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.
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