'K' stands for 1000, for example 3K tow has 3000 fibers per strand.
U
UNIDIRECTIONAL- refers to fibers that are oriented in the same direction, i.e. unidirectional fabric or tape, sometimes designated 'UD'.
V 
VACUUM BAGGING- a technique wherein the uncured part is placed in a vacuum tight 'bag', which is then evacuated to remove the air and compress the composite ensuring a complete and even wet-out.

VACUUM-ASSISTED RESIN TRANSFER MOLDING VARTM)- An infusion process where a vacuum draws resin into a vacuum tight mold containing the unsaturated reinforcement.

VENTILATION-a condition where air from the surface is pulled down to form a cavity by the low pressure side of the fin. This condition effectively negates all lift.

VISCOSITY-Tendency of a material to resist flow. As temperature increases, the viscosity of most materials decreases. (see centipoise).

VISCOUS DRAG-The force needed to deform the fluid, or in other words separate the fluid and cause it to go around the shape.

VOIDS-pockets of entrapped gas that have been cured into a laminate. In a properly cured composite void content is less than one percent.

VOLATILES- Materials that can be vaporized at room or slightly elevated temperature.
W
WARP-Yarns running lengthwise and perpendicular to the narrow edge of woven fabric.

WARPAGE-Dimensional distortion in a composite part.

WATER ABSORPTION-Ratio of weight of water absorbed by a material to the weight of the dry