随机短纤维复合材料复合型开裂方向的预测

PREDICTING THE MIXED-MODE CRACKING DIRECTION IN RANDOM SHORT FIBRE COMPOSITE MATERIALS

本文采用五种方法对随机短纤维复合材料双槽拉剪试件层间剪切断裂的开裂方向进行了预测,其中两种方法已有人用过,而其余三种是本文作者提出的,指出了应变能密度准则的问题,提出一个比应变能密度准则。此外,对Tsai-Hill准则与Norri,准则进行了推广,用来预测开裂方向。缺口根部近场应力分布用八节点四边形等参元方法作了计算。 预测结果与实验结果作了对比。另外,根据有限元结果,对槽底根部应力奇异场控制区的大小给出了一个估值。

The prediction of cracking direction in composite materials is of significance to the design of composice structures. This paper presents several methods of predicting the-cracking direction in the double grooved tension-shear specimen which is of mixed mode cracking. Five different criteria are used in this analysis, two of them have been used by other investigators and the others are proposed by the present authors. The strain energy den-sity criterion proposed by G. C. Sih is modified to take into account of the influence of the nisotropy of the strength on the direction of crack. The two failure criteria of Tsai-Hill and Norris are extended to predict the crack orientation. The stress distribution in the near notch zone are calculated by using the 8-node quadrilateral isoparametric FEM. The predictions of all the criteria (except one) are in good agreement with the experimental measurement. In addition, based on the FEM results the size of the zone in which the singular term is dominant is estimated.