Effect of resin-missing defects on tensile properties of carbon fiber-reinforced composites lap joint

This study focuses on the mechanical lap joints of composite laminates, and adopts a damage evolution analysis method for equivalent homogeneous composite laminates with resin-missing defects. It explores the coupling effects of defect location, defect volume, and joint type, and reveals the influence mechanisms of resin-missing defects on mechanical lap joints of composite laminates. For single-bolt and multi-bolt lap joints in composite laminates, when resin-missing defects exist near the open hole, their impact on joint stiffness is minimal. However, when defects are located in the extrusion side, they significantly affect the extrusion strength. The presence of defects causes discontinuous force transmission, leading to premature joint failure. For composite single-bolt lap joints, the presence of resin-missing defects in the 0° layup and the 90° layup more significantly impacts the mechanical properties of lap joints compared to the 45° layup and the −45° layup. The mechanical properties of mechanical lap joints in composite laminates with resin-missing defects are largely affected by the coupling effects of layup structure and defect volume, resulting in a nonlinear relationship between tensile strength and defect volume.