THE PROPERTIES OF WET-FORMED THERMOPLASTIC SHEET COMPOSITES

Glass fiber reinforced thermoplastic matrix sheet composites of polypropylene and poly(ethylene terephthalate) were produced in a two-stage pilot scale impregnation and consolidation process. The first stage consisted of preparing wet-formed mats of long, discontinuous fibers and polymer powder on an inclined wire paper-making machine. The second stage consisted of consolidating approximately 15 wet-formed mats into a solid composite laminate by the application of heat and pressure in a compression press. The resulting composites had a nominal glass content of 26 wt% (approximately 12 vol %). Flexural strengths as high as 108 MPa for polypropylene composites and 132 MPa for poly(ethylene terephthalate) composites were measured on specimens cut from stamped parts. The flexural modulus of the polypropylene composites reached 5.4 GPa, while the modulus of the stiffest poly(ethylene terephthalate) composite was 8.1 GPa. The impact properties of the composites were equally good. Polypropylene composites absorbed up to 62 J/cm during an instrumented falling dart impact test. while poly(ethylene terephthalate) composites absorbed as much as 32 J/cm during the same test.