Definitions /Dictionary/Glossary - nptel

Aramid: A manufactured fiber in which the fiber-forming substance consisting of a long-chain
synthetic aromatic polyamide in which at least 85% of the amide (-CONH-) linkages are attached
directly to two aromatic rings.
Aramid: (Kevlar(R)) Aromatic polyamide fibers characterized by excellent flame-resistance,
high-temperature, and electrical properties. Aramid fibers are used to achieve high-strength,
high-modulus reinforcement in plastic composites.
Arcing: This spray method should normally be avoided as it consists of directing spray passes
by gun rotation at the wrist (arcing), as opposed to the conventional stroke from the shoulder,
keeping the fan pattern perpendicular to the mold.
Arial Weight: The weight of fiber per unit area (width times the length) of tape or fabric.
Arial Weight of Fiber: The weight of fiber per unit area of prepreg. This is often expressed as
grams per square meter.
Aromatic: Unsaturated hydrocarbon with one or more benzene ring structures in the molecule.
Artificial Weathering: Exposure to laboratory conditions which may be cyclic, involving
changes in temperature, relative humidity, radiant energy and any other elements found in the
atmosphere in various geographical areas.
Ash Content: The solid residue remaining after a reinforcing substance has been incinerated (or
strongly heated).
ASTM: American Society of Test Methods.
Aspect Ratio: In an essentially two-dimensional rectangular structure (e.g., a panel), the ratio of
the long dimension to the short dimension. However, in compressive loading, it is sometimes
considered to be the ratio of the load direction dimension to the transverse dimension. Also, in
fiber micro-mechanics, it is referred to as the ratio of length to diameter.
Assembly line: The time interval between the spreading of the adhesive on the adherend and the
application of pressure and/or heat to the assembly.
Autoclave: A closed vessel for producing an environment of fluid pressure, with or without heat,
to an enclosed object which is undergoing a chemical reaction or other operation.
Autoclave Molding: A process similar to the pressure bag technique. The lay-up is covered by a
pressure bag, and the entire assembly is placed in an autoclave capable of providing heat and
pressure for curing the part. The pressure bag is normally vented to the outside.
Auto- Ignition Temperature: The lowest temperature required to initiate or cause self-sustained
combustion in the absence of a spark or a flame.