Thermoplastic prepreg manufacture by solution impregnation

Advanced thermoplastic composites are commonly manufactured from "'prepreg" materials, where the reinforcing fibers are preimpregnated with resin. The objectives of this investigation were to identify the critical parameters in impregnation of the fiber tow by a thermoplastic solution, and to produce high quality thermoplastic prepreg. Continuous carbon fibers (AS4 and AU4) were impregnated with a thermoplastic resin solution using a research scale, single tow, drum winding prepreg machine. The parameters varied to control the degree of impregnation of the fiber tow were, weight percent polymer in solution, die size, fiber tow tension, fiber tow velocity, and the use of impregnation pins.

These parameters were varied during the prepregging operation and prepreg samples were evaluated to determine resin content. Viscosity studies were performed on the polymer solutions by means of a Rheometrics Mechanical Spectrometer. Thermogravimetric analyses were performed on the thermoplastic solution and the prepreg. Cross-sectional photomicrographs were obtained to determine the degree of impregnation and the fiber/resin distribution.

Unidirectional laminates were fabricated from the prepreg. Transverse tensile and double cantilivered beam mechanical tests were performed. Fractography photomicrographs were taken. X-Ray photoelectron spectroscopy was used to investigate the possibility of residual solvent in the laminates.

High quality prepreg was manufactured and the critical parameters in the prepregging process were identified and their effect on the prepreg was quantified.