Experimental and Numerical Study of Hybrid Steel-to-Fiber Reinforced Polymer Joints Under Tensile Loading

Hybrid metal-to-fiber reinforced polymer (FRP) joints are being used more commonly for load bearing applications. However, these hybrid joints usually entail geometry and material discontinuities which can induce stiffness mismatch and cause local stress concentrations. The shock impedance mismatch caused by the different wave propagation characteristics can also be crucial to the structural response of the hybrid joints under impulsive loads due to sources such as an air blast or underwater explosion (UNDEX). Recent research at Imperial College London (ICL) and the U.S. Naval Academy (USNA) has focused on characterizing the behaviour and ultimate load capacity of metal-to-composite hybrid joints with different configurations under various loading conditions. This paper presents results from tensile strength testing of steel-to-vinyl ester GRP double lap joints, comparing pseudo-static strength with dynamic strength and comparing joints that exploit perforated steel plates with those manufactured with non-perforated steel plates. An intentional manufacturing flaw also was incorporated into half of the joints, both perforated and non-perforated joints, in order to assess the effect of this flaw type on joint strength. These experimental results are compared to Finite Element Analysis (FEA) results for both perforated and non-perforated joints.