On November 10, reporters learned from the University of Science and Technology of China (USTC) that its research team, in collaboration with Shanghai Jiao Tong University and other institutions, drew inspiration from the structure of natural nacre. By adjusting the arrangement of tiny platelets inside the material, the team developed a new biomimetic composite material with superior toughness and fatigue resistance. Compared with conventional structural materials, the new material delivers improved mechanical performance under various loading conditions including compression, bending and torsion. Under the same maximum stress, its fatigue life is more than 1,000 times that of traditional flat-plate structural materials.

Natural nacre features a distinctive internal architecture. It consists of hard mineral platelets interleaved with soft organic substances, forming a “brick-and-mortar structure” analogous to bricks bound by mortar. This structure endows nacre with both high strength and toughness, offering inspiration for the development of high-performance composite materials.

Nevertheless, most conventional nacre-mimetic composites adopt a flat-plate arrangement, where internal interlayer interfaces share largely the same orientation. Their mechanical performance is therefore highly sensitive to loading directions. Under complex loads, these interfaces tend to serve as pathways for crack propagation and compromise material reliability.

To address this challenge, the USTC-led research team proposed a design strategy named the “concentric brick-and-mortar structure”. Unlike the traditional flat layout, the team arranged alumina platelets around a central axis to form layered concentric architectures. This distributes the originally aligned weak interfaces toward diverse orientations and prevents the formation of through-thickness weak planes across the material.

The team fabricated two composite materials with similar composition and density but different internal structures, and conducted mechanical tests covering compression, bending and torsion. The results show that the new material with the concentric structure achieves higher strength and energy dissipation capacity under all three loading modes.

The two materials exhibit markedly different fracture behaviors. Cracks in traditional flat-plate materials propagate mainly along interlayer interfaces, frequently causing delamination and step-like fractures. In contrast, cracks in the concentric-structured material follow tortuous paths in multiple directions. Computer simulations further confirm that the concentric arrangement optimizes internal stress distribution, disperses loads and mitigates local stress concentration.

The new material stands out particularly in fatigue resistance. Repeated loading can lead to gradual internal damage accumulation and eventual fracture. Cyclic bending tests by the research team reveal that under identical maximum stress, the fatigue life of the concentric-structured material exceeds that of the flat-plate counterpart by over 1,000 times. Even after normalization by the respective static bending strength of each material, its fatigue life remains more than 100 times longer within the comparable test range.

Source: Hefei Daily