Interlaminar Fracture Toughness of 5 Harness Satin Woven Fabric Carbon Fiber/Epoxy Composites

Abstract

This paper presents experimentally obtained results of mode-I and mode-II interlaminar fracture toughness (G IC and G IIC) of unidirectional and 5 harness satin (5HS) woven fabric carbon fiber/epoxy composites (CFRPs). The mode-I delamination resistance of 5HS specimens, which was evaluated using a double cantilever beam (DCB) method, depends on the weave pattern and the ply stacking sequence at the delamination growth plane. Higher toughness was observed for crack propagation between surfaces with more transverse bundles (L–T and T–T plane) than those with more longitudinal bundles (L–L plane) because of transverse tow delamination pinning the crack and causing it to arrest. The intrinsic mode-I fracture toughness values of the 0°/0°, 0°/90° and 90°/90° fiber combinations were estimated from the G IC values obtained from three kinds of 5HS specimens which have different mid-plane stacking patterns (L–L, L–T and T–T). The G IC of 0°/0° combination corresponded to that of unidirectional specimen. The G IC of 0°/90° combination was almost identical to that of 90°/90° combination. Results suggest that the interlaminar fracture toughness of woven fabric composites can be estimated from the G IC of 0°/0° and 0°/90° (or 90°/90°) combinations.