Experimental and numerical studies on the tensile behaviors of thin-ply and thick-ply open-hole laminates

Laminated composites with thin-ply unidirectional prepregs are popular due to their higher in-situ strength as compared with thick-ply laminates due to different failure mechanisms. Thin-ply and thick-ply open-hole laminates were fabricated and the tensile failure characteristics were studied by combining experimental and numerical simulation approaches. Charge-coupled device camera and de-ply technology were used to obtain failure morphologies of open-hole specimens under tensile loading. A finite element model considering progressive damage and bilinear cohesive model was built based on ABAQUS to study the damage mechanism of open-hole laminates. In thin-ply laminates, the damage plane was relatively neat while in thick-ply laminate broom-shaped damage morphologies were observed. Based on de-ply experiments and numerical prediction, it was found that thin-ply laminates had delamination suppression effect and could restrain the propagation of delamination along the loading direction, which explains the distinct damage patterns existed in thin-ply and thick-ply laminates. Based on numerical prediction, it was found that drilling-induced delamination did not affect the tensile strength of open-hole laminates. Propagation of drilling-induced delamination was also restrained in thin-ply laminates. The results of this research suggested that thin-ply prepregs should be considered when delamination poses critical threat to the structural integrity of laminated composite structures.