Endless carbon-fibre reinforced plastics (CFRP) are important lightweight construction materials. While the majority contains a thermoset matrix material, latest developments see an increase of CFRP with a thermoplastic matrix (CFRTP). This is due to their enhanced machinability and versatile material characteristics. However, high-performance thermoplastics and endless carbon fibres are both expensive resources. During the production of parts made from CFRTP, scrap-pieces and left-overs from the cutting process are usually disposed of. To increase the resource efficiency, a process is developed that includes the autonomous laser cutting of such CFRTP remnants to chips of unified dimensions, which can then be reused in the production of long-fibre reinforced CFRTP laminates.
This study focuses on the laser process development for the cutting of CFRTP with a polyether ether ketone (PEEK) matrix. The development aims for short processing times and minimum thermal alteration of the PEEK. Laser cutting of semi-finished CFRTP is especially challenging, because although most fibres within a carbon fibre roving might be cut, individual fibres might still be intact and may cause fibre pull-out that would severely reduce the cutting-edge’s quality. Therefore, to verify that the CFRTP was completely cut, an optical process monitoring system is developed.
In this investigation, process parameters are evaluated in terms of cutting time, surface appearance, and the completeness of the cuts. Surface analysis shows colour changes of the PEEK on an area of less than 1mm from the cutting edge. The monitoring system for cut completeness was introduced and showed good detection results.