A computational procedure for the determination of fracture parameters at interfacial contact cracks in composite laminates

This article presents a method to calculate the fracture parameters at interfacial cracks in laminated composites. Depending on the applied loading and crack length, a contact region may develop that changes the nature of the resulting stress intensity factors and energy release rates with respect to the open crack. A combined analytical and numerical model based on frictionless contact is used to eliminate the overlapping of the crack faces where applicable to obtain the correct results. In cases where the contact region is very small, an approximate method to obtain the fracture parameters is derived by consideration of the J-integral. The laminates studied include cross-ply and angle-ply laminates in three-point bending containing a central delamination. The present results are compared with results in the literature obtained by the virtual crack closure integral technique for the special case of cross-ply laminates and a close agreement is found. In addition, results are given for the extent of the contact zone as well as Mode I and II stress intensity factors and energy release rates as a function of the lamination angle. Overall, the method used provides an effective way to analyze interfacial cracks and delaminations in composite plates in cylindrical bending subjected to transverse loads or low velocity impacts.