## 2 Manufacturing the Composite Main Reflector
### Verification of Manufacturing Process Variables  
As shown in Figure 3, the composite main reflector of the deployable reflector antenna is manufactured using prepreg (carbon fiber and resin-impregnated sheet) and an aramid material honeycomb core, and it is laminated through a hand-layup method in which materials are stacked on a metallic mold that is designed and manufactured in consideration of a reflective surface. Due to the manufacturing characteristics of composite structures, there are process variables, such as the workability, the application of the adhesive film between the layers, and the curing method. In this study, four types of composite main reflectors were manufactured according to these process variables, as shown in Table 3.  
The first variable for the manufacturing process was considered to be the curing method. The composite main reflector is a sandwich composite with an aramid core. Because the aramid core has a lower compressive strength in the thickness direction than the aluminium core, deformation may occur in the thickness direction of the honeycomb core when high curing pressure is applied. \begin{table}
\begin{tabular}{c c c} \hline  & **High-Density Core** & **Low-Density Core** \\ \hline Mass, Unit Main Reflector [kg/1 EA] & 2.725 & 2.487 \\ \hline Mass, Main Reflector [kg/24 EA] & 65.4 & 59.69 \\ \hline
1 st Mode Frequency [Hz] & 35.38 & 36.47 \\ \hline
1 st Mode Frequency [Hz] & 3.345 & 3.475 \\ (Deployed Condition) & & \\ \end{tabular}
\end{table} 
Table 2: Analysis results of the initial design of the main reflector and the antenna. Figure 3: Stacking of composite main reflector. \begin{table}
\begin{tabular}{c c c c c} \hline
**Case** & **Curing Method** & **Adhesive Film** & **Perforated Hole** & **Additional Layup** \\ \hline
1 & Co-Bonding & O & X & X \\ \hline
2 & Co-Curing & O & X & X \\ \hline
3 & Co-Curing & X & O & X \\ \hline
4 & Co-Curing & X & O & O \\ \hline \end{tabular}
\end{table} 
Table 3: Finite element analysis results of the main reflector and the antenna. Considering this effect, if the sandwich composite is cured in low-pressure conditions, the fiber volume fraction is low, which may result in low structural performance of sandwich composites. In addition, because the main reflector is manufactured with 2 to 8 numbers of ply, pin-holes may occur due to resin flow if the curing pressure is not high enough. For Case 1, the reflector face was laminated in the metallic mold, and the first curing was performed under high pressure (40 psi, 0.276 MPa), and then the honeycomb core and the outer surface were laminated. Then, the second curing was performed under low pressure (10 psi, 0.068 MPa) using the co-bonding method. For Cases 2-4, a co-curing process was applied in which the reflective surface, the honeycomb core, and the outer surface were all laminated on the mold and then cured at once under low pressure (10 psi, 0.068 MPa). The second variable for the manufacturing process was considered to be the application of the adhesive film. Generally, when manufacturing a sandwich composite by applying an aluminium honeycomb core, an adhesive film should be applied to the contact surface for adhesion between the honeycomb core and the carbon fiber sheet. However, when applying an aramid core, the core and the sheet can be bonded through the resin impregnated in the prepreg, so, in Cases 3 and 4, the adhesive film was excluded, and the production was performed using the co-curing process [19]. In the case of the initial design of the main reflector described in Section 2.1, the area where the adhesive film is applied is large, so the weight of the adhesive film per unit of main reflectors is expected to be approximately 100 g, and if the adhesive film for all 24 main reflectors is excluded, the weight of approximately 2.4 kg can be reduced. The third variable for the manufacturing process was considered to be the perforation of the honeycomb core wall (perforating the hole).