Definitions /Dictionary/Glossary - nptel

Hardener: A substance used to promote or control curing action by taking part in it; as opposed
to catalyst.
Heat-distortion temperature: Temperature at which a test bar deflects a certain amount under
specified temperature and a stated load.
Honeycomb: Resin-impregnated material manufactured in, usually, hexagonal cells that serves
as a core material in sandwich constructions. Honeycomb may also be metallic or polymer
materials in a rigid, open-cell structure.
Hoop stress: Circumferential stress in a cylindrically shaped part as a result of internal or
external pressure.
Hybrid composite: A composite with two or more reinforcing fibers.
Impact strength: A material's ability to withstand shock loading as measured by the work done
in fracturing a specimen.
Impregnate: To saturate the voids and interstices of reinforcement with a resin.
Impregnated fabric: See Prepreg.
Interface: The surface between two different materials: in fibers, the area at which the glass and
sizing meet; in a laminate, the area at which the reinforcement and the laminating resin meet.
Interlaminar: Existing or occurring between two or more adjacent laminae.
Interlaminar shear: The shearing force tending to produce displacement between two laminae
along the plane of their interface; usually the weakest element of a composite.
Isotropic: Having uniform properties in all directions independent of the direction of load
application.
Laminate ply: One layer of a laminated product.
Lap joint: A joint made by bonding overlapped portions of two adherends.
Lay-up: The placement of layers of reinforcement in a mold.
Liquid-crystal polymers: A newer type of thermoplastic, melt processible, with high orientation
in molding, improved tensile strength, and high-temperature capability.
Mandrel: The form around which resin-impregnated fiber or tape is wound to form structural
shapes or tubes.