Sandwich panel behavior under low-velocity impact with polyurethane core

In this article, the aim is to numerically and experimentally investigate the energy absorption of sandwich panels composed of polyurethane foam cores and composite facesheets consisting of epoxy resin reinforced with Kevlar® 29 fibers with different numbers of layers under low-velocity impact. Therefore, factors influencing energy absorption in sandwich panels, such as the density of foams, the arrangement of foam layers, core thickness, and the number of composite layers in the skins, were investigated. Additionally, the damage modes occurring in the composite facesheets were examined. Damage initiation in the composite facesheets is predicted using the three-dimensional Hashin criterion with VUMAT coding, and cohesive elements model interlayer delamination. The results show strong agreement between numerical simulations and experiments. Key parameters such as contact force–time curves, the maximum force needed to initiate damage in composite layers, energy absorption, and SEA are analyzed. Among the experimental samples, increasing the number of composite layers had a greater effect on the overall energy absorption of sandwich panels compared to increasing the thickness of foam cores. However, increasing the number of composite layers in the facesheets performed poorly in terms of improving the SEA parameter. Notably, panels with integrated cores at a density of 75 kg/m³ exhibit the highest energy absorption at 11.7868 J. Moreover, increasing the number of composite layers on the back facesheet results in a 4.94% and 6.96% energy absorption increase compared to panels with more composite layers on the upper facesheet or an equal distribution between the upper and lower facesheets.