## 3 Application of Integrated Transducer Arrays for Generation of Sound Waves
### Manufacturing Process  
For investigations regarding the application of structure-integrated transducers for sound wave generation, manufacturing of the active textile-reinforced thermoplastic composites (TRTC), the application of thermoplastic-compatible piezoceramic modules (TPMs) on the surface of a fiber-reinforced semi-finished plate (organic sheet) was necessary. The organic sheet consists of a glass fiber-reinforced polyamide 6 (type: 102-RG600(x)/47% Roving Glass--PA 6 Consolidated Composite Laminate produced by Bond-Laminates GmbH). The _ePreform_ consists of a polyamide 6 (PA 6) film with a thickness of 100 \(\upmu\)m. In regard to the built up of the TPM, commercially available monolithic wafers (type: PZT 5A1, electromechanical properties can be found in Table 11) with a square area of 100 mm\({}^{2}\) and a thickness of 0.2 mm were used (see Figure 7B). The outer surfaces of the wafers were metallized by silver printed electrodes and contacted by conductive copper tapes. This layup was embedded into two PA 6 carrier films with a thickness of 100 \(\upmu\)m (see Figure 7A). The TPMs are polarized in the thickness direction and work in the d\({}_{31}\) mode, which means a principal deflection normal to the polarization direction. A major precondition for the embedding of the TPMs into the composite structures is the use of identical thermoplastic materials for the TPM carrier films and the matrix of the fiber-reinforced structure. During the consolidation, the module will be matrix homogeneous integrated into the composite structure. Compared to adhesively-bonded modules the integration of TPM enables an efficient coupling of the piezoceramic layer to the reinforcement as shown in Figure 8.  
The conceptual manufacturing process for active TRTC, which bases on a press technology, starts with the first process step, the so-called _ePreforming process_. It comprises the rollup and cutting of a thermoplastic film, the precise positioning, and fixing of TPMs, the application of conductive paths and the accompanied electrical contacting (see Figure 9). Figure 8: Micrograph of a matrix homogeneous integrated TPM. Figure 7: Prototypic thermoplastic-compatible piezoceramic modules (TPM) configuration. (**A**) Built up; (**B**) Consolidated TPM (d\({}_{31}\) mode). In the developed manufacturing process (see Figure 10) the _ePreform_ is positioned in the pressing die and covered by a preheated and melted organic sheet and, subsequently, the press closes. During the consolidation the TPMs are simultaneously polarized [28]. In regard to the manufacturing of the _ePreform_ an especially-developed _ePreforming_ unit was used in order to assure the automated assembly of thermoplastic films with TPM and the necessary conductors. The transfer of TPM from storage to the predefined position is realized by a vacuum gripper, whereas the fixation to the thermoplastic film can be realized by thermal stapling or ultrasonic welding. In this investigation the TPM were fixed by thermal stapling. The leads are automatically rolled up from the wire coil, fixed by thermal welding points, and cut at the end of the conductive paths. In these studies the leads consists of tin-coated copper wires with a diameter of 0.21 mm. Furthermore the TPMs, shown in Figure 11, are arranged to a linear pattern of six elements which have an offset of the piezoceramic wafers of 15 mm (see Figure 11). For the initial prototypic tests the _ePreform_ was positioned and fixed at the organic sheet plate manually using thermal resistant polyimide tape. The plate had dimensions of 1000 mm length, 600 mm width, and 2 mm thickness, and the TPM pattern was positioned 250 mm from the short side in the middle of the plate. In contrast to the introduced manufacturing process of such active parts, the consolidation of the investigated plate was performed by an autoclave process because of its prototypic configuration.