Co-authors​ :

 Shoya YAMASHITA (JAPAN), Sho KAJIHARA (JAPAN), Tomohiro YOKOZEKI (JAPAN), Yusuke SAKAMOTO (JAPAN), Aoi IZUMI (JAPAN), Akihito WATANABE  

Carbon Fiber Reinforced Plastic (CFRP) bistable boom is an open-section cylindrical beam. This is made of woven CFRP, which is a lightweight, high-strength, and high-rigidity material, and has structural characteristics to stabilize in both stowed and deployed configurations, which is called bistability. Therefore, it is suitable for space deployable structures that require light weight, stowability, and a large area. Recently, it has been considered for use as a support component for the solar array panel (SAP) of a lunar manned pressurized rover currently under development shown in Fig.1(a). In this rover, the CFRP bistable boom will be used to support the SAP. This SAP will be tilted toward the sun because the rover will be operated under the various regions from the polar regions to the equator, resulting in various directions of the SAP’s weight loading applied to the boom. However, there are some problems with the application. Since the rover will be operated under lunar gravity, buckling due to its weight and the load supporting the SAP is a serious concern. In addition, as the boom is repeatedly stowed and deployed, it will be operated in a shape that includes a transition area with a curvature change between the stowed and deployed areas as Fig.1(b). The right picture is a real boom, and the left one is a finite element model (FEM). This area affects boundary conditions and complicates the buckling behavior because the boom will be supported at a part in this area. Thus, it is essential to consider a model including the transition area. In this study, to find more advantageous conditions for operation with considering the above utilization conditions, a buckling analysis using FEM of the CFRP bistable boom including its transition area was conducted to clarify the effects of geometry and restraint conditions on buckling behavior. First, displacements were applied to one end of the boom to create the transition area. Next, the point load simulating the SAP weight assuming it is hung at this point was applied to the other end of the boom like Fig.2(a), varying the distance of the restraining position from the bottom of the boom as Fig.2(b). Fig.2(c) shows the shape of the cross-section at each position. To compare the effect of the transition area on the buckling, buckling behaviors were observed using the load-displacement graphs like Fig.2 and the deformation shapes of the model. From these results, it was found that the buckling behavior of the boom changes depending on the constraint position on the transition area. In addition, the effects of changes in boom geometry on buckling behavior were also discussed through the similar analysis by changing the boom length, diameter, and subtended angle. This analysis revealed that a shorter boom length, larger diameter, and larger subtended angle will make the boom more resistant to buckling. These results provided insight into the future operation of the CFRP bistable booms under gravity.