Macro‐Meso Studies on Mechanical Behaviors of the Nano‐ <scp> SiO <sub>2</sub> </scp> Modified Structural Adhesive
Songbo Wang, Zhuo Duan, Jiayi He, Siyuan Yang, Yaqi Li, Yang Li, Yaodong Liu
Abstract
ABSTRACT Adhesive joints have been widely used across various industries due to their strong bonding performance, and recent advancements in nanotechnology offer opportunities to enhance their mechanical properties. This study investigates the reinforcement of the adhesive with nano‐SiO 2 by assessing both macroscopic and mesoscopic effects. A total of 24 macroscopic tests were conducted on the adhesives with varying SiO 2 nanoparticle contents (0%, 1.0%, 1.5%, 2.0%, and 2.5%). Dog‐bone tensile and single‐lap shear tests were repeated twice, while glass transition properties were assessed once for each SiO 2 content and compared to existing data on neat adhesives. To further investigate the underlying mechanisms, scanning electron microscopy, Fourier transform infrared spectroscopy, Energy Dispersive Spectroscopy, and Transmission Electron Microscopy were employed to examine the interfacial failure modes and potential changes in functional groups between the neat adhesive and the nano‐SiO 2 ‐modified adhesive. The results show that nano‐SiO 2 modification improved the mechanical properties of adhesives due to both physical and chemical interactions: nano‐SiO 2 filled voids in the adhesive, increased friction between the adhesive and adherend, enhanced van der Waals forces, and improved the cross‐linking density of the epoxy resin. At a nano‐SiO 2 content of 2.0%, both tensile and single‐lap shear strengths showed the most significant improvements, increasing by 14.0% and 35.0%, respectively. Additionally, the glass transition temperature rose by approximately 7.6% at 2.0% nano‐SiO 2 , while it increased by 25.0% at 1.0% nano‐SiO 2 . Based on these findings, the addition of 2.0% nano‐SiO 2 is recommended, as it substantially enhances strength while maintaining satisfactory thermal stability.