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 inthis study is an epoxy- based Araldite 2014. Hybrid- doped joints containing 1.2% HNT and 0.3% BNP by weight demonstrateda 48.94% increase in maximum shear strength compared to the pure specimen. The most significant displacement atrupture—approximately 2.5 mm—was observed in these specimens, resulting in a 72.41% increase in ductility relative tothe pure adhesive. Fracture mode analysis revealed a transition from adhesive failure in pure samples to cohesive fail-ure 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, theseeffects provide a synergistic toughening mechanism. Additionally, Fourier Transform Infrared (FTIR) analyses demon-strated 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 demandingapplications.