Ribbonizing of electrostatic powder spray impregnated thermoplastic tows by pultrusion

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Process models have been developed for thermoset pultrusion and thermoplastic pultrusion using melt impregnated prepregs. Thermoplastic towpregs are manufactured using new innovative methods such as those using dry powder impregnation. The morphology of dry powder impregnated ‘towpregs’ consists of a dry fibre bundle surrounded by a layer of polymer. In this study a two-dimensional finite element model using non-Newtonian fluid properties was developed to predict the pulling force for ribbonizing of a single thermoplastic powder impregnated towpreg via pultrusion. This is the first model that used a dual medium finite element approach to capture the microstructure of the dry powder impregnated towpregs. The model was experimentally verified using PEKK (Poly Ether Ketone Ketone) powder coated glass fibre tows for two die taper angles of 0.17° and 0.34°. The experiments were conducted at 350°C and the pulling speeds used ranged from 3 mms 1 to 19 mms −1. The model predicted that the pulling force increased monotonically as a function of the pulling speed. The experimentally obtained pulling force increased as a function of pulling speed until the pulling speed was ∼8 mms −1 and then reduced. The pulling force increased with increase in the taper angle for the same total die length. The model predicted that the shear force was the dominant part of the pulling force.