RIBBONIZING OF ELECTROSTATIC POWDER SPRAY IMPREGNATED THERMOPLASTIC TOWS BY PULTRUSION

Process models have been developed for thermoset pultrusion and thermo plastic pultrusion using melt impregnated prepregs. Thermoplastic towp regs are manufactured using new innovative methods such as those using dry powder impregnation. The morphology of dry powder impregnated 'to wpregs' consists of a dry fibre bundle surrounded by a layer of polyme r. In this study a two-dimensional finite element model using non-Newt onian fluid properties was developed to predict the pulling force for ribbonizing of a single thermoplastic powder impregnated towpreg via p ultrusion. This is the first model that used a dual medium finite elem ent approach to capture the microstructure of the dry powder impregnat ed towpregs. The model was experimentally verified using PEKK (Poly Et her Ketone Ketone) powder coated glass fibre tows for two die taper an gles of 0.17 degrees and 0.34 degrees. The experiments were conducted at 350 degrees C and the pulling speeds used ranged from 3 mm s(-1) to 19 mm s(-1). The model predicted that the pulling force increased mon otonically as a function of the pulling speed. The experimentally obta ined pulling force increased as a function of pulling speed until the pulling speed was similar to 8 mm s(-1) and then reduced. The pulling force increased with increase in the taper angle for the same total di e length. The model predicted that the shear force was the dominant pa rt of the pulling force. (C) 1996 Elsevier Science Limited.