Surface modification of nano‐SiO₂ and its interaction mechanism in the interface of fiber metal laminates: Experimental and MD simulation analysis

Abstract

In order to optimize the reinforcing effect of nano‐SiO2 on the interface of fiber metal laminates (FMLs), the nano‐SiO2 was treated by ultraviolet irradiation and silane coupling agent for different surface properties. The interaction mechanisms of nano‐SiO2 were studied by mechanical test, chemical analysis, morphology observation, and molecular dynamics (MD) simulation. The results showed that the average failure strength of FMLs with untreated, hydrophilic and lipophilic nano‐SiO2 increases by 31.80%, 48.77%, and 51.38% compared to the FMLs without SiO2, respectively, and the interface fracture energy for those increases by 31.50%, 74.82%, and 21.47%, respectively. The disparity among the properties is primarily attributed to the surface polarity. The surface group of untreated and hydrophilic SiO2 is hydroxyl, which shows stronger attraction to resin but also easy to agglomerate, while the lipophilic is silane group that shows lower polarity, resulting in weaker attraction to resin but easier dispersion within the resin. Specifically, the surface polarity was verified by characterizing the particle center distance and the number of atoms surrounded by the particle in the two‐particle model. Moreover, the simulation revealed that nano‐SiO2 and resin molecules are mainly connected by chemical bond and hydrogen bond to transfer the load.Highlights The mechanism was explored by experiment and molecular dynamic simulation. The addition of lipophilic SiO2 increased the failure strength by 51.38%. The incorporation of hydrophilic SiO2 enhanced fracture energy by 74.82%. The polarity of the surface group of SiO2 affected the agglomeration/dispersion. The SiO2 and resin were mainly connected by chemical bond and hydrogen bond.