Carbon powerhouses
20 August 2009 | By Angela in Composite production, Exhibitors, Innovation
Very light, very sturdy and very expensive. The characteristics of carbon fibres can be briefly described in this way. Consequently, their applications were primarily restricted in the past to aircraft and aerospace as well as to sports equipment. In addition, the so-called monocoque and other components of Formula 1 racing cars are produced using a carbon fibre reinforced plastic. Very large CRP components are employed in the wings and hull of aircraft.
After carbonization of the basic organic raw materials into carbon, the fibres are tensioned and thus achieve higher strengths and rigidities. Further processing takes place as rovings. This involves several thousand fibres which are combined into a strand and are then used as reinforcing fibres in woven fabrics. As low filaments (short fibres) they can be added to polymers. Suitably reinforced plastic components can be produced by means of processing equipment such as extruders or injection moulding machines.
To produce carbon fibre reinforced plastics (CRP), several layers of carbon fibres are embedded in a plastic matrix of epoxy resin, thermoplastics or ceramics. Analogue to glass-fibre reinforced plastics (GRP), press or autoclave processes for prepregs or fibre wrappings are used for production. CRP manual laminates are only employed for small scale runs or for individual production.
With the prepreg process, the component form is treated with a liquid parting compound into which the pre-cut prepreg is placed by hand. A bleed out fabric or a release and bleed out film is then placed on the final prepreg layer, followed by a layer of absorption fabric. The bagging film is then draped over it, laid in pleats and stuck down on the edges with a sealing tape. Using autoclave hoses, a vacuum is produced and the component is then cured in a special oven at a pressure of up to ten Bar and at up to 200 degrees Celsius.
With an annual growth rate of 15 per cent, economic experts expect that the CRP market will have virtually doubled by 2013. At the Composites Europe Trade Fair, which will take place in Stuttgart from 27 to 29 October 2009, CRPs and their applications have always been a central topic. Numerous innovative production technologies and processing methods have been presented to the public for the very first time at the fair.
Thus Saertex GmbH & Co. KG from Saerbeck (North Rhine-Westphalia), which specializes in stitch bonded constructions, will be offering the injection process worldwide as the general licensee. In the method which is also known as membrane-supported low-pressure infiltration engineering, the component to be infiltrated is covered by a gas and air permeable, microporous membrane constituting a resin barrier.
The pore size of the membrane is selected so that gas and air can pass unhindered to a chamber outside the membrane, in which there is a vacuum, from where they can be removed. The resin supplied within the membrane is held back and thus remains in the so-called injection chamber. According to the company, this innovative production process increases the flexibility during mass production.
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