Effect of fiber orientation and moisture absorption on the interlaminar fracture toughness of CFRP laminates

This study has clarified the effects of fiber orientation and the moisture content on G(IC)/G(IR) (Mode I energy release rate at initiation/propagatio n) and G(IIC)/G(IIR) (Mode II energy release rate at initiation/propagation ) in CFRP laminates. The interlaminar fracture toughnesses at the 0/0, 30/- 30, 60/- 60, 0/90, and the (0/90)/(0/90) plain weave interfaces were measu red using the DCB (Double Cantilever Beam) test and the ENF (End Notched Fl exure) test. For the 0/0 interface, the interlaminar fracture toughness und er dry, 50% relative humidity equilibrium, and wet conditions were also mea sured. Fiber orientations at delaminated surfaces were found to affect the interlaminar fracture toughness at initiation (G(IC) and G(IIC)) slightly, and the interlaminar fracture toughness during propagation (G(IR) and G(IIR )) strongly. Also, the degree of moisture absorption affected G(IC) slightl y, anf G(IR) strongly. In Mode II, G(IIC) was strongly affected by the degr ee of moisture absorption. Contrary to this, G(IIR) was not affected by moi sture absorption.