基于热力学的HTPB/AP复合底排药损伤本构模型及损伤差异分析

为研究HTPB/AP复合底排药（CBBG）单轴拉伸力学性能，进行了准静态（233~301 K，8.3×10^-5~8.3×10^-1 s^-1）和冲击（233~323 K，1 200~8 000 s^-1）加载实验。实验结果表明，各工况下的真应力应变曲线均有明显的屈服点，初始模量、屈服应力及后屈服阶段形态均呈现显著的温度和应变率相关性。在不可逆热力学框架内，推导了热力学力表达式和内变量演化法则，结合初始模量和屈服应力模型，建立了黏弹-黏塑-损伤本构模型。根据HTPB/AP CBBG宽泛温度和应变率实验数据，利用一维形式的本构模型进行了参数辨识和模型验证。结果表明，该模型能较准确描述黏弹性阶段和后屈服阶段。不同工况下的损伤演化律表明，冲击加载和低温均有利于损伤扩展。

Thermodynamics-based damage constitutive model and its application to damage analysis for HTPB/AP composite base bleed grain

To investigate tensile mechanical properties of HTPB/AP Composite Base Bleed Grain (CBBG), quasi-static (233-301 K, 8.3×10^-5-8.3×10^-1s^-1) and impact (233-323 K, 1 200-8 000 s^-1) loading experiments are conducted. Results show that the true stress-true strain curve has an obvious yield point under each experimental condition. The initial modulus, yield stress and the shape of the post-yield region of true stress-true strain curves all present clear dependence on temperature and the strain rate. In the framework of irreversible thermodynamics, the expressions of thermodynamic forces and evolution laws of internal variables are derived. With the additional initial modulus and the yield stress models, a novel viscoelastic-viscoplastic constitutive model considering damage evolution is proposed. Based on experimental data, the one-dimensional version of the constitutive model is used to identify the material parameters. The model validation shows that the proposed model can accurately present the initial viscoelasticity and post-yield behaviors of HTPB/AP CBBG over a wide range of temperature and strain rates. Damage evolution laws indicate that both the impact loading and low temperature boost damage development.