Ply thickness influence in compression after impact damage on carbon/epoxy test specimens

Abstract

This study aims to map the ply arrangement and thickness influence on the impact damage, and subsequent compression damage, in composite compression after impact (CAI) test specimens, using Hashin failure criterion [20] as the main failure criteria. Both thick and thin ply models have standard CAI test specimen dimensions, with same thickness and different ply number. Also, different ply arrangements, as Quasi-isotropic and Cross-ply layups were considered. The specimens were modeled using 3D finite elements with and/or without inter-ply surfaces connected using cohesive elements [6]. Both thick and thin ply models have standard CAI test specimen dimensions [5], with same thickness and different ply number. Thick-to-thin ply thickness ratio was assumed to be 4. Quasi-isotropic and cross-ply layups were considered, with eight plies for the thick ply model, respectively stacked as [+45/0/45/90] S and [0/90] 2S , and thirty-two plies for the thin ply model, respectively stacked as [+45/0/45/90] 4S and [0/90] 8 S. Complex test programs are still necessary to fully characterize the material and the failure modes in order to develop accurate numerical methods, however, based in this study is possible to evaluate the effects of damage generated due to compression after low velocity impact in carbon/epoxy composite laminates. The goal of this work is to fully understand the possible benefits offered by different ply thickness in composite materials, being possible to observe, based on preliminary studies, a tendency of greater local stiffness and residual strength for thin laminates. © 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. All rights reserved.