title: Characteristics of the tensile mechanical properties of fresh and dry forewings of beetles.
abstract: Based on a tensile experiment and observations by scanning electron microscopy (SEM), this study demonstrated the characteristics of the tensile mechanical properties of the fresh and dry forewings of two types of beetles. The results revealed obvious differences in the tensile fracture morphologies and characteristics of the tensile mechanical properties of fresh and dry forewings of Cybister tripunctatus Olivier and Allomyrina dichotoma. For fresh forewings of these two types of beetles, a viscous, flow-like, polymer matrix plastic deformation was observed on the fracture surfaces, with soft morphologies and many fibers being pulled out, whereas on the dry forewings, the tensile fracture surfaces were straightforward, and there were no features resembling those found on the fresh forewings. The fresh forewings exhibited a greater fracture strain than the dry forewings, which was caused by the relative slippage of hydroxyl inter-chain bonds due to the presence of water in the fibers and proteins in the fresh forewings. Our study is the first to demonstrate the phenomenon of sudden stress drops caused by the fracturing of the lower skin because the lower skin fractured before the forewings of A. dichotoma reached their ultimate tensile strength. We also investigated the reasons underlying this phenomenon. This research provides a much better understanding of the mechanical properties of beetle forewings and facilitates the correct selection of study objects for biomimetic materials and development of the corresponding applications.
authors.affiliation: School of Civil Engineering & International Institute for Urban Systems Engineering, Southeast University, Nanjing 210096, China; School of Civil & Architectural Engineering, Anyang Institute of Technology, Anyang 455000, China.
authors.forename: Wanyong
authors.initials: W
authors.lastname: Tuo
authors.affiliation: School of Civil Engineering & International Institute for Urban Systems Engineering, Southeast University, Nanjing 210096, China. Electronic address: chenjpaper@yahoo.co.jp.
authors.forename: Jinxiang
authors.initials: J
authors.lastname: Chen
authors.affiliation: School of Civil Engineering & International Institute for Urban Systems Engineering, Southeast University, Nanjing 210096, China.
authors.forename: Zhishen
authors.initials: Z
authors.lastname: Wu
authors.affiliation: School of Civil Engineering & International Institute for Urban Systems Engineering, Southeast University, Nanjing 210096, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Xie
authors.affiliation: Nantong Vocational University, Nantong, Jiangsu 226007, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000818:Animals; D040761:Biomimetic Materials / Q000737:chemistry; D001517:Coleoptera / Q000737:chemistry; D005260:Female; D008297:Male; D008855:Microscopy, Electron, Scanning; D013718:Tensile Strength; D014921:Wings, Animal / Q000737:chemistry*
keywords: Beetle forewing; Biomimetic materials; Chitin fibers; Tensile mechanical properties; Tensile strain