拉挤-编织成型纤维复材筋弯曲性能与破坏机制研究

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

  • 摘要: 针对碳纤维增强复合材料(CFRP)筋在锚固区等关键部位横向抗弯性能不足的问题,本研究提出一种外层编织碳纤维的增强策略,采用拉挤-编织成型工艺制备了编织角度分别为±30°、±45°和±60°的增强型CFRP筋,并与传统拉挤CFRP筋进行对比。三点弯曲试验结果表明,编织层显著提高了弯曲峰值极限位移,其中±60°试件的峰值位移达6.99 mm,较对照组提高182%。然而,弯曲强度随编织角增大呈下降趋势,±30°、±45°和±60°试件的弯曲强度较对照组分别降低了7.1%、9.7%和28.5%。小角度试件呈现三阶段破坏,大角度试件则表现出更高的峰值位移。通过建立微观-介观-宏观多尺度渐进损伤模型进行有限元仿真,揭示了编织层的环向约束效应是性能改变的内在机制,该约束抑制了芯棒受压区的早期压溃,使损伤进程转向编织层内部,从而提升了延性。计算机断层扫描(CT)和扫描电子显微镜(SEM)的损伤观测结果与模拟结果相互验证,多尺度有限元仿真结果表明,峰值荷载与位移的模拟值与试验结果误差分别小于8.5%和14.7%,验证了模型的有效性。本研究为通过编织角度设计优化CFRP筋横向抗弯性能提供了理论与实验依据。

     

    Abstract: 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.

     

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