EFFECTS OF STRAIN-RATE ON MODE-II INTERLAMINAR FRACTURE-TOUGHNESS IN CARBON-FIBER EPOXY LAMINATED COMPOSITES

The strain rate dependence of Mode II interlaminar fracture toughness in unidirectional CF/epoxy composite laminates was studied by the dyna mic End Notched Flexure (ENF) test using a Split Hopkinson Pressure Ba r (SHPB) system. The experimental technique using a ramped incident wa ve was adopted to suppress the influence of the flexural vibration of the specimen. Finite element analysis confirmed that the estimating fo rmula for static Mode II fracture toughness can be applied to dynamic Mode II fracture toughness as well. The experimental results indicated that the Mode II fracture toughness tends to decrease with increasing shear strain rate. This tendency is thought to be due to the fractogr aphic differences between static and dynamic fractures.