聚酰亚胺薄膜（Kapton薄膜）作为一种航天膜材，其蠕变效应对结构的影响至关重要。为研究其蠕变力学性能，首先选用厚度为25 μm的Kapton薄膜，在极限抗拉强度的35%、50%、65%、80% 4组应力水平下，进行单轴蠕变拉伸试验。其次根据得到的蠕变力学曲线分析不同初始应力下薄膜蠕变的变化规律，结合蠕变伸长率描述薄膜随初始应力的蠕变特性并探讨其内在机理。最后采用经典Kelvin、经典Maxwell、四元件Burgers、三参数广义Kelvin、五参数广义Kelvin 5种蠕变本构模型对试验数据进行拟合，并对比分析各模型的拟合效果。结果表明：Kapton膜材具有明显的粘弹性性能，在设计中应予以考虑；初始应力对Kapton膜材的蠕变性能影响显著，初始应力越大，蠕变初期应变越大，稳态蠕变阶段应变保持值越高，粘弹性越明显；不同方向上的拉伸断裂应力水平导致蠕变性能的差异性，各应力状态下总应变TD（机器展开方向）大于MD（垂直方向）；随着初始应力的增大，薄膜的蠕变伸长率先增大后减小，这是因为初始应力对薄膜内部的应力状态和位错运动的影响是复杂的，并且存在一个平衡点。本研究采用的五参数广义Kelvin模型能够较好地预测Kapton膜材的蠕变性能，拟合结果的可决系数均超过0.99，Burgers模型次之；经典Kelvin、三参数广义Kelvin以及经典Maxwell模型拟合可决系数在0.71~0.86之间，其拟合结果满足实际工程的需要。

As a kind of aerospace membrane material, polyimide film’s (Kapton film) creep effect is very important to its structure. In order to study its creep mechanical properties, firstly the study selected Kapton film with a thickness of 25 μm, and carried out the uniaxial creep tensile test under the four stress levels of 35%, 50%, 65% and 80% of the ultimate tensile strength. Secondly, according to the creep mechanics curves obtained, the creep characteristics of the film under different initial stresses were analyzed, and the intrinsic mechanism was discussed by combining the creep elongation. Five creep constitutive models of classical Kelvin, classical Maxwell, four-element Burgers, three-parameter generalized Kelvin and five-parameter generalized Kelvin were used to fit the experimental data, and the fitting effects of each model were compared and analyzed. The results show that Kapton film has obvious viscoelastic properties, which should be considered in the design. The initial stress has a significant effect on the creep properties of Kapton film. The greater the initial stress, the higher the strain at the initial creep stage, the higher the strain retention value at the steady creep stage, and the more obvious the viscoelasticity is. The tensile fracture stress levels in different directions lead to the differences of creep properties, and the total strain of TD (Transverse Direction) is greater than that of MD (Machine Direction) under each stress state. With the increase of the initial stress, the creep elongation of the film first increases and then decreases. This is because the influence of the initial stress on the stress state and dislocation motion inside the film is complex, and there is an equilibrium point. The five-parameter generalized Kelvin model adopted in this paper can well predict the creep properties of Kapton film, and the coefficient of determination of the fitting results is more than 0.99, followed by the Burgers model. The fitting coefficients of classical Kelvin, three-parameter generalized Kelvin and classical Maxwell model are between 0.71 and 0.86, and the fitting results meet the needs of practical engineering.