Manufacture of Composites with Flexible Towpregs

Abstract

Thermoplastic resin matrix systems are preferred over thermosets for their high strength, ability to be re-formed repeatedly with heating, flexibility in handling, recyclability, and being environmentally friendly. The thermoplastic polymer matrices are highly cross-linked high-molecular weight polymers, and thus, they are solid at room temperature. The thermoplastic polymers need to be heated above the melting point to achieve melt flow, which helps in wetting and impregnation during consolidation to form a thermoplastic composite. Thus, the flexible preforms in the form of hybrid yarns, hybrid fabric, and prepreg sheets are used in manufacturing thermoplastic composites. In the flexible preforms, the reinforcement fiber is mixed with the thermoplastic matrix resin as fibers or polymer powder coating over the reinforcement fiber. Such a preform has reinforcement fiber that is not wetted by the thermoplastic resin. Thus, further processing is required to achieve fiber wetting and impregnation through consolidation to form a fiber reinforced thermoplastic composite. Here in this chapter, the mechanism involved in the consolidation of the thermoplastic composite is explained. Different methods of processing flexible thermoplastic preformed to achieve consolidation are discussed in detail. Methods like compression molding, filament winding, thermal forming, roll forming, automatic tape placement, autoclave molding, and other are discussed.