# Thermoforming Simulation of Woven Carbon Fiber Fabric/Polyurethane Composite Materials
## 2 Material Characterization and Thermoforming  
The thermoplastic composite blanks consisted of 2 \(\times\) 2 twill woven carbon fabrics (CFs) and thermoplastic polyurethane (TPU) and were created by Formosa Plastics Corporation. The fabrics were woven with TAIRYFIL TC-300 3K carbon fiber yams. A differential scanning calorimeter was used to test the thermoplastic composite blank to understand its temperature properties. The temperature increasing rate was set to be 5 \({}^{\circ}\)C/min. From the obtained results, the glass transition temperature was about 83 \({}^{\circ}\)C and the melting temperature was about 190 \({}^{\circ}\)C, as shown in Figure 1. Furthermore, this composite blank was tested using a dynamic mechanical analysis under a 2 \({}^{\circ}\)C/min temperature increasing rate. From this test, the [PERSON]'s modulus of the composite material could be obtained; then, the Young's modulus of the thermoplastic polyurethane was deduced. In Figure 2, the variation of [PERSON]'s modulus of thermoplastic polyurethane was shown with respect to temperature. There was a slight variation in the modulus between 120 \({}^{\circ}\)C to 200 \({}^{\circ}\)C because of the variation from the original data. These variations had less effect on the simulation results. Two structures created from thermoplastic composites using thermoforming were considered in the present work. The first one was named the U-shaped structure, and the second was called small luggage. To thermoform the U-shaped structure, punch and die processing was used as shown in Figure 3a,b. Due to its simple shape, the manufacture of U-shaped structures could be considered as one-dimensional thermoforming. The forming conditions for U-shaped structures are shown in Figure 4. The thermoplastic composite blank had a dimension of 255 \(\times\) 120 \(\times\) 1 mm, and it had four same layers. The forming temperature of  
Figure 1: The measured glass transition temperature and melting temperature from the differential scanning calorimeter. the thermoplastic composite was chosen to be 170 \({}^{\circ}\)C, which was above the glass transition temperature and under the melting temperature. The temperatures of the punch and the die were set to 100 \({}^{\circ}\)C and 160 \({}^{\circ}\)C, respectively, and the reason for these temperatures was due to trial and error and in order to have better part quality. The forming rate and the final forming pressure were 25 mm/s and 40 kg/cm\({}^{2}\), respectively. A blank holder with a pressure of 10 kg/cm\({}^{2}\) was used. These forming conditions were selected by trial and error to avoid rough surfaces, wrinkles, and fractures. Two types of stacking sequences were utilized to consider the influence of the fiber angle on the final products. They were \([(0^{\circ}/90^{\circ})]_{4}\) and \([(+45^{\circ}/-45^{\circ})]_{4}\), in which the parenthesis represented a thermoplastic composite layer. When the thermoplastic composite blank was laid on the die, an infrared heater was used to increase its temperature to the set value. Then, the forming process was conducted. The pressure was kept constant until the temperature of the workpiece was naturally cooled to room temperature. After that, the product was demolded. Figure 3: Punch and die for the U-shaped structure. Figure 2: Variation of the Young’s modulus of thermoplastic polyurethane with temperature. For the small luggage, the punch and die are shown in Figure 5. There are no detailed dimensions because of their complicated structures. In this case, the thermoplastic composite blank had a dimension of 313.5 \(\times\) 209 \(\times\) 1 mm, and the dimension of the final product was about 203 \(\times\) 130 \(\times\) 48 mm, where the product thickness was still close to 1 mm. The two types of stacking sequences, [(0\({}^{\circ}\)/90\({}^{\circ}\))]\({}_{4}\) and [(+45\({}^{\circ}\)/\(-45^{\circ}\))]\({}_{4}\), were also considered.