Experimental study of roving configuration’s influence on the flow field in a full-scale transparent pultrusion injection box

Abstract

Resin injection pultrusion gains increasing attention as it enables the use of highly reactive resins and resins sensitive to environmental conditions, while also decreasing the emission of harmful volatile organic compounds. Nevertheless, a comprehensive understanding of the flow field based on the geometric characteristics within open injection boxes is lacking due to a multitude of interdependent parameters. In this research, a novel setup for an experimental evaluation of the flow field in injection pultrusion practically is proposed. The setup consists of a full size, two-dimensionally tapered, transparent injection box that is installed within a pultrusion line and is operated with non-reactive fluids. Investigations are conducted with two different guide plate setups. Pulling forces and filling degree are evaluated for four pulling speeds, four fiber volume fractions and for four fluids. The non-reactive fluids are three grades of sucrose solution and Mesamoll with viscosities ranging from 13 to 246 mPa.s.Obtained pulling forces correlate linearly with the product of viscosity and pulling speed. Better fiber wettability properties and additional fiber guiding plates result in lower pulling forces. Backflow fill length displays an asymptotic correlation to pulling forces, indicating different governing mechanisms for these two phenomena. Backflow fill length corresponds directly with resin residence time, which ranges from about 10 to 3 min. The results indicate the possibility of manipulating pressure build-up and resin residence time separately, which would enable tailoring injection box cavity geometries systematically to a specific profile.