On residual mechanical behavior of aluminum-to-composite bonded joints after low velocity transverse impact

Abstract

The widespread usage of adhesively bonded joints in advanced engineering structures has increased the importance of developing design concepts under special loading conditions. As bonded connections in wind turbine blade, automotive, and aircraft structures usually experience different types of impact loads, it is important to evaluate residual mechanical performance of bonded joints after these loads. The present research aims to conduct an experimental and numerical investigation on the influence of low-velocity transverse impact with different impact energies of 1 J, 1.5 J, 2 J, and 2.5 J, and two impactor shapes (spherical and cylindrical) on the residual lap shear strength of glass fiber reinforced polymer (GFRP) composite to 2024 aluminum lap bonded joints. The numerical modeling procedure includes two steps of damage, the first induced in the joint due to the transverse impact and the second due to a tensile shear load applied statically. For this purpose, Hashin damage criterion and cohesive zone damage model were implemented to simulate post-impact damage in the composite and adhesive layer and after applying the lap shear loading. Results revealed that, for a low impact energy of 1 J, there is no significant loss of strength for both impactors, while, for other impact energies, the residual strength of the joints impacted by the spherical impactor was lower than that of the cylindrical one, specially for higher impact energies. It was found that the error between numerical and experimental results was greater for specimens impacted by spherical impactor compared to the cylindrical one. Finally, it was deduced that, under high impact energies, the impact energy contributed in causing matrix damage in the composite substrate rather than inducing damage in the adhesive layer.