Vacuum-bag molding

Molding technique wherein a part layed up on an open mold is cured under a layer of sealed film from which entrapped air has been removed by vacuum. The technique more effectively consolidates the laminate and reduces void content, compared to conventional open molding.


Vacuum-assisted resin transfer molding (VARTM)

An infusion process by which a vacuum draws resin into a one-sided mold; a cover, either rigid or flexible, is placed over the laminate and taped or otherwise fixed to form a vacuum-tight seal. (See previous entry.)


Veil

An ultrathin, nonwoven mat often composed of organic fibers as well as glass fibers and used primarily as a corrosion barrier.


Vinyl esters

A class of thermosetting resins containing ester of acrylic and/or methacrylic acids.


Viscosity

Describes the tendency of a material to resist flow. Viscosity is measured in comparison with water, and computed in centipoise (cps). The higher the number, the greater the resistance to flow.


Void

Any pocket of enclosed gas or air within a composite.


Volatiles

Materials, such as water and alcohol, in a sizing or resin formulation that can be vaporized at ambient or slightly elevated temperatures.


Volatile content

The percent of volatiles that are driven off as a vapor from a plastic or an impregnated reinforcement during cure.


Volatile organic compounds (VOCs)

Chemical substances, such as solvents, that readily evaporate or volatilize into the air. Many VOCs also are considered hazardous air pollutants (HAPs) because of potential health concerns.