用能量法确定层状复合材料疲劳裂纹的扩展方向

含裂纹体疲劳寿命的预测,必须首先了解裂纹扩展路径的全过程,而在层状复合材料中,裂纹扩展的路径非常复杂,不仅可以拐弯,而且可以分叉.因此,首先提出一个简单、适用、统一的裂纹扩展方向的相对强度准则,即应变能释放率比值判据;然后,利用有效解决高梯度问题的数值方法--任意线法,对实测试件的关键时刻(例如,拐弯或进入界面),进行了数值分析;并对典型试件进行了疲劳断裂实验研究.3方面的结果,得到相互的验证.这种一致性,不仅初步证明了这一方法的正确性和适用性,而且为疲劳裂纹扩展全过程的解决,提供了必要的基础.

The Study of Fatigue Crack Growing Directions in Laminated Composites by Using Energy Method

In order to predict the fatigue life of the cracked bodies, it is necessary, first of all, to find cot the whole process of the crack growth. Because the crack can not only kink out of the interface but also bifurcate in the laminated composites, its growing path is very complicated. So, at first, a relative Strength criterion. (i. e. the energy release rate ratio criterion), which is simple, suitable and unified, should be proposed to determine the growing direction of the fatigue crack. Then, the numerical method-Method of Arbitrary line (i. e. MAL), which is very effective to solve the high gradient problems, is used to analyze the experiment at the key moments (for example, turning into the interface or bifurcating). Moreover, the fatigue fracture tests are carried out for the typical specimen of the laminated composites. The prediction of the numerical results for the crack growing directions according to the above criterion is in good accord with the experimental results. It proves the correctness and the applicability of this approach and facilitates to solve the whole process of the fatigue crack growth in the laminated composite.