Please enable Flash content.

Composites Terminology Database

This glossary is not an exhaustive list, however it does contain the majority of terms used in the composites industry and as part of the management of our website, it is updated on a continual basis.

The terms are accessed by clicking on the appropriate letter below, all the terms beginning with the letter C can be found below.

terminology image map Terms A Terms B Terms D Terms E Terms F Terms G Terms H Terms I Terms J Terms K Terms L Terms M Terms N Terms O Terms P Terms Q Terms R Terms S Terms T Terms U Terms V Terms W Terms X Terms Y Terms Z

Terms C

Click on a term and it will take you to the coresponding explanation.

A glass with a soda-lime-borosilicate composition that is used for its chemical stability in corrosive environments. See:

The back-and-forth scanning of a specimen with ultrasonics. A non-destructive testing technique for finding voids, delaminations, defects in fibre distribution, and so forth.

The final stage in the reaction of certain thermosetting resins in which the material is practically insoluble and infusible. Sometimes referred to as resite. The resin in a fully cured thermoset moulding is in this stage. See:

To produce a smooth finish and a desired dimensional thickness for sheet material by passing it between sets of pressure rollers.

carbon fibre
Fibre produced by the pyrolysis of organic precursor fibres, such as rayon, polyacrylonitrile (PAN), and pitch in an inert environment. The term is often used interchangeably with the term graphite; however, carbon fibres and graphite fibres differ.

The basic differences lie in the temperature at which the fibres are made and heat treated, and in the amount of elemental carbon produced. Carbon fibres typically are carbonised in the region of 1315°ree; C (2400°ree; F) and assay at 93 to 95% carbon, while graphite fibres are graphitised at 1900 to 2480 °ree; C (3450 to 4500°ree; F) and assay at more than 99% elemental carbon. See also pyrolysis (of fibres).

A composite material consisting of carbon or graphite fibres in a carbon or graphite matrix.

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. See:

The process of pyrolysation in an inert atmosphere at temperatures ranging from 800 to 1600°ree; C (1470 to 2910°ree; F) and higher, usually at about 1315°ree; C (2400°ree; F). Range is influenced by precursor, individual manufacturer's process, and properties desired. See: precursor

This term describes parts of the complexity and detail as would be manufactured by a casting process in the metal sector.

A substance that changes the rate of a chemical reaction without itself undergoing permanent change in composition or becoming a part of the molecular structure of the product. A substance that markedly speeds up the cure of a compound when added in minor quantity as compared to the amounts of primary reactants. See also accelerator, curing agent, hardener, inhibitor, and promoter. See:

catastrophic failures
Totally unpredictable failures of a mechanical, thermal, or electrical nature.

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 more than the others.

caul plates
Smooth metal plates, free of surface detects, the same size and shape as a composite lay-up, used immediately in contact with the lay-up during the curing process to transmit normal pressure and temperature, and to provide a smooth surface on the finished laminate.

The space inside a mould in which a resin or moulding compound is poured or injected. The female portion of a mould. That portion of the mould that encloses the moulded article (often referred to as the die). Depending on the number of such depressions, moulds are designated as single cavity or multiple cavity.

cell size
The diameter of an inscribed circle within a cell of honeycomb core.

In honeycomb core, a cell is a single honeycomb unit, usually in a hexagonal shape..

centrifugal casting
A production technique for fabricating cylindrical composites, such as pipe, in which composite material positioned inside a hollow mandrel designed to be heated and rotated as resin is cured.

A rigid, frequently brittle material made from clay and other inorganic, non-metallic substances and fabricated into articles by sintering, that is, cold moulding followed by fusion of the part at high temperature.

Composite materials consisting of two constituents, one being either an oxide, carbide, boride, or similar inorganic compound, and the other a metallic binder.

chain length
The length of the stretched linear macromolecule, most often expressed by the number of identical links.

Dry, chalklike appearance of deposit on the surface of a plastic.

Charpy impact test
A test for shock loading in which a centrally notched sample bar is held at both ends and broken by striking the back face in the same plane as the notch.

The heating of a composite in air to reduce the polymer matrix to ash, allowing the fibre content to be determined by weight.

chemical valour deposited (CVD) carbon
Carbon deposited on a substrate by pyrolysis of a hydrocarbon, such as methane.

chemical vapour deposition (CVD)
Process used in manufacture of several composite reinforcements, especially boron and silicon carbide, in which desired reinforcement material is deposited from vapour phase onto a continuous core, for example, boron on tungsten wire (core).

See: thin-layer chromatography

circuit board
A sheet of insulating material laminated to foil that is etched to produce a circuit pattern on one or both sides. Also called printed circuit board or printed wiring board.

In filament winding, one complete traverse of a winding band from one arbitrary point along the winding path to another point on a plane through the starting point and perpendicular to the axis.

circumferential winding
In filament wound reinforced plastics, a winding with the filaments essentially perpendicular to the axis (90°ree; or level winding).

clamping pressure
In injection moulding and transfer moulding, the pressure that is applied to the mould to keep it closed in opposition to the fluid pressure of the compressed moulding material.

The complete coverage of a mandrel with one layer (two plies) of fibre. When the last tape circuit that completes mandrel coverage lays down adjacent to the first without gaps or overlaps, the wind pattern is said to have 'closed.'


The act of curing a composite laminate and simultaneously bonding it to some other prepared surface, or curing together an inner and outer tube of similar or dissimilar fiber-resin combination after each has been wound or wrapped separately. See: secondary bonding.

coefficient of elasticity
The reciprocal of Young's modulus in a tension test. See: compliance.

coefficient of expansion
A measure of the change in length or volume of an object, specifically measured by the increase in length or volume of an object per unit length or volume.

coefficient of friction
A measure of the resistance to sliding of one surface in contact with another surface.

coefficient of thermal expansion (CTE)
The change in length or volume per unit length or volume produced by a 1°ree; rise in temperature.

The propensity of a single substance to adhere to itself. The internal attraction of molecular particles toward each other. The ability to resist partition of itself. The force holding a single substance together.

cohesive failure
Failure of an adhesive joint occurring primarily in an adhesive layer.

cohesive strength
Intrinsic strength of an adhesive.

coin test
Using a coin to tap a laminate in different spots, listening for a change in sound, which would indicate the presence of a defect. A surprisingly accurate test in the hands of experienced personnel.

Carbonaceous residue resulting from the pyrolysis of pitch.

cold flow
The distortion that takes place in materials under continuous load at temperatures within the working range of the material without a phase or chemical change. See: pitch.

cold-setting adhesive
A synthetic resin adhesive capable of hardening at normal room temperature in the presence of a hardener.

A rigid, lateral container for the mould forming material. A dam, a restriction box. The drive wheel that pulls glass fibres from the bushing. A forming tube is placed on the collet, and a package of strand is wound up on the tube. A metal band, ferrule, collar, or flange, often used to hold a tool or workpiece.

collimated roving
Roving that has been made using a special process (usually parallel wound), so that the strands are more parallel than in standard roving.

Rendered parallel.

A state of suspension in a liquid medium in which extremely small particles are suspended and dispersed but not dissolved.

The application of a temporary vacuum bag and vacuum to remove trapped air and compact the lay-up.

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. Non reactivity or negligible reactivity between materials in contact.

complex dielectric constant
The vectorial sum of the dielectric constant and the loss factor.

complex shear modulus
The vectorial sum of the shear modulus and the loss modulus.

complex Young's modulus
The vectorial sum of Young's modulus and the loss modulus. Analogous to the complex dielectric constant

Tensile compliance: the reciprocal of Young's modulus. Shear compliance: the reciprocal of shear modulus. Also, a term used in the evaluation of stiffness and deflection.

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.

composite-material curing
Chemical cross-linking of the molecular chains of a thermoset polymeric composite material by using heat.

The intimate admixture of a polymer with other ingredients, such as fillers, softeners, plasticisers, reinforcement, catalysts, pigments, or dyes. A thermoset compound usually contains all the ingredients necessary for the finished product, while a thermoplastic compound may require subsequent addition of pigments, blowing agents, and so forth.

compression moulding
A mould that is open when the material is introduced and that shapes the material by the pressure of closing and by heat.

compressive modulus
Ratio of compressive stress to compressive strain below the proportional limit. Theoretically equal to Young's modulus determined from tensile experiments.

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.

compressive stress
The normal stress caused by forces directed toward the plane on which they act.

condensation polymerisation
A chemical reaction in which two or more molecules combine, with the separation of water or some other simple substance. If a polymer is formed, the process is

Subjecting a material to a prescribed environmental and/or stress history before testing.

Reciprocal of volume resistivity. The electrical or thermal conductance of a unit cube of any material (conductivity per unit volume).

In metal matrix or thermoplastic composites, a processing step in which fibre and matrix are compressed by one of several methods to reduce voids and achieve desired density.

constant cross section
Parts with constant cross section, such as tubes, bars.

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

contact adhesive
An adhesive that is apparently dry to the touch and which will adhere to itself simultaneously upon contact. An adhesive applied to both adherends and allowed to become dry, which develops a bond when the adherends are brought together without sustained pressure.

contact moulding
A process for moulding reinforced plastics in which reinforcement and resin are placed on a mould. Cure is either at room temperature using a catalyst-promoter system or by heating in an oven without additional pressure.

contact pressure resins
liquid resins that thicken or polymerise on heating, and, when used for bonding laminates require little or no pressure.

An impurity or foreign substance present in a material or environment that affects one or more properties of the material, particularly adhesion.

continuous filament yarn
Yarn formed by twisting two or more continuous filaments into a single, continuous strand.

A long-chain molecule formed by the reaction of two or more dissimilar monomers. See: polymer

core crush
A collapse, distortion, or compression of the core

core depression
A localised indentation or gouge in the core

core separation
A partial or complete breaking of the core node bond.

core splicing
The joining of segments of a core by bonding, or by overlapping each segment and then driving them together.

The central member of a sandwich construction (honeycomb material, foamed plastic, or solid sheet) to which the faces of the sandwich are attached.

cored mould
A mould incorporating passages for electrical heating elements, steam, or water.

corrosion resistance
The ability of a material to withstand contact with ambient natural factors or those of a particular artificially created atmosphere, without degradation or change in properties. For metals, this could be pitting or rusting; for organic materials, it could be crazing

For fabric, number of warp and filling yarns per inch in woven cloth. For yarn, size based on relation of length and weight.

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.

Usually, a specimen for a specific test, as a tensile coupon.

crack growth
Rate of propagation of a crack through a material due to a static or dynamic applied load.

An actual separation of material, visible on opposite surfaces of the part, and extending through the thickness. A fracture

Region of ultrafine cracks that may extend in a network on or under the surface of a resin or plastic material. May appear as a white band. Often found in a filament wound pressure vessel or bottle.

A device for holding the required number of roving balls (spools) or supply packages in desired position for unwinding onto the next processing step, that is, weaving, braiding, or filament winding.

creep, rate of
The slope of the creep-time curve at a given time. Deflection with time under a given static load.

The change in dimension of a material under load over a period of time, not including the initial instantaneous elastic deformation. (Creep at room temperature is called cold flow.) The time-dependent part of strain resulting from an applied stress. See also: cold flow

The waviness of a fibre or fabric that determines the capacity of fibres to cohere under light pressure. Measured by the number of crimps or waves per unit length.

critical length
The minimum fibre length required for shear loading to its ultimate strength by the matrix.

critical longitudinal stress
Applied to fibres, the longitudinal stress necessary to cause internal slippage and separation of a spun yarn. The stress necessary to overcome the interfibre friction developed as a result of twist.

critical strain
The strain at the yield point.

cross-linking, degree of
The fraction of crosslinked polymeric units in the entire system.

Applied to polymer molecules, the setting-up of chemical links between the molecular chains. When extensive, as in most thermosetting resins, cross-linking makes one infusible supermolecule of all the chains.

cross-ply laminate
A laminate with plies usually oriented at 0°ree; and 90°ree; only.

crosswise direction
Crosswise refers to the cutting of specimens and to the application of load. For rods and tubes, crosswise is any direction perpendicular to the long axis. For other shapes or materials that are stronger in one direction than in another, crosswise is the direction that is weaker.

For materials that are equally strong in both directions, crosswise is an arbitrarily designated direction at right angles to the lengthways direction.

crystalline plastic
A polymeric material having an internal structure in which the atoms are arranged in an orderly three-dimensional configuration.

cure cycle
The time/temperature/pressure cycle used to cure a thermosetting resin system or prepreg.

cure monitoring, electrical
Use of electrical techniques to detect changes in the electrical properties and/or mobility of the resin molecules during cure. A measuring of resin cure.

cure stress
A residual internal stress produced during the curing cycle of composite structures. Normally, these stresses originate when different components of a wet lay-up have different thermal coefficients of expansion.

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.

curing agent
A catalytic or reactive agent that, when added to a resin, causes polymerisation. Also called hardener

CVD carbon
Chemical vapour deposition of carbon fibre, process can be used to produce carbon-carbon structures such as brake discs.

Jump to: Start of page