Fiberset Incorporated's Glossary of Composite Terms

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VACUUM-ASSISTED RESIN TRANSFER MOLDING (VARTM)
An infusion process where a vacuum draws resin into a one-sided mold. A cover, either rigid or flexible, is placed over the top to form a vacuum-tight seal.

VACUUM BAG MOLDING
A molding technique in which the part is cured inside a layer of film, from which entrapped air is removed by vacuum.

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.

VAPOR BARRIER
A material through which water vapor will not pass readily or at all.

VARIANCE
See Sample Variance.

VEIL
An ultra thin mat similar to a surface mat, often composed of organic fibers as well as glass fibers.

VISCOSITY
The property of resistance to flow exhibited within the body of a material, expressed in terms of relationship between applied shearing stress and resulting rate of strain in shear. Viscosity is usually taken to mean Newtonian viscosity, in which case the ratio of shearing stress to the rate of shearing strain is constant. In non-Newtonian behavior, which is the usual case with plastics, the ratio varies with the shearing stress. Such ratios are often called the "apparent viscosities" at the corresponding shearing stresses.

VINYLESTER
A laminating resin which is processed much like polyester, but has cured properties similar to some epoxy resins.

VOIDS
Pockets of entrapped gases that have not been cured into a laminate.

VOID CONTENT
The percentage of voids in a laminate.

VOLATILES
Materials in a sizing or a resin formulation that can be vaporized at room or slightly elevated temperature.

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.

VOLATILE PORTIONS
Those portions vaporizing under specific conditions short of decomposition. Non-volatiles remain.

VOID FREE
A laminate containing no entrapped air cavities, blisters, or voids. 



Glossary Section (V) Last Updated: 7/28/00 12:23 PM