Bio-inspired, epoxy-based lamellar composites with superior fracture toughness by delignified wood scaffold

Abstract Inspired by the wood sponge and lamellar structure, delignified wood was introduced into epoxy as a scaffold to improve its fracture toughness. By chemically removing lignin and hemicellulose from natural wood and subsequently freeze-drying, a delignified wood template with a grid-like structure was obtained. The isotropic and anisotropic bulk epoxy/delignified wood biocomposites with 8 wt% delignified wood were prepared. The anisotropic biocomposite exhibits a KJC of 6.74 MPa m1/2, 8.31 times that of neat epoxy resin. Further studies reveal that the wood layer can generate micro-cracks and induce crack deflection through debonding and plastic deformation, causing fracture toughness to increase. Considering the strength and stiffness of delignified wood template, the biocomposites show unexpectedly excellent mechanical properties. The tensile strength and Young's modulus of the anisotropic materials are as high as 88.5 MPa and 3.5 GPa, respectively.