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

Abstract

This study has clarified the effects of fiber orientation and the moisture content on GIC/GIR (Mode I energy release rate at initiation/propagation) and GIIC/GIIR (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 measured using the DCB (Double Cantilever Beam) test and the ENF (End Notched Flexure) test. For the 0/0 interface, the interlaminar fracture toughness under dry, 50% relative humidity equilibrium, and wet conditions were also measured. Fiber orientations at delaminated surfaces were found to affect the interlaminar fracture toughness at initiation (G1C and GIIC) slightly, and the interlaminar fracture toughness during propagation (GIR and GIIR) strongly. Also, the degree of moisture absorption affected GIC slightly, anf GIR strongly. In Mode II, GIIC was strongly affected by the degree of moisture absorption. Contrary to this, GIIR was not affected by moisture absorption.