Impact resistance of metal-composite hybrid joints produced by frictional heat

Abstract

The impact resistance of aluminum alloy 2024-T3 and carbon-fiber-reinforced polyphenylene sulfide joints was investigated using drop weight test. The joints were aluminum-side and composite-side impacted to provide a preliminary design guideline for hybrid joints. Four energy levels were investigated for each side: 2 J, 4 J, 6 J and 8 J. The joints presented rebounding behavior for all the energy levels. It implies that in all the cases, the impact energy was not totally absorbed by the joints, although the joints failed at 8 J of impact energy. The interface of the joint presented its threshold for absorption of impact energy around 6.5 J, which was reached when the joint was impacted with 8 J of potential energy, independently of the surface under impact. Thus, this study showed that a single friction spot joint could absorb up to 103 kJ.m−2 of joined area. The joints impacted from the aluminum side presented residual strengths of 84% (2 J), 30% (4 J), and 25% (6 J). For composite-side impacted joints, the residual strengths were 80% (2 J), 54% (4 J), and 45% (6 J). Generally, the aluminum-side impacted joints showed lower residual strength than the composite-side impacted joints. The impact energy introduced from the aluminum side was mostly absorbed in the plastic deformation of the aluminum part, bending the aluminum and promoting the detachment of the interface. Otherwise, the impact energy introduced from the composite side was mostly absorbed by the creation/extension of internal damage through the plies of the composite. Thus, it is expected that the impact energy was only partially transferred to the interface of the joint in the case of composite-side impact. Consequently, these joints presented higher residual strength after impact than the aluminum-side impacted joints.