Paper number 276

EFFECTS OF TEMPERATURE AND FIBER ORIENTATION ON THE MODE I INTERLAMINAR FRACTURE TOUGHNESS OF CARBON/EPOXY COMPOSITES

Hyoung Soo Kim¹, Wen-Xue Wang² and Yoshihiro Takao²

1Department of Aeronautics and Astronautics, Graduate School of Engineering, Kyushu University, 6-10-1, Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
2Research Institute for Applied Mechanics, Kyushu University, 6-1, Kasuga-koen, Kasuga, Fukuoka 816-8580, Japan

Summary

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/ 0 8 /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 fracturetoughness of the specimen with 0//0 is little affected by the temperature. However, G IR 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.

Keywords

temperature, fiber orientation, composite materials, DCB testing, mode interlaminar fracture toughness.