3D finite element modeling of mechanical response in nacre-based hybrid nanocomposites

Abstract

Nacre (mother-of-pearl), the inner layer of seashells is a ceramic laminated biocomposite with exceptional mechanical properties of fracture toughness and strength. The organic layers in the composite play a significant role in the mechanical response of nacre to stresses. In this work, three dimensional finite element models of nacre (constructed in our previous work to design ‘brick and mortar’ micro-architecture of nacre) were used to study influence of nonlinear response of organic component. In this work, nonlinear elasto-plastic models for organic component are applied to model the mechanical response of nacre. Nanoscale material parameters (elastic modulus and hardness) were obtained using nanoindentation experiments. The yield stress of the organic was maintained at 40×10⁻⁶, 50×10⁻⁶, 60×10⁻⁶, 80×10⁻⁶, 120×10⁻⁶, 240×10⁻⁶, 320×10⁻⁶, and $\text{400×10}{}^{\mathrm{-6}}\text{N/μm}{}^2$ (40–400 MPa). The choice of initial value of yield stress of organic phase is the onset of nonlinearity in nacre response at that value. Tensile tests were simulated for each of these values of yield stress of organic phase under identical loading conditions of $\text{0–60×10}{}^{\mathrm{-6}}\text{N/μm}{}^2$ in increments of $\text{2.5×10}{}^{\mathrm{-6}}\text{N/μm}{}^2\text{.}$ For each value of organic phase yield stress stress–strain response of nacre is plotted. The resulting yield stress of nacre was compared to experimentally obtained value. This indicates that a much higher yield stress of organic is necessary to obtain the experimentally obtained yield stress of nacre. Microstructural implications of this result are suggested.