Study On Dynamic Characteristics Of Shape Memory Composites And Its Application In Space Expansion Inflatable Tubes

The space inflatable structure is a research hotspot in the field of aerospace structures of foreign countries,focusing on the design and manufacture of reflective surface film materials,the hardening of thin-film materials,the design and analysis of inflatable flexible structures,and the on-orbit testing of inflatable structures.At present,the research of key technologies is relatively mature,and many inflatable structures have been applied in engineering.The inflatable antenna has the characteristics of light weight and small collection volume.And the larger its diameter,the more obvious its advantages However,at present,it is undeniable that the film-material made of inflatable tube also has many disadvantages,so that its application has been greatly hindered,such as its low strength,poor rigidity,easy to damage,etc.The insufficiency of these materials leads to unsatisfactory structural applications.Therefore,this is an urgent problem to be solved.In view of the rapid progress in the study of the shape memory polymer structure at home and abroad,a variety of new research results have emerged,especially the exploratory application in the aerospace field is becoming increasingly fierce.Therefore,research of inflatable tube structure could also be combined with the shape memory polymer.This dissertation designed and manufactured a composite pneumatic tube structure with shape memory effect embedded inside the aerodynamic structure.The external composite material can realize the deployment of the tube structure in the space through its shape memory effect,and the composite material has the characteristics of strength and rigidity compared with the existing film material,which enhances the reliability.The internal aerodynamic structure can both increase the stiffness of the structure and accelerate the deployment process.In this dissertation,the author carried out substantial research work,including static study of shape memory polymers and composites,influence of temperature on the natural frequency and damping ratio of the dynamic characteristics of the composite sheet,dynamic analysis of the stress distribution of the bending of the inflatable tube structure.The major accomplishments are as follows:(1)Based on the domain separation method and composite lamination theory for the calculation of fiber-braided composites,tensile test results for shape-memory polymers are known parameters.Using MSC Digimat software to predict the elastic properties of composites with different carbon contents and temperatures,and DMA test to verify,the author obtained the regular phenomenon that at the same temperature,elastic properties of the material increase as the carbon content increases,the elastic modulus of the same carbon content material decreases with increasing temperature,and the different elastic properties resulting from different layup angles.(2)Utilizing simulations and experiments,this dissertation explores the effects of changes in the dynamic properties of carbon fiber composites with temperature,such as natural frequency and damping ratio;the influence of different temperature fields on the dynamic properties of the composite sheet,including full temperature field and local temperature field.As the temperature rises,the natural frequency decreases and the damping ratio rises.In addition,different changes caused by diverse regions of temperature are also discussed,which fully reflects the designability of the dynamic characteristics of shape-memory composites.(3)The author designed and successfully produced a shape-memory composite circular tube and combined it with a pneumatic structure to create an inflatable tube structure.This structure has good sealing performance and can be airtight under high pressure.In addition,the folding process of the composite tube was simulated and the stress distribution and counter-torque of the structure were obtained.The dynamic characteristics of the composite tube were verified by vibration test,providing a reference for the design of future performance conditions.