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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 W can be found below.

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Terms W

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


wafer
A reinforcement for motorcase port openings.


warp
The yarn running lengthwise in a woven fabric. A group of yarns in long lengths and approximately parallel. A change in dimension of a cured laminate from its original moulded shape.


water absorption
Ratio of the weight of water absorbed by a material to the weight of the dry material.


water jet
Water emitted from a nozzle under high pressure (70 to 410 MPa, or 10 to 60 ksi or higher). Useful for cutting organic composites.


weathering, artificial
See artificial weathering
"artificial weathering"


weathering
Exposure of plastics to the outdoor environment.


weave
The particular manner in which a fabric is formed by interlacing yarns. Usually assigned a style number.


weeping
Slow leakage manifested by the appearance of water on a surface.


weft
The transverse threads or fibres in a woven fabric. Those fibres running perpendicular to the warp. Also called fill, filling yarn, or woof.


weld line
The mark visible on a finished part made by the meeting of two flow fronts of plastic material during moulding. Also called weld mark or flow line.


weld mark
See above
"weld line"


wet installation
A bolted joint in which sealant is applied to the head and shank of the fastener so that after assembly a seal is provided between the fastener and the elements being joined.


wet lay-up
A method of making a reinforced product by applying the resin system as a liquid when the reinforcement is put in place.


wet winding
In filament winding, the process of winding glass on a mandrel in which the strand is impregnated with resin just before contact with mandrel. "dry winding"


wet-out
The condition of an impregnated roving or yarn in which substantially all voids between the sized strands and filaments are filled with resin.


wet-strength
The strength of an organic matrix composite when the matrix resin is saturated with absorbed moisture, or is at a defined percentage of absorbed moisture less than saturation. (Saturation is an equilibrium condition in which the net rate of absorption under prescribed conditions falls essentially to zero).


wetting
The spreading, and sometimes absorption, of a fluid on or into a surface.


whisker
A short single crystal fibre or filament used as a reinforcement in a matrix. Whisker diameters range from 1 to 25 mm (40 to 980 min.), with aspect ratios between 100 and 15000.


Width-tolerance
Dimensional tolerance given on width of part, given in mm/inches.
"width"


width
Measure of longest side of a cross-sectional area, given in inches. In pultrusion, the side that is parallel to the layered construction (perpendicular to rovings in all products.) "pultrusion size" ()


wind angle
The angular measure in degrees between the direction parallel to the filaments and an established reference. In filament-wound structures it is the convention to measure the wind angle with reference to the centreline through the polar bosses, that is, the axis of rotation.


winding pattern
The total number of individual circuits required for a winding path to begin repeating by laying down immediately adjacent to the initial circuit. A regularly recurring pattern of the filament path after a certain number of mandrel revolutions, leading eventually to the complete coverage of the mandrel.


winding tension
In filament winding or tape wrapping, the amount of tension on the reinforcement as it makes contact with the mandrel.


woof
See weft
"weft"


work hardening
Increase in resistance to further deformation with continuing distortion. Hardening and strengthening of a metal or alloy caused by the strain energy absorbed from prior deformation.


working life
The period of time during which a liquid resin or adhesive, after mixing with a catalyst, solvent, or other compounding ingredients, remains usable.
"gelation time""pot life"


woven fabric
A material (usually a planar structure) constructed by interlacing yarns, fibres, or filaments, to form such fabric patterns as plain, harness satin, or leno weaves.


woven roving
A heavy glass fibre fabric made by weaving roving or yarn bundles.


wrinkle
A surface imperfection in laminated plastics that has the appearance of a crease or fold in one or more outer sheets of the paper, fabric, or other base, which has been pressed in. Also occurs in vacuum bag moulding when the bag is improperly placed, causing a crease.

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