Research On Influencing Factors Of Mechanical Properties Of Airship Envelope Material With Initial Damage

Stratospheric airship is a kind of floating vehicle that relies on its own buoyancy to provide lift and can be stationed in the air for a long time.It has great application prospect and development potential in military and civil fields such as monitoring and early warning,communication relay and so on.Flexible airship is widely used because of its unique advantages such as simple structure,light dead weight and low cost.However,because its main material is flexible composite material,the performance of its airship envelope material is required to be higher.In the process of pre-preparation and transportation,the airship capsule may be damaged to some extent.At the same time,there are harsh environmental factors in the stratosphere,such as large temperature difference between day and night,strong ultraviolet radiation,frequent rain and snow,etc.The airship envelope material will be torn and damaged to a certain extent,which will eventually destroy the overall structure of the airship and reduce the service life of the airship.Based on this,this paper studies the failure modes and mechanical properties of stratospheric airship envelope material with initial damage and non-integral structure before and after high and low temperature alternating treatment.Firstly,the initial slits of stratospheric airship envelope were preset,and the failure process of envelope material under different slits was investigated by uniaxial tensile test and trapezoidal tear test.The effects of slits length,slits angle and slits position on the tensile tear properties of envelope material were analyzed.The results show that the maximum tear strength of the surface and envelope material decreases with the increase of the length of the slit.When the length of the slit is small,the angle of the slit has a great influence on the tear strength.Then,the airship envelope material with initial center slit was treated with different cycles of high and low temperature alternating treatment.By setting different test parameters,the effects of loading rate,upper limit of load and loading-unloading cycles on the shape of slit,residual strain and mechanical properties of the envelope material were explored.Test results show that with the increase of the number of loading cycles and the upper limit of load,the initial slit of envelope material expands more,and the loading rate has little effect on the shape of the slit.The more high and low temperature alternating cycles,the higher the crimp and strain of the envelope material,but the lower the tensile tear strength.Finally,the mechanical properties of stratospheric airship envelope material under different splicing modes were studied.Through uniaxial tensile test,uniaxial cyclic tensile test,compression cyclic test and bending cyclic test,the fracture mode and mechanical properties of envelope material splicing belt were explored.envelope material splicing belt is mainly broken at the lap of two envelopes or separated and broken at the envelope itself and envelope patch.The fracture strength of double-layer overlapping splicing belt samples increases with the increase of splicing length,and the fracture strength of weft splicing belt is greater than that of warp splicing belt.