Effect of Water Absorption on Compressive Strength after Impact and Post Impact Fatigue Behavior of Woven and Knitted CFRP Laminates

Abstract

The effect of water absorption on the compressive strength after impact (CAI strength) and the post impact fatigue (PIF) properties of CFRP laminate were evaluated. Materials used were plain woven T300B-3K CFRP laminates and multi-axial knitted T700S-12K CFRP laminates molded by the vacuum assisted resin transfer molding (VARTM) method with vinylester as the matrix. Coupon specimens, which were applied the impact energy (1 J per unit thickness), were soaked in a water bath at 95oC for 120 hours up to the saturation water content of 0.6 wt%. CAI and PIF strengths of ‘Dry’ and ‘Wet’ specimens of plain woven CFRP showed almost same values. Thus, for T300B plain woven CFRP laminates, the effect of water absorption on PIF properties was small. On the other hand, multi-axial knitted CFRP laminates showed the large effect of water absorption, and Wet specimens showed lower PIF properties than Dry ones. However, net CAI and PIF strengths of multi-axial knitted CFRP were larger than that of plain woven CFRP.