Experimental and numerical investigation of mechanical and thermal residual strains in adhesively bonded joints

This paper describes an investigation of residual and mechanical strains in aluminium/aluminium (Al/Al) and aluminium/carbon fibre-reinforced polymer (Al/CFRP) adhesively bonded double-lap joints. Residual strains were measured inside the adherends by means of neutron diffraction (ND) and modelled using finite element analysis (FEA). In the Al/Al joints the measured residual strains were negligible, showing good agreement with FE predicted results. However, considerable strains developed in the Al/CFRP joint because of differential thermal contraction of the two materials during joint manufacture. Although considerable scatter was seen in the ND results, the measured and predicted trends showed similar behaviour and were of comparable magnitude. The paper also reports measurements of internal strains in an Al/CFRP joint under tensile load using ND and of surface strains using moiré interferometry (MI). In general, good agreement was observed between FE predictions, surface strains measured with MI and internal strains measured with ND for the loaded Al/CFRP joint.