Three-point bending, interlaminar shear, and impact strength in bioinspired helicoidal basalt fiber/epoxy composites: A comparative experimental analysis

This study investigates the mechanical characteristics of basalt fiber/epoxy polymer composites (BPC) inspired by nature's higher-order designs especially helicoidal structures found in fish scales. The present work includes the experimental analysis of 20-layered bioinspired BPC composites in single helicoidal ([90/80/70/60/50/40/30/20/10/0]s), and double helicoidal ([130/40/120/30/110/20/100/10/90/0]s) layups. The hand layup technique, followed by the vacuum bagging method, is used to fabricate composite laminates. The layup design significantly influenced the mechanical properties of both helicoidal structures with different stacking sequences, including load capacity, deformation, energy absorption, and fracture modes. Interestingly, failure mechanisms demonstrated both bending and twisting (attributed to specific ply orientation, resulting in a twisting effect) occurring majorly under flexural loading, leading to improved energy absorption. The flexural strength of single helicoidal laminate was observed to be 28.8% higher than double helicoidal laminate design. On the other hand, the double helicoidal laminate showed 46.8% and 19.4% higher inter-laminar shear strength (ILSS) and impact resistance properties, respectively, compared to the single helicoidal laminate design. Therefore, this comparative experimental analysis of both stacking structures provides insights into potential changes in conventional stacking sequences and enhances understanding of mechanical responses in bioinspired composites. Highlights Mechanical characterization of bioinspired helicoidal laminates is done. The flexural strength of single helicoidal laminates is 28.8% higher than double helicoidal laminates. Double helicoidal laminates showed better interlaminar shear strength and energy absorption.