Definitions /Dictionary/Glossary - nptel

Ply Schedule: Lay-up of individual plies or layers to form a laminate. Plies may be arranged in
alternating fiber orientation to produce multi-directional strength in a part.
Poisson's Ratio: The absolute value of the ratio of transverse strain to the corresponding axial
strain resulting from uniformly distributed axial stress below the proportional limit of the
material.
Polar Winding: A type of filament winding in which the filament path passes tangent to the
polar opening at one end of the chamber and tangent to the opposite side of the polar opening at
the other end of the chamber.
Polyacrylonitrile (PAN): A product used as a base material in the manufacture of certain carbon
fibers.
Polyamide: A polymer in which the structural units are linked by amide or thioamide groupings.
Many polyamides are fiber-forming.
Polyesters: Thermosetting resins, produced by dissolving unsaturated, generally linear, alkyd
resins in a vinyl-type active monomer such as styrene, methyl styrene, and diallyl phthalate. Cure
is affected through vinyl polymerization using peroxide catalysts and promoters, or heat, to
accelerate the reaction. The resins are usually furnished in solution form, but powdered solids are
also available.
Polyester Resing (Unsaturated): The product of an acid-glycol reaction commonly blended
with a monomer to create a polymer resin. In its thermosetting form it is the most common resin
used in the FRP industry.
Polymer: An organic material composed of molecules characterized by the repetition of one or
more types of monomeric units.
Polymerization: A chemical reaction in which the molecules of monomers are linked together to
form polymers via two principal reaction mechanisms. Addition polymerizations precede by
chain growth and most condensation polymerizations through step growth.
Polymerize: To unite molecules of the same kind to form a compound having the elements in
the same proportion but possessing much higher molecular weight and different physical
properties.
Polyvinyl Alcohol (PVA): A liquid water soluble release agent.
Population: The set of measurements about which inferences are to be made or the totality of
possible measurements which might be obtained in a given testing situation. For example, "all
possible ultimate tensile strength measurements for carbon/epoxy system A, conditioned at 95%
relative humidity and room temperature". In order to make inferences about a population, it is
often necessary to make assumptions about its distributional form. The assumed distributional
form may also be referred to as the population.