Molecular dynamics simulation of the effect of nanomaterial dimensions on the mechanical properties of epoxy adhesives

Abstract

Nanomaterials may significantly improve the mechanical properties of epoxy adhesives, but the mechanisms by which nanomaterial size affects this enhancement remain unclear. This study uses molecular dynamics simulations to investigate how nanomaterial size influences the mechanical properties of epoxy adhesives at the microscale. Using molecular dynamics software, we constructed models of epoxy adhesives modified with SiO₂ nanoparticles of different radii (10 Å, 11.25 Å, 12.5 Å, 13.75 Å) and carbon nanotubes with varying aspect ratios (4.53, 5.44, 6.35). We analyzed key parameters, including glass transition temperature, mechanical properties, free volume, mean square displacement, and interaction energy to evaluate how SiO₂ radius and carbon nanotube aspect ratio affect epoxy adhesive performance. The results revealed that as SiO₂ radius increased, the glass transition temperature (Tg) of the modified epoxy adhesive first decreased, then slightly increased beyond a certain threshold, but overall exhibited a declining trend. Mean square displacement rose with SiO₂ radius, whereas interaction energy peaked and then declined as the radius increased. In carbon nanotube-modified epoxy adhesives, higher aspect ratios resulted in elevated Tg but reduced mean square displacement and interaction energy. These findings elucidate how nanomaterial size affects the glass transition temperature of epoxy adhesives, providing theoretical insights into enhancing adhesive strength and toughness by modifying nanomaterial dimensions, and contributing to the design of high-performance adhesives.