Identification of bearing failure in composite-aluminium bolted joints using digital image correlation

Abstract

The quasistatic failure of composite-aluminium bolted joints is investigated experimentally using the stereo Digital Image Correlation (DIC) technique. Single-shear, two-bolt lap joints made of carbon fibre reinforced polymer (CFRP) laminates and aluminium plates are subjected to tensile load while being monitored using stereo-DIC. The measured displacements are processed by removing outliers using the Grubbs test and reducing noise by exploiting symmetries of the specimen geometry. The development of the Gauss curvature across the CFRP is computed from DIC displacement data, and a sudden onset of curvature in the vicinity of the bolts is observed as a precursor to bearing failure. Fractographs of cross-sections of partially failed CFRP near the bolts confirm compressive damage of laminates as the source of this localised curvature. We conclude that stereo-DIC is useful as a non-contact measurement of bearing failure initiation.