Definitions /Dictionary/Glossary - nptel

Wet-Process: A process for forming a non-woven web from water slurry on "papermaking’
equipment. It is also known as "wet-laid" or "wet-formed".
Wet Strength: It is strength of paper when saturated with water, especially in discussions of
processes whereby the strength of paper is increased by the addition, in manufacture, or plastic
resins; the strength of an adhesive joint determined immediately after removal from a liquid in
which it has been immersed under specified conditions of time, temperature and pressure.
Wet-Through: The degree and/or rate of encapsulation of sized glass fiber bundles in a
laminate. Also, the rate and/or degree of which the polymer matrix resin system can flow
through a bed of sized glass bundles or strands and encapsulate each bundle of filaments.
Wides: Term describing bundles of roving that are wider than most of the other bundles in a bed
of chopped glass fibers. They usually contain 3 to 4 times more filaments than most of the other
bundles in the roving (See Matchstick).
Woven Roving Fabric: Heavy fabrics woven from continuous filament in roving form. It is
usually in weights between 18-30 per square yard.
Wrinkle: Surface imperfection pressed into laminated plastics similar to a crease or fold in
paper, fabric or other base. Also occurs in vacuum bag molding when the bag is improperly
placed, causing a crease.
Yardage: Similar to Yield, but used to describe the linear density of "bare glass" or an un-sized
product. Yardage specifies the number of yards of glass required to weigh one pound, measured
in hundreds. For example, K18 is a K fiber diameter that has 180yards in one pound of glass.
Yarn: Generic term for a continuous strand of textile fibers, filaments or material in a form
suitable for knitting, weaving or intertwining to form a textile fabric.
Yield: Linear density of a roving or yarn, measured by the number of yards per pound.
Yield Point: First stress in a material, less than the maximum attainable stress, at which strain
increases at a higher rate than stress. It is the point at which permanent deformation of a stressed
specimen begins to take place. Only materials that exhibit yielding have a yield point.
Yield Strength: Stress at the yield point. It is a stress at which a material exhibits a specified
limiting deviation from the proportionality of stress to strain. It is the lowest stress at which a
material undergoes plastic deformation. Below this stress, material is elastic; above it, material is
viscous. Often it is defined as the stress needed to produce a specified amount of plastic
deformation (usually a 0.2% change in length).
Young's Modulus: Ratio of normal stress to corresponding strain for tensile or compressive
stresses less than the proportional limit of the material.