抄録
In order to clarify the strain rate effects on mode I, mode II and mixed mode (I+II) fracture behavior of graphite/epoxy laminates, fracture toughness was investigated over a wide range of loading rate from static to impact. MMF (Mixed Mode Flexure) and MMB (Mixed Mode Bending) specimens were used to evaluate the mixed mode fracture toughness. The mixed mode fracture toughness clearly showed strain rate dependence regardless of mode ratio; the mixed mode impact fracture toughness was about 10% lower than the local maximum value under static loading. Local maximum values existed at static loading rate for mixed mode fracture toughness, G_C. The mixed mode fracture toughness conform to the linear criterion for the region of high mode ratio, G_<II>/G_1=13,regardless of loading rates. However, it did not conform to the linear criterion for the region of low mode ratio, G_<II>/G_I≤3,and high loading rate, G≥(10)^2 J/m^2/s.
