Research On Energy Dissipation And Deformation Characteristics Of Airship Envelope Material Under Tensile Cyclic Load

The airship envelope material has to withstand high temperature and pressure for a long time during the production and preparation process;at the same time,during daily use and transportation,the material itself has to withstand the thermal expansion and contraction caused by gusts,rain and snow,and external temperature changes.Airship envelope materials are usually in a state of repeated loading and unloading due to changes in tension caused by processes such as recovery and release,and the airship envelope materials will be damaged and deformed during the above process.The initiation,expansion and deformation of material damage are essentially the process of non-uniform energy dissipation.In the absence of in-depth understanding of the damage and failure mechanism of airship envelope materials,the use of energy and deformation analysis methods can be more essential Understand the initiation,expansion and deformation mechanism of various damages of airship envelope materials.The durability and stability of the airship envelope material are very important to the structural stability and flight control of the airship.Therefore,understand the influence mechanism of the hot-pressing preparation process,the external cyclic load of different magnitudes,and the high and low temperature alternating environment on the energy dissipation and deformation characteristics of the airship envelope material It is of great significance to the development and engineering application research of airship envelope materials.In order to explore the influence mechanism of the process parameters of the hot-pressing compound on the energy dissipation and residual strain characteristics of the airship envelope material,the polyvinyl fluoride(PVF)film is used as the weather resistant layer,the TPU film as the helium barrier layer,and the polyarylate Vectran fiber woven plain weave as load-bearing layer,and the TPU film as the adhesive layer.The airship envelope materials with various hot-pressing process parameters were prepared by hot-pressing composite method,and the mechanical properties of airship envelope materials are tested and analyzed after cyclic loading-unloading.The influence of hot pressing temperature and hot pressing time on dissipation energy and residual strain is analyzed,and theoretical formulas are proposed.The results show that the hot-pressing temperature and hot-pressing time have the same influence on the energy dissipation and residual strain characteristics of the airship envelope materials,and the fitting degree of the fitting equation is good,and the coefficients are positively correlated with the hot-pressing temperature and hot-pressing time;The energy dissipation and residual strain characteristics of the materials show a two-stage linear characteristic,which is not only dependent on the hot pressing process,but also closely related to the times of cyclic loading and unloading;By comparing the dissipated energy and residual strain of the airship envelope materials prepared under different hot pressing process parameters after cyclic loading and unloading,the optimal preparation process was obtained as follows: hot pressing temperature 160℃,hot pressing time 600 s.In order to have a more comprehensive understanding of the influence mechanism of different magnitudes of applied cyclic loads on the energy dissipation and deformation characteristics of the airship envelope material,the airship envelope material was prepared based on the optimal preparation process obtained in the previous chapter and carried out.The test results show that the cyclic test parameters have the same influence on the energy dissipation and deformation characteristics of the longitudinal and weft specimens;when the number of cycles is the same,the greater the cyclic loading load,the higher the total strain energy of the longitudinal and latitudinal specimens and can be recovered The higher the strain energy,the higher the dissipation energy,the lower the strain energy recovery rate,the higher the energy dissipation rate,the greater the residual strain,the greater the cumulative residual strain,the greater the maximum elongation,the greater the minimum elongation,and the relative The greater the residual deformation index;the greater the cyclic unloading load,the smaller the recoverable strain energy of the warp and weft specimens,the greater the dissipation energy,the lower the strain energy recovery rate,the higher the energy dissipation rate,and the greater the residual strain.The greater the cumulative residual strain,the greater the minimum elongation,and the greater the relative residual deformation index;the greater the cyclic loading speed,the smaller the total strain energy of the warp and weft specimens,the smaller the dissipation energy,and the greater the recoverable strain energy.The higher the energy recovery rate,the lower the energy dissipation rate,the smaller the residual strain,the smaller the cumulative residual strain,the smaller the maximum elongation,the smaller the minimum elongation,and the smaller the relative residual deformation index.The influence mechanism of the high and low temperature alternating environment on the energy dissipation and deformation characteristics of the airship envelope material under cyclic loading-unloading is explored.The results show that the airship envelope material is subjected to400 times ±80℃ high and low temperature alternating treatments.Compared with the sample after high and low temperature alternating treatment,its total strain energy,dissipation energy and energy dissipation rate in the cyclic stretching process are larger,and the recoverable strain energy and strain energy recoverable rate are lower,The residual strain and cumulative residual strain are more,the maximum elongation and minimum elongation,the relative residual deformation index is larger,mainly due to the physical and chemical changes of the material in the high and low temperature alternating environment.