Definitions /Dictionary/Glossary - nptel

Surfacing Agent: It is a material, which allows the surface of polyesters to cure. It limits
adhesion of another coat of resin if the first is thoroughly cured. It may be removed by sanding
or rubbing with steel wool.
Surfacing Mat: It is a thin mat of fine fibers used primarily to produce a smooth surface on an
organic matrix composite.
Surfacing Veil: Used with other reinforcing mats and fabrics to enhance the quality of the
surface finish. Designed to block out the fiber patterns of the underlying reinforcements; also
called surfacing mat.
Surfactant: Chemicals used to modify or change the surface of a layer of resin or polymer.
Usually used to form a film on a curing resin, producing a tack-free surface.
Symmetrical Laminate: A composite laminate in which the sequence of plies below the
laminate mid-plane is a mirror image of the stacking sequence above the mid-plane.
Syntactic Foam: A foam made by mixing microspheres with a resin.
Tack: Stickiness of the prepreg. Stickiness of an adhesive or filament reinforced resin prepreg
material.
Tangent Modulus: The slope of the line at any point on a static stress-strain curve expressed in
psi per unit strain. This is the tangent modulus at that point in shear, extension, or compression as
the case may be.
Tape: Prepreg fabricated in widths up to 12 inches wide for carbon and 3 inches for boron. Cross
stitched carbon tapes up to 60 inches wide are available commercially in some cases.
Tape Laying: It is an automated fabrication process in which prepreg tape is laid side by side or
overlapped to form a structure.
TBPB: Abbreviation for tertiary-butyl peroctoate used in high speed, heated cures of polyester
resin systems.
TBPO: Abbreviation for tertiary-butyl peroctoate used in high speed, heated cures of polyester
resin systems.
Tenacity: The tensile stress expressed as force per unit linear density of the unstrained specimen
i.e., grams-force per denier or grams-force per Tex. The term generally used in yarn manufacture
and textile engineering to denote the strength of a yarn or of a filament of a given size.
Numerically it is the grams of breaking force per denier unit of yarn or filament size; grams per
denier, gpd. The yarn is usually pulled at the rate of 12 inches per minute. Tenacity equals
breaking strength (grams) divided by denier.