Reliability of the Young's modulus of crab exoskeleton materials estimated from nanoindentation tests

The local and global mechanical properties of a mineralized biological material using the mud crab as a model material were investigated and compared. The stress–strain (s–s) curves for wet and dry conditions of the endocuticle were exactly examined by performing tensile tests with strain gauges. The local properties were examined through nanoindentation testing (NI) in a dry condition. The global Young's modulus, E , evaluated from the slope of the linear part of the s–s curve, did not vary with wet or dry specimen conditions; however, the stress and strain required to fracture depended on the conditions. The E was compared with the results of property mapping obtained from NI. Due to local differences in the grade of mineralization in the exoskeleton, the mapping indicated that nanoindentation tests should be performed for an extensive region of the cuticle. The results will provide useful information for future material development based on biomimetics.