Mode II fracture toughness related to ply angle for composite delamination analysis

Inter-laminar fracture toughness is an important parameter to characterize the delamination propagation performance of composite laminates. Compared with the mode I fracture, the results of mode II fracture behavior are limited. In this study, the effect of varying ply angle on the mode II delamination behavior of carbon/polymer was studied. T800 carbon fiber/EH104 epoxy resin laminates with different ply interfaces were prepared and tested according to ASTM D7905 standard. Four kinds of straight ply interfaces (0°//−0°, 15°//−15°, 30°//−30°, and 45°//−45°) and two kinds of curved ply interfaces with the curvature radius of 300 mm and 500 mm were considered. The fracture toughness GIIC of different ply interfaces was obtained by compliance method. The experimental results revealed that the mode II toughness of the variable angle ply interface is significantly larger than that of the straight ply interface. The mode II delamination behavior was characterized by finite element model with a bilinear traction separation law and was validated by the experimental data.