---

The analysis of notched composite parts in a structure due to the existence of high stress concentration and undetermined behavior is an exigent issue. In this research, the progressive damage analysis has been applied to predict the failure of notched woven glass- epoxy composite laminates under tensile loading. Stress analysis and investigation of the effect of the hole size on it have been performed by the analytical and numerical methods. Developing an UMAT in the ABAQUS finite element package has made the utilization of the 3D progressive damage analysis feasible. Max. Stress, Yamada- Sun and Tsai- Wu failure criterions have been implemented to predict the damage initiation due to the absence of significant failure criteria for woven composites. Instantaneous and recursive property degradation methods have been used to simulate the damage propagation. The tensile characteristic distance has been computed without any experiments. The comparison of stress and failure analysis with experimental results shows good agreement. Finally, using tensile characteristic length obtained by progressive damage method, the possibility of safety factor determination in the composite joints in order to optimum design has been provided.

---

In this study, the effect of delamination interface fiber angle orientation on the initiation and propagation fracture toughness of plain woven composites with stacking sequences of [012//012], [011/30//0/011] and [011/45//0/011] under mode I loading were investigated. These stacking sequences are chosen in order to eliminate the effect of the remote ply orientation on the delamination behavior of the double cantilever beam (DCB) specimens. Samples were manufactured by the wet hand lay-up method and fracture tests were conducted on specimens using the universal testing machine (SANTAM STM-150) according to ASTM standard. The experimental results showed that the interface ply orientation had a negligible effect on magnitudes of the initiation and propagation fracture toughness of plain woven composites due to delamination propagation in the resin-fiber interface of delamination interface. Experimental investigations of the fracture surface have shown the effect of different mechanisms on the delamination propagation, which crack propagation in the resin-fiber interface is one of the main mechanisms for increasing the fracture toughness in these specimens. In addition, the experimental evidence revealed that the fiber bridging was not the main mechanism of increasing fracture toughness during the delamination propagation, unlike the unidirectional DCB specimens.