GlossaryKind of term: Manufacturing termFibre-reinforced plastic (GF, CF)
What is fibre-reinforced plastic?
Fibre-reinforced plastic is plastic with glass or carbon fibres that carry load: stiffer and stronger, but abrasive on tools and dusty to machine.
GF and CF in a designation stand for glass fibre and carbon fibre; other fibres are less common. There are two main groups. Short-fibre reinforced thermoplastics, such as PA6-GF30 or PEEK-CF30, come as rod and plate; the number gives the fibre content as a percentage by mass. Laminates with long or continuous fibres in a resin matrix, such as glass-epoxy or carbon-fibre sheet, come as plate and tube. The fibres make the material stiffer, stronger and more stable under heat, often with differences by direction.
What do fibres do in machining?
Glass and carbon fibres are hard and abrasive and wear the cutting edge quickly; high-speed steel lasts only briefly, carbide is the usual choice and diamond-coated or PCD tooling lasts longer. Laminates with a resin matrix give mostly fine dust rather than a chip; short-fibre reinforced thermoplastics give a chip carrying fibre fragments, plus dust. Carbon dust is electrically conductive. In laminates, fibres can fray and layers can separate, especially where a drill enters and exits or along an edge. Strength, stiffness and expansion can differ by direction, depending on how the fibres lie.
How does fibre-reinforced plastic work in practice?
Tool cost per part is higher than in unfilled plastic; whether more expensive tooling pays for itself depends on tool life, quantity and the edge requirement. The dust needs extraction, and the machine has to be cleaned afterwards; the protective measures that apply follow from workplace dust regulations. A fraying edge calls for an adapted strategy, backing material or a finishing step. Costing fibre-reinforced work as unfilled plastic can underestimate both tooling and time.
What is fibre-reinforced plastic often confused with?
A fibre is not a filler: fillers such as talc, glass beads, graphite or bronze change stiffness, wear, friction or price, but do not carry load the way a fibre does. And glass-filled is often trade shorthand for glass-fibre reinforced; the data sheet shows whether it means fibres or beads.
Frequently asked questions
Why do my tools wear so fast in glass-filled material?
Glass fibre is hard and abrasive and grinds the cutting edge down. Plan for shorter tool life, or for diamond-coated or PCD tooling that lasts longer and costs more. Which is cheaper per part depends on quantity.
Do you need extraction when machining carbon fibre?
Yes. Machining produces fine dust that does not belong in the air or the machine, and carbon dust conducts electricity. Extraction, personal protection and cleaning afterwards are part of the operation.
How do you stop the edge from fraying?
With sharp tools, a geometry that cuts the fibres into the material, backing at the exit and an adapted feed. If it frays anyway, a finishing step follows, which you plan into the route beforehand.