不同拉伸速率下的ECTFE薄膜单轴拉伸试验

Experiment and Analysis of Uniaxial Tensile Mechanical Properties of ECTFE Foils Under Different Strain Rates

针对厚度为250μm的乙烯-三氟氯乙烯共聚物(ethylene-chlorotrifluoroethylene,ECTFE)薄膜,沿MD及TD方向裁取哑铃形试样,分别进行不同拉伸速率下(0.02、0.20、0.50、1.00、2.00、4.00、6.00、10.00 min-1)单轴拉伸试验,通过分析应力-应变曲线,得到了弹性模量、屈服强度、抗拉强度和断裂延伸率等力学参数及其变化规律.试验结果与分析表明:ECTFE薄膜材料沿MD及TD方向的单轴拉伸力学性能基本相同;应力-应变曲线呈现明显的非线性,从拉伸初始至断裂共经历线弹性、应变软化、冷拉和应变硬化4个主要阶段;弹性模量、屈服强度、抗拉强度和断裂延伸率等主要力学参数与拉伸速率之间呈现非线性指数关系,并给出了其非线性拟合公式,可用于预测ECTFE薄膜在不同拉伸速率下的的相关力学参数.

Uniaxial tensile tests of ethylene-chlorotrifluoroethylene(ECTFE)foils were conducted in this paper.ECTFE foils with a thickness of 250μm were used.The dumbbell-shaped specimens were manufactured according to the machine direction(MD)and the transverse direction(TD)of the foils.The stress-strain curves of the foils were obtained under eight constant strain rates(0.02,0.20,0.50,1.00,2.00,4.00,6.00,and 10.00 min^-1).Based on the stress-strain curves,tensile strength,tensile strain at break,yield stress,yield strain,and elastic modulus were analyzed and calculated.Based on the test results and analysis,some useful findings could be derived.The uniaxial tensile mechanical properties of the ECTFE foils along the MD and TD directions were almost identical.The stress-strain curves showed obvious nonlinearity,in which there were four main stages of linear elasticity,strain softening,cold tension,and strain hardening from the beginning of tension to fracture.Main mechanical parameters such as modulus of elasticity,yield strength,tensile strength,and elongation at break showed nonlinear exponential relation with the strain rate.The nonlinear fitting formulas are also given,which can be used to predict the mechanical parameters of ECTFE foils under different strain rates.