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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 O can be found below.

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Terms O

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


offset yield strength
The stress at which the strain exceeds by a specific amount (the offset) an extension of the initial approximately linear proportional portion of the stress-strain curve. It is expressed in force per unit area.


olefin
A group of unsaturated hydrocarbons of the general formula CnH2n named after the corresponding paraffin's by the addition of "ene'' or "ylene" to the root, for example, ethylene, propylene, and pentene.


open-cell foam
Foamed or cellular material with cells that are generally interconnected. Closed cell refers to cells that are not interconnected.


orange peel
An uneven surface somewhat resembling that of an orange peel; said of injection mouldings that have unintentionally ragged surfaces.


organic
Matter originating in plant or animal life or composed of chemicals of hydrocarbon origin, either natural or synthetic.


orientation
The alignment of the crystalline structure in polymeric materials in order to produce a highly aligned structure. Orientation can be accomplished by cold drawing or stretching in fabrication.


oriented materials
Materials, particularly amorphous polymers and composites whose molecules and/or macroconstituents are aligned in a specific way. Oriented materials are anisotropic. Orientation can generally be divided into two classes, uniaxial and biaxial.


orthotropic
Having three mutually perpendicular planes of elastic symmetry.


out time
The time a prepreg is exposed to ambient temperature, namely, the total amount of time the prepreg is out of the freezer. The primary effects of out time are to decrease the drape and tack of the prepreg while also allowing it to absorb moisture from the air.


ovaloid
A surface of revolution symmetrical about the polar axis that forms the end closure for a filament-wound cylinder.


oven dry
The condition of a material that has been heated under prescribed conditions of temperature and humidity until there is no further significant change in its mass.


overlay sheet
A non-woven fibrous mat (of glass, synthetic fibre, and so forth) used as the top layer in a cloth or mat lay-up, to provide a smoother finish, minimise the appearance of the fibrous pattern, or permit machining or grinding to a precise dimension. Also called surfacing mat.


oxidation
In carbon/graphite fibre processing, the step of reacting the precursor polymer (rayon, PAN, or pitch) with oxygen, resulting in stabilisation of the structure for the hot stretching operation. In general usage, oxidation refers to any chemical reaction in which electrons are transferred.

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