On the Damage Tolerance of Bioinspired Gradient Composites with Nacre‐Like Architecture

The evolution of natural armor materials has led to gradient structures with specific architectures to achieve high damage tolerance, thus offering valuable inspiration for the design of man‐made materials. Here, bioinspired gradient composites with a nacre‐like brick‐and‐mortar architecture are fabricated by infiltrating a polymer phase into porous ceramic scaffolds with position‐specific ceramic content. These composites demonstrate an integrated structure with notable several‐fold variations in local hardness and modulus across the thickness. The asymmetric mechanical properties and toughening mechanisms of the composites are investigated and compared to those of uniform composites. Specifically, when loaded along the direction of decreasing stiffness – resembling the typical loading configuration of natural armors, the gradient composites exhibit superior damage tolerance compared to the opposite direction and a uniform composite with equivalent ceramic content. This is attributed to the decreased peak stress, broader stress distribution, and increased deformation capacity, along with enhanced toughening effects that impede crack growth through mechanisms of crack deflection, crack bridging by uncracked ligaments, together with their frictional pull‐out from crack surfaces. This study deepens the understanding of the damage tolerance of gradient materials and offers insights for the bioinspired design of highly damage‐tolerant materials.