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

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.