Lightweight lattice metamaterials face critical brittle failure risks under bending loads due to severe stress concentration. The natural cross-lamellar structure of Strombus gigas (queen conch) shell delivers outstanding toughness via multi-scale stress redistribution, offering a promising biomimetic solution to this issue.

In a study published in Thin-Walled Structures, a research team led by Dr. YANG Yongtai from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences developed a novel cross-lamellar lattice metamaterial with layerwise stiffness tuning for superior anti-fracture performance.

Inspired by conch shell lamellar stacking rules, researchers designed orthogonal-orientated lattice unit cells. They fabricated three multi-layer configurations (y-x-y, y-y-y, x-y-x) via vat photopolymerization additive manufacturing using PC20 photopolymer resin, with classic Octet lattice as the control group.

Through quasi-static three-point bending and single-edge notched bending tests, combined with finite element simulations, researchers verified the mechanical performance of all designs. Monolayer tests revealed two distinct mechanical modes: y-type lattices possessed high stiffness yet brittle fracture, while x-type lattices showed great ductility and large deformation capacity.

Among three-layer notched specimens, the y-x-y layout (rigid outer layers + compliant intermediate layer) showed the optimal toughening effect. Its J-integral reached 8.45 kJ/m², twice that of uniform y-y-y lattices and over 20 times higher than Octet lattice. The middle compliant layer redistributed stress, delayed crack initiation and extended stable deformation range significantly.

Besides, the alternating strut orientation and layered stiffness gradient of the y-x-y structure replicated the shell's natural toughening mechanism, alleviating stress concentration and promoting sustained plastic energy dissipation. This advantage remains stable across relative densities from 17.5% to 32.5%.

This study provides a guideline for the biomimetic design of high-toughness lightweight metamaterials, which wide application prospects in aerospace thin-walled components and protective energy-absorbing structures.