Hybrid steel-to-composite joint behavior under tensile loading

Hybrid steel-to-composite 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. Recent research at Imperial College London (ICL) and the U.S. Naval Academy (USNA) has focused on characterizing the behavior and ultimate load capacity of hybrid steel-to-composite joints with different configurations under various loading conditions. This paper presents results from tensile strength testing of steel-to-composite double lap joints, comparing pseudostatic 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. Finite Element Analysis (FEA) results are compared to experimental results for both perforated and non-perforated joints.