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Scanning electron microscope (SEM) observation shows that tumblebug's elytra are a kind of chitin fibre reinforced biocomposite. In the biocomposite, the chitin fibres possess a laminated microstructure and distribute in a kind of particular helicoidal pattern. More careful observation indicates that there is a kind of fibre helicoidally rounding hole in the elytra. Based on the SEM observation, a kind of composite laminate with biomimetic fibre helicoidally rounding hole was fabricated through a special mould and moulding process. The extrusion strength of the biomimetic fibre helicoidally rounding hole was investigated and compared with that of the conventional drilling hole in the composite laminate. It is shown that the extrusion strength of the biomimetic fibre helicoidally rounding hole is markedly larger than that of the conventional drilling hole. [ABSTRACT FROM AUTHOR]

The observation of scanning electron microscope (SEM) showed that Tumblebug elytra consist of almost parallel upper and lower cuticles. Both of which are a kind of chitin-fiber-reinforced composite. There is a kind of chitin-fiber-reinforced composite pillars between the upper and lower cuticles, which support and connect the upper and lower cuticles uprightly. More careful observation showed that the chitin fibers in the pillars smoothly extend to the upper and lower composite cuticles forming a kind of fiber-continuous pillar-board composite (FCPBC) structure. Based on the observation, two kinds of pillar-board composite structure specimens, respective with continuous and discontinuous glass fibers, were fabricated with molding and felting processes. The rupture strengths of the two kinds of the specimens were tested and compared. It showed that the rupture strength of the specimens of the FCPBC structure is markedly larger than that of the specimens of the fiber-discontinuous pillar-board composite (FDPBC) structure. At last, the experimental result was analyzed for illumining the mechanism of the FCPBC structure in the enhancement of the strength. [ABSTRACT FROM AUTHOR]