Interfacial strengthening in bio-inspired materials: a review

This article extensively explores various bio-inspired techniques of interfacial strengthening. Bio-inspired composites fabricated by emulating five natural materials: nacre, byssus thread, plant roots, bone, and spider silk have been discussed. A detailed account of the strengthening mechanisms active in these natural materials responsible for improving fiber/matrix adhesion in artificial composites is presented. Dendritic growth on fiber surfaces is crucial in enhancing the mechanical properties via interlocking in root-inspired composites. Micro-waviness, nano-asperity interlocking, shear deformation, and mineral bridge fracture are the main strengthening mechanisms active in the nacre-inspired composites. Byssal threads have exceptional adhesive properties due to the sacrificial bonds, hidden length, and strong metal coordination cross-links. The typical ‘Bouligand’ microstructure of bone has inspired different composite materials with excellent crack deflection and arresting. Spider silk fibers have a highly oriented proteinous structure surrounded by a semi-amorphous matrix. Their skin-core structure provides tensile strength and toughness to these fibers, inspiring various artificial composites. This article explores additive manufacturing and chemical modification as the implementation techniques for bio-inspired strengthening. Applications of bio-inspired composites include biomedical, marine, aerospace, and tissue engineering. Challenges, such as optimal mechanical properties, sustainability, simulation, and integration with Industry 5.0, must be addressed systematically to augment their applicability.