Development of CFRE composite scarf adhesive joints with SiC and Al2O3 nanoparticle

Abstract

The present work aims to strengthen scarf adhesive joints (SAJs) with 5° and 10° scarf angles in carbon fiber composite adherends via introducing SiC and Al2O3 nanoparticles into the adhesive epoxy. The SAJs were characterized under thermal and moisture environments. The ultimate tensile strengths (UTSs) of 5° and 10° SAJs were respectively improved by 41.2% and 8.4% for SiC/E-SAJs and 22.5% and 26.5% for Al2O3-SAJ compared to neat epoxy-SAJs. The UTSs and stiffness of the moist SAJs were marginally decreased. Although the UTSs of SAJs were decreased at 50°C, the strain at ultimate load and fracture toughness were tremendously increased and accordingly, the SAJs are not prone to sudden failure. Interfacial shear cracks were initiated between the adhesive layer and the stiffer-adherends at the joint-overlaps, whereas the adhesive layer remains attached to the lower stiffness adherend tip-ends. Crack initiation was detected effectively at about 65% of UTS of the SAJs using instrumented-SAJs with eight strain gauges. Applying such technique on composite structures can contribute in prolonging their service life by carrying out the necessarily repairs before the catastrophic failure of the structure. The experimental and predicted UTSs of SAJs using three-dimensional finite element analysis model are in good agreement, R2=0.9884.