Background and Objectives Nanostructured devices are finding ever increasing use in industrial applications which has prompted a need to further understand their mechanical properties. Research has shown that as the size of structures such as reinforcing particles and fibres is reduced to nanometers, their particular mechanical properties vary. This variation of the material behaviour has mainly been attributed to surface/interface energy around the free surface or interface of the nanostructures. Since such nanostructured materials exhibit characteristic length in nanometers, their elastic properties are affected by surface stresses that can displace atoms from the equilibrium positions which they normally occupy in bulk macroscopic assemblies. As such properties are not normally noticed in macroscale, as they are limited to only a few atomic layers, the free surface/interface effects are often neglected in the classical continuum mechanics. This paper investigates the effect of the surface/interface elasticity on the dynamic stress state in a matrix around the nano-particle reinforcements due to asymmetric dynamic loading. Methods In the surface/interface elasticity theory, an interface between a nano-particle reinforcement and matrix is considered a negligibly thin surface or a membrane glued to the underlying bulk materials without slipping. The elastic constants of the membrane are different from those of its adjoining materials, and its inertia can be neglected in the dynamic problem. This leads to a set of non-classical boundary conditions at the interface. Results: Different surface properties are investigated under varying frequencies of shear waves as well as different matrix and nano-reinforcement material properties. The stress concentrations values around the nano-particles are found to be significantly dependent on the frequency of excitation and surface properties. The effect is localized near the nano-particle matrix interface and disappears away from the interface into the matrix bulk. Conclusions: Dynamic stress field at the reinforcement-matrix interface is significantly affected by surface/interface elasticity as the reinforcing particle size reduces to nanometers. The increasing surface elastic constant μs can significantly reduce the stress concentration values at the nano-particle matrix interface.


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