POST-IMPACT FATIGUE BEHAVIOR OF CFRP LAMINATESFOR MARINE USE

摘要

The damage tolerance performance was comparatively evaluated in terms of CAIstrength and damage progression under tension–compression fatigue loading based on the samecoupon specimen level in CFRP woven fabric laminates for marine use. The concerned materials areT300 plain woven fabric, / vinyl-ester based on resin transfer molding (RTM). Fatigue tests wereconducted on impact damaged coupon specimens of CFRP laminates with two damage levels forBVD (barely visible damage) and NVD (non visible damage) under three levels of maximum stress,75 %, 65 % and 55 % of CAI strength, at a frequency of 5 Hz and stress ratio of R=-1. The impactdamage and its growth behavior of CFRP laminates were successfully monitored using thermo elasticstress analyzer (TESA) and ultrasonic C-scan. It was clarified that the images of damage area wereapparently different between the C-scan and the TESA, but that the damage growth behavior was wellmonitored similarly either by the TESA image and the ultrasonic C-scan image. As the TESA imagegives the sum of principal stresses at surface, it was shown that the damage growth behavior was wellobserved by the “in-situ” damage imaging. The apparent stress relaxation at surface in the TESAimage was successfully simulated by a FEM damage model in which delamination and crack aresimultaneously combined.