Kapton薄膜偏轴拉伸试验研究

Research on off-axis tensile tests of Kapton film

为深入揭示Kapton高分子膜材强度和刚度特征,对其进行7个偏轴角度(0°、15°、30°、45°、60°、75°、90°)下的单轴拉伸试验,获得了材料在各角度下的应力-应变关系、强度和断裂延伸率等数据,推导了相应的弹性模量-应变关系。结果表明:Kapton薄膜为典型的非线性、各向异性材料,整个拉伸过程的应力-应变曲线可以分为3个阶段,即近似弹性段、应变强化段、应力强化段;Kapton膜材强度随偏轴角度的变化表现出“N”形分布规律,异于Tsai-Hill等强度准则的“U”形规律,这是由于膜材内部分子链的择优取向,导致偏轴角度30°时抗拉强度最大,偏轴角度60°时抗拉强度最小;断裂延伸率随偏轴角度的增大呈现出增大的趋势;不同偏轴角度下的弹性模量均有所差异,正交各向异性板的弹性理论可以较好预测Kapton膜材的等效弹性模量;研究所得结论可为Kapton膜材强度、变形预测及相应的充气可展结构设计分析提供参考。

In order to deeply reveal the strength and stiffness characteristics of Kapton polymer film material,uniaxial tensile tests were carried out at 7 off-axis angles(0°,15°,30°,45°,60°,75°and 90°).The stress-strain relationship,strength and fracture elongation of the material at various angles were obtained,and the corresponding elastic modulus-strain relationship was deduced.The results show that Kapton film is a typical nonlinear and anisotropic material.The stress-strain curve of the whole tensile process can be divided into three stages,including approximate elastic stage,strain strengthening stage and stress strengthening stage.Kapton film strength shows an“N”shape distribution law with the change of off-axis angle,which is different from the“U”shape law of Tsai-Hill strength criterion.This is due to the preferred orientation of molecular chains in the film material,resulting in the maximum tensile strength when the off-axis angle is 30°and the minimum tensile strength when the off-axis angle is 60°.The fracture elongation increases with the increase of off-axis angle.The elastic modulus under different off-axis angle is different.The elastic theory of orthotropic plates has a good prediction for the equivalent elastic modulus of Kapton film.The conclusions of the study can provide reference for the strength and deformation prediction of Kapton film and the corresponding design and analysis of inflatable deployable structure.