Influence of Platelet Boundary Irregularity on the Nonlinear Mechanical Behavior of Platelet-Reinforced Composites.

Defects, such as cell wall thickness variations, significantly influence cellular materials' mechanical characteristics. For instance, during a compression test in deformation mode, the crush bands are initiated at cells with a thinner wall thickness. This paper examines the effect of boundary irregularity on the nonlinear elastoplastic mechanical behavior of platelet-reinforced composite materials. Two types of stochastic (random distribution) platelets: with rounded corners and with sharp corners are generated using the Voronoi tessellation method. To better compare the effect of boundary irregularity, the composites are analyzed for three different volume fractions. The microstructure of the composite studied consists of isotropic and linear elastic platelets embedded in a perfectly plastic elastic matrix. Nonlinear numerical simulation of the tensile test was carried out using FE Zebulon software. The results show that the composites exhibit bilinear stress-strain behavior, consisting of two lines representing, respectively, the linear behavior (whose slope is Young's modulus) and the plastic behavior (whose slope is the strain hardening modulus). The effective Young's modulus, yield strength, and tangent modulus of the composites are calculated and compared in terms of the shape and volume fraction of the platelets. In the elastic zone, the results indicate that the curves of the two types of stochastic platelets overlap, giving very close results for Young's modulus. In the plastic zone, the effect of platelet irregularity is noticeable. It has been found that the platelets with rounded corners have a higher tangent modulus than those with sharp corners. This deference can improve the composite's ability to withstand more deformation under high loads, unlike platelets with sharp edges. [ABSTRACT FROM AUTHOR]