Exploring the impact of graphene nanoplatelets on adhesive mechanical strength: A comprehensive investigation into single-lap joint elastoplastic behavior via cohesive zone method

This research conducted a thorough examination on the effects of graphene nanoplatelets (GNPs) reinforcement on the mechanical strength of low-viscosity epoxy and elastic-plastic strength of single-lap joints (SLJs) by using finite element analysis (FEA) and experimental procedures. The reinforcing process of GNPs within low strength adhesive was accomplished by using controlled mixing techniques and the SLJ configuration samples were fabricated using AW 6063-T6 Aluminum adherends (that were mechanically and chemically treated). Tensile tests on bulk composite adhesive showed that the inclusion of GNPs significantly enhanced the mechanical properties of epoxy matrix. Maximum improvement of 775.46 % in ductility was noted with the addition of 0.1 % GNPs. Moreover, 51.43 % and 166 % improvements in elasticity and tensile strength were obtained by adding 1 % GNPs, respectively. Besides, 123.21 % maximum improvement in SLJ shear strength was obtained by adding 1 % GNPs. Thereafter, the experimental results were incorporated into the computational modeling workflow, where the trapezoidal cohesive law was employed based on cohesive zone modeling (CZM) scheme. Prediction accuracy of the numerical model was examined by comparing its results with experiment results and strong agreement was observed with relative error of 6 % in the case of 0.1 % wt. GNPs. At the same wt.%, the effects of geometric modifications on the joint performance were explored. A significant decrease in the concentration of stress at important joint locations was observed, indicating improved joint integrity and failure resistance. Peel stress was seen to rise with overlap duration, indicating that longer overlaps had higher peel stress.