Mechanism Of Strength And Toughness Of Microstructure Of Chafer Cuticle

Generally, biological materials in nature are composites, so biological materials can be called as natural biocomposites. Coming through natural evolution over many centuries, natural biocomposites include various excellent microstructures. The microstructures make that the natural biocomposites possess excellent mechanical properties. The research on the microstructures of natural biocomposites can offer instructive guidance for the research of man-made high-performance composites. Chafer cuticle is a kind of representative natural biocomposite which possess excellent microstructures and mechanical properties. In the research, the microstructures of a chafer cuticle are observed with a scanning electron microscope (SEM). The observation shows that the cuticle is a kind of fiber-reinforced biocomposite consisted of chitin fibers and protein matrix. The observation also shows that there are many particular microstructures which include: (1) abnormal fiber end; (2) spinous fiber;(3) fiber-round-hole ply;(4) dual-trumpet-shape pillar; (4) heterogeneous fiber ply.Based on the observed results of the SEM, the analyses of the finite element models on the simple composite elements with the abnormal-fiber end, spinous fiber, fiber-round-hole ply, dual-trumpet-shape and heterogeneous fiber ply are conducted. These composite elements can well present the main characteristics of the observed microstructures of the chafer cuticle. The excellent mechanical properties of these microstructures are analyzed by the finite element tools. They are also compared with the models of the conventional structures of man-made fiber-reinforced composites. Following profitable conclusions for designing man-made advanced composites are obtained:(1) Abnormity end of fiber can decrease the convergence of interface shearing stress between the fiber and matrix and can markedly improve the strength and toughness of fiber-reinforced composite. The rigidity of the composite with the abnormity end of fibers can also be increased compared to conventional composite.(2) Spinous fibers can increase the pullout force of the fiber and decrease the convergence of the shearing stress between the fiber and matrix, which can improve the strength and toughness of fiber-reinforced composite.(3) Fiber-round-hole ply can decrease the stress convergence and well transfer...