Abstract
Objective Carbon fiber reinforced polymer(CFRP)lenticular tube wrap-rib reflectors are lightweight,simple in structure,have a high stowage ra-tio,high deployment reliability,and offer promising application prospects for both small-aperture and several-meter large-aperture deployable an-tennas.Currently,the application of such deployable reflectors mainly faces two challenges:ensuring the reliability of stowage and deployment strategies under large-deformation wrapping,and achieving and maintaining the surface accuracy of flexible wrap-rib reflectors.This paper pro-poses a CFRP lenticular tube wrap-rib reflector scheme and investigates its stowage and deployment performance,as well as surface accuracy.
Methods First,a 3 m aperture wrap-rib reflector scheme for the X-band was proposed,which includes a central hub,wrap-ribs,metal mesh,side cables,and a locking and unlocking device.The wrap-ribs were made of lightweight,high-strength,and high-stiffness CFRP lenticular tubes,and the[45°/-45°/-45°/45°]lay-up and section design were achieved using prepregs with a single-layer thickness of 0.05 mm.To ensure installation accuracy and deployment rigidity of the wrap-ribs,they were rigidly connected to the central hub.To solve the problem of high stress in the root area of the wrapped wrap-ribs,a method involving the installation of a wrapping guide at the root area of the wrap-ribs was proposed.A finite ele-ment model was established based on material parameters obtained from tensile tests,and the stress during the wrapping process of a single CFRP lenticular tube with a wrapping guide was analyzed using an explicit dynamic method.Second,according to the requirements of the X-band,the surface accuracy of the 3 m aperture reflector was estimated using an approximate theoretical formula.The focal length-to-aperture ratio of the re-flector and the number of wrap-ribs were determined.Due to the low stiffness of the wrap-rib reflector,the wrap-ribs deform to a certain degree during the reflector forming process,and a back-pillow effect is observed in each sector mesh.Both these factors affect the surface accuracy of the reflector.To address this issue,the shape of the flexible wrap-rib reflector was determined through form-finding analysis.The shape of the len-ticular tube wrap-ribs was optimized by combining the form-finding analysis results of the flexible reflector with a genetic algorithm.Finally,a re-flector prototype was designed and assembled,and deployment tests,fundamental frequency tests,and surface accuracy measurements were car-ried out.
Results and Discussion Adding a wrapping guide to the root area of the CFRP lenticular tube wrap-rib can prevent excessive wrapping stress in this area and improve the wrapping performance of the wrap-rib reflector.The focal length-to-aperture ratio of the reflector is 0.55,the number of wrap-ribs is 36,and the root mean square error(RMSE)of the estimated surface accuracy calculated using the theoretical formula is 0.89 mm,which meets the application requirements for the X-band.When the upper edge curve of the reflector wrap-rib lies on the design paraboloid,the surface accuracy of the reflector after form-finding analysis is 1.51 mm,which is significantly higher than the 0.89 mm calculated using the theo-retical formula.This discrepancy arises because the elastic deformation of the wrap-ribs and the back-pillow effect of the metal mesh cause the mesh to deviate from its initial position after form-finding analysis of the flexible wrap-rib reflector.Taking the root of the wrap-rib as the origin,the curve equation of the wrap-rib after optimization is z=0.000 148x2+0.035 9x(0 £ x £ 1 410 mm),and the surface accuracy of the reflector is 0.78 mm,which is significantly better than the 1.51 mm obtained before shape optimization of the wrap-rib.By optimizing the shape of the wrap-rib,the surface accuracy of the reflector was effectively improved.The mass of the wrap-rib reflector prototype is approximately 6 kg,and the stowage size is 0.7 m×0.7 m×0.15 m.It took approximately 6 s from the time the Dyneema rope was fused until the reflector was fully de-ployed.The deployment test verified both the stowage mode of the CFRP lenticular tube wrap-rib reflector and the deployment mode driven by the elastic energy of the wrap-ribs.At the same time,the feasibility of the proposed stowage tool and the locking and unlocking device was also verified.The measured fundamental frequency of the deployed reflector prototype is approximately 1.69 Hz,indicating good overall rigidity.In the surface accuracy measurements,the best-fit paraboloid under condition 1 was taken as the reference.The difference in surface accuracy be-tween after installation and after one stowage and deployment cycle is minimal,and it is close to the theoretical design value.After four deploy-ment cycles and three days of placement,the surface error increases slightly but remains below the design target value of 1 mm.The reflector pro-totype surface has basically achieved the design goal for surface accuracy.The surface accuracy measurement results show that the reflector proto-type exhibits stable surface accuracy,although the surface accuracy decreases slightly after long-term stowage and multiple stowage and deploy-ment cycles.
Conclusions The results show that the CFRP lenticular tube wrap-rib reflector scheme has the advantages of a simple structure,reduced weight,a high stowage ratio,and good overall rigidity.The wrapping guides and the locking and unlocking device contribute to improving the reliability of stowage and deployment.By optimizing the shape of the wrap-ribs,the flexible wrap-rib reflector can achieve good and stable surface accuracy.The CFRP lenticular tube has the characteristics of reduced weight,easy wrapping,and high rigidity after deployment,making it an important op-tion for wrap-ribs in such reflectors.Further research should be carried out on reflector performance under multiple stowage and deployment cycles,long-term storage conditions,and on-orbit environments,as well as on the maintenance of surface accuracy.关键词
缠绕肋/反射面/可展开天线/CFRP豆荚杆/形面精度/样机验证Key words
wrap-rib/reflector/deployable antenna/CFRP lenticular tube/surface accuracy/prototype verification分类
航空航天
