Homogenizing interfacial shear stress in brick-and-mortar structured composites via gradient modulus for enhanced mechanical properties

Inspired by nature, various biomimetic materials have been synthesized for enhanced mechanical properties, among which composites with brick-and-mortar structures attract the most attention. In such bio-inspired composites, the matrix layer mainly functions to transfer load between bricks through shearing, while the shear stress in the matrix is not uniform but highly concentrated on the interface ends, which tends to initiate cracks and evoke interface delamination in composites. To enhance the composites’ resistance to interface delamination, we propose to homogenize the shear stress by adopting a matrix with a gradient modulus. A theoretical solution to the optimal gradient modulus of the matrix layer is obtained, followed by computational validations. Moreover, composites with such functionally graded matrices are further demonstrated to possess higher elastic limits, higher resilience, and flaw tolerance than the uniform controls. The results of this paper should be of great value to the design and synthesis of advanced structural materials for superior mechanical performance.