Molecular dynamics simulations of the micro mechanism of functionalized SiO2 nanoparticles and carbon nanotubes modified epoxy resin adhesives

The bonding interface of carbon-fiber-reinforced polymer (CFRP)-reinforced steel structure is a weak part, and nanomaterial-modified adhesives are expected to improve its comprehensive performance. This paper investigates the micro- modification mechanisms of nanomaterials on epoxy resin adhesives using molecular dynamics simulation method. It explores how the functionalized nano SiO2 and carbon nanotubes affects the thermal and mechanical properties of the epoxy resin adhesive. The models established using Materials Studio software include the pure epoxy resin adhesive model (EP) with varying degrees of crosslinking, the functionalized nano-SiO2-modified epoxy resin adhesive model (EP + SiO2/OH), the single-walled carbon nanotube-modified epoxy resin adhesive model (EP + SWNT), and the synergistic enhancements model of the epoxy resin adhesive with nano-SiO2 and carbon nanotubes (EP + SWNT + SiO2/OH). Based on the aforementioned models, the Forcite module is used to calculate the free volume, glass transition temperature and mechanical properties of the adhesive. The results show that the degree of crosslinking effects significantly the mechanical performance of epoxy resin adhesive. A high degree of crosslinking restricts the movement of the molecular chain, enhancing the strength of the epoxy resin adhesive. Furthermore, the trend of the mechanical and thermal properties of the four models remains constant with the rise of temperature, and the properties decrease most significantly in the range of the glass transition temperature. Moreover, the epoxy resin adhesive doped with nanomaterials exhibits varying degrees of enhancement in mechanical and thermal properties. The epoxy resin adhesive reinforced with functionalized nano-SiO2 and carbon nanotubes exhibits better properties compared to those with a single nanomaterial.