Scale Dependence of the Mechanical Properties of Interfaces in Crustaceans Thin Films

Abstract

Crustacean exoskeletons in the form of thin films have been investigated by several researchers in order to understand the role played by the exoskeletal structure in affecting functioning of species such as shrimps, crabs and lobsters. These species exhibit similar design in their exoskeleton microstructure. Bouligand pattern (twisted plywood structure), layers of different thicknesses across cross section, changes in mineral content through the layers etc. are common feature changes. Different parts of crustacean exoskeletons exhibit a significant variation in mechanical properties based on the variation in the above mentioned features. Mechanical properties have been analyzed by authors using imaging techniques such as SEM (Scanning Electron Microscopy), EDX (Energy Dispersive X-ray) and using mechanical characterization based on nanoindentation. Analyses show that the confinement effect arising from interfaces sandwiched in crustacean microstructure layers along with the strain rates of deformation plays a major role in the deformation of such layered systems. A new constitutive model is proposed that couples the effect of strain-rate and confinement to predict interface deformation behavior. The model predictions are validated based on experiments in glass/epoxy interfaces.