Study on Tensile-Shear Strength of Single Lap Joint Laminates with Defects

Abstract

Carbon-fiber-reinforced plastic (CFRP) has gained extensive application in aerospace engineering due to its exceptional specific strength, stiffness, and corrosion resistance. However, practical manufacturing processes often face limitations in mechanical precision and inaccuracies in the layup path. These deviations often manifest as fiber tow misalignments, such as gaps, overlapping defects, and mixed patterns. In this paper, these typical defects were examined as the research focus, and the debonding failure behavior at the interface between the structural skin and the stiffener was systematically studied. The influence of defects on the interlaminar shear strength was investigated through tensile-shear tests. Furthermore, the failure mechanisms of composite laminates containing defects were analyzed through numerical simulation. Experimental findings demonstrate that the 6-mm overlap causes a significant reduction in tensile-shear strength (18.13%), whereas the 6-mm gap substantially enhances tensile-shear strength (24.78%). For mixed defect configurations, the gap defect predominantly influences the macroscopic mechanical performance. It should be noted that the numerical model demonstrated a maximum error of 11.3% in predicting the failure load of the mixed defect group, though it captured the overall failure trends effectively. The specimens from the gap group and the mixed defect group did not fail completely under large displacement loads, demonstrating their secondary bearing capacity. A significant discrepancy exists between the model’s prediction and the experimental value for the secondary bearing capacity, identifying this as a key area for future model optimization.