Cross-scale analysis of the effect of interfacial carbon fiber orientation on laser joining TC4/CFRTP

Abstract In this study, the influence of carbon fiber reinforced thermoplastics (CFRTP) anisotropy on the performance of Ti-6Al-4 V (TC4)/CFRTP joints was investigated through experiments and simulations. In particular, a new meso-macro cross-scale thermal model was proposed for the laser joining of TC4/CFRTP. In meso-scale simulations, using a Fiber-PPS (polyphenylene sulfide) Representative Volume Element (RVE) model, CFRTP’s thermal properties were obtained, ranging from 25 ℃ to 3000 ℃. These results were then applied to calculate the macro-scale temperature distribution of TC4/CFRTP joints. The simulated joint features closely matched experimental observations, with an error of less than 5% in cross-section and interface morphology. Compared to the common simulation method, this method can effectively capture the influence of CFRTP anisotropy on temperature distribution, enabling precise strength analysis. In the experiments, two TC4/CFRTP joints were designed: Joint A, with carbon fibers at the interface perpendicular to the laser joining direction, and Joint B, with fibers parallel to it. The joint strength of Joint A was found to be 1.706 times that of Joint B. Experimental and simulation results indicated that carbon fibers perpendicular to the joining direction enhance interfacial heat transfer capability from the joining center to both sides, reducing energy aggregation in the central bonding area, decreasing pyrolysis zone and pores, and promoting thorough CFRTP melting near the interface for stronger bonding.