Prediction of the anisotropic damage evolution of dry common millet (Panicum miliaceum) seed under quasi-static blunt indentation

Abstract

Common millet (Panicum miliaceum) seed is a prevalent crop worldwide with high adaptability and survivability. The outer seedcoat of common millet seed has an interesting and complex microstructure, with epidermal cells being articulated with wavy sutures, to form a jigsaw-like sutural tessellation. Experimental flatwise compression tests were performed on full common millet seeds and kernels (by removal of the outer seedcoat). Finite element models for the seed and kernel were developed. A brittle crushing model and Hashin progressive damage model were used to simulate the damage initiation and evolution of the kernel and the seedcoat, respectively. The anisotropic strengths of the seedcoat were derived from the seedcoat microstructure comprising suture tessellation. The finite element models were able to accurately capture the overall force-displacement responses of both the kernel and full seed. This integrated theoretical, numerical and experimental methodology developed in this investigation shows a promising toolkit to explore the damage initiation and evolution of microstructured biological and bio-inspired materials under large deformation.