Interfacial Fracture Toughness of Carbon Fiber Reinforced Composites

Abstract

Interfacial fracture toughnesses of composite Mode I and Mode Ⅱ were investigated by double cantilever beam (DCB) and end notch bending (ENF) test. Using stereo microscope to record crack tip and CCD camera position to observe the evaluation of lesion, the phenomenon of matrix cracking and layer extension were analyzed, and the characteristics of interlayer fracture were studied. The effect of curing method on fracture toughness was analyzed through contrast experiment. The results show that crack propagation process is not stable and the load fluctuates up and down with the increase of displacement and crack length in fracture toughness test of Mode I , while the crack produced in fracture toughness test of Mode Ⅱ does not extend initially and the load increases linearly with the displacement. When the load approaches the critical load P_c, the crack propagates unsteadily along the layer and the load drops sharply. Fracture toughness of Mode I material prepared by autoclave curing is 43% more than that of the material prepared by hot-bonder curing, while fracture toughness of Mode Ⅱ material prepared by autoclave curing is 19% more than that of material prepared by hot-bonder curing.