Investigations Of Strengthening-toughening Mechanisms Of Stag Beetle Elytra

In this paper,the strength and toughening mechanisms of the microstructure of elytra of stag beetle is studied by the observation of scanning electron microscopy(SEM),analyses of theoretical model,calculations of finite element and bionic experiments.Following works are completed and some useful conclusions are obtained.? The microstructures of the elytra of stag beetle,are observed by scanning electron microscopy.Following microstructures are observed:(1)The microstructure of sensory hair-hole(hair-hole microstructure);(2)The microstructure of fiber-spiral layers;(3)The structure of spinous microfibers;(4)The microstructure of square fibers;(5)The structure of fiber-round dual-cone pillars;(6)The structure of cylindrical fiber pillar.? The finite element models of the hair-hole microstructure with interval and without interval are established respectively.Their stress distribution are calculated and analyzed.It is indicated that the stress concentration in the hair-hole microstructure with interval is larger than that of the hair-hole microstructure without interval,which makes that the beetles possess high sensibility to the change of outside airflows.? Crack bifurcation and the expansive paths of the cracks along the spinous fibers and square fibers in the elytra are calculated through the fractal theory.It is proved that crack bifurcation and these especial microstructures of the fibers in the elytra can enhance the fracture strength of the elytra.? The debonded course of the fibers in the conical pillars of the elytra of stag beetle and the fiber-spiral-wound cylindrical pillars of elytra of unicorn beetle are analyzed by the Euler formula of the plane problem and the generalized Euler formula of three-dimensional problem,respectively.The factors of effect of the viscous,inclined angle and spiral angle of the fibers on the debonded course are analyzed.The toughening mechanism of the elytra is revealed;? The composite laminated plates with fiber-spiral structure are biomimetic fabricated.The composite laminated plates with parallel structure are also made for comparison.The flexural rigidity of the two kinds of the composite laminated plates are tested and compared through the tests of three-point bending.It is shown that the bionic composite laminated plates possess a proper flexural rigidity and also better ability to bear the complex external loads than the composite laminated plates with the parallel structure.