Hybrid adhesive-woven lap mode and mechanical properties of steel-CFRP joints

CFRP (Carbon Fiber Reinforced Polymer) is widely used in aerospace, automotive, civil engineering and petroleum industries due to its lightweight and high-strength characteristics. However, the strength of connections between steel and CFRP remained a significant challenge in current research. This paper investigated the optimal design of single-layer steel-CFRP hybrid adhesive-woven lap joints under different hole spacing and hole shapes through five types of experiments, each with 3 parallel tests, totaling 15 specimens. Based on the results from single-layer experiments, six types of experiments were further conducted, each with 3 parallel tests, totaling 18 specimens, the mechanical performance of multi-layer steel-CFRP hybrid adhesive-woven lap joints under the influence of three different joint overlap configurations and four different overlap lengths were examined. The load-displacement curves, failure modes, peak unit thickness strengths, and ultimate load under different configurations and lengths were analyzed. Concurrently, detailed strain distribution and evolution processes of joints were analyzed using digital image correlation (DIC) methods. The results indicate that compared to elliptical holes, rectangular hole joints exhibit 11.99% increase in mechanical strength, and the mechanical strength reaches its maximum at a 20 mm hole spacing. In multi-layer joints, double-layer carbon fiber cloths and double-layer steel configurations significantly enhance the strength of joints compared to the other two configurations, improved by 160.33% and 119.26% respectively. It’s found that increasing overlap length also effectively enhances joints’ ultimate load. However, when the overlap length exceeds a certain value, the mechanical strength of joints gradually stabilizes and slightly decreases. At the overlap length of 60 mm, the joint mechanical strength reaches its peak and is improved by 20.94% compared to the overlap length of 40 mm.