TACK
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
A thin unidirectional prepreg, in widths up to 12 inches for carbon fiber, for example.

TAPE LAYING
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 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.

TENSILE ELONGATION
An engineering term referring to the amount of stretch a sample experiences during tensile strain.  ASTM D-638.

TENSILE LOAD
A dulling load applied to opposite ends of a given sample.

TENSILE MODULUS
When a bar is pulled in tension, it has to get longer. The tensile modulus is used to calculate how much longer it will get when a certain load is applied to it. Units are normally millions of pounds per square inch. (10 6 psi) - Giga Pascals (gPa). Higher numbers indicate materials, which will not elongate as much as others when they are being compared under equal tensile loading conditions.

TENSILE STRENGTH OR STRESS
The maximum tensile load per unit area of original cross section, within the gage boundaries, sustained by the specimen during a tension test. It is expressed as psi. Tensile load is interpreted to mean the maximum tensile load sustained by the specimen during the test, whether or not this coincides with the tensile load at the moment of rupture.

TEX
A unit for expressing linear density, equal to the mass in grams of 1 km of yarn, filament, fiber or other textile strand.

THERMAL COEFFICIENT OF EXPANSION
Measures dimensional change of a material when heated or cooled.  Measured in inches per inch per degree.

THERMAL CONDUCTIVITY
This property is known as the K factor. It is a measure of the transfer of heat by conduction. It tells how much heat is transferred from one side of a plate to the other side. It is measured as BTUs per hour per unit area (square feet) for a thickness of one inch and temperature difference of one degree.

THERMOPLASTICS
A group of plastic materials that become elastic or melt when heated, and return to their rigid state at room temperature.  Examples are PVC, ABS, polystrene, polycarbonates, nylon, etc.

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 readings.

THERMOSET
A plastic which, when cured by application of heat or chemical means, changes into a substantially infusible and insoluble material.

THIXOTROPIC, THIXOTROPY
Concerning materials that are gel-like at rest but fluid when agitated; having high static shear strength and low dynamic shear strength, at the same time.

THIXOTROPIC INDEX (T.I.)
A measurement of thixotropy nature determination, using a Brookfield viscometer, as the low speed viscosity divided by the high-speed viscosity.

TOLERANCE
The total amount by which a quantity is allowed to vary.

TOLERANCE LIMIT
A lower (upper) confidence limit on a specified percentile of a distribution. For example, the B-basis value is a 95% lower confidence limit on the tenth percentile of a distribution.

TOLERANCE LIMIT FACTOR
The factor, which is multiplied by the estimate of variability in computing the tolerance limit.

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 GEL COAT/LAMINATING RESIN
Special polyesters designed to give ultimate strengths and cure values for moldmaking.

TOOLING RESINS
Plastic resins, chiefly epoxy and silicon that are used as tooling aids.

TOUGHNESS
Tendency of a material to absorb work.

TOW
An untwisted bundle of continuous filaments, usually designated by a number followed by "K", indicating multiplication by 1000; for example, 12K tow has 12,000 filaments.

TRANSLUCENT
Permits a percentage of light to pass but not optically clear like window glass.

TRANSVERSELY ISOTROPIC
Descriptive term for a material exhibiting a special case of orthotropy in which properties are identical in two orthotropic dimensions, but not the third; having identical properties in both transverse directions but not the longitudinal direction.

TRAVELLER
A small piece of the same product (panel, tube, etc.) as the test specimen; used, for example, to measure moisture content as a result of conditioning.

TYPICAL BASIS
A typical property value is a sample mean. Note that the typical value is defined as the simple arithmetic mean which has a statistical connotation of 50% reliability with a 50% confidence.

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Glossary Section (T) Last Updated: 9/3/99 1:16 PM

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