Optimizing Mechanical Properties and Structural Integrity of Lightweight Sandwich Composites Through Core Stitching

Abstract In this study, polyvinyl chloride (PVC) foam cores with densities of 60 and 80 kg/m 3 and thicknesses of 10 and 20 mm were stitched using E-glass fiber yarns (300-600-1200 tex thread densities) and sandwiched between plain woven E-glass fiber fabrics. The effects of core reinforcement on the mechanical properties were investigated through compression and flexural tests. The non-stitched sandwiches exhibited plastic deformation under compression at constant stress, while stitched-core sandwiches demonstrated multiple stress peaks, leading to an increase in compressive strength by up to 102.61%. Flexural tests revealed that delamination, typically observed in polymer foam core sandwiches, was effectively prevented, and load transfer between face sheets was improved due to the enhanced shear resistance of stitched cores. The flexural load-bearing capacity increased by up to 53.90%. A two-way ANOVA was conducted to analyze both individual and interactive effects of the experimental parameters on the results, and reliable empirical equations were introduced to predict the compressive and flexural forces. The failure mechanisms indicated that core stitching improves stiffness and shear resistance, attributed to strong interfacial adhesion, as the glass fiber yarns act as rigid rods between the facings. Overall, sandwich structures with stitching, particularly those with low-density foam cores, offer significant mechanical advantages and are proposed as a cost-effective solution for engineering applications where weight is critical.