Effect of cellular core topology on the mechanical performance of carbon/epoxy sandwich composites with 3D-printed PVA cores

Core shape has a significant impact on sandwich composites’ mechanical and impact properties. The four fundamental topologies of sandwich composite structures—honeycomb, re-entrant, grid, and full-shape—were examined experimentally in this study. The face sheets were made of carbon fiber/epoxy laminates, whereas the core material was polyvinyl alcohol (PVA). Sandwich panels were created by bonding the additively generated core components between the composite face sheets. The specimens’ structural behavior was assessed using three-point bending, dynamic mechanical analysis (DMA), low-velocity impact (LVI), and Charpy impact tests. According to the bending data, the re-entrant core showed the maximum bending strength and elongation at break, showing better deformation capability, while the full-shape core showed the best bending modulus because of its continuous structure. The full-shape configuration produced the maximum peak force of around 15 kN, according to low-velocity impact tests, while the re-entrant core’s auxetic deformation mechanism produced the highest energy absorption capacity of about 88 J. On the other hand, under high strain-rate loading conditions, the honeycomb core had the highest Charpy impact energy and specific impact energy values. The findings show that in sandwich composite constructions, core geometry is crucial for regulating stiffness, damage tolerance, and energy absorption methods.