Effects Of Short-term Aging And Creasing Damage On Air Leakage Properties Of Airship Envelope Materials And Structures

The semi-rigid airship consists of the main and auxiliary airbags and keel.The main airbag controls the flight altitude and position of the airship by adjustment of air pressure.The internal auxiliary airbags are filled with helium to provide lift for the airship.The types of damage of envelope material can be divided into surface damage,internal closed damage,and penetration damage.Among them,penetration damage can cause air leakage to the envelope material.From production to service,aging and creasing can cause penetration damage to the envelope material,affect its air barrier performance,accelerate gas leakage and shorten single flight time of airship.In this paper,Uretek3216-LV,was used as the research interest.The natural aging,creep,rolling and the flexural durability tests were conducted to simulate the aging and creasing damage of the envelope material.Through air leakage test,the impact degree of aging and creasing damage on the air leakage performance of envelope material is revealed.The leakage time of airship models with different flex conditioning levels is obtained by numerical simulation.The main research contents and results of this paper are as follows:(1)The damage caused by short-term natural aging to the envelope material is negligible and has almost no effect on the air leakage rate.Outdoor natural aging test was used to simulate the aging damage caused by ultraviolet and high radiation temperature during the service period of the envelope material.The experimental results were grouped and compared to conclude that aging had almost no effect on the air leakage rate of the envelope material.SEM was used to observe the microstructure of new and aging envelope materials.(2)Creep and rolling damage have almost no effect on the air leakage rate of the envelope material,while creasing damage can seriously affect the air leakage performance.Creep test,rolling test and flexing test was respectively used to simulate creep deformation damage rolling or crease damage of the envelope material.Through the comparison of test data,it can be concluded that creep and rolling have no effect on the air leakage performance of envelope materials.The air leakage is proportional to the pressure difference,and the relationship between the air leakage and the number of flex cycles is changed from the nonlinear positive correlation of the initial segment to the linear relationship.The deformation process of the material damage is observed by scanning the material with an electron microscope;the failure mechanism and deformation process was analyzed under the macroscopic and microscopic phenomena of the envelope material.The failure process goes through three stages: initial stage of loosening and twisting of fiber,the stage of functional layer failure and the final stage of fiber breakage leading to formation of pin hole.(3)Creasing will damage the envelope material,affect its air leakage rate,and shorten single flight time of airship.By numerical simulation and mathematical statistics,the diameter of pinhole,damage rate and leakage time of envelope material under different flex cycle conditions were obtained.Then,by using them results,the diameter of the leak hole and the leakage time of airship under different flexing conditions are obtained.