Effects of temperature and stacking sequence on the mode I interlaminar fracture behavior of composite laminates

The purpose of the present study was to clarify the effects of temperature and fiber orientation on the Mode I interlaminar fracture toughness, G_I (G_IC: G_I at initiation, G_IR: G_I at propagation), of carbon/epoxy composite laminates. In our previous study, the conventional double cantilever beam (DCB) tests were performed to investigate the effects of temperature and fiber orientation in CFRP laminates. It was shown that G_I was obviously affected by the temperature and fiber orientation. Especially, in case of the specimen with [45//-45] interface, G_IR was considerably affected by both failure mechanisms of crack jumping and fiber bridging. Therefore, in the present study, to suppress the effects of crack jumping and fiber bridging occurred in multidirectional laminates, the side notched double cantilever beam (SN-DCB) specimen is used. DCB tests of [22.5//-22.5] and [45//-45] SN-DCB specimens are conducted at three temperatures, that is, -100°C, 25°C and 150°C. G_IC was affected by temperature and fiber orientation, obviously and slightly, respectively. In contrast to G_IC, G_IR was considerably affected by both temperature and fiber orientation.