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A collaborative R&D project between The University of Birmingham’s School of Metallurgy and Materials and a UK consortium of companies has successfully developed a new environmentally friendly ‘clean’ filament winding technology for the production of high-performance composites that will be showcased at JEC Europe, Porte de Versailles, Paris, France, next week.
According to the consortium, this new wet-filament winding technology offers a clean and efficient method of production. Unique design components in this new wet-filament winding technology include a custom-built modular fibre bundle spreading station and a mixed resin fibre impregnation unit, which together provide effective fibre wetting. Waste and solvent usage is also significantly reduced compared with traditional wet bath filament winding production; up to 80% less cleaning solvent consumption has been achieved, along with an equivalent reduction of mixed resin waste. A variety of thermosets, including faster curing resins, have been successfully trialled with this new clean filament winding technology, which can be retrofitted and adapted for other manufacturing processes, such as pre-pregging and pultrusion.
The consortium explains that traditional bath-based impregnation method, which has been the predominant filament winding technique used for thermosetting resins by the composites industry over the last 50 years, has until now remained largely unchanged. This new, environmentally friendly, clean production technology, with improved productivity and significantly less waste, offers a next generation alternative technology for manufacturers, which can be retro-fitted to existing filament winding machines.
With this new ‘clean’ wet-filament winding process the conventional wet resin bath is replaced by the modular mixed resin fibre impregnation unit, typically mounted on the traverse-arm of the filament winding machine, close to the mandrel. The thermoset resin and hardener are contained in separate reservoirs, metered electronically and delivered on-demand by two precision gear-pumps via a custom-made manifold into the static mixer, which is connected to the mixed resin fibre impregnation unit. The system is able to apply a very precise volume of mixed resin to impregnate the fibre bundle, so minimising over-impregnation; the precision pumps fitted in the fully operational prototype are capable of delivering 10–110 g.min-1 of resin and hardener and handling liquids with viscosities of 20–10,000 mPa.s. A feedback control system between the rotating mandrel and the resin dispensing unit is used to control the relative throughput of the resin and hardener. The resin dispensing unit was manufactured by CTM, which is also part of the UK consortium.
The other important component in this clean wet-filament winding technology is the fibre bundle spreading station; the controlled spreading out of the fibres prior to resin impregnation increases the width of the tow and at the same time reduce its nominal thickness. This has the positive effect of efficiently increasing the impregnation of the mixed resin system into the fibres prior to being wound onto the mandrel.
For manufacturers, the consortium says there are several major productivity advantages over a conventional wet resin bath in using this new filament winding technology with its metered static mixer and resin impregnation head. The custom built metering system automatically draws the resin and hardener in the required stoichiometric ratio as needed from the individual bulk reservoirs. This eliminates the need to do any pre-weighing and manual mixing of the resin and hardener, with the subsequent benefits of no longer needing to use any disposable consumables, such as containers, stirrers and paper and, more importantly, avoiding the problem of air entrapment, a real issue with manual mixing. The other key productivity and cost saving gain of this new automated clean technology system is that the process can be truly ‘continuous’ and not limited by the mixed resin volumetric capacity of a wet bath, which must be replenished manually; the resin and hardener reservoirs can be replenished during production with no interruption to the line.
The UK Consortium members of this collaborative project are: The University of Birmingham; Mouldlife; Pultrex; CTM; Halyard Marine; Luxfer Gas Cylinders, PPG Industries, and Bruker. The project started in 2010 with backing from the UK’s innovation agency, The Technology Strategy Board, a Government funded body which helps companies develop and commercialise new manufacturing innovations
This new technology is being showcased at the show by the UK consortium on the Pultrex stand (U39). Commercial representatives from both Mouldlife and Pultrex will be available during the show for discussions with any companies interested in acquiring this new technology, which is being offered globally under licencing agreements.
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