Modeling the Organic-Inorganic Interfacial Nanoasperities in a Model Bio-Nanocomposite, Nacre

摘要

Nacre, the inner iridescent layer of several mollusk seashells is a model nanocomposite with exceptional mechanical properties, that is composed of layers of organic (proteins and polysaccharides) and inorganic (aragonite). A 3D finite element model of nacre was constructed that incorporates the nanometer sized asperities at the organic-inorganic interfaces to evaluate their role on mechanical response of nacre. Simulations were performed on a 3 x 3 x 1 block model of nacre to evaluate the influence of nano-asperities on overall mechanical response of nacre. A small increase in elastic modulus results from the presence of asperities. In inelastic regime, the effect of nano-asperities on yield stress was marginal, and the strain-hardening slope was seen to decrease upon introduction of nano-asperities. In addition, the nano-asperities resulted in increase in the magnitude of plastic strains after the yield. These series of simulations suggest that nano-asperities have marginal effect on the overall mechanical response of nacre. Although our simulations show that the presence of nano-asperities only marginally improves the mechanical properties, their presence in the biological nanocomposite may provide large surface area for the organic to attach and interact with the inorganic. The organic matrix in nacre has previously been shown to be a material with exceptional properties. The nano-asperities could also provide confinement of biopolymers (proteins and polysaccharides) resulting in enhanced mechanical properties of the organic layer.