U
UNDERCUT
An area of a part or mold that has acute angle between two surfaces. If a part has an undercut, a split mold is necessary.
UNIDIRECTIONAL
Strength lying mainly in one direction. A glass reinforcement in which the fiber is oriented in one direction
UV STABILIZER
A chemical compound that improves resistance to degradation from ultraviolet radiation.
V
VACUUM INFUSION PROCESSING
A process where the reinforcement is laid-up in the mold dry, then vacuum bagged and the resin is pulled into the mold at lower then atmospheric pressure.
VACUUM BAG MOLDING
Process for eliminating voids and forcing out entrapped air and excess resin from lay-ups by drawing a vacuum from a plastic film that blankets a laminate.
VISCOSITY
The liquid properties of a material. Resistance to flow.
VOIDS
Pockets of air that have been trapped in a laminate.
VOLATILE ORGANIC COMPOUNDS (VOC)
Carbon-containing chemical compounds (e.g., solvents or liquids) that evaporate readily at ambient or process temperatures. Environmental, safety and health regulations often limit exposure to
these compounds, making low VOC content is preferable.
VOID FREE
A laminate containing no entrapped air cavities, blisters or voids.
W
WATER ABSORPTION
The amount of water that a laminate will absorb.
WAX
A compound used as a release agent. See Release Agent.
WEAVE
Pattern by which fabric is formed from woven yarns.
WEFT
Yarns running perpendicular to the warp in a woven fabric; also called ‘woof.’
WET-OUT
The action of saturating a glass fabric with resin. Also a measure of the speed with that a fabric soaks up resin.
WETTING AGENT
Surface-active agent that promotes wetting by decreasing the cohesion within a liquid.
WHISKER
Short single crystal fiber or filament used as reinforcement in a matrix.
WOVEN ROVING FABRIC
Heavy fabrics woven from continuous filament in roving form. Usually in weights between 18-30 oz. Per square yard.
Y
YARN
Twisted strands of roving, used to weave textile reinforcements.
