On-line consolidation of thermoplastic composites using laser scanning

A novel technique to process thermoplastic composites by laser-assisted tape winding has been developed and evaluated. Previous investigations were limited to a stationary beam and consolidation of narrow prepreg tapes. The technology was extended to process wider prepreg tapes using a galvanometer-based scanning system. The energy distribution along the consolidation line is affected by the triggering signal used to position the scanning mirror. This distribution is predicted using a geometrical model and the results are confirmed experimentally with imprints of the scanned beam in Plexiglas. It was found that the most homogenous heating of the surface is achieved if a triangular triggering signal is used. Density and short beam shear tests are used to evaluate the bond quality that can be achieved using the beam scanning system in comparison to parts fabricated with a stationary beam. Tests have been performed on parts processed with different laser power settings and scanning frequencies. The shear strength increases with increasing laser power to an optimum value after which it decreases due to the degradation of the thermoplastic matrix. The scanning frequency in contrast had no influence on the shear strength. The possibility to process wider tapes using the scanning system was demonstrated by consolidating a one-inch wide PPS/Carbon prepreg tape. (C) 1999 Elsevier Science Ltd. All rights reserved.