Non-woven discontinuous reinforcement-adhesive bonded reinforcements
- Chopped strand mat
A carbon fiber csm consists of a random array of chopped fibers held together by a thermoset or thermoplastic binder. A carbon fiber csm is compatible with polyester and epoxy resin systems and can be incorporated into carbon preforms and held in position by sewing. Composites made from a csm will have low volume fractions, of about 20-25% v/v.
- Carbon fiber tissue
An air knife can be used to spread a carbon fiber tow and form a thin veil of carbon fiber or tissue, which can be used to hold a resin rich gel coat on the surface of a fiberglass laminate construction to give a high surface finish concurrent with added microcrack suppresision, as well as provide additional chemical resistance. It will give better performance than a glass tissue due to the absence of wicking.
An electrically conductive veil can be made using metal coated carbon fiber, to provide a wide range of surface conductivity, from electrostatic dissipation levels to electromagnetic and radio frequency shielding levels.
- Carbon fiber paper reinforcement
A paper based on carbon fiber can be made using a conventional paper making plant, where chopped fiber is dispersed in a liquid carrier containing wetting and binding agents. The dispersed fiber is removed from the slurry by vacuum deposition onto a perforated screen, washed and the carbon paper removed from the screen and dried. If a water flume is used to spread the fibers, then it is possible to give a product with more than 80% fiber orientation. Paper is used for specialist applications like loudspeaker cones.
Needled mat:
A carbon fiber needled mat is dry laid, having no binder, with the chopped fibers being held together by entanglement. The entanglement is done by using a machine that passes a fiber web under a reciprocating beam holding a large number of barded needles, which penetrate the fiber web and entangle the fibers as the hooks are withdrawn. Needled mats can be incorporated into preforms. This type of process was adapted by SEP to form Novoltex, based on the entanglement of a stack of woven fabric layers by needle punching a non-woven web through a number of layers to bind them together. The use of opf will minimize damage to the fibers. After needling, the preforms are heat treated to convert them into carbon fiber, coated with a pyrocarbon interface, machined to near net shape, followed by a succession of SIC CVI densification stages and machined to produce the final part.