Abstract
Natural fibers can be attractive reinforcing materials in thermosetting polymers due to their low density and high specific mechanical properties. Although the research effort in this area has grown substantially over the last 20 years, manufacturing technologies to make use of short natural fibers in high volume fraction composites; are still limited. Natural fibers, after retting and preprocessing, are discontinuous and easily form entangled bundles. Dispersion and mixing these short fibers with resin to manufacture high quality, high volume fraction composites presents a significant challenge. In this paper, a novel pneumatic design for dispersion of natural fibers in their original discontinuous form is described. In this design, compressed air is used to create vacuum to feed and convey fibres while breaking down fibre clumps and dispersing them in an aerosolized resin stream. Model composite materials, made using proof-of-concept prototype equipment, were imaged with both optical and X-ray tomography to evaluate fibre and resin dispersion. The images indicated that the system was capable of providing an intimate mixture of resin and detangled fibres for two different resin viscosities. The new pneumatic process could serve as the basis of a system to produce well-dispersed high-volume fraction composites containing discontinuous natural fibres drawn directly from a loosely packed source.
Highlights
Natural fiber reinforced composites have been an increasing focus of the materials research community over the past 20 years [1]
In addition to environmental benefits, they offer potential for both weight and cost savings when compared to conventional fiberglass composites [2]
Another challenge impeding the more widespread use of natural fibers in high production composite applications is the difficulty in handling inhomogeneous fibres in automated processing equipment
Summary
Natural fiber reinforced composites have been an increasing focus of the materials research community over the past 20 years [1]. There are efforts to address this issue by controlling the harvesting plan for industrial grade natural fibers [7] as well as sorting natural fibers and providing a comprehensive data base for fiber properties [8] Another challenge impeding the more widespread use of natural fibers in high production composite applications is the difficulty in handling inhomogeneous fibres in automated processing equipment. A fiber roving is fed to a mixing head, late nineties by Krauss Maffei [14] In this method, a fiber roving is fed to a mixing head, and and chopped chopped as as in in aa conventional conventional fiberglass fiberglass system, system, but but instead instead of of mixing mixing with with the the sprayed sprayed resin resin externally, externally, fibres fibres are combined with polyurethane in a mixing chamber just before discharge to the mold
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