Definitions /Dictionary/Glossary - nptel

Overlay Sheet: A non-woven fibrous mat (of glass, synthetic fibre, etc.) used as the top layer in
a cloth or mat lay-up to provide a smooth finish.
Over-expanded Core: The standard hexagon cell honeycomb pulled out into a rectangle cell
shape.
Oxidation: In carbon/graphite fibre processing, the step of reacting the precursor polymer
(rayon, pitch or PAN) with oxygen, resulting in stabilization of the Structure for the hot
stretching operation.
PAN: See Polyacrlonitrile.
PAN Fibers: Reinforcement fiber derived from the controlled pyrolysis of poly (acrylonitrile)
fiber.
Parallel Laminate: A laminate of woven fabric in which the plies are aligned in the same
position as originally aligned in the fabric roll.
Parallel Wound: A term used to describe yarn or other material wound into a flanged spool.
Parting Agent: Also, see Mold Release.
Part Consolidation: A process of composites fabrication in which multiple discrete parts are
designed and fabricated together into a single part, thus reducing the number of fabricated parts
and the need to join those parts together.
Parting Line: It is a mark on a molded piece where the sections of a mold have met in closing.
Pattern: The initial model for making fiberglass molds.
Peel Ply: Layer of material applied to a lay-up surface that is removed from the cured laminate
prior to bonding operations and leaves a clean resin-rich surface ready for bonding. A layer of
resin free material used to protect a laminate for later secondary bonding.
Peel Strength: Strength of an adhesive bond obtained by stress that is applied "in a peeling
mode."
Peroxides: Category of compounds containing an unstable O - O Group: Oxygen to Oxygen
atoms.
pH: A measure of acidity or alkalinity of a solution, with neutrality represented by a value of 7,
with increasing acidity corresponding to progressively smaller values, and increasing alkalinity
corresponding to progressively higher values.
Phenolic Resin: Thermosetting resin produced by condensation of an aromatic alcohol with an
aldehyde, particularily phenol with formaldehyde.