Full-field through-the-thickness strain distribution study of hybrid multi-bolted/bonded single-lap composite joints using digital image correlation

Abstract

This study proposes a digital image correlation (DIC) technique for through-the-thickness deformations of multi-bolted single-lap (SL) shear hybrid bolted/bonded joints made of carbon/epoxy laminates. Through-the-thickness peel strains are obtained throughout the overlap region during the entire tensile test. It is observed that real-time monitoring of the strain in the overlap region informs on the location of the failure before the load reaches 50% of its ultimate value. The peel strain-load curves for both the overlap ends superimpose perfectly up to about 40% − 50% of the applied tensile load and diverge considerably beyond this level. Similar behavior occurs for shear strain and is confirmed for quasi-isotropic (QI) and cross-ply (CP) laminate stacking sequences. It is also found that peel and shear strains, as well as joint rotation in CP, are higher than those of QI. These results can be useful for the design of this type of joint.