experimental and numerical analysis of inflatable boom under bending loads
- Paper number
IAC-08.C2.2.11
- Author
Mr. Tian Zhenhui, Harbin Institute of Technology, China
- Coauthor
Mr. Z Du, China
- Coauthor
Mr. changguo wang, China
- Coauthor
Dr. Huifeng Tan, Harbin Institute of Technology, China
- Year
2008
- Abstract
Inflatable space structures have become a wide application in aerospace structures because of their potential for exceptional packaging efficiency, low-cost launch. Typical examples include space inflatable antenna, and airships. These applications require a large membrane, which can be efficiently deployed and supported in its deployed shape with the used of large supporting structures. The members of the supporting structures must be ultra lightweight so that they can be packaged into a small volume for space transportation. These requirements have prompted an interest in space inflatable booms. Inflatable booms are the key supporting parts of the inflatable structures. The design is focus on the considerations of the load-carrying ability of the inflatable boom. Since 1960, some studies on the bending and buckling characteristics of the inflatable booms had been carried on. In these studies, the inflatable booms are assumed as a cantilever beam with the internal pressure. Comer et al. used this assumption to study the buckling behaviours of the inflatable boom under bending loads. They found that the wrinkles occurred when the bending loads reached the critical value, and the wrinkles are the local deformation behaviours. William used the small deflection theory to study the bending stiffness of the cantilever inflatable boom. In this method, the large deflection characteristics of the local wrinkling behaviours can not be obtained due to the adopted small deflection theory. Main et al. used the similar method to study the bending and the wrinkling characteristics of the inflatable boom with the textile material. They found that the bending behaviours have the same characteristics with the general solid elastic beam before the inflatable boom wrinkled. In this paper, we lay our stress on the bending behaviors of an inflatable boom. The nonlinear buckling finite element analysis was used to simulate the bending deflection of the inflatable boom and the results are compared with the experimental test. In addition, we analyzed the influence of the inflated pressure on the bending behaviors of the inflatable boom. A cylinder-shaped Kapton membrane structure under internal inflated pressure with 0.025mm thickness, 3GPa elastic modulus, 0.34 Poisson’s ratio is chosen as the bending analytical model. In this model, one edge is fully fixed through the analysis, and the other edge is a rigid surface and loaded along the perpendicularity of the axial direction. The bending analysis is performed by the nonlinear buckling solution followed by the increased transverse tip loads. The inflated pressure is 10KPa, and the tip load is from 0N to 2N. The length of the inflatable boom is 0.5m, and the radius is 0.025m. According to the simulation results of the minor principal stress, an obvious wrinkled region can be observed from the results, and the boom under the bending load occurs a local wrinkling. According to the relationship between the tip deflection and the tip load, we can determine the limited load, Fcr, is 1.15N. The limited load is the intersection between two tangent lines along two different deformed phases. In the first phase, the tip deflection increase slowly with the tip load increase. In the other phase, the tip deflection increases greatly with the small increment of the tip load. The influence of the inflated pressure on the bending behavior of the inflatable boom is also analyzed in this paper. According to the results, the limited tip load increases with the inflated pressure increases. In addition, we observed that the bending stiffness is a constant which is independent of inflated pressure. An experimental test is performed to verify the validation of the numerical results. The test is carried out on a glass plane so that an effect of no-friction is modeled during the test. The material and structural parameters are same with the simulation. In the test, the tip load is modeled as the weight of the poise. The inflated pressure is test and balanced in the test by a digital variometer. The test is ended until the inflatable boom fully wrinkled in the fixed edge. The local wrinkles are obviously observed near the fixed edge. According to the test results, we plot the relationships of the tip deflection and the tip load when the inflated pressure is 10KPa, and obtained that the mean of the limited force value is 1.32N, which is very close to the numerical results. In addition, we obtained also the test results of the influence of the inflated pressure on the bending behaviors of the inflatable boom. The inflated pressure is from 10KPa to 40KPa at a 10KPa individual. Corresponding to different inflated pressure, 10KPa, 20KPa, 30KPa, 40KPa, the limited load is 1.32N, 2.33N, 3.32N, 4.31N, respectively. While, these values obtained from the simulation are 1.15N, 1.95N, 2.7N, 3.65N, respectively. The experimental results are closed to the simulation. The discrepancy comes from the errors of the modeling of the friction in the test, the numerical calculation errors in the finite element analysis, and the variation of the inflated pressure in the test.
- Abstract document
- Manuscript document
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