Definitions /Dictionary/Glossary - nptel

Hydrophobic: Moisture resistant capability, moisture repelling.
Hygroscopic: Capable of absorbing and retaining atmospheric moisture.
Hygrothermal Effect: Change in properties due to moisture absorption and temperature change.
Hysteresis: The energy absorbed in a complete cycle of loading and unloading.
Ignition Loss: The difference in weight before and after burning; as with glass, the burning
off of the binder or size.
Impact Strength: The ability of a material to withstand shock loading; the work done in
fracturing a test specimen in a specified manner under shock loading.
Impact Test: Measure of the energy necessary to fracture a standard notched bar by an impulse
load.
Impregnate: In reinforced plastics, the saturation of the reinforcement with a resin.
Impregnated Fabric: Also see Prepreg.
Inclusion: A physical and mechanical discontinuity occurring within a material or part, usually
consisting of solid, encapsulated foreign material. Inclusions are often capable of transmitting
some structural stresses and energy fields, but in a noticeably different manner from the parent
material.
Inhibitor: A substance which retards a chemical reaction; used in certain types of monomers and
resins to prolong storage life.
Initial Entry Point: The spot where the lightning flash channel first enters the aircraft (usually
an extremity).
Initial Exit Point: The spot where the lightning flash channel first exits the aircraft (usually an
extremity).
Initiator: A substance that initiates the curing reaction at elevated temperatures.
Injection Molding: Method of forming a plastic to the designed shape by forcing the heat
softened plastic into a relatively cool cavity under pressure.
Inorganic: Designating or pertaining to the chemistry of all elements and compounds not
classified as organic.
Inorganic Pigments: Natural or synthetic metallic oxides, sulphides and other salts that impart
heat and light stability, weathering resistance, colour and migration resistance to plastics.