Composites Terminology
Composite A material created by the synthetic combination of two or more dissimilar materials to obtain specific properties more desirable that the properties of the individual constituent materials. In FRP composites, the structural fiber is held together by a resin matrix, much the same as structural rebar is held in place by concrete. Most often differentiation in composite materials is designated by the structural fiber used. It can be carbon fiber, Kevlar, fiberglass(E-glass or S-Glass).
CFRP -- Carbon fiber reinforced plastic (or Carbon fiber reinforced polymer) is a very strong, light weight composite in which Carbon constitutes the reinforcing fibers. The matrix resin system will usually be epoxy, polyester, vinyl ester or nylon.
GFRP -- Glass Fiber Reinforced Plastic uses fiber glass material with an appropriate matrix resin system.
Matrix – The material in which the reinforcing fabric of a composite is embedded. Matrix materials include thermosetting and thermoplastic polymers, metal and ceramic compounds. In advanced development of composite material, the focus on the next generation has shifted from the structural fiber to the resin matrix..
Mandrel – A rigid male form which can be used as a base for composite production of a part around which the material can be wound or laid up. It is generally removed after the composite material has cured.
Master Plug -- Once a composite part has been designed and captured in a digital format, the CAD program can be used to create a master plug by using a CNC mill. The master plug should be carefully scanned and inspected to ensure congruency with the original design. The master plug then becomes the physical standard for production. It is used to fabricate production molds which are in turn used to fabricate the parts. The master plug must be controlled and stored because as parts are produced the molds witll experience normal wear. Though molds can be maintained and repaired, they will at some point in repeated production use have to be replaced. At that time the master plug will be used to produce a replacement mold.
Male Mold -- Male mold generally describes a form which is convex in overall shape and will be used to fabricate a part with a concave finished surface. To be able to remove the mold after the part is cured the mold must have sufficient draft to permit the mold to be removed. Since the 'finished' surface of the composite part is that which is next to the mold, during fabrication the fiber laminate is build out from the mold surface. The outside surface is the material is then compressed against the mold during cure.
Female Mold -- Generally a concave mold which will produce a composite component with a smooth surface on the outside of the curve.
Closed-Molding- A molding process that uses two matched molds. This method of fabricating reinforced plastic provides a finished inside and outside surface. It is more expensive than open mold tooling but can result in lower production costs because is reduces the need for labor to vacuum bag the molded component.
Peel Ply – A layer of tightly woven fabric which is applied directly to the surface of a prepreg lay-up. The peel ply (which is removed after component curing) helps produce a clean surface texture and minimized surface preparation for bonding.
Prepreg refers to the material produced by the practice of mixing resin and fiber reinforcement and effecting a partial cure before use. The prepreg material is slightly tacky to the touch, but allows the lay-up technician to work with a ‘dry’ fabric. Generally, the resulting laminate is cured under vacuum bag pressure in a curing oven at a temperature and time profile dictated by the prepreg manufacturer.
Resin transfer molding (RTM) - A closed mold process in which catalyzed resin is drawn or injected into a double sided mold to impregnate a pre-formed fiber reinforcement structure. The resin and mold may or may not be heated during this process. If vacuum is used to increase the resin transfer the procedure is sometimes called Vacuum Assisted Resin Transfer Molding (VARTM). RTM is exacts less wear on the molds and is often used for larger structure fabrication.
Wet Lay-up , a process where the technician impregnates the resin into the fabric by hand. This is usually accomplished by rollers or brushes. Laminates are left to cure under standard atmospheric conditions. Some resin systems utilizing wet lay-up may be vacuum bagged to remove trapped air during the cure cycle. This can be used with a male or female mold which will determine which side of the part will be the finished surface.
How to speak composite
