Crack-induced stress conentration is suppressed in nacreous composites

Linear elastic fracture mechanics (LEFM) indicates that crack-like flaws tend to intensify stress in brittle materials with stress intensity proportional to the square root of the crack size. Under given loading, monolithic brittle materials can only endure cracks smaller than a critical size. In this paper, however, our exploration into the stress state of nacreous composites shows that the crack-induced stress intensification/concentration and its dependence on crack size can be suppressed in composites with ‘brick-and-mortar’ structure. This feature can be attributed to the unique ‘brick-and-mortar’ (B-and-M) structure and the complementary dissimilarity between ‘brick’ (e.g. minerals) and ‘mortar’ (e.g. proteins) phases in mechanical properties. Our findings provide a profound insight into the origin of high strength and high toughness in nacreous composites.