## 3 Experimental Verification
### Parts Evaluation  
Automotive headliners are composed of both skin and base layers. The skin layer of the headliner that uses a conventional PU composite board comprises a combination of knitted fabric and soft PU foam and hot melt film or nonwoven fabric and hot melt film. In our study, the improved model replaced the soft PU foam (area density: 104 g/m\({}^{2}\), density: 26 kg/m\({}^{3}\), thickness: 4 mm) of the skin layer with a melt-blown nonwoven fabric (area density: 80 g/m\({}^{2}\)) that formed the vacuum insulation layer to reduce the thermal load. In addition, a polyethylene terephthalate (PET)-needle-punched nonwoven fabric (area density: 180 g/m\({}^{2}\)) was applied to the substrate layer to increase the sound absorption area. Figure 9 shows the forming process of the headliner fabricated in this study as per the standard headliner manufacturing process. First, the substrate of the headliner is molded, and subsequently, the substrate is formed by cutting. The fabric attachment process is followed by attaching the knit fabric and nonwoven fabric to the substrate, and finally, the headliner is trimmed. Figure 10 shows the modeling and prototype of the headliner. Figure 11 shows the schematic of the headliner insulation performance evaluation facility, which consists of outdoor- and indoor-condition chambers. In the outdoor-condition chamber, I/O control was  
Figure 8: Comparison of formability improvement: (**a**) Conventional; (**b**) Improved. Figure 10: Headliner: (**a**) Modeling; (**b**) Prototype. performed to replicate sunlight and the outdoor temperature conditions. The indoor-condition chamber was used to perform I/O control of the temperature of the indoor air and the heating and cooling airflow. The headliner parts for the evaluation were positioned between the outdoor-and indoor-condition chambers to measure and evaluate the heat transfer amount or thermal insulation performance. Figure 12 shows the procedure for evaluating the headliner insulation performance. The purpose of the evaluation procedure was to identify the heating time required to change the indoor temperature condition from 0 \({}^{\circ}\)C to 23 \({}^{\circ}\)C and the time for which the indoor temperature was subsequently maintained. Therefore, the initial outdoor and indoor temperatures of the evaluation facility shown in Figure 11 were set to 0 \({}^{\circ}\)C; the outdoor temperature condition was maintained at 0 \({}^{\circ}\)C, and the indoor temperature condition was manually set to 23 \({}^{\circ}\)C, after which heating was applied. After the target temperature of 23 \({}^{\circ}\)C was reached, heating is stopped, and the time required to maintain this (room) temperature was recorded. Here, we note that for the evaluation the speed of the heated wind flowing into the indoor chamber upon heater operation had to be estimated. Figure 13a shows the increase in wind speed caused by the blower switching mechanism of an actual compact car, whereas Figure 13b shows the wind speed according to the blower output of the evaluation facility. In general, passengers use three to five \"shifts\" of the blower for heating. Thus, the blower of the evaluation facility should afford an output of 60 W to 100 W, and this output range was decided as the evaluation range in the study. Figure 11: Configuration of headliner insulation performance evaluation facility. Figure 12: Evaluation procedure of headliner insulation performance. To reproduce the outdoor conditions under which the actual headliner is subjected to in terms of receiving solar energy, we mounted solar and infrared (IR) lamps to irradiate the headliner. Figure 14a shows the illumination intensities of the solar and IR lamps and the combined intensities according to the wavelength. We note that IR lamps are a type of incandescent lamp with enhanced IR radiation characteristics. Their input energy is emitted as infrared energy, with the visible light emitted being lower than that of solar lamps. Figure 14b shows the IR lamp irradiance as a function of the output.