热塑性复合材料的Ⅰ型层间断裂韧性

对一种新型热塑性复合材料的Ⅰ型层间断裂韧性进行了研究。将非线性能量释放率作为层间断裂的控制参量,并提出用非线性因子法和改进的能量面积积分法计算。两种方法的结果非常接近,均能较好地反映韧性基体复合材料的层间断裂韧性。SEM照片分析表明,纤维和树脂界面强度过低是造成热塑性复合材料层间断裂韧性远低于基体断裂韧性的原因。另外,层间断裂韧性随加载速率增加而减小,在单对数坐标系下两者呈线性关系。

MODE I INTERLAMINAR FRACTURE OF THERMOPLASTIC COMPOSITES

The mode 1 inierlaminar fracture toughness of a new thermoplastic composite T300 / PEK-C is investigated in this paper. The hinged double cantilever beam specimen is used to test Inierlaminar fracture toughness. The load-displacement curve appears nonlinear before unstable deiamination growth. This is caused mainly by matrix plasticity near crack tip. In order to evaluate interlaminar fracture properties of thermoplastic composite laminates correctly, the nonliner energy release rate G1C is defined which is taken as the interlaminar fracture toughness of thermoplastic composite, and the nonlinear correction and modified energy area integration methods are adopted to calculate G 1C. The results indicate that the values of G calculated by nonlinear correction method are in good agreement with those from modified area method and both of them are about ten percent higher than the results obtained by linear compliance and area methods. But the interlaminar fracture toughness of composite T300 / PEK-C is only half of the fracture toughness of the matrix. The SEM photos show that the reason for low interlaminar fracture toughness is the poor interface strength In addition, the G1C of composite T300/PEK-C decreases with increase in loading speed, and under coordinates of G 1C and logarithmic loading speed a linare relation is shown. The SEM micrograph shows that its mechanism is the tough-brittle transform of matrix.