title: Mechanical response of common millet (Panicum miliaceum) seeds under quasi-static compression: Experiments and modeling.
abstract: The common millet (Panicum miliaceum) seedcoat has a fascinating complex microstructure, with jigsaw puzzle-like epidermis cells articulated via wavy intercellular sutures to form a compact layer to protect the kernel inside. However, little research has been conducted on linking the microstructure details with the overall mechanical response of this interesting biological composite. To this end, an integrated experimental-numerical-analytical investigation was conducted to both characterize the microstructure and ascertain the microscale mechanical properties and to test the overall response of kernels and full seeds under macroscale quasi-static compression. Scanning electron microscopy (SEM) was utilized to examine the microstructure of the outer seedcoat and nanoindentation was performed to obtain the material properties of the seedcoat hard phase material. A multiscale computational strategy was applied to link the microstructure to the macroscale response of the seed. First, the effective anisotropic mechanical properties of the seedcoat were obtained from finite element (FE) simulations of a microscale representative volume element (RVE), which were further verified from sophisticated analytical models. Then, macroscale FE models of the individual kernel and full seed were developed. Good agreement between the compression experiments and FE simulations were obtained for both the kernel and the full seed. The results revealed the anisotropic property and the protective function of the seedcoat, and showed that the sutures of the seedcoat play an important role in transmitting and distributing loads in responding to external compression.
authors.affiliation: Department of Mechanical Engineering, University of New Hampshire, Durham, NH, USA.
authors.forename: Benjamin P J
authors.initials: BPJ
authors.lastname: Hasseldine
authors.affiliation: Department of Mechanical Engineering, University of New Hampshire, Durham, NH, USA.
authors.forename: Chao
authors.initials: C
authors.lastname: Gao
authors.affiliation: Department of Mechanical Engineering, University of New Hampshire, Durham, NH, USA.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Collins
authors.affiliation: Liquid Processing & Casting Technology R&D Group, Korea Institute of Industrial Technology, Incheon, South Korea.
authors.forename: Hyun-Do
authors.initials: HD
authors.lastname: Jung
authors.affiliation: Department of Materials Science and Engineering, Seoul National University, Seoul, South Korea.
authors.forename: Tae-Sik
authors.initials: TS
authors.lastname: Jang
authors.affiliation: School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore.
authors.forename: Juha
authors.initials: J
authors.lastname: Song
authors.affiliation: Department of Mechanical Engineering, University of New Hampshire, Durham, NH, USA. Electronic address: yaning.li@unh.edu.
authors.forename: Yaning
authors.initials: Y
authors.lastname: Li
mesh_terms: D016880:Anisotropy; D001696:Biomechanical Phenomena; D020342:Finite Element Analysis; D008954:Models, Biological; D008897:Panicum / Q000502:physiology*; D012639:Seeds / Q000502:physiology*; D013314:Stress, Mechanical
keywords: Anisotropy; Common millet; Compression; Finite element; Seed; Suture