Microstructural Characterization and Hardness Behavior of a Biological Saxidomus purpuratus Shell

The microstructures of the Saxidomus purpuratus shell were observed. It was found that the inner and middle layers of the shell are composed of crossed lamellae, while the outer layer exhibits porous structures. With the characteristic structure of each layer, the hardness of inner layer with narrow domains in crossed lamellar structure is the highest, and that of middle layer with wide domains is lower, while the outer layer has the lowest hardness. The damage morphologies of the indentations change a lot, depending not only upon the magnitude of the indentation load, but also upon the orientation between the indentation direction and the crossed lamellae in the microstructure of the shell, which illustrates the anisotropy in mechanical properties of such shells.