Failure behavior of single-lap CFRP hybrid joints fastened using micro-bolt

This study examines the mechanical response and failure behavior of a hybrid joint fastened using multiple micro-bolts subjected to quasi-static tensile loading numerically and experimentally. The hybrid joint fastened using a single standard bolt and only adhesively bonded joint configuration are also evaluated for a comparative purpose. These joint performances are also further analyzed under tensile-tensile fatigue loading experimentally. Carbon fiber reinforced plastic (CFRP) laminates with [0/+45/90/−45]s lay-up sequence are used to make adherends. In this work, 3D digital image correlation (DIC) technique is used to capture the whole field deformation and strain field over the overlap region. An acoustic emission (AE) technique is employed to capture the damage evolution upon loading qualitatively. After failure, a scanning electron microscope (SEM) and optical microscope are used to capture the extent of damage and failure modes within the adherends. A finite element method (FEM) based analysis is performed involving a progressive damage model (PDM) to understand the damage evolution in CFRP adherend upon static tensile loading. From the observations, it has been found that the hybrid joint fastened using micro-bolts deformed greater at the peak load before the adhesive layer got disbanded, thereby demonstrating a greater fatigue life with gradual stiffness degradation behavior as compared to the other two joint configurations.