Fatigue strength of copper and mild steel single lap joints bonded with epoxy-alumina nanocomposite adhesive

Abstract

An In-situ polymerization technique was used to create an epoxy nano-alumina composite adhesive. Ultrasonication was used to achieve the distribution of nano-alumina particles in an epoxy matrix containing weight percentage 0.5,1,1.5 and 2% nanoparticles. Single lap joints with adherents of Copper-Copper (CC), Mild Steel-Mild Steel (MM) and Copper-Mild Steel (CM) were prepared following ASTM D1002 standards. Lap shear strength tests in tension of bonded joint samples (CC, MM, and CM) were conducted on UTM at 1.27 mm/min cross head travel rate. The fatigue strength of bonded specimens was tested at a stress ratio of R 0.1 and a frequency 5HZ by following ASTM D3166 standards. Stress amplitudes of fatigue test were taken at 70%, 65%, 60% and 55% of shear strength of corresponding single lap joints. Six samples were tested to calculate the average number of cycles to failure. For each combination of joints shear strength and fatigue life were increased with an increase in wt.% but maximum increment was obtained at 1.5 wt.% of nanoparticles addition. An increment of 40% for CC joints, 66% for MM joints and 47% for CM joints was obtained in nanocomposite’s shear static strength containing 1.5 wt.% nanoparticles over neat epoxy joints. Increment in fatigue life of CC, MM, and CM joints at 1.5 wt.% of spherical nanoparticle inclusions was 401%, 500%, and 409% respectively.