Flexural performance of Kevlar-reinforced sandwich composites with lightweight pumice-filled epoxy cores

The current investigation evaluates the flexural behavior of a novel sandwich composite with a lightweight pumice core reinforced by Kevlar fibers. Four different types of epoxy cores with varying pumice content (2.5, 5, 7.5 and 10 wt%) were prepared with constant 40 wt% of Kevlar fiber content. Open mold casting was used to prepare the core while the sandwich composites were manufactured using an in-house built closed mold. Influence of pumice content on the flexural properties of sandwich composites were evaluated by experimental and numerical approach. 3-point flexure test results indicate pumice reinforcement significantly enhances the modulus and strength of composites owing to the higher tendency to resist buckling loads. Composites with 10 wt% of pumice content reveal 31 % higher strength as compared with 2.5 wt% composites, owing to well-bonded and evenly distributed pumice particles leading to a higher interfacial shear strength and thereby mitigating core failure and delay in delamination. The correlations between the structure and property were analyzed using scanning electron micrographs. The numerical simulation results serve to reinforce the conclusions drawn from the study. These findings demonstrate a strong alignment with experimental observations, with a notable 3 % reduction in accuracy. The developed sandwich composites show potential for diverse structural and semi-structural applications, including protective panels, aerospace and automotive structures.