Experimental study on shear-dominant fiber failure in CFRP laminates by out-of-plane shear loading

Understanding the shear behavior and resulting fiber failure of fiber-reinforced plastics is required for better prediction of their behavior during the machining process, but knowledge regarding the shear strength of fiber failure is limited. In this study, out-of-plane shear tests were conducted to observe the shear behavior of carbon fiber-reinforced plastic laminates subjected to high shear stress exceeding the shear strength of matrix failure. The longitudinal fibers in carbon fiber-reinforced plastic unidirectional laminates were cut by shear loading without severe internal damage and the maximum shear stress causing progressive fiber breaks was much higher than the shear strength of matrix failure. This result suggested the possibility of out-of-plane shearing as a machining method for fiber-reinforced plastics and shear tests were subsequently performed for carbon fiber-reinforced plastic cross-ply laminates. Delamination was generated by high shear stress to cut the reinforcing fibers, but the size of the remaining damage was small even in the thermoset carbon fiber-reinforced plastic laminates in which delamination likely occurs, without any optimization of the trimming conditions.