In this study, the interlaminar fracture characteristics of a Graphite/Epoxy composite materials are investigated under opening, shearing, and mixed mode loading conditions on the crack interface (0/0). Also, the stability of crack extension is investigated with various mixed ratio, $G_1/G_c$.
Modified Mixed Mode Flexural(MMF) specimen was proposed to evaluate the interlaminar fracture toughness with various mixed ratios. Data reduction to calculate the interlaminar fracture toughness is based upon linear beam theory and its theoretical mixed ratio was compared with FEM analysis in case of $G_1/G_c$=0.57.
Finally, in order to predict the mixed mode interlaminar fracture behavior, two mixed mode fracture criteria were compared to experimental data.
The interlaminar fracture toughness was identical with DCB (Double Cantilever Beam) specimen result for the case of mode I and identical with ENF (End Notched Flexure) specimen result for the case of mode II. The mixed mode test results showed good agreements with the mixed mode fracture criteria.
