Thermal Characterization of the Laser-Assisted Consolidation Process

Abstract

The laser-assisted consolidation process is a novel technology to produce thermoplastic composite parts of excellent quality and structural integrity. It combines the advantages of the traditional thermosetting filament winding technology with the faster processing times of thermoplastic composites in using automated tape laying processes based on on-line consolidation of the prepreg tape with the substrate The maximum sur face temperature and the time that the resin remains above the melt temperature are critical factors in determining the consolidation quality of the part. A thermal analysis of the fila ment winding process utilizing a CO2 laser beam is presented. Comparison of experimen tal process temperatures, measured using very fast response thermocouples, with tempera tures computed using a heat transfer model proposed by Beyeler and Güçeri, suggests that only 20% of the laser energy is absorbed by the composite material in the process con figuration used in these experiments. It is hypothesized that the low absorption of the laser energy is a result of the high incidence angle at which the laser beam strikes the material. This model implies that the temperature at the surface of the prepreg tape and substrate are sensitive to factors such as process geometry and surface roughness. Experiments also showed that using a narrow infrared laser beam as the sole heating source produces rapid cooling rates at the surface in excess of 1000°C/s resulting in very short melt times of less than 0.1 second. Experiments showed that the addition of a preheater alters the tempera ture profile significantly, producing smaller cooling rates and longer melt times.