Principle of precision forming for sandwich panel of large antenna reflector

To solve the precision forming problem of the antenna panels with large non-developable double-curvature surface, the precision forming principle was proposed, based on discrete nails die, vacuum negative pressure, honeycomb sandwich, stress release in-plane, and resilience compensation. The problem of rectangle thin plate with free edges and constrained at arbitrary inner points with large deflection was discussed. An explicit/implicit hybrid finite element method was used to simulate the forming process and resilience to determine the processing parameters. The slotting and notching techniques were used for releasing the compression stresses of panel in order to ensure good fitness of panel on nails die. The resilience compensation was carried out by modifying discrete nails die, and the adjusting coefficient of nail-head height was obtained by minimizing the shape error between the modified surface and simulation shape. The CAE system for precision forming of antenna panels has been used for several actual projects of compact antenna test range and millimeter wave antenna. The root mean square (RMS) of reflector panel can reach below 25 μm.