Experimental Study On High Temperature Mechanical Properties Of Building Membranes

As a new type of building structure,the membrane structure is widely used in practical engineering,and the architectural membranes that make up the membrane structure are getting more and more people's attention.Most of the researches on architectural membranes focus on the mechanical properties and finite element modeling of membranes at room temperature.There are few studies on the mechanical properties of membranes at high temperatures.Meanwhile,the finite element modeling methods are more complicated.In this paper,the mechanical properties and finite element modeling of building membranes at high temperature are studied,and the effects of high temperature on the tensile mechanical properties of the membranes were investigated through a large number of experiments.On the basis of experiments,a finite element simulation considering the high temperature properties of the membranes was proposed.The method and the method for estimating the high temperature strength of the film from the normal temperature intensity.The specific contents are as follows:(1)Two kinds of coated fabric membranes were used as the main research objects.Sixty-six groups of uniaxial high-temperature tensile tests were carried out,and the test temperature was increased to about two hundred degrees Celsius.The stress-strain curve,tensile strength and fracture of the membrane were obtained,and the variation law of elongation and fracture morphology with temperature.The fitting formula of corresponding mechanical performance index with temperature is analyzed.The fracture of the membrane after stretching is observed by electron microscopy.The reason for the change of the tensile curve of the membrane from nonlinear to linear is explained from the microscopic level.(2)A typical nonlinear characteristic is presented for the stress-strain curve of the membrane.Based on the piecewise linear theory,the stress-strain curve is segmented by genetic algorithm,and the optimal segmentation point position of the curve segment is obtained,then the material stress-strain curve is simplified to the optimal three linear segments.The elastic modulus of the three linear segments of the film and the expression of the elastic modulus with temperature are given,and the high temperature constitutive model of the film considering the elastic modulus changes with temperature is established.The numerical simulation of high temperature tensile test of the film was carried out,and the high temperature constitutive model of the film can be used to describe the high temperature tensile behavior of the film through the simulation results agree well with the experimental results.(3)Aiming at the large dispersion of tensile mechanical properties of building membranes,high-temperature tensile tests were carried out on different types of PVC membranes,and the stress-strain curves,tensile strength,elongation at break and elasticity of each type of membrane were obtained.The variation law of modulus with temperature were obtained,and the fitting formula with temperature were also given.By analyzing the high temperature tensile test results of PVC film,the optimal segmentation position of different film materials was unified,and then an estimation method for estimating the high temperature strength of PVC film from normal temperature intensity was proposed and the estimation method was accurately verified.