Nacre from mollusk shell is a high-performance natural composite composed of microscopic mineral tablets bonded by a tough biopolymer. Under tensile stress, the tablets slide on one another in a highly controlled fashion, which makes nacre 3000 times tougher than the mineral it is made of. Significant efforts have led to nacre-like materials, but none can yet match this amount of toughness amplification. This article presents the first synthetic material that successfully duplicates the mechanism of tablet sliding observed in nacre. Made of millimeter-size wavy poly-methyl-methacrylate tablets held by fasteners, this “model material” undergoes massive tablet sliding under tensile loading, accompanied by strain hardening. Analytical and finite element models successfully captured the salient deformation mechanisms in this material, enabling further design refinements and optimization. In addition, two new mechanisms were identified: the effect of free surfaces and “unzipping.” Both mechanisms may be relevant to natural materials such as nacre or bone.
Keywords: Biomimetic; Toughness; Composite