The Combined Effects of Hybrid HNTs and Pure Boron Nanoparticles on Shear Strength and Failure Characteristics of Adhesive Joints

ABSTRACT This study investigates the effect of a hybrid incorporation of halloysite nanotubes (HNT) and pure boron nanoparticles (BNP) on the shear strength of single‐lap joints bonded with Araldite 2014 epoxy adhesive. The adhesive matrix used in this study is an epoxy‐based Araldite 2014. Hybrid‐doped joints containing 1.2% HNT and 0.3% BNP by weight demonstrated a 48.94% increase in maximum shear strength compared to the pure specimen. The most significant displacement at rupture—approximately 2.5 mm—was observed in these specimens, resulting in a 72.41% increase in ductility relative to the pure adhesive. Fracture mode analysis revealed a transition from adhesive failure in pure samples to cohesive failure and fiber tearing in nanoparticle‐doped samples, indicating enhanced adhesion between the adhesive and substrates. Detailed Scanned Electron Microscopy (SEM) analyses showed that HNT particles increase toughness through crack‐bridging, while BNP particles enhance toughness via crack‐deviation and particle segregation mechanisms; together, these effects provide a synergistic toughening mechanism. Additionally, Fourier Transform Infrared (FTIR) analyses demonstrated that chemical interactions between nanoparticles and the Araldite 2014 matrix further improve adhesive strength. These findings contribute to the development of high‐performance epoxy adhesive formulations for structurally demanding applications.