Experimental investigation of the elastic–plastic deformation of mineralized lobster cuticle by digital image correlation

This study presents a novel experimental approach to the characterization of the deformation of a mineralized biological composite using arthropod cuticle as a model material. By performing tensile tests combined with a detailed strain analysis via digital image correlation, the elastic–plastic deformation behavior of the endocuticle of the American lobster Homarus americanus is examined. The test specimens originate from the pincher and crusher claws. For evaluating the effect of moisture on the deformation behavior, the samples are tested both in dry and in wet state. Sample characterization using the digital image correlation method requires a stochastic spot pattern on the sample surface. Digital images are then taken at subsequent deformation stages during the mechanical test. These images are used to calculate the displacement, the displacement gradient, and the strain fields via pattern correlation. The method is applied both, at a global scale to measure with high precision the stress–strain behavior of the bulk cuticle and at a microscopic scale to reveal strain heterogeneity, strain patterning, and strain localization phenomena.