Study of the effect of liquid shim on single-lap joint using 3D Digital Image Correlation

The influence of a liquid-shim layer in place at the interface between the two laminates of single-lap joints used in primary aircraft structures have been investigated in this study. To this end, experiments were performed to evaluate the complex structural behaviour under tensile loading of single-lap bolted joints. Two cases were considered: with and without a shim layer. Three-dimensional Digital Image Correlation (DIC) has been used to provide the complete surface strain fields and to analyse the out-of-plane phenomena of the joints, and successfully helped to identify the effect of a liquid-shim layer. It has been shown that the introduction of a shim layer magnifies secondary and tertiary bending and the out-of-plane deformations of the joint and modifies the strain distribution, potentially leading to higher tensile strains in the laminates.