Negative Pressure Forming of Double-Curved Reflector Panels with Honeycomb Sandwich Structure Based on Reconfigurable Discrete Mold

The ultra-large high-precision reflector panel is technical bottlenecks in construction of large-scale compact antenna test rang (CATR). To solve the problem, a negative pressure forming process was proposed to manufacture reflector panels with the sandwich structure based on reconfigurable discrete mold. Firstly, the deformation behaviours of each sheet at forming stage and sandwich structure at the springback stage were analyzed, and then, their mechanical model was established. Secondly, the technical factors affecting forming accuracy were researched, such as segmenting criterion, stress release, springback prediction and compensation. The control curve of segmenting ultra-large reflector surface was established. The process of releasing stress by slotting was developed. The finite element model of springback prediction was established to accurately predict forming precision. The process of negative pressure forming has been successfully used in the construction of an ultra-large CATR with 12 m quiet zone. The shape accuracy of a single reflector panel with area 6.4 square meters reached 0.03 mm (RMS), and the average forming accuracy of 30 panels was 0.034 mm (RMS). The final shape accuracy of the whole reflector with area 368 square meters reached 0.054 mm through on-site installation and alignment.