Effects of Nano‐ <scp> SiO ₂ </scp> and Core–Shell Particles on the Cryogenic Bonding Performance of Epoxy Structural Adhesives

ABSTRACT In this work, the Nano‐SiO 2 and core–shell particles (BM) were incorporated into the epoxy resin to improve the bonding performance of epoxy structural adhesives on Carbon fiber reinforced polymer matrix composites (CFRP) in cryogenic environments. Furthermore, the mechanisms of the influence of adhesive layer thickness and room temperature/ultra‐low temperature thermal cycling treatment on the bonding performance of the epoxy structural adhesive were investigated in detail. Test results indicated that the incorporation of Nano‐SiO 2 and BM significantly enhanced the shear strength, tensile strength, and elongation at break of the epoxy structural adhesive at both room temperature (RT) and 90 K. Specifically, the tensile strength of Nano‐SiO 2 ‐5/BM‐3 epoxy structural adhesive increases by 25.28% at RT and 6.46% at 90 K, elongation at break by 53.97% at RT and 11.38% at 90 K, and the shear strength of single lap joints by 22.98% at RT and 15.86% at 90 K compared with the neat epoxy structural adhesive. Additionally, the shear strength of epoxy structural adhesive decreased with increasing thickness of the adhesive layer. Finally, with an increasing number of room‐temperature/ultra‐low‐temperature thermal cycling treatments, thermal stress accumulated at the epoxy/CFRP interface, resulting in the formation of microcracks at the interface and thereby reducing the bonding performance.