Abstract
We investigated a microstructure and mechanical properties of a claw of Japanese fresh water crab (Geothelphusa dehaani) using X-ray diffraction (XRD), scanning electron microscope (SEM) and scanning acoustic microscope (SAM). It was observed using SEM that the microstructure of the claw consists of epicuticle (outermost layer), exocuticle (outer layer) and endocuticle (inner layer). Evaluations of Young's modulus, density and Poisson's ratio performed by using SAM. As a result, Young's modulus and density of exocuticle (outer layer) tend to increase gradually toward the inside and those properties of endocuticle (inner layer) tend to decrease gradually towards the inside. In the area of the exocuticle to the endocuticle, the maximum value of Young's modulus was 42.0 GPa and the minimum value was 12.5 GPa. The maximum value of density was 1.05 g/cm3 and the minimum value was 0.25 g/cm3. It was observed that the tendency for the mechanical properties of the crab hard tissue to change from the exocuticle continuously toward the endocuticle. By changing mechanical properties continuously, it was expected that hardness and toughness are ensured for the whole structure of crab claw.
