Impact responses and residual flexural properties of narrow CFRP laminates

Abstract

This study aims to identify the impact responses and residual flexural properties of narrow carbon fiber reinforced plastic (CFRP) laminates using the energy profile diagram (EPD). A serial of impact tests was performed with different thicknesses of narrow CFRP laminates to examine the damage process and extent from initiation to complete breakage. The quasi-static three-point bending tests were carried out to characterize the degradation of residual flexural properties induced by the impact. The overall impact energies are clearly separated into three regions by the penetration threshold and crack threshold respectively determined by the EPD. The main damage modes are matrix cracking for lower impact energies, delamination and fiber breakage for middle impact energies and complete breakage for higher impact energies. It is also found that the degradation of normalized residual flexural properties can be divided into three regions using these abovementioned two thresholds, of which the greatest loss occurs in the middle energy region, whilst the maximum reductions of normalized flexural strength and flexural modulus are smaller than 20% in the first region. By comparison, the 6-ply specimens are of lower impact resistance and lower residual flexural properties than the 9-ply specimens under same impact energy; and the residual flexural strength is more sensitive to impact loading than flexural modulus.