## 2 Manufacturing of Hybrid Laminates with Sensor Functionality
To further limit the forming temperature, DSC (differential scanning calorimetry)  
Figure 1: Process chain for mass production-enabled manufacturing of hybrid laminates: 1 Foil extrusion, 2 Jining, 3 Forming, 4 Polarization, 5 Signal Processing. analysis of the piezoceramic compound was carried out. DSC confirmed the results of the preliminary tests: the melting starts at 110 \({}^{\circ}\)C and the maximum enthalpy of melting is reached at 167.8 \({}^{\circ}\)C, which also represents the melting point. The findings were transferred to the manufacture of a cover for the center console of an automobile. With this part, it should be possible to carry out different actions in the car by localizing impacts. A new tool concept was developed for the forming process. Figure 3 shows the overall structure of a servo-electric press. Instead of heating cartridges, a variothermal heater was used, which uses water to heats the tool to 190 \({}^{\circ}\)C and cools it down to 20 \({}^{\circ}\)C again. This occurs by two separate circuits, which are connected by valves. Furthermore, an oven for preheating was omitted, and the heating was placed directly in the press by means of infrared radiators (Figure 3, right B). The procedure is as follows: The sample is inserted into the sample holder and preheated by means of infrared radiation. The specimen holder can be moved and is pushed on a guide to the tool. The free programming of the servo-electric press allows initial bending of the outer cover geometry when the tool is closed in a path-controlled manner, and then switches to a force-controlled control system in order to deep-draw the inner contour with the drawing cushion. Upon completion of the forming process, the hot forming tool is rapidly cooled by the variotherm unit. Thus, the plastic solidifies, and the component can be removed afterward. To adjust the process, a sample made only of aluminum was provided with thermocouples in order to record the working temperature (Figure 4). The rate of the temperature change was determined by the first derivative over time, which clearly showed the alternation of heating, holding, and cooling. The process steps described above are indicated in Figure 4.  
Figure 3: Variothermal forming tool in a servo-electric press and a detailed side view (B). Figure 2: Continuous joining of aluminum sheets with piezoceramic foil and the top view (A). In the tests, the preheating temperature and the die temperature proved to be the most important parameters for defect-free forming. If these temperatures are set too low, tears and/or delamination occurs. Figure 5 shows the behavior if the temperature in the process is too high and the viscosity of the plastic is too low. It can be seen that the plastic flows out of the drawing gap, and thinning occurs in the middle. The parameters for the experiment were: preheating temperature infrared radiator 200 \({}^{\circ}\)C and tool temperature 170 \({}^{\circ}\)C. These parameters are identical to those from the test in Figure 4, and, when looking closely at the measured value, it can be determined that the temperature was above the melting temperature of the DSC analysis. After further tests, and by adjusting the parameters to the preheating temperature of the infrared radiator 180 \({}^{\circ}\)C and the tool temperature 150 \({}^{\circ}\)C, a component could be produced without thinning and melting, and without cracks. Two variants formed with these parameters are shown in Figure 6. The first variant is without copper strips (Figure 6a); it is mainly used for the individual application of electrodes. The second variant represents the complete mass production of a component with electrodes (Figure 6b). The results showed that the process is mastered and that, with the right parameters, a component can be produced without defects. Figure 4: Temperature measurement of a sample during the process.