With the purpose of investigating the effects of confining pressure and aging on the mechanical properties of Hydroxyl-terminated polybutadiene (HTPB) based composite solid propellant, tensile tests of thermal accelerated aged propellant samples under room temperature and different confining pressure conditions were performed through the use of a self-made confining pressure device and conventional testing machine. Afterwards, the maximum tensile stress ${\sigma }_{\text{m}}$ and the corresponding strain ${\epsilon }_{\text{m}}$ for the propellant under different test conditions were obtained and analyzed. The results indicate that confining pressure and aging can significantly affect the mechanical properties of HTPB propellant, and the coupled effects are very complex. On the one hand, the stress ${\sigma }_{\text{m}}$ increases as a whole when confining pressure becomes higher or thermal aging time rises. Besides, this stress is more sensitive to aging with increasing confining pressure. There are almost three regions in the stress increments $\left({\sigma }_{\mathrm{mP}}-{\sigma }_{\mathrm{m}0}\right)/{\sigma }_{\mathrm{m}0}$ and thermal aging time curves for HTPB propellant. The maximum value of the stress increment $\left({\sigma }_{\mathrm{mP}}-{\sigma }_{\mathrm{m}0}\right)/{\sigma }_{\mathrm{m}0}$ for the propellant is about 98% at 7.0 MPa and 170 d. On the other hand, the strain ${\epsilon }_{\text{m}}$ decreases with increasing thermal aging time under the whole confining pressure conditions. However, the variation of this strain with confining pressure is more complex at various thermal aging time, which is different from that of unaged solid propellant in previous researches. In addition, this strain is slightly less sensitive to aging as the confining pressure increases. Furthermore, there is also a critical confining pressure in this investigation, whose value is between 0.15 MPa and 4.0 MPa. Beyond this critical pressure, the trends of the stress ${\sigma }_{\text{m}}$ and the corresponding strain ${\epsilon }_{\text{m}}$ all change. Moreover, there are some critical thermal aging time for the stress increment $({\sigma }_{\mathrm{mP}}-{\sigma }_{m0})/{\sigma }_{m0}$ and strain increment $({\epsilon }_{\mathrm{mP}}-{\epsilon }_{m0})/{\epsilon }_{m0}$ of HTPB propellant in this investigation, which are about at 35, 50 and 170 d. Finally, based on the twin-shear strength theory, a new modified nonlinear strength criterion of thermal aged HTPB propellant under confining pressure was proposed. And the whole errors of fitted results are lower than 6%. Therefore, the proposed strength criterion can be selected as a failure criterion for the analysis the failure properties of aged HTPB propellant under different confining pressures, the structural integrity of solid propellant grain and the safety of solid rocket motor during ignition operation after long periods of storage.

为了研究围压和老化对端羟基聚丁二烯（HTPB）基复合固体推进剂力学性能的影响，通过使用热加速老化推进剂样品在室温和不同围压条件下进行拉伸试验。自制围压装置和常规试验机。之后，最大拉应力${\sigma }_{\text{米}}$和相应的应变${\epsilon }_{\text{米}}$对不同试验条件下的推进剂进行了获取和分析。结果表明，围压和老化会显着影响HTPB推进剂的力学性能，其耦合作用非常复杂。一方面，压力${\sigma }_{\text{米}}$当围压变高或热老化时间增加时，整体增加。此外，随着围压的增加，这种应力对老化更为敏感。应力增量几乎有三个区域$\left({\sigma }_{\mathrm{甲基苯丙胺}}-{\sigma }_{\mathrm{米}0}\right)/{\sigma }_{\mathrm{米}0}$HTPB推进剂的热老化时间曲线。应力增量的最大值$\left({\sigma }_{\mathrm{甲基苯丙胺}}-{\sigma }_{\mathrm{米}0}\right)/{\sigma }_{\mathrm{米}0}$推进剂在 7.0 MPa 和 170 d 时约为 98%。另一方面，应变${\epsilon }_{\text{米}}$在整个围压条件下，随着热老化时间的增加而减小。然而，该应变随围压的变化在不同热老化时间下更为复杂，这与以往研究中未老化的固体推进剂不同。此外，随着围压的增加，该应变对老化的敏感性稍差。此外，本次调查还存在一个临界围压，其值在0.15～4.0 MPa之间。除了这个临界压力之外，压力的趋势${\sigma }_{\text{米}}$和相应的应变${\epsilon }_{\text{米}}$全部改变。此外，应力增量存在一些临界热老化时间$({\sigma }_{\mathrm{甲基苯丙胺}}-{\sigma }_{米0})/{\sigma }_{米0}$和应变增量$({\epsilon }_{\mathrm{甲基苯丙胺}}-{\epsilon }_{米0})/{\epsilon }_{米0}$本次调查中 HTPB 推进剂的使用时间约为 35、50 和 170 d。最后，基于双剪强度理论，提出了一种新的改进的围压下热老化HTPB推进剂非线性强度准则。拟合结果的整体误差低于6%。因此，本文提出的强度准则可以作为失效准则，分析不同围压下老化的HTPB推进剂的失效特性、固体推进剂颗粒的结构完整性以及固体火箭发动机在长时间储存​​后点火运行时的安全性。 .