Experimental Study On Mechanical Properties Of Envelope Materials For Airships

The stratospheric airship has great value in the military and civil aspects such as ecological protection,hydrological monitoring,urban planning,high altitude warning and reconnaissance,satellite relay and so on.In order to promote the development of stratospheric airship,our country has formulated a series of related development plans.Because the stratospheric airship needs to be made very big and the working environment is complex,the performance of the membrane material of the airship is put forward higher request.In this paper,a variety of new type of airship skin fabric is studied,which is used to carry out the experiment of uniaxial tension,uniaxial cycle,biaxial tension,biaxial shearing,DIC digital speckle technique,etc..Comprehensive test is used to analysis membrane material.Based on the theoretical model,the experimental data is studied deeply.The difference between single and double axis measuring method is compared.First,the uniaxial tensile strength and uniaxial cyclic test of the membrane material Uretek5876 are done based on industry standards to explore the effects of different shapes and sizes on the uniaxial strength and failure mode.The applicability and prediction accuracy of the laminate are verified by the theory of orthotropic laminates.Secondly,the basic principle and mathematical model of DIC digital speckle technique are introduced in this paper,this paper presents a new method for the manufacture of speckle,the difference of displacement field and strain field is compared with the method of making different speckle patterns.The effectiveness of water transfer paper was validated on four different types of membrane materials,four kinds of membrane materials of strain field is measured in the initial,middle and late process.Again,Biaxial tensile test is done on material 4297 E,seven kinds of basic stress ratio combinations are selected,and 6 kinds of high stress ratio and 3 kinds of low stress ratio are considered.The elastic modulus under different stress ratio is obtained.The elastic modulus and Poisson's ratio of 4297 E were measured by uniaxial cyclic test and digital speckle technique,the comparison of the elastic constants measured by uniaxial and biaxial tests was carried out.Finally,shear cyclic tests on the 4494 ET of a new type of membrane material are carried out under five shear stress.The shear strain curves,shear stress shear strain curves and shear modulus are obtained.Comparison and analysis of shear modulus is done between uniaxial and biaxial test.