Low-velocity impact damage research on CFRPs with Kevlar-fiber toughening

This paper provides a comprehensive understanding of the influence mechanism of short fiber toughening on low-velocity impact resistance of carbon fiber reinforced polymer composite laminates (CFRPs). Three kinds of layup laminates with and without short Kevlar-fiber toughening were designed and experimental tests were conducted using a drop-weight impact machine. After the low-velocity impact test, ultrasonic C-scan and industrial computed tomography (ICT) were utilized to comprehensively reveal the internal damage, including damage area and damage distribution. Based on the energy absorption and the impact dynamic responses, mechanical behaviors of CFRPs were analyzed in detail. Furthermore, the residual compression strength and failure strain of CFRPs with and without short Kevlar-fiber toughening were tested. It was observed that damage resistance of toughened laminates at lower impact energy did not show obvious advantages, but the compression-after-impact (CAI) strengths and the failure strain values improved under all energy levels with short Kevlar-fiber toughening. Three-dimensional distribution of internal damage and electron microscope analysis, together with fracture toughness analysis, were employed to explain the experimental findings and relevant mechanisms.