Effects of Temperature and Fiber Orientation on the Mode I Interlaminar Fracture Toughness of Carbon/epoxy Composites

Delamination is a predominant failure mechanism in composite structures. In the present study, double cantilever beam tests were performed to investigate the effects of temperature and fiber orientation on the Mode I interlaminar fracture toughness, G I , of carbon fiber-reinforced epoxy composites, T800H/#3631. The values of G I for three kinds of laminates, [0 12 //0 12 ], [22.5/-22.5/0 8 /-22.5/22.5//-22.5/22.5/0 8 /22.5/-22.5] and [45/-45/0 8 /-45/45//-45/45/ 08/45/-45], with a pre-cracked interface, that is // in each laminate, were obtained at various temperatures, i.e., -100°C, 20°C and 150°C. Fracture surface observation was also carried out by a scanning electron microscope and optical microscope. It is shown that G I is obviously affected by the temperature and fiber orientation. In the case of the specimen with delamination at 0//0, the fracture morphology changes as the delamination increases, but the value of fracture toughness for initiation G IC is not so different from the one for propagation G IR , and the fracture toughness of the specimen with 0//0 is little affected by the temperature. However, GIR of the specimen with 22.5//-22.5 shows a remarkable temperature dependence at a large crack length region. In case of the specimen with 45//-45, G IR is considerably affected by both failure mechanisms of crack jumping and fiber bridging, and the effect of temperature on G IR is less than the case of 22.5//-22.5.