The Mechanical Characteristic Of Membrane Based On The Uniaxial And Biaxial Experiment

Membrane structure is a stable surface formed by tension and compression of high strength flexible thin film materials,which can withstand certain external loads.Its shape is free,light,flexible,full of strength,flame retardancy,easy making,quick installation,energy saving,easy cleaning and safe use,so all kinds of membrane structures are also widely used in construction engineering.With the rapid development of membrane structure in China,considerable progress has been made in the study of theoretical and computational aspects of membrane structure.However,the lack of research on the basic properties of membrane materials,especially the mechanical properties,has become one of the factors that restrict the healthy development of membrane structure industry in China.This paper focuses on the constitutive relations of membrane materials and conducts targeted uniaxial and biaxial experiment.In order to distinguish the influence of test equipment,this paper carried out unidirectional loading test at Shanghai Jiao Tong University near ground space test center laboratory and TongJi university membrane structure.Finally,based on the experiment,the elastic modulus of PVDF membrane and the loading force of the PVDF film material are analyzed through theoretical derivation,and the relationship between the warp and the Angle of the yarn is analyzed and verified by numerical simulation.In this paper,the uniaxial and biaxial tensile tests were carried out with the sh-1050p PVDF film as the object.The results show that the elastic modulus is linearly dependent with the sine of double Angle.Through the analysis of biaxial tensile failure test results,the elastic modulus and Poisson ratio under biaxial stress are obtained.The following conclusions are drawn:(1)The nonlinear PVDF membrane material can be used as a bilinear elastic model.(2)In the case of biaxial stress,the film material can be used as an orthotropic elastic material.The elastic modulus and the stress ratio of the membrane material are related,but the Poisson ratio is independent of the stress ratio.When the stress ratio is the same(1:1),the elastic modulus is the same as the uniaxial axis.(3)It is deduced that,under uniaxial tension,the elastic modulus of the film are proportional to the modulus of the surface layer and the yarn,and are linearly dependent with the sine of 2 times the Angle.The theoretical formula is:E=E_b-E_ssin(2α).After comparing the tests,the results are in good agreement.The results of this paper not only provide the calculation basis for the design and structure calculation of the membrane structure,but also can supplement the existing norms.