Adhesive Behavior in Aircraft Applications Adhesive Behavior in - PowerPoint PPT Presentation

RESEARCH / DESIGN / TESTING / CERTIFICATION Adhesive Behavior in Aircraft Applications Adhesive Behavior in Aircraft Applications N y N x John Tomblin Waruna Seneviratne N xy Paulo Escobar N xy Yoon-Khian Yap N xy Pierre Harter N xy National Institute for N x N y Aviation Research Wichita State University FAA Workshop on Key Characteristics for Advanced Material Control September 16 – 18, 2003

NATIONAL INSTITUTE FOR AVIATION RESEARCH Wichita State University Program Overview • Coupon Level Testing – Investigation of Thick Bondline Adhesive Joints • Adhesive test methods • Bondline thickness effects • Environmental effects [FAA Report: DOT/FAA/AR-01/33] – Characteristic Shear Responses of Structural Adhesives [FAA Report: DOT/FAA/AR-02/97] – Fatigue & Stress Relaxation of Adhesive Joints [FAA Report: Submitted to FAA] • Subcomponent Testing & Analysis – Box Beam Torsion Lap Shear Test – Shear Loaded Bonded Joint (SLBJ) Theory [Purdue University] [FAA Report: DOT/FAA/AR-03/21] Available electronically at http://actlibrary.tc.faa.gov

NATIONAL INSTITUTE FOR AVIATION RESEARCH Wichita State University Research Effort Funded by FAA Industry Partners Partnered with Purdue University

NATIONAL INSTITUTE FOR AVIATION RESEARCH Wichita State University Motivation • Number of certification programs involve a large range of adhesive bonding applications • Migration from secondary to primary structure • Limited guidance material existed • Limited experimental analytical models that can be effectively used in design

NATIONAL INSTITUTE FOR AVIATION RESEARCH Wichita State University Motivation (contd..) • Traditional bondline thicknesses used : less than 0.010” • Current bondline thicknesses : up to 0.140” • Generate data regarding the effects of thick bondlines • Long term durability of adhesive Closeout A Bonded to Spar Caps joint (fatigue/creep) needs to be Section A-A addressed with respect to thick Bending and A Torsion Loads bondline joints Pinned Joints Through Spar Web Wing Skin Bonded Directly to Spar Caps

NATIONAL INSTITUTE FOR AVIATION RESEARCH Wichita State University Adhesive Test Methods 7000.0 6000.0 Apparent Shear Strength (psi) Adhesive/Cohesive 5000.0 4000.0 Adhesive/Cohesive 3000.0 Adhesive Adhesive 2000.0 ASTM D1002 ASTM D3165 1000.0 ASTM D5656 0.0 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 Average bondline thickness (in) • ASTM D1002 & D3165 for joint characterization • ASTM D5656 for adhesive characterization

NATIONAL INSTITUTE FOR AVIATION RESEARCH Wichita State University ASTM D5656 Test Method • Thick adherend – Adhesive characterization rather than Joint characterization – Elastic Limit & Plastic Strain – Design & Analysis – Reduced peel stresses • Correction for metal deformation • Four-Pin Configuration – Reduces errors due to rotation and slippage – Reduced scatter in data

NATIONAL INSTITUTE FOR AVIATION RESEARCH Wichita State University Failure Modes ASTM D5656

NATIONAL INSTITUTE FOR AVIATION RESEARCH Wichita State University Bondline Thickness Effects 4500 4000 3500 3000 PTM&W ES6292 Shear Stress 2500 Bondline Thickness 2000 t = 0.013 in 1500 t = 0.043 in t = 0.083 in 1000 t = 0.123 in 500 0 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 Shear Strain • Increasing bondline thickness resulted in reduced plastic strain and lower yield stress

NATIONAL INSTITUTE FOR AVIATION RESEARCH Wichita State University Environmental Effects 7000 CTD Bondline Thickness = 0.013" nom. 6000 Tg (dry) = 175°F RTD Tg (wet) = 135°F MGS 5000 A100/B100 Shear Stress (psi) ETD 160° 4000 ETW 160° ETD 200° 3000 ETW 200° 2000 1000 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Shear Strain • Yield stress and stiffness decreased with increasing temperature and humidity • Environmental condition affects failure mode

NATIONAL INSTITUTE FOR AVIATION RESEARCH Wichita State University Characteristic Shear Responses of Structural Adhesives • 18 Adhesive Types – 6 Film Adhesives – 12 Paste Adhesives • ASTM D5656 [4 pin holes] • Three Environmental Conditions – Room Temp. ambient [RTD] – Elevated Temp. (180°F) dry [ETD] – Elevated Temp. (180°F) wet [ETW] • 145 °F and 85% relative humidity for 1000 hrs • Bondline Thickness – Film Adhesives: 0.01” – 0.03” – Paste Adhesives: 0.03” – 0.05”

NATIONAL INSTITUTE FOR AVIATION RESEARCH Wichita State University Adhesive Types Investigated � Film Adhesives (6) � Paste Adhesives (12) – AF 126 – EA 9309.3 NA – EA 9628 – EA 9346.5 – EA 9695 – EA 9359.3 – EA 9696 – EA 9360 – FM 300 – EA 9392 – FM 73 – EA 9394 – EA 9396 – MGS L418 – PTM&W ES 6292 Adhesives & Aluminum sub-panels – 3M DP-460 EG (Phosphoric Anodized) were provided by Cessna Aircraft, Wichita, KS – 3M DP-460 NS – 3M DP-820

NATIONAL INSTITUTE FOR AVIATION RESEARCH Wichita State University Apparent Shear Strength Comparison 7 RTD ETD ETW 6 Film Adhesive 5 Shear Strength (ksi) 4 3 2 7 RTD 1 ETD ETW 6 0 6 6 0 0 3 3 8 8 5 5 6 2 2 0 0 7 7 2 2 9 9 9 1 3 3 1 6 6 6 6 6 M 5 M 9 9 9 9 9 F F M M F F A A A A A A A F F E E E E E Shear Strength (ksi) Film Adhesive 4 3 2 1 Paste Adhesive 0 A 5 3 3 0 0 0 2 2 4 6 8 2 G S 0 . . . 6 6 6 9 9 9 9 1 9 2 N 6 9 9 E N 3 3 3 3 3 3 3 4 2 8 4 5 5 3 9 9 9 9 L 6 0 - 3 3 3 9 9 9 0 P . 9 9 S 6 6 9 9 A A A A A A A S D 4 4 0 E E E E E E E G E A A A - - 3 P P M E E E M 9 W D D 3 A & M M E M 3 3 T P Paste Adhesive

NATIONAL INSTITUTE FOR AVIATION RESEARCH Wichita State University Shear Modulus Comparison 0.20 RTD ETD ETW 0.18 0.15 Film Adhesive Shear Modulus (Msi) 0.13 0.10 0.08 0.05 0.03 0.00 6 6 0 3 3 8 8 5 5 6 0 2 7 7 2 2 2 9 9 9 0 0 1 1 6 6 6 6 6 3 3 0.20 M M RTD 9 9 9 9 9 F F M M F F A A A A A A A F F E E E E E ETD Film Adhesive 0.18 ETW 0.15 Shear Modulus (Msi) 0.13 0.10 0.08 0.05 Paste Adhesive 0.03 0.00 5 3 3 8 S 0 A 0 0 0 2 2 4 6 2 G . 1 N . . 6 6 6 9 9 9 9 9 N 2 6 9 9 4 E 3 3 3 3 3 3 3 2 8 4 5 5 L 3 9 9 9 9 9 9 9 6 0 0 - 3 3 3 P . 6 6 9 9 9 9 A A A A A A A S S 4 D 0 G 4 A A A E E E E E E E E - - P 3 M P M E E E 9 W D D 3 A & M M E M 3 3 T P Paste Adhesive FAA Final Report: DOT/FAA/AR- -02/97 02/97 FAA Final Report: DOT/FAA/AR

NATIONAL INSTITUTE FOR AVIATION RESEARCH Wichita State University Fatigue of Thick Bondline Adhesive Joints Modified ASTM D3166-99 [Aluminum Adherend of 0.375”] Three Frequencies • Three Adhesives • – F=2 H z , 5 H z and 10 H z – PTM&W [0.060” & 0.160”] – Loctite [0.032”] – EA9696 [0.02”] Three Environmental • Conditions Three Stress Levels • – RTD, RTW – 10 3 , 10 4 and 10 5 cycles – CTD (-40°F)

NATIONAL INSTITUTE FOR AVIATION RESEARCH Wichita State University Stress Level Determination 100 90 Based on the initial SN 80 Curve 70 y=-3.227*ln(x)+100.96 60 % of Ultimate 50 40 100000Cy SL1 ≈ 65% UL ≈ 183% LL Loctite 10000Cy SL2 ≈ 72% UL ≈ 202% LL 30 (RTD) 1000Cy SL3 ≈ 78% UL ≈ 220% LL 20 10 Note: For RTW and CTD, %UL are 0 0 200000 400000 600000 800000 1000000 1200000 different Number of Cycles

NATIONAL INSTITUTE FOR AVIATION RESEARCH Wichita State University Loctite Stress Levels Loctite CTD Loctite RTD 6 0 0 0 3 0 0 0 5 0 0 0 2 3 0 6 p s i 4 0 0 0 2 117 p s i 19 18 p s i 3379 p s i 2 0 0 0 3102 p s i 2810 p s i 3 0 0 0 Lin e a r Lim it Lo a d 3 9 3 lb s (1 04 8 p si) Lin e ar Lim it Load 576 lb s (1536 p s i) 2 0 0 0 10 0 0 10 0 0 0 0 0 0 .1 0 .2 0 .3 0 .4 0 .5 0 .6 0 0 .1 0 .2 0 .3 0 .4 0 .5 0 .6 S h e a r S t ra in (in /in ) S h e a r S t ra in (in /in ) Loctite RTW 3 0 0 0 2 5 0 0 2 0 0 0 Fatigue life in a range below 15 0 0 1324 p s i 1215 p s i 1101 p s i knee point and above linear 10 0 0 Lin e ar Lim it Load 225 lb s (600 p s i) limit point. 5 0 0 0 0 0 .1 0 .2 0 .3 0 .4 0 .5 0 .6 S h e a r S t ra in (in /in )

NATIONAL INSTITUTE FOR AVIATION RESEARCH Wichita State University Fatigue Behavior of Adhesives 100 100 100 95 95 95 RTD RTD RTD RTW 90 90 90 RTW RTW CTD CTD CTD 85 85 85 80 80 80 SL3 SL3 SL3 75 75 75 % of Ultimate % of Ultimate % of Ultimate SL2 SL2 SL2 70 70 70 SL3 SL3 SL3 SL1 SL1 65 65 SL1 65 SL2 SL2 SL2 60 60 60 SL1 SL1 SL1 55 55 55 SL3 SL3 SL3 50 50 50 SL2 SL2 SL2 45 45 45 SL1 SL1 SL1 40 40 40 100 1000 10000 100000 1000000 10000000 100 1000 10000 100000 1000000 10000000 100 1000 10000 100000 1000000 10000000 Number of Cycles Number of Cycles Number of Cycles 2 Hz 5 Hz 10 Hz