Macro- and micro-impregnation phenomena in continuous manufacturing of fabric reinforced thermoplastic composites

Macro- and micro-impregnation of molten thermoplastic polyamide 6.6 into glass and carbon fabrics during continuous manufacturing using a double belt press was investigated. Following the analytical approaches on transverse permeability of fiber bundles, a comprehensive experimental set-up has been derived to verify the effects of temperature boundary conditions, resident time, consolidation pressure and fiber bundle permeability on the degree of impregnation. Samples with reinforcements of glass and carbon fabrics were produced at distinct processing conditions and the degree of impregnation was investigated by microscopic observation and mirrored by measuring the flexural stiffness in a three-point bending test. Hence, contribution of particular processing properties on impregnation was discussed in detail and the results are to be applied to guide the manufacturing process concerning selection of appropriate raw materials and optimized processing conditions. It could be concluded, that the continuous manufacturing process using a double belt press might basically be simulated by applying the current analytical approaches on the impregnation of fibers with thermoplastic polymers, but exhibits its own characteristics with respect to intra-bundle mechanism such as microscopic adhesion and void entrapment. (C) 1998 Elsevier Science Ltd. All rights reserved.