Healable, Shape Memory Polymers for Reflexive Composites

Transcription

1 Healable, Shape Memory Polymers for Reflexive Composites Thomas Barnell Research Engineer This work was funded under a NASA SBIR, Contract number NNL06AA07C from NASA Langley. barnelltj@crgrp.com (937) x 164

2 Presentation Outline Technology Overview Project Objectives Reflexive Structures Applications Material Development Healing Concept Healable Shape Memory Polymers (SMP) Experiments and Results Neat Resin Testing Carbon Fiber Reinforced (CFR) Composite Testing Future Work Formulation Optimization Testing

3 Program Goals and Objectives Program Goal Develop & demonstrate autonomous damage sensing & repairing of composite aircraft structures Technical Objectives Develop discrete heating system Integration of sensor & heating system Optimize healable SMP resins Develop autonomous control system Characterize performance Commercialize healing SMP resins through CRG Industries Commercialize reflexive composite systems through CRG Inc.

4 Damage Occurs Damage Detected Damage Reported Healing Reported Damage Healed Damage Healing

5 Reflexive Structures Structural Health Monitoring (SHM): Sensing layer piezoelectric ceramics Active sensing compare damage data to baseline (healthy) data Intelligent Structural Control System: Damage prioritization size, location, magnitude, etc. Healing implementation time, power, temperature Discrete healing co-cured foil Kapton heater Healable Shape Memory Polymer Recover form Shape memory effect Recover performance Polymer chain diffusion Damaged 2 Min. healing 5 Min. healing

6 Reflexive Structures Benefits: Increased survivability Decreased maintenance Weight savings reduced damage tolerance Implement SHM, healable material, or both Industries Aerospace Wing skins, Structural components Automotive Panels Energy Wind turbine blades Infrastructure Bridge decking Previous Work Microencapsulation White Microvascular Sottos Reversible reaction Wudl Thermoplastic additive Hayes

7 Healable Shape Memory Polymer Dual Healing Mechanisms: Shape memory effect Reptation model (de Gennes) Break Time Ends move Centers move Centers on break Estimated elapsed time t = 0.05 Sec

8 Healable Shape Memory Polymers Materials: Styrene-based SMP modification of Veriflex Materials: Styrene SMP A Styrene SMP B Formulation method: Incorporation of thermoplastics in thermoset matrix Epoxy-based SMP modification of Veriflex E Materials: Epoxy SMP A Epoxy SMP B Formulation method: Increase thermoplastic character of material via reactive additives Chemical Crosslink Free Chain

9 Neat Resin Testing SMP properties Styrene SMP A and Epoxy SMP A T g s are tailorable for specific applications Glass transition, T g ( C) Tensile Elongation (%)* Tensile Modulus (Mpa)* Styrene SMP A Epoxy SMP A * tested at 30 C above T g Tensile and Flexural Properties Styrene SMP A and Epoxy SMP A Baseline: EPON 826 / EPI-CURE 9551 Strength (Mpa) Modulus (Gpa) Deformation (%) Tensile (ASTM D638) Styrene SMP A Epoxy SMP A Epon Flexural (ASTM D790) Epoxy SMP A Epon

10 Neat Resin Testing Neat healing test Epoxy SMP A ASTM D5045: Plane-strain fracture toughness and strain energy release rate of plastic materials Single edge notch bend (SENB) test Specimens taken to complete failure Healed at 92 C for one hour Re-tested Storage Modulus 350 Loss Modulus Values reported: Maximum load 250 Stress intensity factor (K I c) 200 Energy release rate (G I c) 100 Storage Modulus (MPa) Loss Modulus (MPa) Temperature ('C) DMA of Epoxy SMP A UTM Test setup

11 Neat Resin Testing Epoxy SMP A results Maximum Load 80% recovery Stress intensity factor, K I c 66% Strain energy release rate, G I c 37% Average of test specimens (>3x) healing percentages KIc (MPa*m^0.5), GIc (kj/m^2)_ Before Damage KIc (Mpa-m1/2) GIc (kj/m2) Max load (N) Max Load (N) ASTM D5045, SENB 0 After Healing

12 Composite Testing Composite healing test ASTM D790: Flexural properties of unreinforced and reinforced plastics and electrical insulating materials (3-point bend) Composites: 12 ply 3k plain weave [0,90] carbon fabric Styrene SMP A and B, Epoxy SMP A and B, Baseline (EPON 826/EPI-CURE 9551) VARTM infused One specimen of each material taken to complete failure max stress noted Other specimens taken to 110% deformation at max stress induce matrix failure Suspended in oven and healed at 30 C above T g Re-tested for one hour ASTM D790 Specimens after initial failure and subsequent healing

13 Composite Testing 800 Flexural Strength Recovery: 700 Styrene SMP A 89% Styrene SMP B 85% Epoxy SMP A 78% Epoxy SMP B 85% Flexural Strength (MPa) Styrene SMP A Styrene SMP B Epoxy SMP A Epoxy SMP B Epon 826 Epon 826 / Epi-cure % No recovery of form Before Damage After Healing Flexural Modulus Recovery: Flexural Modulus (GPa) Styrene SMP A Styrene SMP B Epoxy SMP A Epoxy SMP B Epon 826 Styrene SMP A 93% Styrene SMP B 88% Epoxy SMP A 80% Epoxy SMP B 78% 5 Epon 826 / Epi-cure % 0 Before Damage After Healing

14 Summary Healing performance: Rapid, simple, and repeatable healing mechanism Epoxy SMP A offers superior combination of healing and performance Restores shape and mechanical performance Future work (resin system): Neat healing testing on baseline Resin reformulation based on results Marine compatible resin system Fiber/matrix interface investigation Further healing testing Different times and temperatures Repeated healing cycles Compression after impact (CAI)

15 Acknowledgements NASA Langley: Mark Cagle CRG: Sam Knutson Chris Jensen