RTM
Glossary |
This page lists some of the terms commonly used in liquid molding processes. It is by no means exhaustive. If there is a term that doesn't appear below that you'd like to see added to the list or need an explanation about, please contact CCM with your request/question. Use the "Back" button on your browser to return you to the previously visited page, or click on the icon at the left to return you to the Techsite index.
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Air Vent
A small outlet, to prevent entrapment of gases in a molding or tooling fixture.
Anisotropic
Exhibiting different properties when tested along axes in different directions.
Anisotropic Laminate
A laminate one in which the properties are different in different directions.
Bismaleimide
A type of polymide that cures by an addition rather than a condensation reaction, thus avoiding problems with volatiles formation, and which is produced by a vinyl-type polymerization of a pre-polymer terminated with two maleimide groups. Intermediate in temperature capability between epoxy and polyimide.
Braiding
Weaving of fibers into a tubular shape instead of a flat fabric, as for graphite-fiber-reinforced golf club shafts.
Bundle
A general term for collection of essentially parallel filaments or fibers.
Carbon
The element that provides the backbone for all organic polymers. Graphite is a more ordered form of carbon. Diamond is the densest crystalline form of carbon.
Carbon Fiber
Fiber produced by the pyrolysis of organic precursor fibers, such as rayon, polyacrylonitrile, and pitch, in an inert environment.
Compatibility
The ability of two or more substances combined with one another to form a homogeneous composition of useful plastic properties; for example, the suitability of a sizing or finish for use with certain general resin types.
Composite Material
A combination of two or more materials (reinforcing elements, fillers, and composite matrix binder), differing in form or composition on a macroscale. The constituents retain their identities; that is, they do not dissolve or merge completely into one another although they act in concert. Normally, the components can be physically identified and exhibit an interface between one another.
Compressive Strength
The ability of a material to resist a force that tends to crush or buckle. The maximum compressive load sustained by a specimen divided by the original cross-sectional area of the specimen.
Continuous-Filament Yarn
Yarn formed by twisting and or plying two or more continuous filaments into a single continuous strand.
Core
The central member, usually foam or honeycomb, of a sandwich construction to which the faces of the sandwich are attached or bonded. The central member of a plywood assembly. A channel in a mold for circulation of heat transfer media. A device on which prepreg is wound.
Cure
To irreversibly change the properties of a thermosetting resin by chemical reaction, that is, condensation, ring closure, or addition. Cure may be accomplished by addition of curing (cross-linking) agents, with or without heat and pressure.
Cure Cycle
The time/temperature/pressure cycle used to cure a thermosetting resin system or prepreg.
E-Glass
A family of glasses with a calcium alumina borosilicate composition and amaximum alkali content 2.0%. a general-purpose fiber that is often used in reinforced plastics, and is suitable for electrical laminates because of its high resistivity.
Epoxy Plastic
A polymerizable thermoset polymer containing one or more epoxide groups and curable by reaction with amines, alcohols, phenols, carboxylic acids, acid anhydrides, and mercaptans. AN important matrix resin in composites and structural adhesive.
Exotherm
The liberation or evolution of heat during the curing of a plastic product.
Fiber
A general term used to refer to filamentary materials. Often, fiber is used synonymously with filament.
Fiber Content
The amount of fiber present in a composite. This is usually expressed as a percentage volume fraction or weight fraction of the composite.
Gel
The initial jellylike solid phase that develops during the formation of a resin from a liquid. A semisolid system consisting of a network of solid aggregates in which liquid is held.
Gelation
The point in a resin cure when the resin viscosity has increased to a point such that it barely moves when probed with a sharp instrument.
Hybrid
A composite laminate consisting of two or more composite material systems. A combination of two or more different fibers, such as carbon and glass or carbon and aramid, into a structure.
Insert
An integral part of plastic molding consisting of metal or other material that may be molded into the part or pressed into position after the molding is completed.
Isotropic
Having uniform properties in all directions.
Laminate
To unite layers with a bonding material, usually with pressure and heat (normally used with reference to flat sheets, but also rods and tubes). Also a material consisting of layers bonded together.
Orientation
The alignment of the crystalline structure in polymeric materials in order to produce a highly aligned structure.
Permeability
The passage or diffusion (or rate of passage) of a gas, vapor, liquid, or solid through a barrier without physically or chemically affecting it.
Polymerization
A chemical reaction in which the molecules of a monomer are linked together to form large molecules whose molecular weight is a multiple of that of the original substance. When two or more monomers are involved, the process is called copolymerization.
Postcure
Additional elevated-temperature cure, usually without pressure, to improve final properties and/or complete the cure, or decrease the percentage of volatiles in the molding.
Pot Life
The length of time that a catalyzed thermosetting resin system retains a viscosity low enough to be used in processing.
Preform
A preshaped fibrous reinforcement formed by distribution of chopped fibers or cloth by air, water flotation, or vacuum over the surface of a perforated screen to the approximate contour and thickness desired in the finished part.
Reinforcement
A strong material bonded into a matrix to improve its mechanical properties.
Resin
A solid or pseudosolid organic material, usually of high molecular weight, that exhibits a tendency to flow when subjected to stress.
Resin Transfer Molding (RTM)
A process whereby catalyzed resin is transferred or injected into a closed mold in which the fiberglass reinforcement has been placed.
Rib
A reinforcing member designed into a plastic part to provide lateral, horizontal, hoop, or other structural support.
Roving
A number of yarns, strands, tows, or ends collected into parallel bundle with little or no twist.
S-Glass
A magnesium aluminia silicate composition that is especially designed to provide very high tensile strength glass filaments.
Stiffness
A measure of modulus. The relationship of load and deformation.
Thermoplastic
Capable of being repeatedly softened by an increase of temperature and hardened by a decrease in temperature.
Toughness
A property of a material for absorbing work. The actual work per unit volume or unit mass of material that is required to rupture it. Toughness is proportional to the area under the load-elongation curve from the origin to the breaking point.
Vent
A small hole or shallow channel in a mold that allows air or gas to exit as the molding material enters.
Viscosity
The property of resistance to flow exhibited within the body of a material, expressed in terms of a relationship between applied shearing stress and resulting rate of strain in shear.