Numerical and Experimental Investigations of Branched Thermal Crack Systems in Self-Stressed Models of Unidirectionally Reinforced Fibrous Composites

Summary

Branched thermal crack systems consisting of a combination of curvilinear matrix cracks and interface cracks, respectively, arising in self-stressed models of fibrous composites due to a steady cooling process are investigated by numerical as well as experimental methods of fracture mechanics. Further, by implementation of a maximum strain energy release rate criterion as well as by using the substructure technique a finite element procedure has been constructed for the simulation of a quasistatic crack propagation along the prospective crack path known from a cooling experiment. Finally, by using the method of caustics in transmission and reflection, respectively, stress intensity factors K, at the tips of propagating matrix cracks were determined. A comparison of those fracture mechanical quantities obtained experimentally with associated finite element calculations using a modified crack closure integral showed a very good agreement in the region of stable crack propagation.