低温动态加载下HTPB复合固体推进剂力学行为研究

The dynamic mechanical behaviors of solid propellants at low temperatures and strain rates from 1 to 100/s are very important to effectively analyze the structure integrity of propellant grain for solid rocket motor (SRM) of the tactical missiles during ignition at low temperatures. However, up to now, experimental researches, theoretical analysis and numerical simulations on mechanical behaviors of solid propellant at low temperatures under various dynamic loading conditions are very inadequate. Therefore, a new testing machine, designed multiple configuration samples and new designed gripping jaws will be applied for conducting the experimental researches on mechanical properties of HTPB propellant at low temperatures under various dynamic loading conditions. Meanwhile, based on the test results, the variation of typical mechanical parameters will be obtained. Furthermore, based on the comprehensive experimental researches with application of various methods and mesoscale numerical simulations on the microscopic damage, the effects of different loading conditions on the microscopic damage of the propellant will be analyzed. Meanwhile, the relationship between the microscopic damage and macro-mechanical properties of the propellant will be also discussed. Then, the corresponding strength criterion and nonlinear viscoelastic constitutive relationship will be developed according to analyzing the mechanical properties test results and microscopic damage. This program is aimed at providing effective theoretical and technical supports for analyzing the structural integrity of propellant grain for SRM of the tactical missiles during ignition at low temperatures. At the same time, this program can also provide help for investigating the mechanical behaviors of other particle-filled viscoelastic materials at low temperatures under various dynamic loading conditions.

低温动态(应变率1~100/s)加载下固体推进剂的力学行为对有效分析低温点火条件下战术导弹固体火箭发动机(SRM)药柱的结构完整性具有重要意义。但公开文献中针对复杂应力低温动态加载下固体推进剂力学行为的实验、理论和数值仿真研究还不够深入。因此，本项目拟采用新型试验机、多构型实验件和新实验夹具，开展复杂应力低温动态加载下丁羟(HTPB)复合固体推进剂的力学性能实验研究，获得典型力学性能参数变化规律；基于多种细观损伤实验观测方法和细观数值模拟方法，揭示不同加载条件对推进剂细观损伤的影响规律，并建立细观损伤和宏观力学性能之间的内在关系；分析力学性能实验结果和细观损伤，建立固体推进剂的强度准则和非线性粘弹性本构关系。本项目的研究成果，可为低温点火下战术导弹SRM药柱的结构完整性分析提供有效的理论和技术支持，也可为研究其它颗粒增强粘弹性材料在复杂应力低温动态加载下的力学行为提供借鉴。

低温动态加载下固体推进剂的力学行为研究对深入分析与有效评价低温点火条件下战术导弹固体火箭发动机（SRM）药柱的结构完整性具有重要意义。本项目以HTPB丁羟三组元复合固体推进剂为研究对象，首先基于新型单轴高速液压伺服试验机（INSTRON VHS 160/100-20），提出了适合于1~100/s应变率范围内具有低模量、低强度、易燃易爆属性的复合固体推进剂的复杂应力状态低温动态加载力学性能试验方法，开展了变比例双轴拉伸、双轴压缩及剪切加载下推进剂的低温动态力学性能试验，揭示了不同温度、应变率及应力状态条件对推进剂模量、强度和伸长率等典型力学性能参数的影响规律；基于微CT原位表征技术，定量获得了推进剂的细观结构组分和孔隙率信息，结合试验、理论和细观有限元数值计算，揭示了典型试验工况下推进剂的细观损伤机理和损伤演化规律，建立了宏细观力学性能之间的内在关系；采用双剪统一强度理论，建立了考虑应力状态和温度因素影响的动态加载下推进剂的双轴强度准则和剪切强度准则，获得了评估推进剂失效的破坏包络线和理论极限线（面）；提出了1~100/s应变率范围内考虑温度和损伤影响的固体推进剂的非线性本构模型和模型参数求解方法，通过开展数值仿真计算，验证了所建本构关系的有效性。研究结果表明：温度降低和应变率升高，均能提高推进剂的双轴抗拉和抗压强度、抗剪强度以及模量，但其伸长率变化规律表现出非单调性；不同温度下推进剂呈现明显的SD效应，其单双轴、拉压及拉剪力学性能不等，且随温度降低差异性更加显著，在剪切载荷下推进剂更易发生断裂，考虑静水应力影响的三参数统一强度理论在描述上述特性时具有更好的适应性；随温度降低或应变率持续升高，推进剂的细观损伤机理由“脱湿”转变为以AP颗粒断裂为主，但剪切加载角由0度增至90度时，AP颗粒断现象减弱，而“脱湿”现象增强，且推进剂的细观损伤特性呈现明显的各向异性。通过本项目的研究，突破了复杂应力低温动态加载下固体推进剂的力学性能试验方法，揭示了相应工况下HTPB推进剂的宏细观力学性能变化规律，建立了描述推进剂变形行为和失效特性的强度准则和非线性本构关系，研究成果为低温动态加载下颗粒增强复合材料力学行为试验及理论研究中存在的关键问题的解决提供了新方法，并为低温点火下战术导弹SRM药柱的结构设计和完整性分析以及推进剂配方研制，提供了重要的数据和模型支撑。