Static Shear Strength of Single-Lap Joint Using Eggshell-Toughened Epoxy as Adhesive Agent

Eggshells are daily food waste disposed of in landfills, producing environmentalissues and an unpleasant odour. Eggshells were crushed to form eggshell powder and may be suitably applied as a filler in epoxy resins to improve their mechanical properties. The shear strength of toughened epoxy with eggshell powder (TEEP) wasstudied. Single-lap joint (SLJ) sheartests were conducted toinvestigate the shear strength of the SLJbonded with different volume fractionsof TEEP. For this purpose, the eggshells were dried and crushed into particles of size 150μm. The volume fraction of eggshell powder in the epoxy resin is 0%, 2.5%, 5%, and 10% by epoxy weight. The epoxy resin system was made of EPIKOTE Resin 828 and Hardener 651 with a mixing ratio of 5:2 by weight.The results show that the shearstrength greatly depended upon overlap lengthand filler volume fractions.The improvement was up to 72.7% and 39.9%,with the longest overlap length and 5% TEEP fraction.Hence, an overlap length of 38.1 mm and a 5% eggshell volume fraction gave the optimum shear strength of 5.045 kN.