Optimizing mechanical properties of bio-inspired composites through functionally graded matrix and microstructure design

Inspired by biological composites, the brick-and-mortar microstructure has been adopted in many synthetic composites to achieve improved material strength and toughness. Recently, introducing gradient in the matrix property is found to be a novel approach to provide additional enhancements in composites' mechanical performance. In this study, we present a theoretical approach to investigate the mechanical properties of the brick-and-mortar composites in which the shear modulus of the matrix varies periodically. Using the parabolic distribution of the shear modulus as an example, we show that the shear stress concentration along the interface can be greatly suppressed, and the material elastic limit and resilience can be improved. Further, we identified two critical aspect ratios of the brick-and-mortar unit cell that optimize the elastic limit and resilience of composites. From analyses and numerical calculations, formulae for these two critical aspect ratios are obtained and validated by finite element simulations.