A Novel Biomimetic Material Duplicating the Structure and Mechanics of Natural Nacre

摘要

Nacre from mollusk shell is a high-performance natural composite, composed of microscopic mineral tablets bonded by a tough biopolymer. Under tensile stress these tablets slide on another in a highly controlled fashion and over large volumes, and this unique mechanism leads to an overall toughness of nacre three orders of magnitude higher than the brittle mineral. This degree of toughness amplification is currently not matched by any synthetic composite. This article presents the first synthetic material based on the structure of nacre that successfully duplicates the mechanism of tablet sliding. This material was made of millimeter size poly-methyl-methacrylate (PMMA) tablets arranged in columns and held by fasteners. Strain hardening was provided by tablet waviness, leading to strains at failure 3-5 times greater than bulk PMMA. Analytical and finite element models successfully captured the locking mechanisms, enabling a rigorous design and optimization of similar composites based on different materials or at different length scale. This work demonstrates how key features and mechanisms in natural nacre can be successfully harnessed in engineering material, and unveils two new mechanisms, the effect of free surfaces and unzipping. Both mechanisms may be relevant to natural materials such as nacre or bone.