Circumcolumnar microstructure of Tumblebug cuticle and biomimetic application

The elegant microstructures of insect cuticle obtained through long-time evolution endow the cuticle with excellent mechanical properties. Scanning electron microscope (SEM) observation shows that the cuticle of Tumblebug (an insect) has a basic characteristic of laminated structure consisting of highly oriented chitin fibers and sclerotized protein matrixes. Compared with manmade advanced composites, it contains more detailed heterogeneous microstructures. The observation also shows that there are many tiny holes in the cuticle and fibers distribute continuously round the holes forming a kind of circumcolumnar layup. With the observed results, a kind of special composite laminate specimen with the circumcolumnar layup is designed and fabricated. Its rupture strength is tested and compared with that of the conventional one with the holes drilled. The comparison shows that the rupture strength of the former is obviously higher than that of the latter. The larger the hole, the larger increase in the rupture strength can be achieved. The experimental result is verified with the representative models of the circumcolumnar and drilling-hole layups.