C-STAGE
The final step in the cure of a thermoset resin, resulting in essentially irreversible hardening and insolubility.

CAD/CAM
Computer-aided design/computer-aided manufacturing.

CARBON/CARBON
A composite of carbon fiber in a carbon matrix.

CARBON FIBER
Fibers produced by the pyrolysis of organic precursor fibers such as rayon, polyacrylonitrile (PAN), and pitch in an inert atmosphere. The term is often used interchangeably with "graphite"; however, carbon fibers and graphite fibers differ in the temperature at which the fibers are made and heat-treated, and the amount of carbon produced. Carbon fibers typically are carbonized at about 2400(F (1300(C) and assay at 93 to 95% carbon, while graphite fibers are graphitized at 3450 to 5450(F (1900 to 3000(C) and assay at more than 99% elemental carbon.

CAROXYL
The chemical group characteristic of organic acids, which are incorporated into the polyester reaction process.

CASTING
The process of pouring a mixture of resin, fillers and/or fibers into a mold as opposed to building up layers through lamination.  This technique produces different physical properties from laminating.

CAST POLYMER
Non-reinforced composite (resin used without reinforcing fibers).  Combines polymers, fillers and additives as composites to meet specific applications requirements.

CATALYST
A substance which changes the rate of a chemical reaction without itself undergoing permanent change in its composition; a substance which markedly speeds up the cure of a compound when added in minor quantity as compared to the amounts of primary reactants.

CATALYST INJECTION
Used with spray equipment to catalyze the polyester at the spray gun, therefore eliminating the need to clean the system within the gel time of the polyester. Internal mix guns do require a solvent flush for cleaning the head. Injector: Atomizing air atomizes the catalyst at the injector unit itself. Pot: Catalyst is supplied to the spray gun, then air is introduced to atomize the catalyst.

CATASTROPHIC FAILURES
Failures of a mechanical or unpredictable nature.

CATENARY
A measure of the difference in length of the strands in a specified length of roving as a result of unequal tension; the tendency of some strands in a taut horizontal roving to sag lower than the others.

CAUL PLATE
Plate or sheet the same size and shape as the composite lay-up with which it will be used. The caul plate is placed in immediate contact with the lay-up during curing to transmit normal pressure and provide a smooth surface on the finished part.

CAUL SHEET
Plate or sheet the same size and shape used in contact with a composite layup to transmit normal pressure and temperature during cure.

CAULK
An elastic material used to protect joints or connections from external elements, particularly moisture.

CAVITY
Depression in mold; the space inside a mold wherein a resin is poured; the molded article; which forms the outer surface of the molded article (often referred to as the die); also, the space between matched molds. (Depending on number of such depressions, molds are designated as Single-Cavity or Multiple-Cavity).

CENTIPOISE
Measurement of viscosity as compared to water (1 centipoise).

CERAMIC-MATRIX COMPOSITES
Materials consisting of a ceramic or carbon fiber surrounded by a ceramic matrix, usually SiC (silicon carbide).

CHAIN-GROWTH POLYMERIZATION
One of the two principal polymerization mechanisms. In chain-growth polymerization, the reactive groups are continuously regenerated during the growth process. Once started, the polymer molecule grows rapidly by a chain of reactions emanating from a particular reactive initiator which may be a free radical, cation or anion.

CHALKING
Dry, powder-like appearance or deposit on gel coat surface.

CHEMICAL VAPOR DEPOSITION (CVD)
A process in which desired reinforcement material is deposited from vapor phase onto a continuous core; boron on tungsten, for example.

CHOPPED STRAND
Continuous strand yarn or roving cut up into uniform lengths, usually from 1/32-2" long. Lengths up to 1/8" are called milled fibers.

CHOPPER GUN
A special piece of equipment used in the manufacture of reinforced plastic parts, which chops glass and sprays resin and catalyst simultaneously onto a molded surface.

CIRCUIT
One complete traverse of the fiber feed mechanism of a filament-winding machine.

CIRCUMFERENTIAL WINDING
A type of filament winding in which the filaments are perpendicular to the axis.

CLOTH
A fine weave of woven fiberglass.

COBALT
Used as the accelerator for Methyl Ethyl Ketone Peroxide catalyzed polyesters.

COCURED
Cured and simultaneously bonded to another prepared surface.

COEFFICIENT of EXPANSION (COE)
Measure of the change in length or volume of an object.

COEFFICIENT of THERMAL EXPANSION
A material's fractional change in length for a given unit change of temperature.

COEFFICIENT OF VARIATION
The ratio of the population (or sample) standard deviation to the population (or sample) mean.

COHESION
Tendency of a single substance to adhere to itself. Also, the force holding a single substance together.

COIN TAP
Tapping a laminate with a coin in different spots to detect a change in sound, indicating the presence of a defect that may require repair.

COLD PRESS MOLDING
Compression Molding without the heat – A technique for molding thermoset plastics in which a part is shaped by placing the fiber and resin into an open mold cavity, closing the mold, and applying heat and pressure until the material has cured or achieved its final form.

COLOR STABILITY
The ability of a surface coating or pigment to resist degradation due to environmental exposure.

COMMINGLED YARN
A hybrid yarn made with two types of material intermingled in a single yarn; for example, thermoplastic filaments intermingled with carbon filaments to form a single yarn.

COMPATIBLE
The ability of different resin systems to be processed in contact with each other without degradation of end product properties.

COMPOSITE
A homogeneous material created by the synthetic assembly of two or more materials (a selected filler or reinforcing elements and compatible matrix binder) to obtain specific characteristics and properties. Composites are subdivided into classes on the basis of the form of the structural constituents; Laminar: Composed of layer or laminar constituents; Particular: The dispersed phase consists of small particles; Fibrous: The dispersed phase consists of fibers; Flake: The dispersed phase consists of flat flakes; Skeletal: Composed of a continuous skeletal matrix filled by a second material.

COMPOUND
An intimate mixture of polymer or polymers with all the materials necessary for the finished product.

COMPRESSION MOLD
A mold which is open when the material is introduced and which shapes the material by heat and by the pressure of closing. See also Compression molding.

COMPRESSION MOLDING
A technique for molding thermoset plastics in which a part is shaped by placing the fiber and resin into an open mold cavity, closing the mold, and applying heat and pressure until the material has cured or achieved its final form.

COMPRESSIVE MODULUS
A mechanical property description which measures the compression of a sample at a specified load.  Described in ASTM D-695.

COMPRESSIVE STRENGTH
The ability of a material to resist a force that tends to crush; the crushing load at the failure of a specimen divided by the original sectional area of the specimen.

CONDENSATION
A polymerization reaction in which simple by-products(for example, water) are formed.

CONDENSATION POLYMERIZATION
This is a special type of step-growth polymerization characterized by the formation of water or other simple molecules during the stepwise addition of reactive groups.

CONDUCTIVITY
Reciprocal of volume resistivity; the conductance of a unit cube of any material.

CONNECTION
Where two panels are attached to each other or a panel is attached to the building.

CONSOLIDATION
A processing step that compresses fiber and matrix to reduce voids and achieve a desired density.

CONSTITUENT
In general, an element of a larger grouping. In advanced composites, the principal constituents are the fibers and the matrix.

CONTACT MOLDING
A process for molding reinforced plastics in which reinforcement and resin are placed on a mold, cure is either at room temperature using a catalyst-promoter system or by heat in an oven and no additional pressure is used.

CONTAMINANT
Impurity or foreign substance that affects one or more properties of composite material, particularly adhesion.

CONTINUOUS FILAMENT
An individual , small-diameter reinforcement that is flexible and indefinite in length.

CONTINUOUS-FILAMENT YARN
Yarn that is formed by twisting two or more continuous filaments into a single continuous strand.

CONTINUOUS HEAT RESISTANCE
This is the maximum temperature the material should be subjected to in a continuous application. Below this temperature the material is acceptable. Above this temperature the material may decompose, melt, or otherwise fail in an application. Units - degrees Fahrenheit ((F) - degrees Centigrade ((C). Higher numbers mean that the material can be used continuously at higher temperatures.

CONTINUOUS LAMINATING
A process for forming panels and sheeting in which fabric or a mat is passed through a resin dip, brought together between cellophane covering sheets, and passed through a heating zone for cure. Squeeze rolls control thickness and resin content as the various plies are brought together.

CONTINUOUS ROVING
Parallel filaments coated with sizing, gathered together into single or multiple strands, and wound into a cylindrical package. It may be used to provide continuous reinforcement in woven roving, filament winding, pultrusion, prepregs, or high-strength molding compounds, or it may be used chopped.

CONTINUOUS STRAND ROVING
A bundle of glass filaments which are fed through a chopper gun in the spray up process.

COPOLYMER
A large chemical chain composed of two or more dissimilar groups.

CORE
The central component of a sandwich construction to which the sandwich faces or skins are attached; also, part of a complex mold that forms undercut parts.

CORE CRUSH
Compression damage of the core.

CORE DEPRESSION
A gouge or indentation in the core material.

CORE ORIENTATION
Used on a honeycomb core to line up the ribbon direction, thickness of the cell depth, cell size and transverse direction.

CORE SPLICING
Joining two core segments by bonding them together.

COUPLING AGENT
Any chemical substance designed to react with both the reinforcement and matrix phases of a composite material to form or promote a stronger bond at the interface; a bonding link.

COWOVEN FABRIC
A reinforcement fabric woven with two different types of fibers in individual yarns; for example, thermoplastic fibers woven side by side with carbon fibers.

CRAZING
Fine cracks, which may extend in a network on or under the surface of a plastic material.

CREEL
A device for holding the required number of roving balls or supply packages in desired position for unwinding onto the next processing step.

CREEP
The change in dimension of a plastic under load over a period of time, not including the initial instantaneous elastic deformation. (Creep at room temperature is called 'cold flow.')

CREEP, RATE OF
The slope of the creep-time curve at a given time.

CRIMP
A fiber's waviness, which determines the capacity of the fiber to cohere.

CRITICAL LENGTH
The minimum length of a fiber necessary for matrix shear loading to develop fiber ultimate strength by matrix.

CROSS LAMINATED
Material laminated so that some of the layers are oriented at various angles to the other layers with respect to the laminate grain. A cross-ply laminate usually has plies oriented only at 0/90(.

CROSS-LINKING
The process of bridging two polymer chains, which converts a thermoplastic to a thermoset.

CROSSPLY
Any filamentary laminate which is not uniaxial. Same as Angleply. In some references, the term crossply is used to designate only those laminates in which the laminae are at right angles to one another, while the term angle ply is used for all others.

CRYSTALLINITY
The quality of having a molecular structure with atoms arranged in an orderly, three-dimentional pattern.

CURE
The polymerization or the transforming from the liquid to the solid state with maximum physical properties, including hardness.

CURE CYCLE
The schedule of time periods at specified conditions to which a reacting thermosetting material is subjected in order to reach a specified property level.

CURE TIME
The time required for the liquid resin to reach a cured or fully polymerized state after the catalyst has been added.

CURING AGENT
A catalytic or reactive agent which when added to a resin causes polymerization, synonymous with hardener.

CURING TEMPERATURE
Temperature at which a cast, molded, or extruded product, a resin-impregnated reinforcement, an adhesive, etc., is subjected to curing.

CURING TIME
The period of time during which a part is subjected to heat or pressure, or both, to cure the resin; interval of time between the instant of cessation of relative movement between the moving parts of a mold and the instant that pressure is released. (Further cure may take place after removal of the assembly from the conditions of heat or pressure.)

CYCLE
The complete, repeating sequence of operations in a process or part of a process. In molding, the cycle time is the period (or elapsed time) between a certain point in one cycle and the same point in the next.

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Glossary Section (C) Last Updated: 7/28/00 12:17 PM

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