Study on the Bending Performance and Failure Mechanism of Pultruded-Braided Fiber Composite bar

To address the insufficient transverse bending performance of carbon fiber reinforced polymer (CFRP) bars in critical regions such as anchorage zones, this study proposed an enhancement strategy involving an externally braided carbon fiber layer. CFRP bars with braiding angles of ±30°, ±45°, and ±60° were fabricated using a pultrusion-braiding hybrid process and compared with conventional pultruded CFRP bars. Three-point bending tests indicated that the braided layer significantly increased the peak deflection, with the ±60° specimen reaching a peak deflection of 6.99 mm, which is 182% higher than that of the control group. However, the bending strength decreased as the braiding angle increased, with reductions of 7.1%, 9.7%, and 28.5% for the ±30°, ±45°, and ±60° specimens, respectively. Small-angle specimens exhibited a three-stage failure process, while large-angle specimens showed higher peak deflections. A micro-meso-macro multiscale progressive damage model was established for finite element simulation, revealing that the circumferential constraint effect of the braided layer was the intrinsic mechanism for the altered performance. This restraint suppressed the early crushing of the core in the compression zone and redirected the damage progression into the braided layer, thereby enhancing ductility. Damage observations via computed tomography (CT) and scanning electron microscopy (SEM) corroborated the simulation results. The multiscale finite element simulations showed errors of less than 8.5% for peak load and 14.7% for displacement compared to experimental results, validating the model’s effectiveness. This study provides a theoretical and experimental basis for optimizing the transverse flexural performance of CFRP bars through braiding angle design.