Definitions /Dictionary/Glossary - nptel

Foamed Plastic: Resins in sponge form, flexible or rigid, with cells closed or interconnected and
density over a range from that of the solid parent resin to 0.030 g/cm3.
Foaming Agent: Chemicals added to plastics and rubbers that generate inert gases on heating,
causing the resin to assume a cellular structure.
Foam-In-Place: The process of creating foam by the combination of two liquid polymers. See
In-Situ.
FPF: First ply failure.
Fracture: A rupture of the surface of a laminate because of external or internal forces, with or
without complete separation.
Fracture Ductility: The true plastic strain at fracture.
Fracture Stress: The true, normal stress on the minimum cross-sectional area at the beginning
of fracture.
Fracture Toughness: A measure of the damage tolerance of a material containing initial flaws
or cracks.
Free Radicals: Highly reactive molecular fragments capable of initiating chemical reactions,
such as polymerization of polyester resins.
FRP: Fibrous-glass reinforced plastic; a general term covering any type of plastic reinforced
cloth, mat, strands, or any other form of fibrous glass.
Fumed Silica (Aerosil, Cabosil): A thickening agent (having very low weight) used in
polyesters or epoxies to increase thixotropic qualities.
Fuzz: Accumulation of short broken filaments over a contact point.
Gap:
(a) In filament winding, the space between successive windings in which windings are
usually intended to lay next to each other.
(b) Separation between fibres within a filament winding band.
(c) The distance between adjacent plies in a lay-up of unidirectional tape materials.
Gauge Length: the original length of that portion of the specimen over which strain or change of
length is determined.
Gel: The initial jelly-like solid phase that develops during formation of a resin from a liquid.
Also, a semi-solid system consisting of a network of solid aggregates in which liquid is held.