly-T

1-B

Po

ly-T

1-C

Ave

rag

e W

ate

r Co

nta

ct An

gle

[de

gre

es]

Ap

pa

ren

t S

he

ar

Str

en

gth

[p

si]

Evaluation of Peel Ply Removal and Exposure D3165 - Single Lap Shear – FM300-2M

A – Immediately before bondingB – Removed and surface exposed to 14 days.C – Immediately before bonding; exposed to for to 14 days.

Evaluation of Peel Ply Removal and Exposure D5528 - Mode I - FM300-2M

16

0

10

20

30

40

50

60

70

80

90

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

Ny-

T1-

A

Ny-

T1-

B

Ny-

T1-

C

Po

ly-T

1-A

Po

ly-T

1-C

Po

ly-T

1-C

Ave

rag

e W

ater

Co

nta

ct A

ng

le [

deg

rees

]

GIC

(5%

/ M

AX

) [K

J/m

2]

Adhesion Failure Cohesion/First Ply Failure


100

% A

dh

3% L

FT

, 97%

Ad

h

100

% A

dh

40

% L

FT

, 60

% A

dh

46

% L

FT

, 54

% A

dh

30%

LF

T, 7

0%

Ad

h

0

10

20

30

40

50

60

70

80

90

0

1000

2000

3000

4000

5000

6000

Ny-

T1-

A

Ny-

T1-

B

Ny-

T1-

C

Po

ly-T

1-A

Po

ly-T

1-B

Po

ly-T

1-C

Ave

rag

e W

ate

r C

on

tact

An

gle

[d

eg

ree

s]

Ap

pa

ren

t S

he

ar

Str

en

gth

[p

si]

Evaluation of Peel Ply Removal and Exposure D3165 - Single Lap Shear – EA 9394


0

10

20

30

40

50

60

70

80

90

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Ny-

T1-

A

Ny-

T1-

B

Ny-

T1-

C

Po

ly-T

1-A

Po

ly-T

1-B

Po

ly-T

1-C

Ave

rag

e W

ater

Co

nta

ct A

ng

le [d

eg

rees

]

GIC

(5%

/ M

AX

) [K

J/m

2]

Evaluation of Peel Ply Removal and Exposure D5528 - Mode I – EA9394

18

Adhesion Failure Cohesion Failure


100

% A

dh

100

% A

dh

100

% A

dh

100

% A

dh

21%

LF

T, 7

9%

Ad

h

10%

LFT

, 90

% A

dh

25%

LF

T, 7

5% A

dh

8%

LFT

, 92

% A

dh

0

20

40

60

80

100

120

0

1000

2000

3000

4000

5000

6000

Ny-

T1-

PP

-M

CC

1

Ny-

T1-

PP

-M

CC

2

Ny-

T1-

PP

R-

MC

C1

Ny-

T1-

PP

R-

MC

C2

Po

ly-T

1-P

P-

MC

C1

Po

ly-T

1-P

P-

MC

C2

Po

ly-T

1-P

PR

-M

CC

1

Po

ly-T

1-P

PR

-M

CC

2

Ave

rag

e W

ate

r C

on

tact

An

gle

[d

eg

ree

s]

Ap

pa

ren

t S

he

ar

Str

en

gth

[p

si]

Evaluation of Peel Ply Removal – Multiple Cure Cycles FM300-2M - D3165 Single Lap Shear

19


Bond Cure Cycle – 90 mins 250F 40 psiSurface Preparation – Peel Ply

Adhesion Failure Low Cohesion/First Ply – High Adhesion

0

20

40

60

80

100

120

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

Ny-

T1-

PP

-M

CC

1

Ny-

T1-

PP

-M

CC

2

Ny-

T1-

PP

R-M

CC

1

Ny-

T1-

PP

R-M

CC

2

Po

ly-T

1-P

P-M

CC

1

Po

ly-T

1-P

P-M

CC

2

Po

ly-T

1-P

PR

-MC

C1

Po

ly-T

1-P

PR

-MC

C2

Ave

rag

e W

ater

Co

nta

ct A

ng

le

[deg

rees

]

GIC

(5%

/ M

AX

) [K

J/m

2]

Evaluation of Peel Ply Removal – Multiple Cure Cycles FM300-2M – D5528 Mode I

20


Bond Cure Cycle – 90 mins 250F 40 psiSurface Preparation – Peel Ply

Adhesion Failure Low Cohesion/First Ply – High Adhesion

Evaluation of Peel Ply Removal – Multiple Cure Cycles Degree of Cure

21

94

95

96

97

98

99

100N

y-T

1-P

P-

MC

C1

Ny-

T1-

PP

-M

CC

2

Ny-

T1-

PP

R-M

CC

1

Ny-

T1-

PP

R-M

CC

2

Po

ly-T

1-P

P-M

CC

1

Po

ly-T

1-P

P-M

CC

2

Po

ly-T

1-P

PR

-MC

C1

Po

ly-T

1-P

PR

-MC

C2

Deg

ree

of C

ure

[%

]

C0 - Initial cure C1 - 1 thermal cycle C2 - two thermal cyles

Evaluation of Mixing MethodHand Mixing vs. Speed Mixer

• Hand mixing

• Materials weighed into cup and mixed for 5 minutes. Mixture is then transferred to second cup and mix for an additional 5-10 minutes or until the consistency of the adhesive has changed to become smoother and easier to mix.

• Speed Mixer

• Materials weighed into FlackTek compatible cup and placed inside machine with holder. An appropriate recipe (depending on weight) is chosen and the machine is run.

Zone

A B C

RPM 1000 1600 2000

Time (secs) 60 40 90

Hand mixing Speed Mixer Flacktek DAC

600.1FVZ

Recipe for 125g of adhesive

Evaluation of Mixing MethodHand Mixing vs. Speed Mixer

0%

5%

10%

15%

0

500

1000

1500

2000

2500

3000

3500

4000

4500

Coef

fici

ent

of

Var

iati

on [

%]

Aver

age

Str

ength

[psi

]

HandMix SpeedMixer

Hand-Mixed

Machine Mixed

Bondline Control Mechanism

• Bondline control mechanisms available

• Glass beads

• Tracer Wires

• Evaluate the mix percentage for optimal bondline control

• 0.0059-inch GB mixed at 0.05% and 0.1% by weight

• 0.01-inch GB mixed at 0.05% and 0.1% by weight

• Effects of cure/pressure application

• In Progress

• Effects on the mechanical properties

• In Progress

24

0.01GB-0.5PCT-6PSI-X (Side 1)

0.01GB-1.0PCT-6PSI-X (Side 2)

Bondline Control Mechanism

25

0%

5%

10%

15%

20%

25%

30%

0.000

0.002

0.004

0.006

0.008

0.010

0.012

0.014

0.016

0.018

0.020

0.0

05

9in

-0.5

%-F

V

0.0

05

9in

-1.0

%-F

V

0.0

1in

-0.5

%-F

V

0.0

1in

-1.0

%-F

V

0.0

05

9in

-0.5

%-6

psi

0.0

05

9in

-1.0

%-6

psi

0.0

1in

-0.5

%-6

psi

0.0

1in

-1.0

%-6

psi

Co

effi

cien

t o

f V

aria

tio

n [

%]

Av

erag

e B

on

dli

ne

Th

ick

nes

s [i

n]

Summary and Conclusion

• Quality assurance through water contact angle measurements for substrate provide reliable data to ensure the substrate preparation is acceptable

• Surface preparation to bonding time assessment provide the state change substrates go through when exposed to environment. This can be used to fine tune the bond process.

• Technicians variability assessment is critical in understanding the sensitivity of some of the manual labor critical activities. Understanding the variability is critical to ensure proper training is provided.

• Exposure duration and configuration in peel ply removal technique show variation in the bond performance. Investigations are currently underway to evaluate the reason for the PP removed exposed substrate showed slightly higher properties.

• Polyester peel ply showed a change in the strength and failure mode when exposed to thermal cycles.

26

Looking Forward/Future Work

• Future Works

• Generate bond process protocols for

• Selecting compatible substrate and adhesive combinations for a robust bond structure

• Provide guidance on protocol development for cure process related activities

• Look into other surface preparation methods and look into critical parameters

• Benefit to Aviation

• Generate bond process protocols

• Provide guidance on the critical parameters in the bond process and how to mechanically test them to generate protocols to ensure the integrity of the final bonded product

27

Summary

28

Evaluation of Peel Ply Removal and related parameters

Material Code Style Finish Thickness [in] Description

Nylon

40000 56180 60 0.0075 – 0.0085 Natural

41661 56137 60 0.0065 – 0.0075 Natural

51789 52006 60 0.0045 – 0.0055 Natural

52008 56115 60 0.004 – 0.005 Natural

Polyester

60001 60001 60 0.005 – 0.006 Natural

60002 56030 60 0.005 – 0.006 Natural

60004 56111 60 0.0045 – 0.0055 Natural

60005 56210 60 0.006 – 0.007 Natural

60005 56210 65 0.006 – 0.007 Very Low Porosity

Road Map

31

Preliminary Screening of

Materials and Processes

Development of Bond Process

Qualification Protocols

Certification of Bonded Structure

Material DatabasesAdhesive & Substrates

• Adhesive and Substrate material database

• Ex – NCAMP material qualification databases (substrates, adhesive, etc.)

• Evaluate physical, thermal and mechanical properties

• Evaluate the operational environmental envelope.

• Preliminary material processing parameters.

• Selection of Bond System Parameters

• Substrate

• Adhesive

• Surface Preparation Methodology

• Adhesive Processing

Goniometer vs. Surface Analysis Comparison

59o

65o

63o

64o

58o

62o

60o

63o

55o

62o

58o

60o

55o

62o

57o

59o



Goniometer vs. Surface Analysis Comparison

• Average difference of 2 degrees between the SA and goniometer measurements, with a maximum difference of 4 degrees.

54

55

56

57

58

59

60

61

62

63

64

65

66

Point 1 Point 2 Point 3 Point 4 Point 5 Point 6 Point 7 Point 8 Point 9 Point 10 Point 11 Point 12 Point 13 Point 14 Point 15 Point 16

An

gle

[d

egre

es]


Contact Angle vs. Bond Strength

33 degrees 38 degrees 47 degrees 64 degrees 80 degrees 94 degrees

• Apparent average shear strength for composite D3165 substrates bonded with FM300-2M

Peel Ply study – Single Lap Shear

0%

5%

10%

15%

20%

25%

30%

0

1000

2000

3000

4000

5000

6000

7000

ME

K

120G

Ny-T

1-A

Ny-T

1-B

Ny-T

1-C

Ny-T

1-P

P-

MC

C1

Ny

-T1-P

PR

-

MC

C1

Poly

-T1-A

Poly

-T1-B

Poly

-T1-C

Poly

-T1-P

P-

MC

C1

Poly

-T1-

PP

R-M

CC

1

Coef

fici

ent

of

Vari

ati

on

[%

]

Ap

pare

nt

Sh

ear

Str

ength

[p

si]

ASTM D3165 T800H/3900-2 – FM300-2M

Peel Ply Thickness Adhesive Test Method

MEK MEK wipe only


A Peel ply removal immediately before bonding

B Peel ply removed, surface exposed for 14 days

C Peel ply intact, substrate exposed for 14 days

PP-MCC1 Peel ply intact, one post cure thermal cycle

PPR-MCC1 Peel ply removed, one post cure thermal cycle

PP-MCC2 Peel ply intact, two post cure thermal cycles

PPR-MCC2 Peel ply removed, two post cure thermal cycles

MEK MEK wipe


PAA PAA + BR 127 primer

AC130.2 AC130-2 + BR 6747-1 primer

Al Aluminum 2024

Ny

EA9394

FM300-2M

D1002

D3167

EA9394

FM300-2M

D3165

D5528

Nylon peel ply

Poly Polyester peel ply

T1

T800 T800H/3900-2 unitape

Substrate Surface Preparation Peel Ply Surface Prep

D3165 Failure Modes - FM300-2M

MEK Ny-T1-A Poly-T1-A120G


Ny-T1-B Ny-T1-C Ny-T1-PP-MCC1 Ny-T1-PPR-MCC1


Poly-T1-B Poly-T1-C Poly-T1-PP-MCC1 Poly-T1-PPR-MCC1

Peel Ply Mode I Failure Mode Pictures

39

0%

10%

20%

30%

40%

50%

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

ME

K

120

G

Ny

-T1-A

Ny

-T1-B

Ny

-T1-C

Ny

-T1-P

P-M

CC

1

Ny

-T1-P

PR

-MC

C1

Ny

-T1-P

P-M

CC

2

Ny

-T1-P

PR

-MC

C2

Po

ly-T

1-A

Po

ly-T

1-B

Po

ly-T

1-C

Po

ly-T

1-P

P-M

CC

1

Po

ly-T

1-P

PR

-MC

C1

Po

ly-T

1-P

P-M

CC

2

Po

ly-T

1-P

PR

-MC

C2

Coef

fici

ent

of

Vari

ati

on

[%

]

GIC

(5%

/ M

AX

) [K

J/m

2]

ASTM D5528 T800H/3900-2 - FM300-2M

D5528 Post Test - FM300-2M

MEK 120G


Poly-T1-B Poly-T1-CPoly-T1-A


Poly-T1-PP-MCC1 Poly-T1-PPR-MCC1


Ny-T1-A Ny-T1-B Ny-T1-C


Ny-T1-PP-MCC1 Ny-T1-PPR-MCC1

• All measurements were taken in the 0o direction.

Peel Ply – Surface Roughness

ME

K

Ny-T

1-A

Ny-T

1-B

Ny-T

1-C

Ny-T

1-P

P-M

CC

1

Ny-T

1-P

PR

-MC

C1

Poly

-T1

-A

Poly

-T1

-B

Poly

-T1

-C

Poly

-T1

-PP

-MC

C1

Poly

-T1

-PP

R-M

CC

1

0%

5%

10%

15%

20%

0

50

100

150

200

250

300

350

400

450

500

Co

effi

cien

t o

f V

ari

ati

on

[%

]

Av

era

ge

Ra

[μ

in]

Road Map - Adhesive Qualification Guidance

• Adhesive Characterization Qualification (ACQ)

• Develop test matrices

• Bulk physical, chemical, and mechanical test matrices

• Adhesive (joint) mechanical tests

• Fluid sensitivity

• Equivalency tests

• Develop databases

• Select adhesive bond systems

• Inclusion to CMH-17 data review group

46

Allowables Database

Qualified Bonding System- Adhesive- Process- Substrate- Surface Prep

Process

Substrate

Surface Prep

Guidelines/Data(CMH-17)

Structural Bonding

Structural Application- Adhesive- Process- Substrate- Surface Prep

Qualify New Bonding System

Yes

No

Yes

No

No

Yes

Bonding System Qualification

Qualify Substrate & Surface Prep

Qualify Adhesive &

Bond Process

Statistical Analysis

Road Map - Adhesive Qualification Guidance

47

Guideline Document(FAA Report)

NCAMP Material Specification (NMS)

NCAMP Process Specification (NPS)

Solvey FM300-2

Loctite EA9394

NMS 300/1FM300-2M 0.06 psf

NMS 394/1EA 9394 AERO

Qualified Product List (QPL)

· NMS 300/1· NMS 394/1· ...

Solvey FM300-2

Loctite EA9394

Material Specifications

Process Specifications

Fabrication of bulk and

mechanical test panels

Adhesive NRP 102Adhesive Process Control Document (PCD) Preparation and Maintenance Guide

Guidelines and Recommended Criteria for the Development of Material/Process Specifications for Adhesive

Development of NCAMP Specifications

NCAMP Test Plan (NTP)

Solvey FM300-2

Loctite EA9394

Test Plans

Conformity

Data Collection Templates (PMC)

Authorized Inspection Representative (AIR)

Authorized Engineering Representative (AER)

Material Property Data Report

Statistical Analysis Report

FAA Special Project Codes (SPC)

Development of NCAMP Test Plans

Development of NCAMP Specifications, Test Plans & Guidelines

48

• Adhesive System 1 – FM300-2M (Film Adhesive)

• NCAMP Material Specification (Base) – NMS300

• NCAMP Material Specification (Slash) – NMS300/1

• NCAMP Process Specifications - NPS 83002

• NCAMP Test Plan - NTP AC-3002Q1

• Adhesive System 2 – EA9394 bare (Paste Adhesive)

• NCAMP Material Specification (Base) – NMS394

• NCAMP Material Specification (Slash) – NMS394/1

• NCAMP Process Specifications - NPS 89394

• NCAMP Test Plan - NTP AC-9394Q1

• Adhesive Process Control Document (PCD) – NRP 105

• NCAMP - Adhesive Data Collection Forms

Current Status

49

C1 C2 C1 C2 C1 C2

CTD 3 3 3 3 3 3

ETD 3 3

ETW 3 3 3 3 3 3

RTD 3 3 3 3 3 3

CTD 3 3

ETD 3 3

ETW 3 3

RTD 3 3

CTD 3 3

ETD 3 3

ETW 3 3

RTD 3 3

CTD 3 3 3 3 3 3

ETD 3 3

ETW 3 3 3 3 3 3

RTD 3 3 3 3 3 3

CTD 3 3

ETD 3 3

ETW 3 3

RTD 3 3

CTD 3 3

ETD 3 3

ETW 3 3

RTD 3 3

CTD 3 3 3 3 3 3

ETD 3 3

ETW 3 3 3 3 3 3

RTD 3 3 3 3 3 3

CTD 3 3 3 3 3 3

ETD 3 3

ETW 3 3 3 3 3 3

RTD 3 3 3 3 3 3

ET 30

RT 30

Batch A Batch B Batch C

Thin Metal

Adherend

Lap Shear

D1002

Thick Metal

Adherend

Lap Shear

D5656 (T1)

Floating

Roller PeelD3167

Mode I

Fracture

Toughness

D3433

Mode II

Fracture

Toughness

D7905

Thick Metal

Adherend

Lap Shear

D5656 (T2)

Composite

Adherend

Lap Shear

D3165

D1002FSFluid

Sensitivity

Flatwise

TensileD897

EA9394

Property Test MethodTest

Environment

C1 C2 C1 C2 C1 C2

CTD 3 3 3 3 3 3

ETD 3 3

ETW 3 3 3 3 3 3

RTD 3 3 3 3 3 3

CTD 3 3

ETD 3 3

ETW 3 3

RTD 3 3

CTD 3 3 3 3 3 3

ETD 3 3

ETW 3 3 3 3 3 3

RTD 3 3 3 3 3 3

CTD 3 3

ETD 3 3

ETW 3 3

RTD 3 3

CTD 3 3

ETD 3 3

ETW 3 3

RTD 3 3

CTD 3 3 3 3 3 3

ETD 3 3

ETW 3 3 3 3 3 3

RTD 3 3 3 3 3 3

CTD 3 3

ETD 3 3

ETW 3 3

RTD 3 3 3 3 3 3

ET 30

RT 30

D3433

Thin Metal

Adherend

Lap Shear

D1002

Thick Metal

Adherend

Lap Shear

D5656

Flatwise

TensileD897

Mode II

Fracture

Toughness

D7905

Floating

Roller PeelD3167

Composite

Adherend

Lap Shear

D3165

Fluid

Sensitivity

FM300-2M

Property Test MethodTest

Environment

D1002FS

Mode I

Fracture

Toughness

Batch A Batch B Batch C

Waiting on Adhesive Batch

Specimen/Panel Bonding in Progress

Specimen Machining in Progress

Conditioning in Progress

Testing in Progress

Testing Complete

EA 9394 FM300-2M

Look Forward

• Future Activities

• Generate the B-Basis allowable for EA9394 and FM300-2M material systems

• Focus on performing equivalency on adhesive materials.

• Analyze failure modes for different test environments and report them accordingly

• Benefit to the Aviation Community

• Guidance on test matrices for mechanical, physical and chemical characterization of adhesives

• Generate adhesive material databases under NCAMP protocols that can be used for a wide variety of applications be different end users

50

Bond Process Qualification Protocols - Road Map

• Bond Process Qualification (BPQ)

• Develop an acceptance criteria

• Requirements (based on information in AC’s and FAR’s , etc.)

• Applicability of existing standards and/or develop new standards

• Select known bond system failures

• Simulate and investigate the BPQ methodology flags the “bad” bonds

• Develop protocols

• Quantify process reliability

• Assess repeatability/maturity

51

Allowables Database

Qualified Bonding System- Adhesive- Process- Substrate- Surface Prep

Process

Substrate

Surface Prep

Guidelines/Data(CMH-17)

Structural Bonding

Structural Application- Adhesive- Process- Substrate- Surface Prep

Qualify New Bonding System

Yes

No

Yes

No

No

Yes

Bonding System Qualification

Qualify Substrate & Surface Prep

Qualify Adhesive &

Bond Process

Statistical Analysis

Bond Process Qualification (Critical Factors)

52

Substrate

Metal Composites

Surface Preparation


Can be combined

Type

Primer





Adhesive


Paste Film

Mixing(for Paste)


TgViscosity





(ex., Amine Blush)

Paste Film


Adhesive Mix

Knit Random Mat

Unsupported




Adhesive





Treatment


• Substrate type• Metal• Composite

• Adhesive types• Film• Paste


Summary of Activities

• Current Activities

• Task 1 – Substrate and adhesive compatibility

• Task 2 – Use of peel ply for composite substrate preparation

• Completed Activities

• Effects of Mix-ratio in two part paste adhesives

• Evaluation of assembly time in paste adhesives

• Amine blush effects

• Fluid Sensitivity of adhesive

• Efficient adhesive screening method testing.

53

54

Qualification of a Bond Process

Substrate Adhesive System

Substrate Surface Preparation

Bonding Process/Curing

1. Composite2. Metal

1. Paste 2. Film

1. Abrasion 1. Grid Blasting2. Hand Sanding

2. Peel Ply1. Nylon2. Polyester

3. Chemical1. PAA + Priming

4. Other1. Plasma Treatment

1. Cure Cycle –Compatibility with Substrate

2. Vacuum or Pressure3. Bondline Control4. Assembly Time5. Adhesive Preparation6. Environment7. Bond Configuration –

Co-bond/Secondary bond

55

Qualification of a Bond Process




1. Composite2. Metal

1. Paste 2. Film

1. Abrasion 1. Grid Blasting2. Hand Sanding

2. Peel Ply1. Nylon2. Polyester

3. Chemical1. PAA + Priming

4. Other1. Plasma Treatment

1. Cure Cycle –Compatibility with Substrate

2. Vacuum or Pressure3. Bondline Control4. Assembly Time5. Adhesive Preparation6. Environment7. Bond Configuration –

Co-bond/Secondary bond

Task 1

Task 2

• When using bonded joints for primary or secondary structure applications, there is a wide variety of substrates and adhesive materials that are available for use. Providing Guidance on selecting a compatible substrate and a adhesive combination is important for designers.

• Main factors to consider during adhesive and substrate selection are the mechanical property requirements, physical compatibility of the substrates (hybrid and non-hybrid) and adhesives for bonding, thermal compatibility of the bond system during the bonding process and service life.

• Objective of this task is to provide establish a set of guidelines to use when selecting an adhesive and substrate combination for a given bond process.

Goal – Develop guidelines on how to select compatible substrate and adhesive combinations to obtain a robust bond system

Task 1 –Qualification of a Bond Process – Substrate and Adhesive Compatibility - Background and Goals

57

Task 1 - Qualification of a Bond Process – Substrate and Adhesive Compatibility

58




Compatibility

Physical Thermal

1. Surface Characterization1. Surface roughness2. Surface energy/ Contact angle3. Wettability envelope

1. CTE Mismatch2. Glass Transition3. Cure Cycle Compatibility

1. Secondary bond2. Co-bonded

Mechanical

1. Material allowable properties1. Substrate data -> NCAMP2. Adhesive data -> NCAMP (in

progress)2. Joint mechanical capability

1. Static 2. Durability

Task 1 - Substrate and Adhesive Compatibility

• Substrates

• Carbon Fiber Composites

• UNI – T800/3900-2

• PW - T300/3900-2

• Glass Fiber Composites

• Fabric – Epoxyglass G10

• Metallic

• AL 2024-T3

• Ti – Grade 2

59

• Adhesives

• Paste Adhesives

• Henkel EA9394

• Henkel EA9390

• Cytec 680-3

• Film Adhesive

• Cytec FM300-2M

• 3M-AF163

• Cure Cycles

• Manufacturer recommended cure cycle

• Surface Preparation Methods

• Carbon fiber composites

• As fabricated – MEK wipe only

• Peel ply only

• Peel ply + Light abrasion (180 grit)

• Abrasion only (120 grit)

• Glass fiber composites

• As fabricated

• Abrasion only(120 grit)

• Metallic substrates

• MEK wipe only

• PAA+BR127

• 3M - AC 130-2 surface treatment

• Abrasion

• Chemical treatment – ASTM D2651 (Ti)

Task 1 - Substrate and Adhesive Compatibility Assessment Physical Compatibility

• Objective

• Generate guidelines to ensure the surface preparation + substrates are physically compatible for bonding.

• Physical Compatibility

• Surface morphology related tests for substrates

• Surface roughness

• Contact angle

• Surface Energy

• Wettability envelope development

• Measure polar and dispersive surface energies for substrate and compare the surface energy of the adhesive.

• Objective:- A simplistic rapid approach to evaluate if the adhesive surface tension falls within the wettability envelope == Good bond

• Perform qualitative tests to assess the bond failures

• Wedge crack

• Rapid adhesion test

• Flatwise tensile

60

A

C

D

0

10

20

30

40

0 10 20 30

Dis

per

sive

/ m

N m

-1

Polar / mN m-1

Task 1 - Substrate and Adhesive Compatibility Assessment Physical Compatibility

• Develop the relationship between the

• Contact angle of substrates vs. bond quality.

• Elapsed time vs contact angle

61

• Use in-situ surface energy measurement techniques (BTG-Labs - Surface Analysts) to assess the substrate characterizations

• Repeat the process for a given adhesive for different mechanical properties (Shear, Peel, Fracture Toughness)

0

1000

2000

3000

4000

5000

6000

20 30 40 50 60 70 80

Bon

d S

tren

gth

Contact angle [°]

25

30

35

40

45

50

0 10 20 30 40 50 60

Con

tact

An

gle

[²]

Time [hrs]

Task 1 - Substrate and Adhesive Compatibility Assessment Physical Compatibility –Current Status

• Fabrication of composites test panels completed.

• Preliminary experiments completed for surface energy/contact angle measurements

• Guideline development for substrate preparation timeline is in progress

62

50

55

60

65

70

75

80

85

90

120 grit Sand Blast 120 grit Hand

Sand

150 grit Hand

Sand

180 grit Hand

Sand

Aver

age

Co

nta

ct A

ngle

[d

egre

es]

Surface Preparation Process

30

35

40

45

50

55

60

Point 1 Point 2 Point 3 Point 4 Point 5 Point 6 Point 7A

ng

le [

de

gre

es]

Second round

Two days

Task 1 - Substrate and Adhesive Compatibility Assessment Thermal Compatibility

• Objective

• Generate guidelines to ensure the thermal properties of substrates and adhesives are compatible for bonding and during service life.

• Thermal Compatibility

• CTE mismatch

• Between substrates and adhesives cured at elevated temperatures

• CTE mismatch in bonded structures during service life – Cold and elevated temperature environments –formation of micro cracks during thermal cycling

• Glass Transition Temperatures

• Mismatch in glass transition temperatures and out it could potentially effect the bond integrity

• Pose cure effect on the substrates (composites) for secondary bonded structures

• Understand how the critical mechanical and thermal properties change after exposing to high temperatures for long durations (cure profile of a adhesive)

63

In -

Pro

gre

ss

Substrate and Adhesive Compatibility Assessment Mechanical Properties

• Mechanical Properties

• Coupon level testing

• Perform coupon level testing to evaluate static and durability capability. (using the actual bond process that will be used for the application)

• Shear

• Peel

• Fracture toughness

• Element/Component level testing

• Fabricate a representative bonded structures

• Perform mechanical testing (static and fatigue)

• Assess the bond quality / Perform NDI

64

Fu

ture

Act

ivit

ies

Task 1 - Substrate and Adhesive CompatibilityAdditional Tasks

• Extend current research with industry partners to further investigate substrate adhesive compatibility.

• Substrate Material – Tencate T350-1/IM7

• Adhesive System – EA 9394

65

#Batch #Spec. #Batch #Spec. #Batch #Spec. #Batch #Spec.

0.015 1 6 1 6 1 6 1 6

0.04 3 18 3 18 3 18 3 18

0.08 1 6 1 6 1 6 1 6

0.125 1 6 1 6 1 6 1 6

Lap Shear and Stress/Strain ASTM D5656 - (Al – thick) 0.015 1 6 3 18 1 6 1 6

T-Peel ASTM D1876 - Composites 0.015 1 6 3 18 1 6 1 6

Floating Roller Peel ASTM D3167 0.015 1 6 3 18 1 6 1 6

Fracture Toughness ASTM D3433 0.015 1 6 3 18 1 6 1 6

Flatwise Tensile ASTM D897 0.015 1 6 3 18 1 6 1 6

Test Type Test MethodBondline

Thickness [in]

ASTM D3165 - Composites

ASTM D1002 - (Al -thin) 1 6 1 6Single Lap Shear 0.015 1 6 3 18

CTD RTD ETD ETW

Single Lap Shear

• Use of peel ply as a surface preparation method reduces the amount of labor involved and simplify the substrate preparation process. It also provides a uniform and repeatable surface for bonding

• Peel ply prepared surface quality vary on many substrate and surface preparation process parameters. Bond surface quality directly effects the bond integrity. Understanding the effects of these parameters is critical. Development of reliable and rapid inspection methods is crucial to ensure the bond process (surface preparation) method is appropriate for a given bond system.

• After an appropriate peel ply surface preparation method is chosen, there are many other parameters associated with handling substrates that could potentially change the quality of the bond surfaces. These parameters and their adverse effect on the bond integrity needs to be evaluated to provide Guidance and Develop Protocols to have a robust bond system.

Goal – Develop guidelines and protocols to handle peel ply prepared surfaces to obtain a robust bond system

Task 2 - Peel Ply Surface Preparation EvaluationBackground and Goals

66

SubstratesSurface

PreparationSurface

InspectionsBonding

X

Peel Ply Surface Preparation Evaluation

• Peel ply removal preparation method provides a repeatable uniformly prepared surface for bonding with, minimum labor.

• For guideline development, need to understand

• The effect of different peel ply materials and thicknesses

• Surface contamination created and ways to reduce it (during application and removal of peel ply and the timeframe of removal)

• Rapid inspection methods to ensure the surface quality of the substrates

• Peel ply prepared surface exposure to extreme environments (hot/wet)

• Any adverse effects to the laminate due to having the peel ply during cure cycle.

• Effects of peel ply prepared surfaces going through multiple cure cycles.

67


• Types of Peel Ply

• Polyester (Non Released)

• Wet (Henkel EA 9895)

• Dry

• T1 – 60002 (0.005 – 0.006-inch)

• T2 – 60005 (0.006 – 0.007 –inch)

• Nylon (Non Released)

• Wet (Henkel EA 9896)

• Dry

• T1 – 60004 (0.0045 – 0.0055-inch)

• T2 – 60005 (0.006 – 0.007 –inch)

• Polyester (Released)

• Dry

• T1 – 60001 (0.005 – 0.006-inch) (SRB)

68

• Carbon Composites Substrates

• Toray T800/3900-2

• Adhesive Systems

• Film – FM300-2M

• Paste – EA 9394

• Cure Cycles

• FM300-2M – 250F for 2 hrs. at 40 psi pressure + full vacuum

• EA 9394 – 150F for 1 hr. 6psi vacuum


• Surface Preparation Details

• Peel ply removal only

• Peel ply removal and light sanding (120 grit)

• Exposure to environment (Room temperature ambient and Elevated temperature wet)

• Remove peel ply immediately after curing

• Remove peel ply immediately before bonding (30 days)

• Effects of prepared substrates going through multiple cure cycles

• Co-bond and repair applications

• Thermal cycle substrates for multiple times to evaluate the effects

• Controlled/non peel ply configuration

• Carbon epoxy laminates without peel ply

• Hand Abrasion (120 grit)

• No surface preparation (MEK wipe only)

69

Peel Ply Surface Preparation EvaluationMethods of Bond Surface Quality Assessment

• Surface Characterization

• Surface roughness measurements

• Contact angle measurements

• Scanning electron microscopic (SEM) inspection for surface details

• X-ray photoelectron spectroscopy (XPS) to detect surface contamination

• Wettability Envelope Development

70

A

C

D

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25

Dis

per

sive

/ m

N m

-1

Polar / mN m-1

Peel Ply Surface Preparation EvaluationMethods of Mechanical and Physical Property Evaluation

• Fiber Volume Fraction Quantification

• Due to the resin absorption in peel plies, fiber volume fraction is affected

• Flatwise tensile testing to quantify the effect.

• Mechanical Property Assessment

• ASTM D1002/D3165 type Single lap shear to determine the shear strength

• ASTM D5528 to determine the fracture toughness properties

• Peel Ply Prepared surfaces going through multiple cure cycles

• Measure the degree of cure for repeated cure cycle – simulation of core bond and repair applications.

71

Summary of Activities

• Current Activities

• Task 1 – Substrate and adhesive compatibility

• Task 2 – Use of peel ply for composite substrate preparation

• Completed Activities

• Effects of mix-ratio in two part paste adhesives

• Evaluation of assembly time in paste adhesives

• Amine blush effects

• Fluid sensitivity of adhesive

• Efficient adhesive screening method testing.

72

Effects of incorrect mix-ratio in two part paste adhesives

• Two part adhesive for smaller quantities are available in cartridge form. (Mix ratio is not a concern) For applications that require larger quantities, common method is to obtain them in separate containers and manually mix it. It is important to evaluate the sensitivity of mix ratio in these applications

• Experimental Approach – used PAA+BR127 and Abrasion + AC120-2 prepared aluminum and carbon composite substrates and fabricated panels with different mix ratios for Part A and part B. Test methods evaluated are D1002 – single lap shear, mode I fracture toughness, and floating roller peel specimens (selected incorrect mix ratios).

• EA 9394 was used for the study with Part A mix ratio error ranging from -40% to +40%

73

Adhesive Adherend Percent 0.005" Glass Bead

Identification Material Mismatch A [g] B [g] Weight [g]

-40% 30.000 3.060 0.00331

-20% 30.000 4.080 0.00341

0.00351

0.00371

20% 30.000 6.120 0.00361

Adhesive Quantity

EA9394Aluminum

0.063"

40% 30.000 7.140

0% 30.000 5.100

Effects of incorrect mix-ratio in two part paste adhesivesTest Results – Single Lap Shear –ASTM D1002

74

0

500

1000

1500

2000

2500

3000

3500

4000

4500

-40% -20% 0% 20% 40%

Aver

age

Str

ength

[psi

]

Incorrect Mix Ratio – Part A Mismatch

Batch 1 - PAA Batch 2 - AC-130-2

Less than nominal Component B

More than nominal Component B

-40% -20% 0% 20% 40%

Adhesive/Cohesive Failures

Effects of incorrect mix-ratio in two part paste adhesivesTest Results – Mode I –ASTM D5528

75

0%

5%

10%

15%

20%

25%

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

-40% 0% 40%

Incorrect Mix Ratio – Part A Mismatch

Coef

fici

ent

of

Var

iati

on [

%]

GIC

(5%

/ M

AX

) [K

J/m

2]

Less than nominal Component B

More than nominal Component B

-40% -0% 40%

First Ply/Adhesive Failures

Effects of incorrect mix-ratio in two part paste adhesivesTest Results –Viscosity Response

76

-300

200

700

1200

1700

2200

2700

3200

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

-50 -40 -30 -20 -10 0 10 20 30 40 50

Visco

sity[p

]

No

rma

lize

d S

tren

gth

Ra

tio

Part A - % Mix RatioLess than nominal

Component BMore than nominal

Component BViscosity during bonding

Minimum viscosity during cure

Effects of incorrect mix-ratio in two part paste adhesivesTest results – Summary

• EA9394 adhesive system showed a ~±15% change in the mechanical properties of single lap shear and fracture toughness at the extreme mix ratios between -40% & +40%

• Repeatability of the experiment was validated with a second data set. Data correlates will with the original testing.

• No change in the failure modes was seen between the extreme ends of the experimental procedure.

• Static response of the properties are desirable. However, understanding of the mix ratio effect on fatigue properties needs to be investigated.

77

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

-50 -40 -30 -20 -10 0 10 20 30 40 50

No

rma

lize

d P

rop

ert

y

Part A - % Mix Ratio

D1002 - PAA

D1002 - AC-130-2

D5528 - Carbon Fiber Substrates

Evaluation of assembly time in paste adhesives

• Manufacturer provided pot life is to be used as a material specification. In bonding applications, assembly time is defined as the time it takes to mix, apply adhesive and mate the two parts together. Depending on the bond area and the complexity (contour) of the structure, this could be a critical parameter.

• Experimental Approach – used PAA+BR127 and Abrasion + AC120-2 prepared aluminum and carbon composite substrates and fabricated panels with different assembly times. Test methods evaluated are D1002 – single lap shear, mode I fracture toughness, and floating roller peel specimens (selected incorrect mix ratios).

• Assembly time for EA 9394 was varied from 0, 5, 45, 60, 90, and 120 minutes

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Evaluation of assembly time in paste adhesivesTest Results – Single Lap Shear –ASTM D1002

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0

500

1000

1500

2000

2500

3000

3500

4000

4500

5MIN 45MIN 60MIN 90MIN 120MIN

Aver

age

Str

ength

[psi

]

Assembly Time [min]

Batch 1 - PAA Batch 2 - AC-130-2

Higher % Adhesive Failures

Adhesive/Cohesive

Cohesive Failures

5 min 45 min 60 min 90 min 120 min

Evaluation of assembly time in paste adhesivesTest Results – Mode I –ASTM D5528

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0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

0.00

0.05

0.10

0.15

0.20

0.25

5MIN 60MIN 120MIN

Coef

fici

ent

of

Vari

ati

on

[%

]

GIC

(5

% /

MA

X)

[KJ/m

2]

5 min 60 min 120 min

First Ply/Adhesive Failures

Adhesive/Cohesive Failures

Cohesive Failures

Evaluation of assembly time in paste adhesivesTest Results –Viscosity Response

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0

2000

4000

6000

8000

10000

12000

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

1.10

0 20 40 60 80 100 120 140

Visco

sity [p

]

No

rma

lize

d S

tren

gth

Assembly Time [min]

Viscosity during bonding

Minimum viscosity during cure

Evaluation of assembly time in paste adhesivesTest results – Summary

• EA9394 adhesive system showed very significant effect for longer assembly times.

• Single lap shear strength reduced by ~ 20% when assembly time was 60 minutes. This started dropping to ~50% for 90 minutes (pot life)

• Mode I fracture toughness data showed a large scatter in test data for increased assembly times.

• Mode I data showed an increase in the properties for 60 minutes assembly and rapidly dropped when the assembly time was increased to 120min.

• Failure modes throughout all the failure modes indicated cohesive/adhesive failures until 60 minute assembly time and changed to cohesive after 60 minute mark.

• Static response of the properties are desirable. However, understanding of the mix ratio effect on fatigue properties needs to be investigated.

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0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

0 20 40 60 80 100 120 140

No

rma

lize

d S

tre

ng

th

Assembly Time [min]

D1002 - PAA

D1002 - AC-130-2

D5528 - Carbon Fiber Substrates

Fluid sensitivity of adhesive

• Current method used to evaluate the fluid sensitivity of adhesives is the D1002 single lap shear specimen configurations.

• D1002 Lap Shear specimen configurations requires treated substrate materials which involves numerous steps form preparation to storage.

• The adhesive area exposed to fluids is minimum. (Adhesive Thickness)

• A relatively simpler (test method + specimen geometry) bulk adhesive specimens were fabricated using the adhesive systems and simpler test configuration (3-pt bending) was used to evaluate the effects and compared with the current D1002 method.

• EA 9394 and FM300-2m material systems were used for the evaluation.

• Fluids used in this study

• Skydrol LD-4 (SAE AS1241, Type IV, Class 1) – 90 days

• MEK washing fluid. ASTM D740 – 90 minutes

• 145F/85% Relative Humidity 1000hrs – Controlled Condition

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Fluid sensitivity of adhesiveTest Results

84

0.0

0.2

0.4

0.6

0.8

1.0

1.2

BASELINE MEK - 90 Minutes Skydrol LD-4 - 90 days Moisture Conditioning

No

rma

lize

d S

tren

gth

3-pt Bend - EA 9394 D1002 - EA 9394

0.0

0.2

0.4

0.6

0.8

1.0

1.2

BASELINE MEK - 90 Minutes Skydrol LD-4 - 90 days Moisture Conditioning

No

rma

lize

d S

tren

gth

3-pt Bend - FM300-2M D1002 - FM300-2M

EA9394 FM300-2M

Adhesive Screening Test Methods

• Currently ASTM D1002 test method is being used to perform screening test/receiving inspections of adhesive material. ASTM D1002 requires a specialized substrates – treated chemical treatment/preparation method.

• As an alternate to this test method/substrate, Epoxyglass G10 substrates has been evaluated to be used in this type of screening testing.

• Different substrate thicknesses has been evaluated as well as a added new test method.

• ASTM D1002 – Al substrates – 0.063-in thick (PAA+BR127)

• ASTM D1002 – Epoxyglass G10 substrates – 0.062-in thick (Abrasion) –Thickness matched

• ASTM D1002 – Epoxyglass G10 substrates – 0.093-in thick (Abrasion) –EI matched

• ASTM D3165 – Epoxyglass G10 substrates – 0.25-in thick (Abrasion) -Standard

• Adhesive systems evaluated

• FM300-2M and EA9394

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ASTM D1002

ASTM D3165

Adhesive Screening Test MethodsTest Results

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0%

1%

2%

3%

4%

5%

0

500

1000

1500

2000

2500

3000

3500

4000

4500

EPOXYGLASS 0.25'' EPOXYGLASS 0.093'' EPOXYGLASS 0.063'' AL 2024 0.063''

Co

effi

cien

t o

f V

ari

ati

on

[%

]

Ap

pa

ren

t S

hea

r S

tren

gth

[p

si]

EA 9394

0%

1%

2%

3%

4%

5%

6%

7%

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

EPOXYGLASS 0.25'' EPOXYGLASS 0.093'' EPOXYGLASS 0.063'' AL 2024 0.063''

Co

effi

cien

t o

f V

ari

ati

on

[%

]

Ap

pa

ren

t S

hea

r S

tren

gth

[p

si]

FM300-2M

Adhesive/Cohesive FailuresAdhesive Failures Adhesive/Cohesive FailuresAdhesive

Failures

Adhesive Screening Test MethodsSummary

• In a receiving inspection/screening tests, it is usually a Pass/Fail criteria

• Epoxyglass substrates can be used for screening/receiving inspection tests. Baseline tests needs to be performed for the identical specimen configurations.

• Higher variation is seen in the bondline thickness for 0.25-inch thick epoxyglass substrates. Bonding process/bondline control mechanism needs to be revisited to get the required bondline thicknesses.

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Looking Forward

• Future Works

• Generate bond process protocols for

• Selecting compatible substrate and adhesive combinations for a robust bond structure

• Provide guidelines on how to select and use peel ply for composite substrate preparation

• Benefit to Aviation

• Generate bond process protocols

• Provide guidance on the critical parameters in the bond process and how to mechanically test them to generate protocols

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Acknowledgement

• Advisory Committee and Program Guidance (FAA)

• Cindy Ashforth

• Curt Davies

• Larry Ilcewicz

• Ahmet Oztekin

• Program Support

• Shannon Jones (Textron Aviation)

• Tony Hinman (Solvay)

• John Marsicano (Henkel)

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• Document Review

• Rachael Andrulonis (NIAR)

• Bryce Floryancic

• Shannon Jones (Textron Aviation)

• Wei Kwan

• Royal Lovingfoss (NIAR)

• Molly Stone

• Mike Stuart (Solvay)

Adhesive Bond Process Qualification Protocols Development & Development of … · 2019-06-03 ·...

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