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Abstract: Biological materials, such as bone and nacre, are nanocomposites of protein and mineral with superior mechanical properties. The basic building blocks of these materials feature a generic nanocomposite structure with staggered alignment of mineral platelets in protein matrix. Because of the structural complexity of the generic structure, its displacement and stress fields are currently still unknown. In this study, a perturbation method was applied for analytically solving the displacement and stress fields of the nanocomposite structure under uniaxial tension. The effect of the elastic modulus, aspect ratio and volume fraction of mineral and protein on the displacement and stress fields in the nanocomposite structure was studied. A non-dimensional parameter γ was then suggested for characterizing the stress and strain fields in this nanostructure. We showed that the assumption of uniform shear stress distribution at the mineral–protein interface in the TSC model is valid when γ is less than 4 which is broadly applicable to most biological materials. The analytical solutions of displacement and stress fields obtained in this study provide a solid basis for further analyses of mechanical properties, such as the buckling and the fracture behaviors of biological materials. [Copyright &y& Elsevier]

Abstract: The influence of nanoclay on the impact damage resistance of carbon fibre–epoxy composites has been investigated using the low-velocity impact and compression after impact (CAI) tests. The load–energy vs. time relations were analyzed to gain insight into the damage behaviours of the materials. The CFRPs containing organoclay brought about significant improvement in impact damage resistance and damage tolerance in the form of smaller damage area, higher residual strength and higher threshold energy level. The presence of nanoclay in the epoxy matrix induced the transition of failure mechanisms of CFRP laminates during the CAI test, from the brittle buckling mode to more ductile, multi-layer delamination mode. Addition of 3wt% clay was shown to be an optimal content for the highest damage resistance. [Copyright &y& Elsevier]