Effect of residual strains on the static strength of dissimilar single lap adhesive joints

Adhesive joints usually experience different thermal conditions not only during their service life but even also when the joints are stored, and no external force is applied. One of the main concerns for such a condition is the residual strains/stresses induced into the adhesive layer due to the cyclic ambient temperature. In this research, the effects of residual strains on the static strength of dissimilar single lap adhesive joints (SLJ) are experimentally investigated. The thermal cycles were applied in an aluminum/carbon fiber-reinforced polymer (Al/CFRP) adhesively bonded SLJ with different adhesive thicknesses. Residual strains due to the differential thermal contraction of the two materials were measured inside the adhesive layer using the digital image correlation (DIC) technique. It was shown that for the studied conditions, the residual strains increase by thermal cycles, leading to a decrease in residual static strength of the joints. A 2D finite element thermal analysis was also performed and the numerical data were compared with the experimental results.