Experimental and numerical investigation of CFRP quasi-elliptical honeycomb sandwich structure under bending loading

This study investigates a novel carbon fiber reinforced polymer (CFRP) quasi-elliptical honeycomb sandwich structure, designed by a bio-inspired approach based on the microstructure of beetle elytra. Compared with conventional straight-walled honeycomb connections, the arc-shaped connections in this innovative design significantly reduce stress concentration under external loading, effectively suppressing local failure risks and enhancing overall structural performance. To overcome the limitations of secondary bonding typically used in traditional honeycomb manufacturing, this study developed specialized molds for the integrated fabrication of quasi-elliptical honeycomb cores using unidirectional CFRP epoxy prepreg through hot-press molding. Employing combined experimental and finite element simulation methods, the investigation systematically examined the failure mechanisms and bending behavior under three-point bending conditions, with a particular focus on the effects of relative density and face-sheet thickness. A parametric analysis was conducted to elucidate the influence of the unit cell dimensions on the structural performance. Key findings demonstrate that specimens with medium relative density achieve optimal specific bending stiffness, while increasing face-sheet thickness significantly enhances both specific peak load and energy absorption capacity. A comparative analysis with competing sandwich structures confirmed the exceptional bending characteristics of the proposed design, which maintained a competitive bending modulus and strength even at low density levels, thereby validating its outstanding bending resistance.