Transverse crack propagation in the specimen width direction of CFRP laminates under static tensile loadings

The damage process of transverse cracks in cross-ply and quasi-isotropic toughened CFRP laminates under static loading is studied. To investigate specimen configuration effect on width-direction propagation of transverse cracks, coupon specimens with ranges of specimen width and transverse ply thickness are tested. Detailed observations of transverse cracks indicate that there are consecutive three-stage processes of edge crack initiation, edge crack increase without inward propagation, and crack propagation across the width in quasi-isotropic laminates, whereas simultaneous transverse crack propagation takes place across the width in conjunction with new edge crack formation in cross-ply laminates. The detailed process of transverse cracking is investigated using three-dimensional FEA in order to clarify the difference of damage process between quasi-isotropic and cross-ply laminates. It is shown that damage mode transition from edge cracking to widthwise propagation can be characterized with energy release rates near free-edges and inner regions. Finally, an average propagation model based on the conventional two-dimensional models is presented and verified with experimental results and FEA. Useful information about experimental results of transverse crack propagation and the characterization of edge cracking and inward propagation is provided.