On the geometric transferability of the delamination shear limit for CFRP laminate in bending

The laminate load bearing capability is often compromised when delamination occurs even though the laminae remain intact. The out-of-plane components of the stress tensor, defined at the interfaces between plies, are typically responsible for the delamination of multi-layered materials. Commonly used failure criteria for delamination make use of both shear and normal interlaminar stresses. In this work the out-of-plane stresses inside a woven laminate were numerically evaluated using a micromechanical model. Under three point bending the existence of local normal interlaminar stress related to the fabric architecture was demonstrated. The influence of the due to texture normal interlaminar stress on the fracture occurrence was discussed. The reduction of the apparent interlaminar shear strength as effect of the span-to-depth ratio increase was successfully reproduced introducing a dependence of the delamination shear limit from the stress triaxiality gradient.