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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 I can be found below.

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Terms I

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


ID-tolerance
Tolerance on inside diameter, measured in inches.


impact strength
The ability of a material to withstand shock loading. The work done in fracturing a test specimen in a specified manner under shock loading.


impact test
Measure of the energy necessary to fracture a standard notched bar by an impulse load. See also Izod impact test, reverse impact test and Charpy impact test

(("Izod impact test") ("reverse impact test") ("Charpy impact test"))


impregnate
In reinforced plastics, to saturate the reinforcement with a resin.


impregnated fabric
A fabric impregnated with a synthetic resin. See also prepreg


inclusion
A physical and mechanical discontinuity occurring within a material or part, usually consisting of solid, encapsulated foreign material. Inclusions are often capable of transmitting some structural stresses and energy fields, but in a noticeably different degree from the parent material. See also voids


inert filler
A material added to a plastic to alter the end-item properties through physical rather than chemical means.


infrared
Part of the electromagnetic spectrum between the visible light range and the radar range. Radiant heat is in this range, and infrared heaters are frequently used in the thermoforming and curing of plastics and composites. Infrared analysis is used for identification of polymer constituents.


inhibitor
A substance that retards a chemical reaction. Also used in certain types of monomers and resins to prolong storage life.


initial (instantaneous) stress
The stress produced by force in a specimen before stress relaxation occurs.


initial modulus
The slope of the initial straight portion of a stress-strain or load-elongation curve. See also Young's modulus


initial strain
The strain produced in a specimen by given loading conditions before creep occurs.


initiator
Peroxides used as sources of free radicals. They are used in free-radical polymerisation's, for curing thermosetting resins, as cross-linking agents for elastomers and polyethylene, and for polymer modification.


injection moulding
Method of forming a plastic to the desired shape by forcing the heatsoftened plastic into a relatively cool cavity under pressure.


inorganic pigments
Natural or synthetic metallic oxides, sulfides, and other salts that impart heat and light stability, weathering resistance, colour, and migration resistance to plastics.


insert
An integral part of a plastic moulding consisting of metal or other material that may be moulded or pressed into position after the moulding is completed.


insulation resistance
The electrical resistance between two conductors or systems of conductors separated only by insulating material. The ratio of the applied voltage to the total current between two electrodes in contact with a specified insulator. The electrical resistance of an insulating material to a direct voltage.


insulator
A material of such low electrical conductivity that the flow of current through it can usually be neglected. Similarly, a material of low thermal conductivity, such as that used to insulate structural shells.


integral composite structure
Composite structure in which several structural elements, which would conventionally be assembled together by bonding or mechanical fasteners after separate fabrication, are instead laid up and cured as a single, complex, continuous structure; for example, spars, ribs, and one stiffened cover of a wing box fabricated as a single integral part.

The term is sometimes applied more loosely to any composite structure not assembled by mechanical fasteners. All or some parts of the assembly may be co-cured.


integral skin foam
Urethane foam with a cellular core structure and a relatively nonporous skin.


integrally heated
A term referring to tooling that is self-heating, through use of electrical heaters such as cal rods. Most hydroclave tooling is integrally heated. Some autoclave tooling is integrally heated to compensate for thick sections, to provide high heat-up rates, or to permit processing at a higher temperature than is otherwise possible with the autoclave.


interface
The boundary or surface between two different, physically distinguishable media. On fibres, the contact area between fibres and sizing or finish. In a laminate, the contact area between the reinforcement and the laminating resin.


interference fits
Supplies the bonding force for the joint.


interlaminar shear
Shearing force tending to produce a relative displacement between two laminae in a laminate along the plane of their interface.


interlaminar
Descriptive term pertaining to an object (for example, voids), event (for example , fracture), or potential field (for example, shear stress) referenced as existing or occurring between two or more adjacent laminae.


intermediate temperature setting adhesive
An adhesive that sets in the temperature range from 30 to 100 degree C (87 to 211 degree F).


interphase
The boundary region between a bulk resin or polymer and an adherend in which the polymer has a high degree of orientation to the adherend on a molecular basis. It plays a major role in the load transfer process between the bulk of the adhesive and the adherend or the fibre and the laminate matrix resin.


interply hybrid
A composite in which adjacent laminae are composed of different materials.


intralaminar
Descriptive term pertaining to an object (for example, voids), event (for example, fracture), or potential field(for example, temperature gradient) existing entirely within a single lamina without reference to any adjacent laminae.


intraply hybrid
A composite in which different materials are used within a specific layer or band.


irradiation
As applied to plastics, the bombardment with a variety of subatomic particles, usually alpha-, beta-, or gamma-rays. Used to initiate polymerisation and co-polymerisation of plastics and in some cases to bring about changes in the physical properties of a plastic.


irreversible
Not capable of redissolving or remelting. Chemical reactions that proceed in a single direction and are not capable of reversal (as applied to thermosetting resins).


isocyanate plastics
Plastics based on resins made by the condensation of organic isocyanates with other compounds. Generally reacted with polyols on a polyester or polyether backbone molecule, with the reactants being joined through the formation of the urethane linkage. See also polyurethane and urethane plastics


isostatic pressing
Pressing powder under a gas or liquid so that pressure is transmitted equally in all directions, for example, in sintering.


isotropic
Having uniform properties in all directions. The measured properties of an isotropic material are independent of the axis of testing.


italic pattern
A pattern of filament winding with a fixed arrangement of open voids.


Izod impact test
A test for shock loading in which a notched specimen bar is held at one end and broken by striking, and the energy absorbed is measured.

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