Dynamic deformation of lap joints and scarf joints under impact loads

The propagation of stress waves and the concentration of dynamic stress under impact loading in single lap joints, tapered lap joints and scarf joints, which were bonded adhesively, were investigated analytically and experimentally. Viscoelastic properties of cured adhesive resin were obtained from the variation of strain waves which propagated in a rod of cured resin. The compliance of the cured adhesive resin depended on the frequency of the strain waves. The viscoelastic properties obtained in the test were formulated by Voigt viscoelastic models. The stress distribution and the time variation of stress and strain in the joints under tensile impact loading were calculated using the finite element method, considering the viscoelastic properties of the adhesive. Stress concentration occurred in both the edges of the adhesive layers of the single lap joints and the tapered lap joints. The stress concentration in the scarf joints was relatively small. The stress occurred in the taper lap joints was smaller than that in the single lap joints when the taper lap joints had enough taper length. Impact test on the joints, which had adherends of aluminum alloy, was conducted to verify the pertinence of the analyses. The deformation of the tapered lap joints and the scarf joints showed good agreement on the analytical results. The deformation of the single lap joints was more complicated than the analytical results.