It is of great significance to monitor the aging state and evaluate the useful life of stored solid-rocket-motor (SRM) propellant grains. In this work, the aging state of hydroxyl terminated polybutadiene (HTPB) propellant grains was studied based on the electromechanical impedance (EMI) method. The relationship between the complex modulus and the mechanical impedance of viscoelastic material was derived. The finite element analysis of the structure with different moduli was carried out. The results show that the peak value of electromechanical impedance increases with an increase of propellant modulus. This report focuses on experimental research on monitoring the aging of cylindrical SRMs based on the EMI method. It is found that the peak of electromechanical impedance spectrum increases with aging time, while the peak frequency decreases slightly. As an aging damage variable, the root mean squared error (RMSD) of electromechanical impedance increases with aging time, and its growth rate is large at first, then decreases, and finally increases. Finally, a tensile test of aging propellant specimens was carried out, and the results show that the rate of change (ROC) of the modulus can be fit by a linear relationship to the RMSD of the electromechanical impedance.

中文翻译：

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使用机电阻抗法监测固体火箭发动机 HTPB 推进剂颗粒的老化

监测储存的固体火箭发动机（SRM）推进剂颗粒的老化状态和评估其使用寿命具有重要意义。在这项工作中，基于机电阻抗（EMI）方法研究了端羟基聚丁二烯（HTPB）推进剂颗粒的老化状态。推导了粘弹性材料的复模量与机械阻抗的关系。对不同模量的结构进行了有限元分析。结果表明，机电阻抗的峰值随着推进剂模量的增加而增加。本报告侧重于基于 EMI 方法监测圆柱形 SRM 老化的实验研究。发现机电阻抗谱的峰值随着老化时间的增加而增加，而峰值频率略有下降。作为老化损伤变量，机电阻抗的均方根误差（RMSD）随着老化时间的增加而增大，其增长率先大后减小，最后增大。最后，对老化的推进剂试样进行了拉伸试验，结果表明，模量变化率（ROC）与机电阻抗的RMSD呈线性关系。