Multiscale Investigation of Interfacial Adhesion Strength of Epoxy Resin Adhesives Over a Wide Range of Loading Rate

Abstract For a reduction of aircraft structural weights, adhesive bonding has attracted attention to joint dissimilar materials. It often uses polymetric resin and it is well known that the strength of resin adhesives depends on the loading rate. Therefore, it is expected that the bonding strength of resin adhesive joints also shows a loading rate dependence. To investigate the effect of loading rate on bonding strength of epoxy resin adhesive with aluminum alloy, this study conducted three experimental methods with different loading rate: quasi-static test, Split Hopkinson Pressure Bar (SHPB) test, and Laser Shock-wave Adhesion Test (LaSAT). LaSAT utilizes an elastic stress wave (laser induced shockwave) generated by laser ablation to delaminate the adhesive from substrate at very high loading velocity. As a result, it is found that interfacial bonding strength significantly depended on loading rate. In addition, fracture toughness of the same adhesive joints was also investigated, and its loading rate dependency was discussed. Finally, in order to clarify the mechanism of the loading rate dependence, we investigated the deformation of the molecular chains using molecular dynamics (MD) and Finite Element Method (FEM) with cohesive zone modeling was employed to simulate a crack propagation for wide ranges of loading rate.