Warp

Fiber bundles in a woven fabric that run parallel to the length of the loom and lengthwise along the longer dimension of the finished fabric.


Warpage

Dimensional distortion in a composite.


Water absorption

Ratio of the weight of water ab-sorbed by a material to the weight of dry material.


Waterjet

High-pressure water stream used for cutting polymer composite parts.


Weave

To interlace fibers in a pattern, often based on a 0°/90° grid; the fabric pattern formed by interlacing yarns. Interlacing patterns vary. In plain weave, for instance, warp and fill fibers alternate to make both fabric faces identical. A satin weave pattern is produced by a warp tow over several fill tows and under one fill tow (e.g., eight-harness satin features one warp tow over seven fill tows and under the eighth).


Weft

See fill.


Wet layup

Application of a resin to dry reinforcements in the mold.


Wet winding

A filament winding technique that impregnates fiber strands with resin immediately before they contact the mandrel.


Wetout

Saturation with resin of all voids between reinforcement strands and filaments.


Wetting agent

A surface-active agent that promotes wetting by decreasing a liquid's cohesion.


Whisker

A short, single crystal fiber or filament used as a reinforcement in a matrix.


Wind angle

Measure in degrees between the direction parallel to the filaments and an established reference point.


Winding

Any process in which continuous material is applied under controlled tension to a rotating form (mandrel) in a predetermined geometric relationship to make a structure. (See filament winding.)


Winding pattern

In filament winding, the recurring pattern of the filament path after a certain number of mandrel revolutions.


Wire

Large diameter (greater than about 2 mils) high-performance fiber (e.g., see boron fiber or silicon carbide fiber). In contrast, see filament and fiber.


Wire mesh

Fine wire screen used to dissipate the electrical charge from lighting.


Woof

Same as fill.


Woven roving

Heavy, coarse fabric produced by weaving continuous roving bundles.


Wrinkle

Imperfection in the surface of a laminate that looks like a crease in one of the outer layers. This occurs in vacuum-bag molding when the bag is improperly placed.