Journal of Micromechanics and Molecular Physics

Here, syntactic foams are considered as a linearly elastic composite medium, which consists of a homogeneous matrix containing hollow glass and unwanted voids. The composite is modeled by the generalized self-consistent scheme and combining the three-phase model and the four-phase model. The overall properties are obtained using a micromechanical approach based on Green’s function techniques and the interfacial operators. The model assumes that all constituents are elastic and perfectly bonded. Comparison with experimental and numerical results shows that the methodology used is capable of predicting, with good accuracy, the elastic moduli of real syntactic foams.

This paper has the objective of studying the propagation of surface waves in a transversely isotropic medium based on nonlocal strain gradient theory (NSGT). A characteristics equation for the existence of surface waves is discussed. This equation could be easily reduced to the ones of the gradient strain theory, nonlocal theory and classical theory. It has also been concluded that there exist escape frequency and cut-off frequency for the wave propagating in size-dependent materials based on the NSGT. Dispersion equation for the propagation of Rayleigh-type waves at the free surface has been derived. The effect of the nonlocal parameter, the strain gradient parameter on the Rayleigh wave propagation is considered through some numerical examples.

Grain boundary (GB) dynamics plays an important role in the mechanical and physical properties of nanocrystalline metals. In this study, we investigate the temperature effect on GB deformation transition using molecular dynamics simulations of [100] symmetric tilt GBs in Au bicrystals. Different deformation behaviours were revealed in GBs with the same structures at varied temperatures. GB sliding occurs as the predominant deformation mechanism at elevated temperatures, while GB migration dominates at low temperatures. The temperature-dependent critical stresses for GB migration and GB sliding were compared, revealing that temperature alters the critical GB misorientation at which GB migration transitions to GB sliding. Our study provides new insight into GB-mediated plastic deformation in nanocrystalline materials.

This study investigated the microscale behaviours and damage evolutions of graphene/epoxy nanocomposites under uniaxial tensile loadings. Computational molecular dynamics (MD) simulation was applied to model the microstructural constituents of graphene/epoxy composites and the evaluation of their mechanical and the damage responses at different temperatures. The computed results revealed the influence of the proportions of graphene and temperatures on the mechanical properties, the damage evolution and the change in strain energy associated with failure of the nanocomposites. The study has added to the understanding of the damage development and failure of the graphene nanoplatelets (GNP)/epoxy composites.

A structure of theoretical models set was suggested to predict the elastic moduli of polyurethane copolymer (PUC)/organic modified montmorillonite (OMMT) nanocomposites (NCs) in terms of length (L) to thickness (t) ratio and volume fraction ($V_f$) of OMMT nanoparticles. The predicted elastic modulus outcomes of PUC/OMMT NCs were compared with experiment data. The outcome demonstrated that the suggested aspect ratio of predicted elastic modulus decreased with increased $V_f$ of OMMT compared to experimental data. The largest value of effective aspect ratio belonged to the Hui–Shia model over all OMMT $V_f$. The modified Halpin–Tsai model incorporated with the factor for decreasing modulus (FFDM) recorded the lowest range of percentage error between theoretical and experimental data around 0.385–0.816% at $V_f<0.125$ (4wt.%) OMMT.