Abstract: To investigate the effects of strain rate on the tensile mechanical behaviour of hydroxyl-terminated polybutadiene(HTPB)propellant，the uniaxial tensile stress-strain curves at room temperature over strain rates ranging from 1.2 × 10-4 to 80s-1 have been determined on a universal testing machine and a hydraulic testing machine. Experimental results indicate that the stress at a given strain level bilinearly increases with the logarithm of strain rate with a sharp increase in gradient at a strain rate of 1s-1，the strain-rate sensitivity linearly enhances with decreasing the strain level. Based on the previous model developed by Mohotti，a modified rate-dependent hyperelastic constitutive model was proposed by combining the mechanical characteristics of both the bilinear strain-rate dependence and the difference in strain-rate sensitivity at different levels of strain in this HTPB propellant. The model comprises a hyperelastic component and a rate-dependent component. The hyperelastic component is considered as a base model to characterise the mechanical behaviour at the selected reference strain rate. The rate-dependent component is multiplied into the hyperelastic component to define strain-rate sensitivity. Comparison of model curves with experimental data shows that it is able to reasonably characterise the uniaxial tensile mechanical properties of HTPB propellant under strain rates ranging from 1.2 × 10-4 to 80s-1 within the strain of 30%.

Key words: HTPB propellant；Intermediate strain rates；Tension；Strain-rate sensitivity；Constitutive model

摘要： 为研究HTPB推进剂拉伸力学行为的应变速率相关性，采用万能试验机和液压试验机，在室温下开展了不同应变速率(1.2 × 10-4 ～ 80s-1)的拉伸实验。结果表明:给定应变对应的应力随应变率对数双线性增加，1s-1为双线性关系的转折点；随应变的减小，HTPB推进剂的应变率敏感性线性增强。在Mohotti建立的模型基础上，结合拉伸力学行为的双线性率相关特性及应变率敏感性的应变依赖性，提出改进的应变速率相关超弹本构模型。该模型以超弹性元件作为基础描述参考应变率下的力学行为，率相关元件乘入超弹性元件描述率相关特性。模型预测与实验曲线对比表明:所提出的率相关超弹本构模型能够描述HTPB推进剂在1.2×10-4 ～ 80s-1应变率、30%应变范围内的拉伸力学行为。

关键词: HTPB推进剂；中应变率；拉伸；率相关性；本构模型