Low velocity impact behavior of auxetic CFRP composite laminates with in-plane negative Poisson’s ratio

Introducing auxeticity or negative Poisson’s ratio is one potential solution to mitigate the low velocity impact damage of fiber reinforced polymer matrix composites, which can be achieved by tailoring the layup of an anisotropic composite laminate. This study aims to investigate the effect of laminate-level in-plane negative Poisson’s ratio on the low velocity impact behavior of carbon fiber reinforced polymer (CFRP) matrix composites using numerical simulations. The layups of the auxetic composites that allow them to produce negative Poisson’s ratios are identified based on the Classical Lamination Theory and verified through fundamental coupon-level experimental tests. To ensure meaningful comparisons, the non-auxetic counterpart composites are designed by allowing them to produce positive in-plane Poisson’s ratio while closely matching the longitudinal effective modulus of the auxetic laminate. The simulation results indicate that the auxetic laminates suffer smaller (12.6% on average) delamination area in top and bottom interfaces, much smaller (38% on average) matrix compressive damage in the top and bottom plies, and smaller (14.6% on average) fiber tensile damage area in each ply of the laminate at relatively higher impact energies (5 and 8 J).