A Hierarchically Architected Bio-inspired Impact Resistant Natural Fiber Reinforced Composite

Abstract

The Bouligand structure, known for helicoidal fiber alignment in biological materials, offers unique mechanisms for enhancing impact resistance and damage tolerance. This study investigated the mechanical performance of a novel bioinspired composite based on the Bouligand architecture using densified wood (Gmelina Arborea) as fiber reinforcement. Composite laminates were fabricated through densification, angular slicing, and epoxy-based lamination to emulate helicoidal layering. The samples were prepared with varying stacking angles and subjected to a comprehensive set of mechanical tests to evaluate their flexural, compressive, impact, shear, and moisture absorption properties. Testing revealed that the composite with the Bouligand structure exhibited significant performance enhancements in multiple domains, whereas anisotropic testing confirmed greater strength in the radial loading directions. The impact strength was approximately 9 times greater than that of untreated wood, which was attributed to energy-dissipative mechanisms such as fiber pull-out and crack deflection. Flexural testing revealed an ultimate strength of 198.22 MPa and a modulus of 27.15 GPa, indicating substantial improvement over conventional stacking configurations. The interlaminar shear strength was highest for the Bouligand configurations, which suggests improved interfacial adhesion due to twisted layering. Microscopic analysis confirmed the role of fiber‒matrix interactions and ply orientation in promoting discontinuous crack propagation. Moisture absorption tests revealed enhancements in hydrophobic characteristics. In addition to being lightweight (0.738 g/cm 3), the renewability of fibers demonstrates strong potential for the composite in structural applications, especially in impact-prone or beam structures in transportation or protective panels. This work provides a scalable, bioinspired framework for engineering natural fiber composites with enhanced multifunctional performance, which is a promising alternative to traditional synthetic composites