Integration of sensor elements in fibre-reinforced thermoplastics using remote laser processing

Within the Collaborative Research Centre 639 the processing chain from filaments up to component parts under the focus of textile-reinforced thermoplastics is considered. Thereby, thermoplastic hybrid yarns (glass/ polypropylene filaments) are processed to multi-layer knitted fabrics and subsequently to complex spacer structures for lightweight constructions. The applications of hybrid yarns facilitate short flow paths of the matrix systems and thus comparatively low impregnation and consolidation pressures. These process conditions are beneficial for the integration of functional elements as sensors and electronic components in fibre-reinforced thermoplastic parts. Nevertheless, to minimize the strain on these elements during the pressing process, especially in thin-walled components, an adapted lay-up has to be examined. For the variation of the single layer thicknesses the material is excavated in the integration relevant area by a remote laser cutting process. Since high intensities are needed to enable laser cutting of glass-fibre textiles a brilliant laser beam source is recommended. Thereby, the remote-technology is used to deflect the beam onto the material with tiltable scanning mirrors. Furthermore, a precise positioning of the laser cutting pathis required. For this reason a camera positioning system is used to detect the working area of the scanner system. Subsequently, the certain work piece features can be extracted by image processing algorithms. The determined data is used for the cutting path generation. Since the cutting process is a thermal process, it is necessary to minimize the heat affected zone to a minimum. Therefore, a tailored remote laser cutting strategy was developed. This strategy allows an ablation of the hybrid and the knitting yarn to achieve a full cut or a partial exposure of single layers. Within this work, the enhancement of integration possibilities of sensor elements in thin-walled components will be presented under the focus of locally cut and partial exposed layers of the multi-layer knitted fabrics