低温高应变率条件下HTPB推进剂拉伸力学性能研究

Tensile Mechanical Properties of HTPB Propellant at Low Temperature and High Strain Rate

关键词:  HTPB推进剂  低温  高应变率  拉伸力学性能

Key words:  HTPB propellant  Low temperature  High strain rate  Tensile mechanical properties

摘要:

为研究固体推进剂在低温高应变率条件下的力学性能，通过单轴拉伸实验和扫描电镜(SEM)断面观察，分别获取了HTPB推进剂在温度范围为-40～25℃及0. 4～14.29s-1应变率下的应力-应变曲线和拉伸断面形貌。结果表明，HTPB推进剂的力学性能具有明显的温度和应变率效应。随温度降低和应变率升高，应力-应变曲线特性变得更加复杂，断面形貌基本上呈现“脱湿”越困难、颗粒断裂越明显的规律，低温和高应变率的“耦合”作用使得推进剂的损伤变得更加严重。初始弹性模量[E]和最大拉伸应力[σm]随温度的降低和应变率的升高而逐渐增加，且均与应变率具有相对较好的线性对数关系。低温和高应变率的“耦合”作用，使得-40℃及14.29s-1条件下的初始弹性模量和最大拉伸应力分别为25℃及0.4s-1条件下数值的1.6倍和3.2倍。与模量和强度相比，应变的规律性较复杂，其值随温度的升高而增加，且在常温下随应变率的升高而增加，但在低温下随应变率的升高而降低。通过双因素方差分析表明，低温高应变率条件下，温度和应变率均对最大拉伸应力有更显著的影响，同时温度较应变率对最大拉伸应力影响更加明显，而对模量则较弱。基于时温等效原理，得到了低温高应变率条件下HTPB推进剂的拉伸力学性能主曲线，该主曲线较大地拓宽了对推进剂力学性能的预测范围。

Abstract:

To investigate the mechanical properties of solid propellant at low temperature and high strain rate，stress-strain curves and tensile fracture surfaces of HTPB propellant were obtained in a wide range of temperature(-40～25℃)and strain rates(0.4～14.29s-1)，respectively，by means of uniaxial tensile tests and electron microscopy scanning on the fracture cross section. The results indicate that mechanical properties of HTPB propellant were influenced distinctly by temperature and strain rate. With decreasing temperature and increasing strain rate，the characteristics of stress-strain curves are more complex. At the same time，the dewetting between particles and matrix is more difficult to occur in propellant，but the particle brittle fracture is easier. With the coupled effects of low temperature and high strain rate，the damage for HTPB propellant is more serious. Secondly，the initial elastic modulus [E] and maximum tensile stress [σm] increase gradually with decreasing temperature and increasing strain rate，and well present linear-log function relation with strain rate. In addition，with the coupled effects of low temperature and high strain rate，the values of the initial elastic modulus [E] and maximum tensile stress [σm] at -40℃ and 14.29s-1 are 1.6 and 3.2 times of their values at 25℃ and 0.4s-1，respectively. But comparing with them，the relationships of the corresponding strain with temperature and strain rate are more complex. With increasing temperature，this strain increases. At room temperature，this parameter increases with increasing strain rate，while it decreases with increasing strain rate at low temperature. The results of variance analysis indicate that low temperature and high strain rate have more significant effects on maximum tensile stress [σm]. In addition，the low temperature has greater influence on this parameter than high strain rate，but there is an opposite law for the initial elastic modulus [E]. Finally，mechanical properties master curves for HTPB propellant at low temperature and high strain rate were calculated by means of time-temperature superposition principle，which widen the prediction range for the mechanical properties of HTPB propellant.