PTFE涂层织物膜材的黏弹性性能研究

发布时间：2018-08-06 16:40

【摘要】：涂层织物膜材料是一种典型的高分子复合材料,具有明显的非线性、非弹性、各向异性、黏弹性特性,其材料力学性能受外界环境、荷载水平、加载历史等因素的影响显著。在实际膜结构工程中,随着时间的推移,徐变和应力松弛会使膜面预张力减小,导致膜面松弛和结构刚度降低,因此十分有必要系统研究膜材的黏弹性性能,这对研究膜结构长期使用性能、保证结构的安全性能具有重要的意义。本文以PTFE涂层织物膜材为研究对象,进行了一系列应力松弛性能、蠕变性能和循环拉伸性能的试验研究,讨论了拉伸速率、加载次序、温度、应力水平等因素对膜材黏弹性力学性能的影响规律,推导了基于各向异性的膜材料黏弹性本构方程。主要的研究内容如下:(1)进行了不同条件下的应力松弛和蠕变试验,分析了温度、应力水平、初始拉伸速率等因素对膜材经、纬向松弛应力和蠕变应变的影响规律。推导了应力松弛-蠕变的转换关系式。采用几种常用的黏弹性模型对上述试验曲线进行了拟合,分析比较了各类模型的拟合精度,得到了用于描述涂层织物膜材黏弹性行为的本构关系模型。(2)进行了不同条件下的单轴循环拉伸试验,得到了加、卸载弹性模量、棘轮应变、滞回环面积等参数,分析了偏轴角度、拉伸速率、加载应力幅等因素对膜材料棘轮行为的影响规律,将膜材料的应变进行了分解处理,采用修正的Burgers模型对膜材料循环拉伸曲线进行了预测。(3)进行了一系列偏轴试验,包括循环拉伸试验、应力松弛试验和蠕变试验,系统地研究了膜材料的各向异性。基于复合材料正交各向异性理论,推导得到了膜材料弹性模量、松弛模量和蠕变柔量与偏轴角度的关系式。由各向异性材料塑性理论及流动法则,通过引入蠕变势函数、等效应力及等效蠕变率等表达式,得到了PTFE涂层织物膜材各向异性本构方程。
[Abstract]:The coated fabric membrane material is a kind of typical polymer composite material, which has obvious nonlinear, inelastic, anisotropic and viscoelastic properties. The mechanical properties of the coated fabric are significantly affected by the external environment, load level, loading history and other factors. In the actual membrane structure engineering, creep and stress relaxation will reduce the pretension of membrane surface with time, resulting in the relaxation of membrane surface and the decrease of structural stiffness. Therefore, it is necessary to study the viscoelastic properties of membrane materials systematically. It is of great significance to study the long-term service performance of membrane structure and ensure the safety performance of the structure. In this paper, a series of experimental studies on the stress relaxation, creep and cyclic tensile properties of PTFE coated fabric membrane were carried out. The tensile rate, loading sequence, temperature and tensile rate were discussed. The influence of stress level on the viscoelastic properties of membrane materials was studied. The viscoelastic constitutive equation of membrane materials based on anisotropy was derived. The main research contents are as follows: (1) stress relaxation and creep tests under different conditions are carried out, and the effects of temperature, stress level and initial tensile rate on warp, zonal relaxation stress and creep strain are analyzed. The relationship between stress relaxation and creep is derived. The experimental curves are fitted with several common viscoelastic models, and the fitting accuracy of these models is analyzed and compared. A constitutive relation model for describing viscoelastic behavior of coated fabric membrane is obtained. (2) uniaxial cyclic tensile tests under different conditions are carried out, and parameters such as loading, unloading elastic modulus, ratchet strain, hysteresis loop area and so on are obtained. In this paper, the influence of axial angle, tensile rate and loading stress amplitude on ratchet behavior of membrane material is analyzed, and the strain of membrane material is decomposed. The modified Burgers model is used to predict the cyclic tensile curves of membrane materials. (3) A series of biaxial tests including cyclic tensile tests stress relaxation tests and creep tests are carried out. The anisotropy of membrane materials is systematically studied. Based on the orthotropic theory of composite materials, the relationship between elastic modulus, relaxation modulus and creep compliance of membrane materials and the axial angle is derived. Based on the plastic theory and flow rule of anisotropic materials, the anisotropic constitutive equation of PTFE coated fabric membrane was obtained by introducing creep potential function, equivalent stress and equivalent creep rate.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU599

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