Long-Term Durability of Pitch-Based High Modulus Carbon Fiber Reinforced Plastics

Abstract

Abstract Static tensile and tensile-tensile fatigue were conducted on PITCH-based high modulus carbon fiber reinforced plastics (CFRP). PAN-based intermediate and high modulus CFRP were also tested for comparison.. Unidirectional laminates were prepared with wet panel method. The damage mode for high modulus CFRP was fiber breakage for both static and fatigue loading, whereas splitting was dominant for intermediate modulus CFRP. The slope of the S-N curve was larger for the intermediate modulus CFRP than that for the high modulus CFRP. This is attributed to the lower failure strain of the high modulus carbon fibers. That is, the larger strain on intermediate modulus CFRP at lower stress level comparing with high modulus CFRP caused severer matrix damages during fatigue loading. This results indicated the higher durability of high modulus CFRP. Residual strength measurement were conducted on the un-broken PITCH-based CFRP up to 1,000,000 cycles with acoustic emission measurements. The Kaiser effect was not satisfied for the specimen with lower residual strength at the stress level of the fatigue test. In addition, gradual acoustic emissions with longer duration and rise time were measured before final fracture in the static tests. These results indicated the possibility to detect the microscopic damage monitoring for the CFRP with acoustic emission measurement focusing on the duration of the acoustic wave.