DAMAGE TOLERANCE
A measure of the ability of structures to retain load-carrying capability after exposure to sudden loads (for example, ballistic impact).

DAMPING
Diminishing the intensity of vibrations.

DAYLIGHT
The distance in the open position, between the moving and fixed tables or the platens of a hydraulic press. In the case of a multi-daylight press, daylight is the distance between adjacent platens.

DEBOND
An unplanned non-adhered or un-bonded region in an assembly.

DEEP-DRAW MOLD
A mold having a core which is long in relation to the wall thickness.

DEFLECTION TEMPERATURE UNDER LOAD
The temperature at which a simple beam has deflected a given amount under load (formerly called heat distortion temperature).

DEFORMATION UNDER LOAD
The dimensional change of a material under load for a specific time following the instantaneous elastic deformation caused by the initial application of the load. (Also, 'cold flow' or 'creep'.)

DEGRADATION
A deleterious change in chemical structure, physical properties or appearance.

DELAMINATE: DELAMINATION
To split a laminated plastic material along the plane of its layers. Physical separation or loss of bond between laminate plies.

DEMOLD
To remove a part from a tool, or a tool from an intermediate model.

DENIER
A numbering system for yarn and filament in which yarn number is equal to weight in grams of 9000 meters of yarn

DENSITY
This is defined as the weight of a material per unit volume. Units - pounds per cubic inch (lb\cu in) grams/cubic centimeter. Higher numbers indicate heavier materials. Note: Density in lbs/cu in, and Specific Gravity are conveniently related by the following ratio:

Density (lb/cu in) Density (gr/cu cm)
--------------------- = 0.0361 ------------------------ = 0.9975
Specific Gravity Specific Gravity

DENSITY, FIBERS
Mass per unit volume of the solid matter of which a fiber is composed, measured under specified conditions.

DESIGN ALLOWABLE
A limiting value for a material property that can be used to design a structural or mechanical system to a specified level of success with 95 percent statistical confidence. B-basis allowable: material property exceeds the design allowable 90 times out of 100. A-basis allowable: material property exceeds the design allowable 99 times out of 100.

DEVIATION
Variation from a specified dimension or requirement, usually defining the upper and lower limits.

DIALLYLPHTHALATE (DAP)
In reinforced plastics, a monomer which will polymerize with heat and catalyst into clear, hard polymer.

DIBUTHYL PHTHALATE
A lubricant for spray equipment.

DIELECTRIC
A nonconductor of electricity. The ability of a material to resist the flow of an electric current.

DIELECTRIC CONSTANT
The ratio of the capacity of a condenser having a dielectric constant between the plates to that of the same condenser when the dielectric is replaced by a vacuum; a measure of the electrical charge stored per unit thickness at unit potential.

DIELECTRIC STRENGTH
1) This is an electrical property and gives an indication of how well the material acts as an electrical insulator. It describes how much of an electrical voltage can be built up on one side of the material before it is communicated to the other side. Units - Volts per mil of thickness (volts/mil). Higher numbers indicate materials which are better insulators. C means that the material conducts electricity and therefore has no dielectric strength. 2) The average potential per unit thickness at which failure of the dielectric material occurs.

DIETHYLANILINE (DEA)
Accelerator used in conjunction with BPO catalyst or as a co-promoter for cobalt/MEKP system.

DILUENT
Diluting (reducing or thinning) agent.

DIMENSIONAL STABILITY
Capability of an item to maintain its constructed dimensions without distorting.

DIMETHYL ANILINE (DMA)
Accelerator used in conjunction with BPO catalyst. More effective than DEA.

DIMPLES
Small sunken dots in the gel coat surface, generally caused by a foreign particle in the laminate.

DIRECT WOUND ROVING
A roving made directly at the bushing that does not go through a roving process. typical characteristics are: single-end roving, coreless, 6-inch diameter centers and no catenary.

DISPERSION
The means of incorporating pigments into a polyester.

DISTORTION
A wavy gel coat image often found in conjunction with print through. Commonly caused by a problem in the laminating system.

DISTRIBUTION
A formula which gives the probability that a value will fall within prescribed limits.

DOCTOR ROLL; DOCTOR BAR
A device for regulating the amount of liquid material on the rollers of a spreader.

DOUBLER
Localized area of extra layer reinforcement, usually to provide stiffness or strength for fastening or other abrupt load transfers.

DRAFT
The tape or slope of the vertical surfaces of a mold designed to facilitate removal of molded parts.

DRAFT ANGLE
A mandrel's taper or angle for ease of part removal.

DRAIN OUT
The leaking, sagging and puddling of the laminating resin from the laminate.

DRAPE
The ability of pre impregnated broad goods to conform to an irregular shape; textile conformity.

DRY SPOT
Area of incomplete surface film on laminated plastics; in laminated glass, an area over which the interlayer and the glass have not become bonded.

DRY CHOP
Chopping a roving without the simultaneous admixture of resin and catalyst.

DRY FIBER AREA
Area of fiber not totally encapsulated by resin.

DRY WINDING
A type of filament winding in which pre-impregnated roving is used.

DUCTILITY
The ability of a material to deform plastically before fracturing.

DUPLICATION MOLD
A mold made by casting over or duplicating another article.

DUROMETER OF HARDNESS
The hardness of a material determined by Shore durometer.

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Glossary Section (D) Last Updated: 4/27/99 10:19 AM

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