Synergistic Effects of Mixed Silica Micro-nanoparticles on Compressive Dynamic Stiffness and Damping of Epoxy Adhesive

Dynamic stiffness and damping of epoxy adhesives are critical for ensuring the safety, reliability, and comfort of structures subjected to vibrations and impact loads. This study conducts split Hopkinson pressure bar (SHPB) tests to investigate the synergistic effects of silica micro-nanoparticles on these critical properties. Micro-nanoparticle content and composition ratio purity are varied at 2, 5, and 10% by weight (wt%) and from 0% (pure microparticles) to 100% (pure nanoparticles), respectively. Positive simultaneous stiffening and energy absorption effects are observed at a silica content of 5 wt% owing to improved nanoparticle dispersion; this increases the interface area and induces cooperative matrix–filler interactions. At this silica content and a composition ratio of 50%, stiffness and damping are 45 and 40% larger than those of neat epoxy, respectively. Silica micro-nanoparticles are less effective in improving particle dispersion at more than 5 wt%. Conventional mechanical dispersion is limited to applications below a certain silica content; the results suggest a simple, low-cost dispersion technique as an alternative to the in-situ technique and provide options for designing epoxy stiffness and damping appropriate for specific applications.