Displacement-based criterion for fracture analysis of fibrous composites

This paper proposes a new displacement-based fracture criterion valid for fiber reinforced composites. In this criterion, the required fracture parameter (critical crack tip opening displacement) can be obtained just from the Mode I fracture experiments of 0 and 90 degrees unidirectional composites with the aid of finite element analysis. This criterion is simple, straightforward and easy to apply. The fracture load of fiber reinforced composites with crack can be predicted quickly. First of all, the prediction ability of the criterion was verified by different methods. The fracture characteristics of the unidirectional composites are the basic property that controls continuous fiber reinforced composites, so some fracture experiments and finite element analysis were performed in this field, including double-edged specimen experiments, four point bending experiments and standard compact tension specimen experiments. From the results of verification, the fracture criterion proposed in this paper can predict not only the failure of composites with different crack lengths but also the failure of the composite with different fiber directions. After understanding the fracture characteristics of unidirectional composites, another formula was proposed to compute the critical crack tip opening displacement of laminate from the physical relations between lamina and laminate. It is successful in predicting the failure of laminate. Finally, the criterion and finite element program were applied to predict the failure of a pressure vessel. The result shows that the process proposed by this paper can be applied effectively and accurately in the analyses of large structures.