Composite Engineering carbon fibre component design and engineering

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 A can be found below.

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Terms A

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

The "A" mechanical property value is the value above which at least 99% of the population of values is expected to fall, with a confidence of 95%. Also called A-allowable. See:

An early stage in the polymerisation reaction of certain thermosetting resins (especially phenolic) in which the material, after application to the reinforcement, is still soluble in certain liquids and is fusible. Also called resole. See:

A material that resists adhesion. A film or coating applied to surfaces to prevent sticking, heat sealing, and so on. For example, a parting agent or mould release agent.

ABL bottle
An internal pressure test vessel about 460 mm (18 in.) in diameter and 610 mm (24 in.) long used to determine the quality and properties of the filament-wound material in the vessel.

The degradation, decomposition, and erosion of a material caused by high temperature, pressure, time, percent oxidising species, and velocity of gas flow. A controlled loss of material to protect the underlying structure.

ablative plastic
A material that absorbs heat (with a low material loss and charring rate) through a decomposition process (pyrolysis) that takes place at or near the surface exposed to the heat.

The penetration into the mass of one substance by another. The process whereby energy is dissipated within a specimen placed in a field of radiant energy. The capillary or cellular attraction of adherend surfaces to draw off the liquid adhesive film into the substrate.

accelerated test
A test procedure in which conditions are increased in magnitude to reduce the time required to obtain a result. To reproduce in a short time the deteriorating effect obtained under normal service conditions.

A material that, when mixed with a catalyst or a resin, will speed up the chemical reaction between the catalyst and the resin (either in polymerising of resins or vulcanisation of rubbers). Also called promoter

acoustic emission
A measure of integrity of a material, as determined by sound emission when a material is stressed. Ideally, emissions can be correlated with defects and/or incipient failure.

acrylic plastic
A thermoplastic polymer made by the polymerisation of esters of acrylic acid and its derivatives. Its full name is polymethyl methacrylate

The (usually) chemical process of making a surface more receptive to bonding to a coating or an encapsulating material.


(("accelerator" "accelerator"))

addition polymerisation
A chemical reaction in which simple molecules (monomers) are added to each other to form long-chain molecules (polymers) without forming by-products.

Any substance added to another substance, usually to improve properties, such as plasticisers, initiators, light stabilisers, and flame retardants. See filler

A body that is held to another body, usually by an adhesive. A detail or part prepared for bonding.

adhesion promoter
A coating applied to a substrate before it is coated with an adhesive to improve the adhesion of the plastic. Also called primer

adhesion, mechanical
See: mechanical adhesion

The state in which two surfaces are held together at an interface by mechanical or chemical forces or interlocking action or both.

adhesive failure
Rupture of an adhesive bond such that the separation appears to be at the adhesive-adherend interface.

adhesive film
A synthetic resin adhesive with or without a film carrier fabric, usually of the thermosetting type, in the form of a thin film of resin, used under heat and pressure as an interleaf in the production of bonded structures.

adhesive strength
Strength of the bond between an adhesive and an adherend.

adhesive, anaerobic
See: anaerobic adhesive

adhesive, cold-setting
See: cold-setting adhesive

adhesive, contact
See: contact adhesive

adhesive, gap-filling
See: gap-filling adhesive

adhesive, heat-activated
See: heat-activated adhesive

adhesive, heat-sealing
See: heat-sealing adhesive

adhesive, hot-melt
See: hot-melt adhesive

adhesive, hot-setting
See: hot-setting adhesive

adhesive, intermediate temperature setting
See intermediate temperature setting adhesive. The location at which two adherends or substrates are held together with a layer of adhesive. The general area of contact for a bonded structure. See: intermediate temperature setting adhesive

adhesive, pressure-sensitive
See: pressure-sensitive adhesive

adhesive, structural
See: structural adhesive

A substance capable of holding two materials together by surface attachment. Adhesive can be in film, liquid, or paste form.

The addition and homogeneous dispersion of discrete components before cure.

The adhesion of the molecules of gases, dissolved substances, or liquids in more or less concentrated form, to the surfaces of solids or liquids with which they are in contact. A concentration of a substance at a surface or interface of another substance.

See: postcure

A hard, coarse material usually of mineral origin used with an epoxy binder (or other resin) in plastic tools. Also used in flooring or as a surface medium.

The effect on materials of exposure to an environment for an interval of time. The process of exposing materials to an environment for an interval of time.

air vent
Small outlet, to prevent entrapment of gases in a moulding or tooling fixture.

air-bubble void
Air entrapment within and between the plies of reinforcement or within a bondline or encapsulated area; localised, non interconnected, spherical in shape.

alkyd plastic
Thermoset plastic based on resins composed principally of polymeric esters, in which the recurring ester groups are an integral part of the main polymer chain, and in which ester groups occur in most cross-links that may be present between chains.

The existence of a substance and especially an element in two or more forms (as of crystals). See also graphite

In plastics, a blend of polymers or copolymers with other polymers or elastomers under selected conditions; for example, styrene-acrylonitrile. Also called polymer blend. In metals, a substance having metallic properties and being composed of two or more chemical elements of which at least one is a metal.

allyl plastic
A thermoset plastic based on resins made by addition polymerisation of monomers containing allyl groups; for example, diallyl phthalate (DAP).

alternating stress amplitude
A test parameter of a dynamic fatigue test: one-half the algebraic difference between the maximum and minimum stress in one cycle.

alternating stress
A stress varying between two maximum values which are equal but with opposite signs, according to a law determined in terms of the time.

The surrounding environmental conditions, such as pressure, temperature, or relative humidity.

amorphous plastic (amorphous phase)
A plastic that has no crystalline component: there is no order or pattern to the distribution of the molecules.

anaerobic adhesive
An adhesive that cures only in the absence of air after being confined between assembled parts.

A characteristic exhibited by certain materials in which strain is a function of both stress and time, such that while no permanent deformations are involved, a finite time is required to establish equilibrium between stress and strain in both the loading and unloading directions.

angle wrap
Tape fabric wrapped on a starter dam mandrel at an angle to the centreline.

angle-ply laminate
A laminate having fibres of adjacent plies oriented at alternating angles.

anisotropic laminate
One in which the properties are different in different directions.

Not isotropic. Exhibiting different properties when tested along axes in different directions. See below.

anisotropy of laminates
The difference of the properties along the directions parallel to the length or width of the lamination planes and perpendicular to the lamination. See above.

In plastics, heating to a temperature at which the molecules have significant mobility, permitting them to reorient to a configuration having less residual stress.

A substance that, when added in small quantities to the resin during mixing, prevents its oxidative degradation and contributes to the maintenance of its properties.

antistatic agents
Agents that, when added to a moulding material or applied to the surface of the moulded object, make it less conducting, thus hindering the fixation of dust or the build-up of electrical charge.

A type of highly oriented organic material derived from polyamide (nylon) but incorporating aromatic ring structure. Used primarily as a high-strength high-modulus fibre.Kevlar and Nomex are examples of aramids.

arc resistance
Ability to withstand exposure to an electric voltage. The total time in seconds that an intermittent arc may play across a plastic surface without rendering the surface conductive.

areal weight
The weight of fibre per unit area (width x length) of tape or fabric.

Unsaturated hydrocarbon with one or more benzene ring structures in the molecule.

artificial weathering
The exposure of plastics to cyclic laboratory conditions consisting of high and low temperatures, high and low relative humidity's, and ultraviolet radiant energy, with or without direct water spray and moving air (wind), in an attempt to produce changes in their properties similar to those observed in long-term continuous exposure outdoors.

The laboratory exposure conditions are usually intensified beyond those encountered in actual outdoor exposure in an attempt to achieve an accelerated effect. Also called accelerated ageing.

ash content
Proportion of the solid residue remaining after a reinforcing substance has been incinerated (charred or intensely heated).

aspect ratio
The ratio of length to diameter of a fibre.

assembly time
The time interval between the spreading of the adhesive on the adherend and the application of pressure and/or heat to the assembly.

The diminution of vibrations or energy over time or distance. The process of making thin and slender as applied to the formation of fibre from molten glass.

The trade name of some equipment used for dynamic dielectric analysis (DDA).

autoclave moulding
A process in which, after lay-up, winding, or wrapping, an entire assembly is placed in a heated autoclave, usually at 340 to 1380 kPa (50 to 200 psi). Additional pressure permits higher density and improved removal of volatiles from the resin. Lay-up is usually vacuum bagged with a bleeder and release cloth.

A closed vessel for conducting and completing a chemical reaction or other operation, such as cooling, under pressure and heat.

automatic mould
A mould for injection or compression moulding that repeatedly goes through the entire cycle, including ejection, without human assistance.

automatic press
A hydraulic press for compression moulding or an injection machine that operates continuously, being controlled mechanically, electrically, hydraulically, or by a combination of any of these methods.

axial strain
The linear strain in a plane parallel to the longitudinal axis of the specimen.

axial winding
In filament-wound reinforced plastics, a winding with the filaments parallel or at a small angle to the axis (0°ree; helix angle). See also polar winding

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