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通过分子动力学模拟研究乙烯-四氟乙烯共聚物(ETFE)在低气压下的击穿性能, 并通过低气压击穿实验对仿真结果进行验证, 从原子尺度揭示ETFE材料在低气压下绝缘失效机制. 首先, 对ETFE进行分子动力学模拟, 随着飞行高度从0 km逐渐增大到24 km, 模拟气压从101.300 kPa逐渐降低到2.951 kPa, ETFE的分子间距离增大9.692%, 链间相互作用能降低8.383%, 自由体积分数增大62.586%, 而密度下降7.737%. 其次, 基于电机械击穿理论, 推导得到ETFE击穿场强降低17.626%. 最后, 通过低气压击穿实验测得击穿场强下降40.078%, 密度测试得到密度下降1.574%. 仿真和实验结果均证明, ETFE的击穿场强随着气压的下降而降低. 这是由于处于低气压条件时, 自由体积分数的增加与密度的降低均为自由电子提供更长的自由行程; 而电荷陷阱能级的下降导致介质对电荷的束缚能力下降, 使自由电子浓度增加. 以上因素的共同作用导致ETFE在不同飞行高度下的击穿场强下降, 为ETFE在航空航天、高飞行高度极端环境下的应用提供了性能预测与失效机理分析, 对航空绝缘ETFE材料的优化设计具有指导意义.
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关键词:
- 乙烯-四氟乙烯共聚物 /
- 低气压 /
- 分子动力学 /
- 击穿场强
By studying the breakdown performance of ethylene-tetrafluoroethylene (ETFE) copolymer under low pressure via molecular dynamics simulations, and verifying the simulation results through low-pressure breakdown experiments, the insulation failure mechanism of ETFE materials under low pressure can be revealed on an atomic scale. First, molecular dynamics simulations are performed on ETFE. As the flight altitude gradually increases from 0 km to 24 km, the simulated pressure decreases from 101.300 kPa to 2.951 kPa. Correspondingly, the intermolecular distance increases by 9.692%, the interchain interaction energy decreases by 8.383%, the free volume fraction of ETFE increases by 62.586%, and the density of ETFE decreases by 7.737%. Subsequently, based on the electromechanical breakdown theory, it is deduced that the breakdown field strength of ETFE decreases by 17.626%. Finally, the low-pressure breakdown experiment shows that the breakdown field strength decreases by 40.078%, and the density measurement test indicates that the density decreases by 1.574%. Both simulation and experimental results confirm that the breakdown field strength of ETFE decreases with the reduction of pressure. This is because under low-pressure conditions, the increase in free volume fraction and the decrease in density provide a longer mean free path for free electrons. And the decrease in charge trap level weakens the charge trapping capability, leading to a higher concentration of free electrons. All these factors contribute to the reduction of the breakdown field strength of ETFE. This study provides performance prediction and failure mechanism analysis for the application of ETFE in aerospace and high-altitude extreme environments, and has guiding significance for the optimal design of aerospace insulation ETFE materials.-
Keywords:
- ethylene-tetrafluoroethylene /
- low atmospheric pressure /
- molecular dynamics /
- breakdown field strength
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飞行高度/km 动能变化率/% 密度变化率/% 0 3.887 3.334 7 4.623 4.054 10 3.448 4.111 14 3.030 4.225 17 3.311 4.286 24 3.367 3.497 
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