24 September 2006
24 September 2006
A carbon fibre SMC, a material recycling concept and an impregnating technique for filament winding won this year’s Innovation Awards presented by the AVK Industrievereinigung Verstärkte Kunststoffe.
With these awards, the Federation annually honours outstanding developments with regard to reinforced plastics in the categories industrial application, ecological value, and academic research.
The awards were presented on 19 September in conjunction with the 9th International AVK Conference. For the first time this year, the AVK Conference was organised as a prelude to the new Composites Europe trade fair at the Congress Center Süd on the Messegelände in Essen. During the press conference which took place right before the presentation of the awards, Frank Bruns, AVK President, informed the press about the award-winning developments.
Carbon fibre SMC products – more rigid and less heavy than their glass fibre counterparts
Among the contenders for the Industrial Award, the jury was particularly impressed by the carbon fibre SMC (sheet moulding compound) developed by Polynt GmbH & Co. KG in Miehlen. This innovative material may be able to open up entirely new areas of application for SMC. A preliminary example is the rim for Golf Caddy vehicles that was developed in close collaboration with the Swiss processor Romay AG, Oberkulm. This part was traditionally made of cast aluminium.
Polynt had tried to develop a carbon fibre material that could be processed by the classical SMC technique without any adjustments. This was made possible by using chopped strands that also allow finished components with complex geometries. Under the name of HUP CF 24/54 RB-9500, Polynt launched such a carbon fibre SMC based on a vinyl ester resin. With a fibre content of approximately 50 wt% and fibre lengths of 25 and 50 mm, respectively, this product achieves a rigidity of 35 000 MPa at 20 % less density – which is about three times as high as the rigidity attained by a typical glass fibre SMC.
The Caddy rim produced by Romay is also made of HUP CF 24/54 RB-9500. By using moulded parts made of carbon fibre SMC instead of cast aluminium, the weight was reduced from about 1300 to less than 500 g. In relation to the total weight of the Caddy, exchanging the two rims will reduce the weight by 12 %. Glass fibre SMC, by the way, is unsuitable for this application since the spoke tends to bend under the load.
The Celstran recycling concept – suitable for the initial application
Ticona GmbH in Kelsterbach received the Ecology Award of the year for their Celstran recycling concept. This was the first raw materials producer to develop a pultrudate containing recycled long glass fibre reinforced production waste. Qualified recycling companies, such as EcoCare in the Netherlands, who were involved in the project development, reprocess the Celstran web scrap created during the manufacture and further machining of structural components. The resulting ground material meets certain defined quality criteria. In the second step, this ground material is pultruded to afford rod-shaped pellets exhibiting the specified properties. This product is then recycled to the initial application.
This approach has the advantage of facilitating the logistics, handling, and dosage for the processing company. At present, the pultrudate has a recyclate content of 10 % and is used to create the dashboard bracket of the VW Golf A 5. Efforts are under way to increase this content to 20 %. Besides, further areas of applications are to switch over to recyclate-containing pultrudate.
The impact of the LFT recycling concept is demonstrated by the fact that, according to the “TA-Siedlungsabfall” (the German Technical Directions for household waste), disposal of fractions with a carbon content in excess of 5 % has been prohibited since 1 June, 2005. Thus, corresponding waste must undergo thermal pretreatment. Owing to the limited incineration capacities, however, the associated costs have recently experienced a drastic increase.
Ring winding payout eye – filament winding enters series production
The research performed by Prof. Dr.-Ing. Alois K. Schlarb and Dr.-Ing. Ralf Schledjewski of the Institut for Verbundwerkstoffe GmbH, Kaiserslautern) [Composites Institute] is to enhance the efficiency of the thermoset filament winding process. The jury gave the award for the best academic effort of the year to the new impregnating technique developed by these researchers, pictured.
In this process, the rovings are being pulled through a siphon-like impregnating unit and are completely immersed in a precisely measured amount of resin. The mobile arms of the winding head guide the rovings directly to the surface of the vessel and deposit them precisely, using rotable feed-eye that can be rotated. The construction was designed specifically to make sure that the bandwidth remains constant within the cylindrical part of the vessel and during rotation around the polar caps, the pulled-through rovings are straightened out, and all the excess resin is scraped off.
Thus, fibre-reinforced pressure vessels targeted for use as hydrogen tanks in automobiles may be produced more efficiently and on a larger scale.
Long-term tests proving the suitability of this approach for continuous mass production were performed with the first prototype of the winding head equipped with modular impregnating units.
Using this unit, the stacking rate may be increased by a factor of 3.2. Shorter travelling distances reduce cycle times and allow units that require less floor space. Besides, the largely closed syphon impregnating system reduces possible resin leakages. After the end of the shift, only the tubes need to be disconnected and disposed of. Adding to these benefits is the reduced resin consumption.
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