Effect of machining conditions on the trimming damage in composite laminates induced by out-of-plane shearing

Fast machining is essential for mass production of composite structures, and out-of-plane shearing, also known as die cutting, is appropriate for trimming. Nevertheless, little is known about shearing of polymer-matrix composites. This study was done to investigate the damaging impact of shearing conditions on carbon fiber reinforced plastic (CFRP) laminates. The clearance and temperature affected the damage progress, while the cutting speed in the tested range had negligible effect. In cross-ply laminates, delamination and matrix cracks first appeared in a narrow shearing zone, and with further loading longitudinal plies broke at the dies’ edges. Although delamination occurred only in a narrow shear-stress concentrated zone in the case of a small clearance, it was significant for a large clearance, owing to the local bending deformation. A temperature slightly lower than the glass transition temperature narrowed the delamination area, owing to the increase in the interlaminar fracture toughness as well as insignificant strength degradation of the matrix.