Influence of matrix inelasticity on the mechanical properties of bioinspired composites

Lightweight structures require materials with superior mechanical properties, prompting engineers to investigate composite materials. Inspired by nature's ingenuity, especially the nacre found in seashells, and the hierarchical structures observed in bone and teeth, which exhibit remarkable strength, stiffness, and toughness, this study investigates the role of inelasticity on the mechanical properties of bioinspired composite materials. In contrast to purely elastic materials, which exhibit reversible stress-strain behaviour and fail suddenly upon reaching their yield point, our study integrates plasticity and damage models to allow for a more progressive and controlled failure process. In nacre-like composites, where non-uniform stress distributions are widespread, plasticity is an important mechanism for reducing stress concentrations and avoiding catastrophic failure. This approach produces a more gradual and predictable failure mode. Here, a controlled degradation of interfaces distributes the applied stress more uniformly across the composite, increasing its overall strength and toughness. Our study utilizes representative volume element and finite element analysis to model and simulate the failure behaviour of nacre-like composites. Using the scalar degradation variable, we note that damage initiates at the interfaces perpendicular to the loading direction, followed by increased stress and eventual failure along the interfaces parallel to the loading direction. We quantify the major contribution of inelasticity in interfaces towards strength and toughness. Additionally, we highlight the previously unexplored contribution of vertical interfaces to toughness by considering influential parameters such as cohesive fracture energy (Gc). The findings of this study provide valuable insights for predicting the strength and toughness of bio-inspired composites when the matrix exhibits inelastic deformation. This work offers valuable results which could greatly help in the design and development of advanced lightweight composite materials for structural applications.