Tack

Stickiness of an uncured prepreg.


Tape

Thin, unidirectional prepreg, available in up to 12-inch widths in carbon fiber. (Also see unidirectional.)


Tape laying

An automated fabrication process in which preimpregnated tape is laid side by side and/or overlapped to form a structure.


Tensile strength

The maximum tensile stress sustained by a test specimen before failure during a tension test.


Tex

A unit of linear density equal to the weight in grams of 1,000m of filament fibers, yarns or strands.


Tg

See glass-transition temperature.


Thermal conductivity

The ability to conduct heat.


Thermal stress cracking

Crazing and cracking of some thermoplastic resins from overexposure to elevated temperatures.


Thermocouple

Wire assembly used with a control device to sense temperature.


Thermoplastics

A class of plastics that can be repeatedly softened by heating and hardened by cooling through a temperature range characteristic of the plastic, and that in the softened state can be reshaped by means of molding or extrusion.


Thermosets

A class of plastics that, when cured by thermal and/or chemical or other means, become substantially infusible and insoluble. Once cured, a thermoset cannot be returned to the uncured state.


Thixotropic

Describes substances that have high static shear strength and low dynamic shear strength, which results in a predictable, time-dependent loss of viscosity under shear (e.g., when mixed, sprayed or otherwise subjected to force) and subsequent substantial to complete return to the higher at-rest viscosity when shear force is removed. Highly thixotropic resins, for example, may be applied easily with spray equipment, yet immediately afterward resist running on a vertical surface.


Tool

The mold, either one- or two-sided and either open or closed, in or upon which composite material is placed in order to make a part.


Tooling resin

A plastic resin, typically epoxy or silicone, used to make a tool.


Toughness

Measure of the ability of a material to absorb energy.


Tow

Continuous, ordered assembly of essentially parallel, collimated filaments, normally continuous filaments without twist. Same as strand but used when the reference is specific to carbon fiber.


Tow size

Designates the number of filaments in a tow, denoted by a number followed by K, indicating multiplication by 1,000 (for example, 12K tow has 12,000 filaments).


Tracer

A visually different or distinctive fiber, tow, or yarn added to a prepreg to verify fiber alignment or to distinguish warp fibers frfill fibers.


Triaxial fabric

Fabric with three non-interwoven layers - oriented at +45°, - 45° and either 0° or 90° - which are bonded together, usually by through-the-thickness stitching, to form a single sheet of fabric. (See also biaxial fabric, quadraxial fabric.)


Twist

Measure of the number of turns per unit length that a fiber bundle makes around its axis. "Z"-twist denotes a right-handed twist, while "S"-twist denotes a left-handed twist. "U" is often used to represent no twist and "N" means never twisted.