Evaluation of Process Control During On-Line Consolidation of Thermoplastic Composites

Laser assisted tape winding is a manufacturing technique to produce thermoplastic composite parts of high quality. It is an additive semi-freeform fabrication process that utilizes thermoplastic composite prepreg tape as the base material. The tape is fused by the heat delivered from a laser beam, while it is wound onto a cylindrical mandrel. To ensure proper consolidation to the substrate, a roller applies the necessary compaction pressure. The fabrication of high quality rings with circular (Beyeler, 1988 and Irwin, 1994) and non-circular (Pistor et al. 1995) shape using quarter inch wide prepreg tape (PPS/Carbon, PEEK/Carbon) has been successfully demonstrated. The shape of the beam utilized in these investigations was determined by a series of lenses that formed the circular beam of the CO2 laser into a vertical narrow ellipse approximately 6.4 mm high and 2 mm wide (Pistor et al., 1995). The area illuminated by the infrared laser was therefore preset and not adjustable, limiting the set-up to the processing of quarter inch wide tape. One of the advantages of using a laser beam for the consolidation of thermoplastic resins is the that extremely high heat trnsfer rates to the resin are possible. This can be exploited not only for laser power adjustments in response to variations in tape laying velocity (Pistor et al., 1995), but also for scanning of a circular beam spot over the desired consolidation area. For the described set-up, a vertical slit of adjustable height was realized by scanning the laser beam vertically with a frequency of 100–500 Hz. Scanning height and frequency as well as motion and laser power are computer controllable.