Xu Mingxue, Wang Anni, Liu Xiaogang
Research Institute of Urbanization and Urban Safety, School of Future Cities, University of Science and Technology Beijing, Beijing 100083, China.
Polymers (Basel). 2025 Feb 24;17(5):595. doi: 10.3390/polym17050595.
Thermoplastic fiber-reinforced polymer (FRP) reinforcement has a significant advantage over traditional thermosetting FRP reinforcements in that it can be bent on site by heating-softening processing. However, current experimental and theoretical research on the thermal conductivity and heating-softening processing characteristics of thermoplastic FRP reinforcements is quite insufficient. Through heating-softening processing tests, numerical simulation, and theoretical calculation, this study investigated the heating-softening processing time of a thermoplastic glass-fiber-reinforced polypropylene (GFRPP) reinforcement. In the heat transfer process, thermal conductivity is typically treated as a constant. However, the experimental results indicated that the thermal conductivity/diffusivity coefficient of the GFRPP reinforcement was temperature-dependent. On this basis, an equivalent modified thermal diffusivity coefficient of glass fiber was proposed to account for the time-temperature-dependent heat conductivity of the GFRPP reinforcement, utilizing a series model. Utilizing the modified thermal diffusivity coefficient, the simulation model presented a heating-softening processing time that coincided well with the experimental results, with a mean ratio of 1.005 and a coefficient of variation of 0.033. Moreover, based on an equivalent homogeneous circular cross-section assumption of the GFRPP reinforcement, an analytical solution to the heat conduction equation was derived. Combining the experimental and simulation results, a semi-analytical and semi-empirical calculation model was also proposed for predicting the heating-softening processing time of a GFRPP reinforcement with a silicone tube cover. The model's calculated results align with the simulation trends, with an average deviation of 1.0% and a coefficient of variation of 0.026, demonstrating strong potential for engineering applications.
热塑性纤维增强聚合物（FRP）增强材料相较于传统热固性FRP增强材料具有显著优势，即它可以通过加热软化加工在现场进行弯曲。然而，目前关于热塑性FRP增强材料的热导率和加热软化加工特性的实验和理论研究相当不足。通过加热软化加工试验、数值模拟和理论计算，本研究调查了热塑性玻璃纤维增强聚丙烯（GFRPP）增强材料的加热软化加工时间。在传热过程中，热导率通常被视为常数。然而，实验结果表明，GFRPP增强材料的热导率/扩散系数与温度有关。在此基础上，利用串联模型提出了玻璃纤维的等效修正热扩散系数，以考虑GFRPP增强材料随时间和温度变化的热导率。利用修正后的热扩散系数，模拟模型得出的加热软化加工时间与实验结果吻合良好，平均比值为1.005，变异系数为0.033。此外，基于GFRPP增强材料等效均匀圆形横截面的假设，推导了热传导方程的解析解。结合实验和模拟结果，还提出了一个半解析半经验计算模型，用于预测带硅胶管套的GFRPP增强材料的加热软化加工时间。该模型的计算结果与模拟趋势一致，平均偏差为1.0%，变异系数为0.026，显示出强大的工程应用潜力。
