Design And Analysis Of Spherical Pneumatic Structure And Uniaxial Mechanical Properties Of Membranes

As a new type of space structure system pneumatic structure can be applied in architecture field,including air-supported membrane structure and air-inflated membrane structure.Meanwhile,it can be applied in aerospace field,including airship and re-entry aeroshell etc.This paper introduced the structural design and simulation analysis of ULDB(ultra-long duration balloon)and the liquid bag of neutrino detector was chosen to be the research object,which were used to study the design and analysis of spherical pneumatic structure.Besides,experimental study on uniaxial mechanical properties of FEP(Fluorinated Ethylene Propylene)foil and Uretek3216 LV foil was taken.Firstly,the structural design of ULDB was introduced,including the theoretical derivation of Taylor’s curve and the dimensional design of lobe.Besides,the stress and deformation situation of two kinds of balloon under different internal pressure and gravity was analyzed by ABAQUS.Secondly,the stress and deformation situation of membrane in crack was analyzed by ABAQUS according to the design characteristics of liquid bag.The cutting pattern of the reduced-scale liquid bag was designed by developing a sphere with an equal area and the theoretical formula of the boundary of the lobe was provided.The lobe with a half gore width was chose for analysis by using symmetries of the liquid bag and the model of a single lobe was obtained by introducing the cutting pattern in the lobe forming process in ABAQUS.The mechanical and deformation characteristics of the lobe under internal pressure and gravity were obtained through the simulation analysis and the differences of the centerline between the practical lobe of the liquid bag and the ideal lobe of a spherical surface were analyzed emphatically.The results were valuable to the practical experiment in the future.Subsequently,A series of uniaxial mechanical property tests have been carried out for the FEP foils(thickness:150μm)and the specimens were cut from foils along the machine direction(MD)and the transverse direction(TD).The yield strength,the tensile strength and the elongation at break were obtained from the uniaxial tensile tests carried out by using four kinds of tensile speed and the linear fitting formulas through using the tensile strain rate as the variable are proposed.The analysis of the secant modulus and the residual strain per cycle were obtained via the uniaxial cyclic tensile tests carried out by using three values of cycle stress.The analysis of creep development trend were obtained from the results of the creep tests carried out by using three kinds of stress.The result of the tests was valuable to practical membrane engineering design of FEP foils.Finally,the Uretek3216 LV fabric was chosen to be the test object to study its uniaxial mechanical properties.The strength of the specimen in warp and weft was comparatively analyzed under two kinds of test conditions via uniaxial tensile test.The elasticity modulus was obtained from the cyclic test and the poisson’s ratio was obtained by using VIC-2D measuring system.The relationship between the tearing strength and four factors(length of crack,angle of crack,tensile speed,dip angle of yarn)was obtained form uniaxial tear test.