Research On The Expansion Model Of Inflatable Structure And Its Dynamic Characteristics

Inflatable structure can be flexibly folded to launch and be inflated in orbit to expand into a large space structure.Its deployment dynamics have a decisive influence on the stability,reliability,even success of the orbital deployment process and disturbance of the spacecraft body.The inflatable structure of analysis of the dynamic characteristics is premise and basic for optimizing the design of the inflatable structure and the design of the deployment scheme.Currently,the analysis for deployment dynamic characteristics of the inflatable structure mainly adopts a thin film unit model.However,for inflatable structures with thick wall thickness and bending stiffness,the analytical result of the thin film unit model is quite different from the actual one.Aiming at this problem,this paper proposes and establishes a model of a thin shell element with an aerated structure considering bending stiffness.It combines the model with control volume method to establish a finite element model of the inflatable structure.Taking the typical inflatable structure-inflatable tube as a research object,a sample of the inflatable tube structure was developed.An experimental research on the deployment dynamic characteristics of the Z-folding of the inflatable tube was carried out.The effects of wall thickness,pipe diameter and material properties on the deployment dynamic characteristics of the inflatable structure were studied.In this paper,in order to verify thin shell element model of inflatable structure proposed,the deployment dynamic characteristics of the inflatable structure are selected as the main characterization basis.The analytical results of the thin shell element model are compared with the experimental results and the results of the thin film unit model analysis.And the results show that when the structural wall thickness is thin,the result of the thin shell element model and the thin film unit model are close,which is consistent with the experimental results.It shows that the thin-walled inflatable structure with smaller bending stiffness can be approximated as a thin film structure,so the thin film unit model can be used for analysis without large deviation.At the same time,it also proves the correctness of the thin shell element model.And the thin shell element model can be degraded into a thin film unit model;as the wall thickness of the inflatable structure increases,the difference between the analysis results of the thin film unit model and the experimental results becomes larger.However,the analytical results of the thin shell element model are always in good agreement with the experimental results.The increasing wall thickness of the inflatable structure leads to increase the bending stiffness of the pipe wall.Compared with the thin film element model,the thin shell element model can better reflect the influence of bending stiffness on the deployment dynamic characteristics of the inflatable structure.This verifies the correctness and effectiveness of the thin-shell element model established in this paper.Finally,the deployment dynamic characteristics of global and local velocity,acceleration,displacement field,strain and stress field during the expansion process of the inflatable structure are analyzed using the established thin shell element model.The effects of material properties,wall thickness and diameter on the deployment dynamic characteristics of the inflatable structure were studied.