Composites Glossary.docx

7/30/2019 Composites Glossary.docx

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A

ABS: Acrylonitrile Butadiene Styrene (Thermoplastic Resin).

Ablative Plastic: A material that absorbs heat (with low material loss and char rate) through a

decomposition process (pyrolysis). Absorption takes place at or near the surface exposed to theheat.

Abrasion: Wearing away by friction. Glass is highly resistant to abrasion from other materials,but can be damaged through contact with itself. Lubrication during processing and fabrication

helps prevent abrasion.

Accelerated Test: Procedure in which conditions are magnified to reduce the time required to

obtain a result, or to reproduce the deteriorating effects of normal service conditions in a very

short time period.

Accelerator (Promoter): A highly active oxidizing agent used to speed up the chemical reaction

(curing) between a catalyst and resin. Examples include diethylaniline, cobalt naphthanate andcobalt octoate.

Activator:See Accelerator.

Acoustic Emission: The amount of integrity in a material after it has been stressed, as

determined by sound emission. Ideally, emissions can be correlated with defects and/or earlyfailure.

Acrylic: Thermoplastic polymer made by the polymerization of esters of acrylic acid and itsderivatives.

Actual End Count: The number of bundles or splits that are actually counted in one doff of

roving. (This is less than the theoretical end count due to splitting efficiencies of less than

100%).

Addition Polymerization: Chemical reaction in which simple molecules (monomers) are added

to each other to form long-chain molecules (polymers) without byproducts.

Additive: A material used to modify the properties of polymer resins. Examples includeplasticizers, initiators, light stabilizers and flame-retardants.

Adhesion: The state in which two surfaces are held together by an interlocking action or force.

Adhesive: A film, liquid or paste capable of holding the surfaces of two materials together.

Admixture: Addition and homogeneous dispersion of discrete components, before cure.


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Aggregate: Hard, coarse material usually of mineral origins used in composite tools. Also used

in flooring or as a surface medium.

Aging: The process of exposing materials to an environment for an interval of time.

Air-Bubble: A localized, non-interconnected, spherically shaped entrapment of air within andbetween the plies of reinforcement.

Air Splice: The coupling made by a jet of air to entwine/snarl two roving doffs together. The air

splice is used instead of a knot.

Air Vent: Small outlet to prevent entrapment of gases in a molding or tooling fixture.

Alkyd Plastics: Resin composed principally of polymeric esters, in which the recurring estergroups are an integral part of the main polymer chain or are part of the cross links present

between chains.

Alligatoring: Visible cosmetic defect in exposed gel coat resembling wrinkled or alligator-like

skin.

Alloy: In plastics, a blend of polymers or copolymers blended with other polymers or elastomers

under select conditions.

Ambient: Surrounding environmental conditions, such as pressure, temperature, or relative

humidity.

Amine Resins: A synthetic resin derived from the reaction of urea, thiourea, melamine or allied

compounds with aldehydes, particularly formaldehyde.

An Isotropic: Exhibiting different properties when tested along axes in differentdirections.see

An Isotropic laminate

An Isotropic Laminate: A laminate whose properties are different in different directions.

Angle-Ply Laminate : A laminate with fibers of adjacent plies oriented at alternating angles.

Antioxidant: Substance that, when added in small quantities to resin, prevents oxidation and

degradation while maintaining the resins properties.

Antistatic Agents: Agents added to a molding material or applied to the surface of a molded

object to make it more conductive and prevent the fixation of dust or buildup of electrical charge.

Arimid: A highly oriented organic material derived from polyamide with an aromatic ring

structure that is used primarily as a high-strength, high-modulus fiber. Examples include Kevlar

and Nomex.


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Arc Resistance: Ability to withstand exposure to an electric voltage. Also, the total time in

seconds that an intermittent arc may play across a plastic surface without rendering it conductive.

Ash Content: Proportion of solid residue remaining after a reinforcing substance has been

incinerated (charred or intensely heated).

Aspect Ratio: Ratio of length to diameter of a fiber.

A-Stage: Early stage in the polymerization reaction of certain thermosetting resins (especially

Phenolic) in which the material, after application to the reinforcement, is still soluble in certain

liquids and is fusible. Also called resole.see B-Stage and C-Stage

ASTM: American Society of Test Methods.

Autoclave: Closed vessel for conducting and completing a chemical reaction or other operation

under pressure and heat.

Autoclave Molding: Process in which an assembly is placed in a heated autoclave, usually at 50

to 200 psi, after lay-up, winding or wrapping. Additional pressure permits higher density and

helps remove volatiles from the resin. Lay-up is usually vacuum bagged with a bleeder andrelease cloth.

Autosprue: Automatic gate at the inlet sprue of the mold that eliminates the need to removethe resin supply during injection.

Axial Winding: Filaments that are wound parallel or at a small angle to the axis (0 helix angle).

B

Bagging: Applying an impermeable layer of film over an uncured part and sealing the edges so

that a vacuum can be drawn.

Bag Molding: Process in which fluid or gas is applied through a flexible membrane to

consolidate material in a mold.

Balanced Construction: Equal parts of warp and fill in fiber fabric. Construction in which

reactions to tension and compression loads result in extension or compression deformations only,and in which flexural loads produce pure bending of equal magnitude in axial and lateraldirections.

Balanced Laminate: Composite laminate whose 0 and 90 angles occur only in + or - pairs(not necessarily adjacent) and are symmetrical around the centerline.

Ball: See Roving
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Band Width: In filament winding, the width of the reinforcement as it is applied to the mandrel.

Barcol-Shore Rockwell Hardness:A materials ability to be indented. The Rockwell methodmeasures the amount of penetration caused when a steel point is forced into the material. The

suffix (alphabetic letter) in the Rockwell reading describes the shape of the point and units

describe how much load was applied during the test. The letter and number cannot be separated.Higher numbers with the same letter indicate harder materials with greater resistance to

penetration by another substance.

Bare Glass: Glass in fiber form as it flows from the bushing before a binder or sizing is applied.

Batch Oven: Large temperature-controlled oven used to heat-clean rolls of glass fiber fabric.

Batt: Felted fabrics or structures built by the interlocking action of compressing fibers, without

spinning, weaving, or knitting.

Beam: A spool on which parallel ends of single or plied yarns are wound for use in weaving orsimilar processing operations.

Beaming: Operation in which many ends of yarn from a creel are combined on a section beam.

Bearing Strength: The maximum amount of stress that can be sustained. Also, the point on the

stress-strain curve where the tangent is equal to the bearing stress divided by n% of the bearinghole diameter.

Bearing Stress: Applied load in pounds divided by the bearing area. Maximum bearing stress isthe number of pounds that can be sustained, divided by the original bearing area.

Bed: The mat of chopped glass fibers deposited over a layer of resin mix on carrier filmfollowing a chopping operation.

Bias Fabric: Warp and fill fibers placed at an angle to the length of the fabric.

Biaxial Load: Loading condition in which a laminate is stressed in two different directions in itsplane. Also, a loading condition of a pressure vessel under internal pressure and with

unrestrained ends.

Biaxial Winding: Filament winding in which the helical band is laid in sequence, side by side,

without any fibers crossing over each other.

Bi-directional: Reinforcing fibers arranged in two directions, usually at right angles.

Bi-directional Laminate (Cross Laminate): A reinforced plastic laminate whose fibers areoriented in two directions in its plane.


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Binder: Coating which is applied to the surface of a chopped glass mat or preform and then

cured to hold bundles or ends together in a stable form during the roving operation.

Birdnest: A large, tangled up collection of continuous glass bundles unable to run through the

guide eye into roving creel. In the field, it can also be a large tangled collection of roving which

does not run through the tube or guide eyes to the chopper.

Bismaleimide (BMI): A polyamide that cures through an addition rather than a condensation

reaction, thus avoiding problems with volatiles forming. It is produced by a vinyl-typepolymerization of a pre-polymer terminated with two maleimide groups. BMI has an

Intermediate temperature capability (between epoxy and polyamide).

Bisphenol A: A condensation product formed by the reaction of two (bis) molecules of phenol

with acetone (A). This polyhydric phenol is a standard resin intermediate along with

epichlorohydrin in the production of epoxy resins.

Blade Packing: Glass bundles or chopper fuzz which build up and pack between the blades of achopper. Blade packing can result in poor choppability. If it falls off, it usually does not wet-through, causing blisters or porosity.

Blanket: Fiber or fabric plies that have been laid up in a complete assembly and placed on or inthe mold all at one time (flexible bag process). Also, the form of bag in which the edges are

sealed against the mold.

Bleeder Cloth: Woven or non-woven layer of material used in composite parts manufacturing

that allows excess gas and resin to escape during cure. The bleeder cloth is removed after the

curing process and is not part of the final composite.

Blister: Flaw either between layers of laminate or between the gel coat film and laminate.

BMC: Bulk Molding Compound (Thermoset).

Bobbin: The spool or shipping package on which textile yarns are wound.

Bond Strength: Amount of adhesion between bonded surfaces. The stress required to separate alayer of material from the base to which it is bonded, as measured by load/bond area.

Boron Fiber: Fiber produced by vapor deposition of elemental boron, usually onto a tungsten

filament core, to impart strength and stiffness.

Braid/Braider: A narrow tubular or flat fabric produced by intertwining a single set of yarns

according to a definite pattern.

Breakup: see Dispersion


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Breathing: Opening and closing a mold so that gas can escape early in the molding cycle. Also

called "degassing"; sometimes called "bumping" in Phenolic molding.

Bridging: Condition in which fibers do not move into or conform to radii and corners during

molding, resulting in voids and dimensional control problems.

Broad Strand:see Wides or Matchsticks

Broken Strand: see Broken End

Broken End: In the roving operation, a severed strand (bundle), which causes the forming caketo stop running.

Broken Fibers: see Fuzz

B-Stage: Intermediate stage in the reaction of certain thermosetting resins in which the material

softens when heated, is plastic and is fusible but may not entirely dissolve or fuse. Also called"resistol" or "resitol." Resin in an uncured prepreg or premix is usually in this stage.

Buckling (Composite): Failure mode generally characterized by an unstable lateral material

deflection due to compressive action on the structural element involved.

Buildup: Glass bundles or chopper fuzz that collect on the chopper, cot, static bars or machine

frame.

Bulk Molding Composite (BMC): Thermosetting resin mixed with short strand reinforcement,

filler, and other materials to form a viscous compound for compression or injection molding.

Bundle: A discrete collection of many parallel glass filaments. A collection of individual

filaments; a sub-strand.

Burst Strength: (1) Hydraulic pressure required to burst a vessel of given thickness. Commonly

used in testing filament-wound composite structures. (2) Pressure required to break a fabric by

expanding a flexible diaphragm or pushing a smooth spherical surface against a securely heldcircular area of fabric. The Mullen expanding diaphragm and Scott ball burst machine are

examples of equipment used for this purpose.

Bushing: Plate with holes through which molten glass is pulled to produce glass fibers.

Bushing Tip: Small tapered protrusions on the bottom of bushings, each containing an orificethrough which molten glass flows and from which continuous filaments are drawn.

C


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Cabled Yarn: Yarn that is plied more than once or made by plying two or more previously plied

yarns.

Carbon: Element that provides the backbone for all organic polymers. Graphite is a more

ordered form of carbon. Diamond is the densest crystalline form of carbon.

Carbon-Carbon: Composite material consisting of carbon or graphite fibers in a carbon or

graphite matrix.

Carbon Fiber: Fiber produced by the pyrolysis of organic precursor fibers, such as rayon,

polyacrylonitrile (PAN), and pitch, in an inert environment.

Carding: The process of untangling and partially straightening fibers by passing them between

two closely spaced surfaces which are moving at different speeds of which one or more is

covered with sharp points, thus converting a tangled mass of fibers into a filmy web.

Casting: Process of pouring resin, fillers and/or fibers into a mold vs. building up layers throughlamination. Casting results in physical properties that are different than those resulting fromlamination.

Catalyst (Hardener): A substance that markedly speeds up the cure of a compound by

decomposing in the presence of a promoter to release an active oxygen radical. Catalyst content

can vary from 0.2% to 2.0% with higher catalyst levels giving faster gel times. Examples aremethyl ethyl ketone peroxide, benzoyl peroxide.

Catastrophic Failures: Totally unpredictable failures of a mechanical, thermal, or electrical

nature.

Catenary: A consolidated group of individual strands which, when checked between two fixedpoints of length, exhibit strands of different lengths. The resulting curve between fixed points of

the inextensionable material is defined as catenary. The amount of catenary is measured by the

distance between the topmost and lowermost strands when stretched between two fixed points.

Caul Plates: Smooth metal plates free of surface defects with the same size and shape as a

composite lay-up that contacts the lay-up during curing. Caul plates transmit normal pressure andtemperature to the finished laminate while providing it with a smooth surface.

Cavity: Space inside a mold in which a resin or molding compound is poured or injected. The

female portion of the mold. That portion of the mold that encloses the molded article (oftenreferred to as the die). Depending on the number of such depressions, molds are designated as a

single cavity or multiple cavity.

Cell: The vertical plane of doffs on a pallet. A pallet may be constructed for 4- or 12-end run-out

depending on application.


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C-Glass: Glass with a soda-lime-borosilicate composition that maintains chemical stability in

corrosive environments.

Chalking: Surface phenomenon indicating degradation of a cosmetic surface. Chalking is a

powdery film that appears lighter than the original color.

Chemical Size: A surface finish applied to the fiber that contains some chemical constituents

other than water.

Choppability: The ease of chopping/cutting the glass fibers to a uniform length.

Clamping Pressure: In injection molding and transfer molding, the pressure that is applied to

the mold to keep it closed in opposition to the fluid pressure of the compressed molding material.

Cloth: Fiberglass reinforcement made by weaving strands of glass fiber yarns.

Clump: A group of chopped bundles of glass fibers that has collected on the SMC machine andthen fallen into the bed of glass. The clump produces areas of high glass content which may not

wet-through.

Coefficient of Thermal Expansion (CTE):How much a materials shape will change per each

degree of temperature fluctuation.

Cold Flow: Distortion that occurs in a material under continuous load within its working

temperature range and without a phase or chemical change.

Collet: A spool on which the gathered strands from the bushing are wound for further

processing.

Compaction: Applying a temporary vacuum bag and vacuum to remove trapped air and

compact the lay-up; also removing air in SMC machines prior to roll-up.

Compatibility: The ability of two or more substances to be combined in order to form a

homogeneous composition of useful plastic properties; for example, the suitability of a sizing orfinish for use with certain general resin types.

Composite: Chemical or mechanical bonding of dissimilar materials such as glass fiber and

polyester resin, whose cumulative properties are superior to the individual materials.

Composite Material: A combination of two or more materials (reinforcing elements, fillers, andcomposite matrix binder). Although they act in concert, the constituents retain their identities;

that is, they do not dissolve or merge completely into one another. Normally, the components can

be physically identified and exhibit an interface between one another.

Compounder: Manufacturer who mixes a polymer, fillers, additives and glass fibers, and sells

the resulting pellets for injection molding.


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Compression Molding: An open molding process in which material is introduced and shaped by

the pressure of closing and by heat.

Compressive Modulus: Ratio of compressive stress to compressive strain below the

proportional limit. Theoretically equal to Young's modulus determined from tensile experiments.

Compressive Strength: The amount of nonmoving load that a bar can take before it is crushed.

Units are normally thousands of pounds per square inch. (103 psi) - Mega Pascals (mPa). Higher

numbers indicate stronger materials that can withstand a heavier load before they break.

Condensation Polymerization: A chemical reaction in which two or more molecules combine,with the separation of water or some other simple substance.

Conductivity: Reciprocal of volume resistivity. The electrical or thermal conductance of a unit

cube of any material (conductivity per unit volume).

Conformability:A mats ability to conform to difficult shapes without wrinkling or leavingexcessively resin-rich or glass-rich radii, which may craze.

Contact Molding: Refers to the use of a single or open mold onto which layers of polymer andreinforcement materials can be applied. Contact molding is characterized by one finished

cosmetic side. Cure is either at room temperature using a catalyst-promoter system or by heating

in an oven, without additional pressure.

Continuous Filaments: Filaments that extend substantially throughout the length of the yarn.

Continuous Heat Resistance: Maximum temperature to which material should be subjected in a

continuous application. Below this temperature, the material is acceptable. At temperaturesabove the maximum, the material may decompose, melt, or otherwise fail in an application.Units - degrees Fahrenheit (F)- degrees Centigrade (C). Higher numbers mean the material can

be used continuously at higher temperatures.

Continuous Laminating: Process for forming panels and sheeting in which fabric or mat is

passed through a resin bath, brought together between covering sheets, and passed through a

heating zone for cure. Squeeze rolls control thickness and resin content as the various plies arebrought together.

Continuous Rovings: Rovings supplied in a package that allows for continuous processing.

Continuous Strand: Fiberglass mat of very long individual fibers that have a regular crossed

pattern and are loosely held together with a binder.

Copolymer: A resin produced by copolymerization. A process in which unlike molecules are

arranged in alternate sequence in a chain.


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Core: A low-density material used between two FRP skins. Examples are end-grain balsa wood,

urethane foam, PVC foam and various honeycomb materials. The central member, usually foam

or honeycomb, has a sandwich construction to which the faces of the sandwich are attached orbonded. The central member of a plywood assembly. A channel in a mold for circulation of heat

transfer media. A device on which prepreg is wound.

Coronizing: Continuous heat cleaning and weave setting.

Corrosion Resistance:A materials ability to withstand ambient natural factors or those of aparticular artificially created atmosphere, without degrading or changing in properties. For

metals, this could be pitting or rusting; for or organic materials, it could be crazing.

Coupling Agent: Any chemical substance designed to react with both the reinforcement and

matrix phases of a composite material to form or promote a stronger bond at the interface.

Crazing: Cracking of gel coat or resin due to stress. Region of ultra-fine cracks, which may

extend in a network on or under the surface of a resin or plastic material. May appear as a whiteband. Often found in a filament-wound pressure vessel or bottle.

Creel: Glass Fiber Manufacturing - A framework used to hold forming cakes so they can be

wound or roved into roving doffs. Creels generally hold 10 to 33 forming cakes that are replacedrandomly when they run out or as doffs are roved. Composite Fabrication - The area in which

pallets of roving are placed and "threaded up" through metal tubes or guide eyes to a chopper.

Creep: The slow movement of a plastic material with time.

Creep, Rate of: Rate of the slope of the creep-time curve at a given time. Deflection with time

under a given static load.

Cross-linking: Chemical links between molecule chains in thermosetting resins. Styrene

monomer is a cross-linking agent in polyester resins.

C-Stage: Final stage in the reaction of certain thermosetting resins in which the material is

practically insoluble and infusible.

CTE:see Coefficient of Thermal Expansion

Cure: Cross-linking or total polymerization of a resins molecules that alters a materials

properties, changing it from a liquid to a solid.

Cure Cycle: The time/temperature/pressure cycle used to cure a thermosetting resin system or

prepreg

Cure Temperature: Temperature at which a cast, molded, or extruded product, resin-

impregnated reinforcement, adhesive or other material is subjected to curing.


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Cure Time: The time required for liquid resin to reach a cured or fully polymerized state after

catalyst has been added.

Curing Agent: A catalytic or reactive agent that, when added to a resin, causes polymerization.

Also called hardener.

Cut Ends on Doff: Severed ends generally caused by abrasion during shipping or by careless

use of a knife when the package is removed from the pallet.

Cycle: The complete, repeating sequence of operations in a process or part of a process. In

molding, cycle time is the period (or elapsed time) between a certain point in one cycle and thesame point in the next.

D

DAP: Diallyl Phthalate (Thermoset Resin).

Damping: The decay with time of the amplitude of free vibrations of a specimen.

Daylight: The distance, in the open position, between the moving and fixed tables or the platensof a hydraulic press. In a multi-platen press, daylight is the distance between adjacent platens.

Daylight provides space so a molded part can be removed from the mold.

Deep-Draw Mold: A mold whose core is long in relation to its wall thickness.

Deflashing: A finishing technique used to remove excess, unwanted material (flashing) on aplastic molding.

Deflection Temperature Under Load: Temperature at which a simple beam has deflected agiven amount under load (formerly called heat distortion temperature).

Deformation Under Load: 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'.)

Delamination: Separation of composite layers, either local or covering a wide area. Can occur in

the cure or subsequent life.

Denier: A direct numbering system for expressing linear density, equal to mass in grams per

9000m of yarn, filament, fiber, or other textile strand.

Density: A materials weight per unit volume. Units refer to 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:


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Density (LB/cu in) Density (gr/cu cm)

-------------------- = 0.0361 -------------------- = 0.9975

Specific Gravity Specific GravityDensity, Fiber:

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

conditions.

Dielectric: A nonconductor of electricity. A materials ability to resist the flow of electrical

current.

Dielectric Constant:An assemblys ratio of capacitance when its two electrodes are separated

solely by a plastic insulating material to its capacitance when the electrodes are separated by air.

Dielectric Heating: Heating materials by dielectric loss in a high-frequency electrostatic field.

Dielectric Strength: An electrical property indicating how well a material acts as an electrical

insulator. It describes how much of an electrical voltage can be built up on one side of thematerial before it is communicated to the other side. Units are measured in volts per mil ofthickness (volts/mil). Higher numbers indicate materials with better insulation properties. C

means that the material conducts electricity and therefore has no dielectric strength.

Dimensional Stability:A plastic parts ability to retain the precise shape to which it was

molded, cast, or otherwise fabricated.

Direct-Sized Yarn: Specially formulated sizing on textile yarns that allows them to be resin

compatible.

Dispersion: Degree to which roving separates into discrete bundles after being chopped. Gooddispersion is characterized by a bed of bundles uniform in width. Poor dispersion is characterized

by a wide distribution in the widths of various bundles in the bed. Poor dispersion can cause poorwet-through and wet-out.

Distortion: Change in shape from that which is intended. Symptomatic of laminatingdifficulties, curing problems, tooling problems or resin shrinkage.

Doctor Blade or Bar: A straight piece of material used to spread resin, as applying a thin film of

resin for use in hot melt prepreg or as an adhesive film. Also called paste metering blade.

Doff:see Roving Doff

Doff Collapse: The failure of the roving doff to maintain its shape and stability during run-out orstorage. Doff collapse generally occurs when there is only a 1/2" to 1/4" ring of roving left from

the original doff.

Draft:The taper or slope of a molds vertical surface allowing molded parts to be removed.


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Drape: The ability of pre-impregnated broad goods to conform to an irregular shape; textile

conformity.

Dry Loft: Height of the bed of chopped fibers.

Dry Spot: A rea of incomplete surface film on laminated plastics; in laminated glass, an areaover which the interlayer and the glass have not become bonded.

Dwell: A pause in the application of pressure or temperature to a mold, made just before it is

completely closed, allowing gas to escape from the molding material.

E

E Glass: A family of calcia-alumina-silicate glasses with a certified chemical composition used

for general purpose and most electrical applications. (ASTM D578-90.)

Elasticity:A materials ability to recover its original size and shape after the force deforming ithas been removed.

Ejection (Demolding): Removing a molded part from the mold by hand, mechanical means oruse of compressed air.

Ejection Plate: A metal plate used to operate ejector pins; designed to apply a uniform pressureto them in the process of ejection.

Elastic Limit: The greatest stress a material can sustain without permanent strain after the stresshas been completely released. A material is said to have passed its elastic limit when the load is

sufficient to initiate plastic, or non-recoverable, deformation.

Elastomer: A material that substantially recovers its original shape and size at room temperature

after a deforming force is removed.

Elongation: As mentioned under tensile modulus, when a bar is pulled it gets longer. The

elongation tells how much longer it gets before it breaks.

Encapsulating: Completely surrounding an object with resin or a fiber resin composite.

Sometimes used specifically in reference to the enclosure of capacitors or circuit board modules.

End: A single bundle of filaments.

End count: An exact number of ends supplied on a ball of roving.


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Environment: The aggregate of all conditions (such as contamination, temperature, humidity,

radiation, magnetic and electric fields, shock, and vibration) that externally influence the

performance of an item.

Epoxy: A polymerizable thermoset polymer containing one or more epoxide groups cured by its

reaction with amines, alcohols, phenols, carboxylic acids, acid anhydrides, and mercaptans. Animportant matrix resin in composites and structural adhesive. Epoxies generally have higher

physical properties than polyester resins. They are also more costly and difficult to process, and

less able to withstand sunlight.

Even Tension: Applying the same amount of tension to each end of roving in a ball.

Exotherm: The liberation or evolution of heat during the curing of a plastic product.

Exothermic Heat: Heat given off during polymerization by chemical ingredients as they reactand the resin cures.

Extend: To add fillers or low-cost materials in an economy producing endeavor. To add inertmaterials to improve void-filling characteristics and reduce crazing.

Extenders: Low-cost materials used to dilute or extend high-cost resins without extensive

lessening of properties.

Extruder: Machine that pushes molten plastic through small holes to form fibers.

F

Fabrication: The process of glass fiber production during which forming cakes are put into

creels and "roved" or fabricated onto doffs.

Fabricator: Manufacturer of reinforced plastic products.

Fall: Shape or pattern of chopped fibers as they drop from the chopper to the bed.

Fan or Curtain: Chopped bundles that fall or are thrown off the chopper and cot.

Fatigue: Failure or decay of mechanical properties after repeated applications of stress. Fatiguetests indicate a materials ability to resist cracking, which eventually causes failure due to a large

number of cycles.

Fatigue Life: How many cycles of deformation it takes before a test specimen will fail under a

given set of oscillating conditions (stresses and strains).


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Fatigue Limit: The maximum level under which a material can be stressed cyclically for an

infinite number of times before it fails.

Fatigue Strength: The maximum cyclical stress a material can withstand for a given number of

cycles before failure occurs. The residual strength after being subjected to fatigue.

Fiber: The major reinforcement material component in a composite matrix. Often, fiber is used

synonymously with filament.

Fiber Content: The amount of fiber present in a composite. This is usually expressed as a

percentage volume fraction or weight fraction of the composite.

Fiber Diameter Letter Designation: Fibers are generally classified in hundred thousandths, i.e.,

a "K" fiber has a mean average diameter of 50+ to 55 height. See chart below,

Fiber Direction: The orientation or alignment of the longitudinal axis of the fiber with respect to

a stated reference axis.

Fiber Glass: Primarily means glass in fiber form. Also used to describe composite processing

and applications, for example, fiber glass molding plant, fiber glass car.

Fiber Glass Reinforcement: Major material used to reinforce plastic. Available in mat, roving,

fabric and other forms, it is incorporated into both thermosets and thermoplastics.

Fiber Orientation: Fiber alignment in a non-woven or a mat laminate where the majority of

fibers are in the same direction, resulting in greater strength in that direction.

Fiber Pattern: Visible fibers on the surface laminate or molding. The thread size and weave ofglass cloth.

Fiber Reinforced Plastic (FRP): A general term for a composite that is reinforced with cloth,mat, strands, or any other fiber form.

Filament: A single, threadlike fiber of glass.

Filament Winding: Process in which a resin-saturated strand of glass filament is wound arounda rotating mandrel.

Filament Yarn: A yarn composed of continuous filaments assembled with or without twist.

Fill: The system of yarns running crosswise in a fabric (short for filling). Also known as weft.

see Warp

Filler: An inexpensive substance that is added to plastic resins to extend volume, improve

properties, and lower cost.


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Fillet: A rounded filing of the internal angle between two surfaces of a plastic molding.

Fines: Bundles that have been split apart into smaller bundles composed of only a few or singlefilaments. Fuzz is usually made of fines.

Finish:see Size

Fire Retardants:Chemicals that reduce a resins tendency to burn.

Fish Eye: Effect of surface contamination causing a circular separation of paint or gel coat.

Flammability: How fast a plastic material will burn when subjected to a particular ASTM test.

In this test, a flame is applied to one end of a strip of material. When the material starts burning

the flame is removed and the time to consume a given amount of material is measured. Units aremeasured in inches per minute (in/min.). Higher numbers indicate that the material will burn

faster under this particular tests conditions. S.E. means self extinguishing; S.E. classified

materials stop burning when the flame is taken away.

Flash: Portion of the charge that flows or is extruded from the mold cavity during the molding.

Also refers to extra plastic attached to a molding along the parting line that must be removedbefore the part is considered finished.

Flash Point: Lowest temperature at which a substance gives off enough vapors to form aflammable mixture.

Flexible Molds: Rubber or elastomeric plastic molds used for casting plastics. They can bestretched to remove cured pieces with undercuts.

Flexural Modulus:A number referring to a materials stiffness. It is used to calculate how far abar will bend when a bending load is applied. Units are normally millions of pounds per square

inch. (106 psi) - Giga Pascals (gPa). In two materials of equal thickness, the one with a higher

number is more resistant to deflection.

Flexural Strength: Also known as bending strength. Describes how much nonmoving load can

be applied to a bar before it yields or breaks. Units are normally thousands of pounds per squareinch. (103 psi) - Mega Pascals (mPa). Higher numbers indicate stronger materials that can

withstand a heavier load.

Flow: The movement of resin under pressure, allowing it to fill all parts of a mold. The gradualbut continuous distortion of a material under continued load, usually at high temperatures; also

called creep.

Flow Line: A mark on a molded piece made by the meeting of two flow fronts during molding.

Also called striae, weld mark, or weld line.


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Flow Marks: Wavy surface appearance of an object molded from thermoplastic resins, cased by

improper flow of resin into the mold.

Fly: Fibers that fly out into the atmosphere during handling and processing.

Foam: Lightweight, cellular plastic material containing glass-filled voids. Typical foams includeurethane, PVC, and polyester.

Force: The male half of the mold that enters the cavity, exerting pressure on the resin and

causing it to flow. Also called punch.

Forming: Process of glass fiber production during which fibers are drawn, attenuated from

molten glass and collected in forming cakes.

Forming Cakes or "Cakes": Package of glass fibers produced during forming. This package is

generally found on a tube placed on a forming carrier and sent through a drying/curing oven.

"Cakes" are subsequently put into a roving creel and collected together into a roving doff.

Fracture: When a surface ruptures without the laminate completely separating, or where there is

complete separation of a body because of external or internal forces.

Fracture Stress: The true, normal stress on the minimum cross-sectional area at the beginning

of fracture.

Fracture Toughness: The damage tolerance of a material containing initial flaws or cracks.

Used in aircraft structural design and analysis.

FRP: Acronym for fiber glass-reinforced or fiber-reinforced plastic, polymer or polyester.

Fuzz: Creel Fuzz - In glass fiber manufacturing, the broken filaments found around and on a

roving creel. Chopper Fuzz - In Composite Fabrication, the broken filaments found around theglasscutter or chopper.see Fines. In the field, the broken filaments found around a roving pallet.

Fuzz Plug: Small, broken, compacted filaments of glass that collect inside the guide eye tubesfeeding the chopper, preventing glass from running through.

G

Gate: Point at which molten thermoplastic enters the injection molding tool cavity.

Gel: A partial cure of plastic resins; a semisolid, jelly-like state similar to gelatin in consistency.

Gel: The initial jelly-like solid phase that develops during a resins formation from a liquid state.A semisolid network of solid aggregates in which liquid is held.


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Gelation: The point during resin cure when viscosity has increased so much that resin barely

moves when probed with a sharp instrument.

Gel Coat: Surface coat of a specialized, quick-setting polyester resin, either colored or clear,

providing cosmetic enhancement and weather ability to a fiberglass laminate. Gel coat is an

integral part of the finished laminate.

Gel Point: When a liquid begins to exhibit pseudo-elastic properties. This stage may be

conveniently observed from the inflection point on a viscosity time plot.

Gel Time: Time required to change a flowable liquid resin into a non-flowing gel.

GFRP: Glass fiber-reinforced plastic, polymer or polyester.

Glass Blends: When several different fiber types, i.e. different lengths and diameters, are

blended in the fiber slurry.

Glass Content: Percentage of glass in the compound.

Glass Fiber Wet-Process: Process of forming a glass mat on modified papermaking equipment.

Glass Transition: Reversible change in an amorphous polymer or amorphous regions of apartially crystalline polymer from or to a viscous, rubbery, or hard and relatively brittle

condition.

Glass Transition Temperature (Tg): The appropriate midpoint of the temperature range over

which glass transition takes place.

Good Side: Side of molding in contact with a mold surface.

Graphite Fiber: Fiber made from a precursor by oxidation, carbonization and graphitizationprocess (which provides a graphitic structure).

Green: Resin, which has not completely cured and is still rather soft and rubbery.

Green Strength: That ability of the material, while not completely cured, to undergo removalfrom the mold and handling without tearing or permanent distortion.

GRP: A derivation commonly used in Europe referring to glass-reinforced plastic, polymer orpolyester.

Glint: A visual defect in a fiberglass reinforced cured organic (usually corrosion- resistant resin)panel. The defect appears as many small visible unwet or foreign substances similar to a salt-

and-pepper effect. The defect is not visible before cure but appears at the panels exotherm.

Guide Pin: A pin which guides mold halves into alignment on closing.


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H

Hand: Fabric softness as determined by touch (individual judgment).

Hand Lay-up: The process of placing (and working) successive plies of reinforcing material or

resin-impregnated reinforcement in position on a mold by hand. Method of molding roomtemperature curing thermosetting polymers, mainly epoxies and polyesters, in association with

glass, mineral, or fiber reinforcements. Catalyzed resin mixtures are sprayed, brushed, or

spatulated on a mold. A precut reinforcing layer is laid on the wet resin. After the resin soaksinto the reinforcement, subsequent layers are built up to the required thickness and are cured,

removed from the mold and trimmed. Some variations of hand lay-up techniques are bag

molding, drape molding, vacuum molding and spray-up molding. Typical parts are custom auto

bodies and boat hulls.

Hardener: A substance or mixture added to a plastic composition to promote or control curingby taking part in it.

Hard Glass: A roving product that is not very soluble in acetone or styrene, causing individual

bundles to retain their integrity (hardness) and not filamentize in the matrix resin. Hard glass isoften stiff and brash. The size is generally less than 40% soluble in acetone.see Soft Glass

Hardness: Resistance to surface indentation usually measured by the depth of penetration (or

arbitrary units related to the depth of penetration) of a blunt point under a given load using a

particular instrument according to a prescribed procedure.

Heat Cleaning: Batch and continuous processes in which organic yarn binder is removed fromglass fabrics.

Heat Distortion Temperature: The temperature at which a material will bend under a given

load. It was developed for thermoplastic materials, which soften considerably when heated. It has

relatively little value as a design figure for thermosetting reinforced plastics. During this test, aload is applied in bending to cause 264 psi stress in the material. The temperature of the material

is then raised until the material bends one-tenth of an inch at the center. Units are measured in

degrees Fahrenheit (F) minus degrees Centigrade (C). Higher numbers mean that the materialcan be heated to a higher temperature before it deflects one-tenth of an inch under the arbitrary

load of 264 psi.

Heat Distortion Point:Temperature at which a materials strength begins to degrade. Now

called deflection temperature.

Heat Resistance: The ability of plastics and elastomers to resist deterioration due to elevated

temperatures.


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Heat Sink: A contrivance for the absorption or transfer of heat away from a critical element or

part. Bulk graphite is often used as a heat sink.

Helical Winding: In filament wound items, a winding in which a filament band advances along

a helical path, but not necessarily at a constant angle (except on cylinders).

Het-Acid Resin: Polyester resin with exceptional fire qualities.

High-Pressure Laminates: Laminates molded and cured at pressures not lower than 6.9 MP

(1.0 ksi), and more commonly between 8.3 to 13.9 Mpa (1.2 to 2.0 ksi).

Homogeneous: Describes a material with a uniform composition.

Homopolymer: A compound produced by polymerization.

Honeycomb: Manufactured product of resin-impregnated sheet material (paper, glass, fabric) or

metal foil, formed into hexagonal-shaped cells. Used as a core material in sandwich construction.

Hoop Stress: The circumferential stress in a material of cylindrical form subjected to internal orexternal pressure.

Hybrid: A composite laminate consisting of two or more composite material systems. Two ormore different fibers, such as carbon and glass or carbon and aramid, combined into a structure.

Hydraulic Press: A press in which molding force is created from pressure exerted by a fluid.

Hygroscopic: Material that absorbs moisture from the air.

Hysteresis: The energy absorbed in a complete cycle of loading and unloading. Mechanical

energy is converted into friction energy (heat).

I

Ignition Loss: With glass, the difference in weight before and after binder or size has been

burned off.

Impact Strength-Izod: A moving load is one that is moving when it strikes a bar. The effect ofsuch a load is denoted by the work "impact". The impact strength of a material is a measure of

how much energy is absorbed by the bar when it is broken by a moving weight. Izod is one of

many different test methods for measuring impact. Units are measured in foot pounds per inch ofwidth; sometimes given as foot pounds per inch of notch. Joules/Meter (J/M). Higher numbers

mean that the material will absorb more energy before it is broken by a moving weight.

Impact Test: Measure of the energy necessary to fracture a standard sample by an impulse load.


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Impregnate: In reinforced plastics, to saturate a reinforcement, especially fiberglass, with a

resin.

Inhibitor: A substance that retards polymerization, thus extending shelf life of a monomer. Also

used to influence gel time and exotherm.

Initiator: Peroxides used as sources of free radicals. They are used in free-radical

polymerization, for curing thermosetting resins, as cross-linking agents for elastomers and

polyethylene, and for polymer modification.

Injection Molding: Method of forming plastic to the desired shape by forcing a heat-softenedthermoplastic polymer into a relatively cool cavity under pressure or thermosetting polymer into

a heated mold.

Inorganic Pigments: Natural or synthetic metallic oxides, sulfides, and other salts that impartheat and light stability, weathering resistance, color, or migration resistance to plastics.

Insert: An integral part of plastic molding consisting of metal or other material that may bemolded into the part or pressed into position after the molding is completed.

In-Situ: In place. In the position which it will finally occupy, e.g. molding or forming foam.

Instron: Instrument for determining the tensile and compressive properties of materials.

Interface: A surface that lies between two different materials.

Interlaminar: Descriptive term pertaining to an object (for example, voids), event (for example,

fracture), or potential field (for example, shear stress) referenced as existing or occurringbetween two or more adjacent laminae.

Interlaminar Shear: Shearing force that produces a relative displacement between two laminaein a laminate along the plane of the interface.

Intumescent: Fire-retardant technology causing an otherwise flammable material to foam,forming an insulating barrier when exposed to heat.

Irreversible: Not capable of re-dissolving or re-melting. Chemical reactions that proceed in a

single direction and are not capable of reversal (as applied to thermosetting resins).

Isocyanate Plastics: Plastics based on resins made by the reaction or organic isocyanates withother compounds.

Isophthalic: Polyester resin based on isophthalic acid, generally higher in properties than ageneral purpose or orthothatic polyester resin.

Isotropic: Having uniform properties in all directions.


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Izod Impact Test: A test for shock loading in which a notched specimen bar is held at one end

and broken by striking, and the energy absorbed is measured.

J

Jackstrawing: Visual effect of glass fiber turning white in a cured laminate. It may not affectthe strength of a laminate, but could indicate air entrapment or water contamination.

K

Kevlar: An organic polymer composed of aromatic polyamides having a para-type orientation

(parallel chain extending bonds from each aromatic nucleus).

Knitted Fabric: A textile structure produced by interlooping one or more ends of yarn or

comparable material.

Knot: The means of joining strands of two doffs of roving. The knot is generally a reduced triple

loop surgeon's knot, square knot or overhand knot.

L

Laminate: Primarily means a composite material system made with layers of fiberreinforcement in a resin. Sometimes used as a general reference for composites, regardless of

how made. Examples of usage: laminate consumption by market, compression-molded laminate.

Land: Portion of a mold which provides the separation or cutoff of the flash from the molded

article; in the screw of an extruder, the bearing surface along the top of the flights; in anextrusion die, the surface parallel to the flow of material; in a semi-positive or flash mold, the

horizontal bearing surface; in a two-piece mold, a platform build up to the split line.

Lay: In glass fiber, the spacing of the roving bands on the roving package expressed in the

number of bands per inch; in filament winding, the orientation of the ribbon with some reference,

usually the axis of rotation.

Laydown: The degree of uniformity in thickness that a bed of chopped glass fibers exhibits

across the width of the chopped pattern.

Layer: The horizontal plane of doffs on a pallet. A pallet usually has four layers of twelve doffs

each. also see Cell
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Lay-up: Act of building up successive layers of polymer and reinforcement. Layers of catalyzed

resin and fiberglass or other reinforcements are applied to a mold in order to make a part. Also

refers to the reinforcing material placed in position in the mold, the process of placingreinforcing material in position in the mold, or the resin-impregnated reinforcement.

L/D Ratio: A term used to define an extrusion screw, which denotes the ratio of the screw lengthto the screw diameter.

Lengthwise Direction: Refers to the cutting of specimens and application of loads. For rods andtubes, lengthwise is the direction of the long axis. For other shapes of materials that are stronger

in one direction than in the other, lengthwise is the direction that is stronger. For materials that

are equally strong in both directions, lengthwise is an arbitrarily designated direction that may bewith the grain, direction of flow in manufacture, longer direction, etc.

Liquid-Crystal Polymer: A newer thermoplastic polymer that is melt process capable anddevelops high orientation in molding, resulting in tensile strength and high-temperature

capability.

Load-Deflection Curve: A curve in which the increasing tension or compression of flexural

load are plotted on the ordinate axis and the deflections caused by those loads are plotted on an

abscissa axis.

Loom: A mechanical device that interlaces fibers at right angles with varying degrees of weave

construction (weight, thickness and design). More modern looms are air jet but rapier and moretraditional shuttle equipment is still in use.

Loom Beam: A large, flanged cylinder onto which all warp yarns are wound and from which

yarns enter the loom.

Loop: Small open place in the strands due to excessive length of one or more strands.

Loss on Ignition: Weight loss, usually expressed as a percent of the total, after burning off an

organic sizing from glass fibers, or an organic resin from a glass fiber laminate.

Low-Pressure Laminates: Laminated, molded, and cured using pressures from 400 psi down toand including the pressure obtained by mere contact of the plies.

Low-Pressure Molding: The distribution of relatively uniform low pressure (200 psi or less)

over a resin-bearing fibrous assembly of cellulose, glass, asbestos, or other material, with orwithout application of heat from an external source, to form a structure possessing definite

physical properties.

Lubricant: A material added to most sizing to improve the handling and processing properties

of textile strands.


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M

Mandrel: The core tool around which resin-impregnated paper, fabric or fiber is wound to formpipes, tubes or structural shell shapes.

Manipulator: Highly efficient system eliminating the need for a press screw driven framestructure that opens and closes the mold in a controlled line of draw to prevent tool damage.

Mat: A fibrous material for reinforced plastic consisting of randomly oriented chopped

filaments, short fibers (with or without a carrier fabric) or swirled filaments loosely held together

with a binder.

Mat Binder: Resin applied to glass fiber and cured during the manufacture of mat that holds

fibers in place and maintains the mats shape.

Matched Metal Molding: A reinforced plastics manufacturing process in which matching male

and female metal molds are used (also called compression molding) to form the part with time,pressure and heat.

Matrix: The resin component of a polymer composite. Both thermoplastic and thermoset resinsmay be used, as well as metals, ceramic and glasses. (Plural: matrices.)

Mat Strength:The mats ability to resist being pulled apart under tension during impregnationand molding.

Matchsticks: Strand-to-strand adhesion. A matchstick is a wide bundle that has 3 to 4 times asmany filaments than the majority of bundles in the bed.

Mechanical Properties:A materials properties, such as compressive and tensile strength andmodulus, that are associated with elastic and inelastic reaction when force is applied. The

individual relationship between stress and strain.

Melamine: Thermoset resin.

Metallic Fiber: Manufactured fiber composed of metal, plastic-coated metal, metal-coated

plastic or core completely covered by metal.

Microballoons: Microscopic bubbles of glass, ceramic or Phenolic, used as a filler or to create

syntactic foam or putty mixtures.

Microcracking: Crack formed in composites when thermal stresses locally exceed the strength

of the matrix.

Micron: One micron = .001 millimeter = .00003937 inch.

Mil: Unit used to measure the diameter of glass fiber strands (1 mil = 0.001 in.).


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Milled Fiber: Continuous glass strands hammer milled into very short glass fibers. Useful as

inexpensive filler or anti-crazing reinforcing filler for adhesives.

M.I.T:see Multiple Insert Tooling

MPG:see Mold Protection Guard

Modulus, Initial: The slope of the initial straight portion of a stress strain or load-elongationcurve.

Modulus of Elasticity: How much a material can bend without losing its ability to return to itsoriginal physical properties.

Moisture: The amount of volatiles on the glass expressed as a percentage of the total weight.

Moisture Content: The amount of moisture in a material determined under prescribed

conditions, expressed as a percentage of the mass of the moist specimen; that is, the mass of thedry substance plus the moisture present.

Mold: The cavity or matrix into or on which the plastic composition is placed and from which it

takes form. The tool used to fabricate the desired part shape.

Molded Edge: An edge that is not physically altered after molding for use in final form, and

particularly one that does not have fiber ends along its length.

Molding: The forming of a polymer or composite into a solid mass of prescribed shape and size.

Molding Compounds: Plastics in a wide range of forms meeting specific processingrequirements. Granules or pellets are popular forms.

Molding Cycle: The period of time required for the complete sequence of operations on amolding press to produce one set of moldings.

Molding Pressure: Pressure applied to the ram of an injection machine or compression or

transfer press forcing softened plastic to completely fill mold cavities.

Molding Pressure, Compression: Unit pressure applied to material in the mold. The area is

calculated from the projected area taken at right angles to the direction of applied force and

includes all areas under pressure during complete closing of the mold. Unit pressure is calculatedby dividing the total force applied by the projected area, expressed in pounds per square inch.

Mold Protection Guard: Prevents over pressurization of the RTM mold during the injection

process.

Mold-Release Agent: Lubricant, liquid or powder (often silicone oils and waxes) that preventsmolded articles from sticking in the cavity.


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Mold Shrinkage: Immediate shrinkage that occurs when a part is removed from a mold and

cooled to room temperature; the difference in dimensions, expressed in inches between a

molding and the mold cavity in which it was molded (at normal temperature measurement); theincremental difference between the dimensions of the molding and the mold from which it was

made, expressed as a percentage of the dimensions of the mold.

Monomer: A simple molecule capable of reacting with like or unlike molecules to form a

polymer; the smallest repeating structure of a polymer (mers); for addition polymers, this

represents the original unpolymerized compound.

Multiple-Cavity Mold: A mold with two or more mold impressions; that is, a mold producing

more than one molding per molding cycle.

Multiple Insert Tooling: Low-risk, high-output composite tooling breakthrough. MIT tooling

technology offers the composite molder quick-change multiple mold surfaces without multipletooling costs. Each surface is an exact clone of its counterpart, guaranteeing mold cavity

accuracy and replication of molded parts.

N

Nesting: In reinforced plastics, placing of plies of fabric so that the yarns of one ply lie in thevalleys between the yarns of the adjacent ply (nested cloth).

NOL Ring: Parallel filament wound test specimen used in whole or in part to measure a

materials mechanical strength properties.

Non-Air-Inhibited Resin: Resin in which the surface cure will not be inhibited or stopped bythe presence of air.

Non-Woven Fabric: A textile structure produced by bonding or interlocking fibers, or both,accomplished by mechanical, chemical, thermal and/or solvent means.

Notch Sensitivity:The extent to which a materials sensitivity to fracture is increased by asurface in homogeneity such as a notch, a sudden change in section, a crack or a scratch. Low

notch sensitivity is usually associated with ductile materials and high notch sensitivity with

brittle materials.

O

Orange Peel: Gel coated or painted finish that is not smooth and is patterned similar to an

orange's skin.
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Organic: Matter originating in plant or animal life, or composed of chemicals of hydrocarbon

origin, either natural or synthetic.

Orientation: Position with relation to flow of polymer in the mold.

Orthophthalic Resin: Polyester resin based on Orthophthalic acid, also known as a generalpurpose resin (GP).

Overlay Sheet: Non-woven fibrous mat (of glass, synthetic fiber or other material) used as the

top layer in a cloth or mat lay-up to provide a smoother finish, minimize the appearance of a

fibrous pattern, or permit machining or grinding to a precise dimension. Also called surfacingmat.

Overspray: A specially formulated binder applied to texturized yarn that helps retain the yarn

bulk after texturizing.

P

Parting Line: A mark on a molded piece where mold sections have met in closing.

PBT: Polybuthlene Therephthalate (Thermoplastic Polyester Resin).

PET: Polyethylene Terephthalate (Thermoplastic Polyester Resin).

Phenolic Resin: Thermosetting resin produced by the condensation of an aromatic alcohol with

an aldehyde, particularly of phenol with formaldehyde. Used in high-temperature applicationswith various fillers and reinforcements.

Pigment: Colorant added to gel coat or resin.

Pinholes: Small holes on the exposed gel coated surface that are about the diameter of commonpins and may be easily counted.

Pit: Small regular or irregular crater in the surface of a plastic, usually of equal width and depth.

Plastic: Material of which an essential ingredient is an organic polymer of large molecular

weight and also contains hardeners, fillers and reinforcements; is solid in its finished state; andhas been shaped by flow during some stage of its manufacture or processing. Made of plastic. A

plastic may be either thermoplastic or thermoset.

Plastic Deformation: Change in dimensions of an object under load that is not recovered when

the load is removed; opposed to elastic deformation.


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Plasticizers: Material added to increase a plastics workability and flexibility. Normally used in

thermoplastics. Also a lower molecular weight material added to epoxy to reduce stiffness and

brittleness, thereby resulting in a lower glass transition temperature for the polymer.

Plastic Tooling: Tools (mostly for metal forming trades) constructed of plastics, generally

laminates or casting materials.

Platens: Mounting plates of a press to which the entire mold assembly is bolted.

Plied Yarn: Yarn formed by twisting two or more single yarns together in one operation.

(Synonyms: folded yarn, formed yarn)

Plug: A composite industry term for a pattern or model.

Ply: The number of single yarns twisted together to form a plied yarn; also the number of plied

yarns twisted together to form a cord. The individual yarn in a plied yarn or in a cord. One of

several layers of fabric.

Poisson's Ratio: The ratio of transverse strain to axial strain during axial load.

Polyamide: A polymer in which the structural units are linked by amide or thioamide groupings.

Many polyamides are fiber-forming.

Polyester Combination Yarn: A polyester/fiber glass hybrid yarn.

Polyester (Unsaturated): Product of an acid-glycol reaction commonly blended with a

monomer to create a polymer resin. In its thermosetting form it is the most common resin used in

the FRP industry.

Polymer: Chain molecule composed of many identical groups, commonly found in plastics.

Polymerization: Chemical bonding of polymer molecules during the curing reaction.

Porosity: Entrapped gas bubbles or voids in a gel coat film.

Positive Mold: Mold that applies pressure to the piece being molded without material escaping.

Post Bake: see Post Cure

Post Cure: Heat cycle that a roving doff goes through after fabrication. Generally used to help

"set" the ribbon on the outside of the doff, improving the doff's stability and resistance to

package collapse.

Pot Life: The length of time that catalyzed resin retains a viscosity low enough to be used in

processing.


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PPO: Polyphenylene Oxide (Thermoplastic Resin).

PPS: Polyphenylene Sulfide (Thermoplastic Resin).

Preform: Preshaped fibrous reinforcement formed when chopped fibers are distributed by air,

water flotation or vacuum over the surface of a perforated screen to the approximate contour andthickness desired in the finished part. Also, a preshaped fibrous reinforcement of mat or cloth

formed to the desired shape on a mandrel or mock-up prior to being placed in a mold press. Also,

a compact "pill" formed by compressing premixed material to facilitate handling and control theuniformity of charges for mold loading.

Pregel: An unintentional extra layerof cured resin on part of a reinforced plastics surface. (notrelated to gel coat)

Premix: A compound prepared prior to and apart from the molding operation containing allcomponents required for molding: resin, reinforcement, fillers, catalysts, release agents and other

compounds.

Prepreg: Either ready-to-mold material in sheet form or ready-to-wind material in roving form,

which may be cloth, mat, unidirectional fiber or paper impregnated with resin and stored for use.

The resin is partially cured to a B-stage and supplied to the fabricator, who lays up the finishedshape and completes the cure with heat and pressure. The two distinct types of prepreg available

are (1) commercial prepregs, where the roving is coated with a hot melt or solvent system to

produce a part meeting specific customer requirements, and (2) wet prepreg, where the basicresin is installed without solvents or preservatives but has limited room-temperature shelf life.

Pressure Bag: A membrane conforming to the inside of a laminate laid up on a mold. The

membrane or bag is then inflated, applying pressure that consolidates and densifies the laminate.

Print Through:Distortion in a parts surface through which the pattern of the core or fiberglassreinforcement is visible. Also known as print out, telegraphing or read through.

Pultrusion: Continuous process for manufacturing composites with a constant cross-sectionalshape. The process consists of pulling a fiber-reinforcing material through a resin impregnation

bath and shaping die, where the resin is subsequently cured.

Putty: Thickened mixture of resin made by adding fillers and reinforcing fibers.

Q
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R

Reaction Injection Molding (RIM): Process for molding polyurethane, epoxy and other liquidchemical systems. Combining two to four components in the proper chemical ratio is

accomplished by a high-pressure impingement-type mixing head, from which mixed material is

delivered into the mold at low pressure, where it reacts (cures).

Re-Chop: Bundles that have clung to the chopper or cot and are chopped again into shorter

lengths. Re-chop causes excessive chopper fuzz as the strands are cut and mashed into smallerbundles.

Reinforced Molding Compound: Compound consisting of a polymer and reinforcement fiber

or filler, supplied by a raw material producer as ready-to-use materials.

Reinforced Plastics: Molded, formed, filament-wound, tape-wrapped or shaped plastic partsconsisting of resins to which reinforcing fibers, mats and fabrics have been added before the

forming operation to provide strength properties greatly superior to those of the base resin.

Reinforced Reaction Injection Molding (RRIM): A reaction injection molding with

reinforcement added.see Reaction Injection Molding

Reinforcement: Strong material bonded into a matrix to improve its mechanical properties.

Reinforcements are usually long fibers, chopped fibers, whiskers and particulates. The termshould not be used synonymously with filler.

Release Agent: Compound used to reduce surface tension or adhesion between a mold and a

part.

Resin: Solid or pseudo-solid organic material, usually of high molecular weight, that tends toflow when subjected to stress. Most resins are polymers. In reinforced plastics, the material used

to bind together the reinforcement material.see Matrix and Polymer

Resin Content: The amount of resin in a laminate, expressed either as a percent of total weight

or total volume.

Resin-Rich Area: Localized area filled with resin and lacking reinforcing material.

Resin-Starved Area: Localized area of insufficient resin, usually identified by low gloss, dry

spots or fiber showing on the surface.

Resin Tearing: Separation of pigments in a gel coat affecting cosmetic appearance.

Resin Transfer Molding (RTM): A process in which catalyzed resin is transferred or injectedinto an enclosed mold where fiberglass reinforcement has been placed.

Rib: Reinforcing member of a fabricated or molded part.


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Ribbon: The propensity of glass bundles to "stick" together and act as a strand or end.

RIM: see Reaction Injection Molding.

Room Temperature Curing Adhesives: Adhesives that set to handling strength within an hour

at 68 to 86 degrees F, and later reach full strength without heating.

Roving: A collection of untwisted strands wound together into a doff (ball). Also, another namefor the fabrication process step.

Roving Ball: A term used to describe the supply package offered to the winder. It consists of anumber of ends or strands wound to a given outside diameter onto a length of cardboard tube.

Roving Doff or "Doff": The final product sold to the customer. Made by roving or pullingtogether a group of forming cakes. (the number of which depends upon the product being made)

RP: Reinforced plastic, polymer or polyester.

RRIM: see Reinforced Reaction Injection Molding

RTM: see Resin Transfer Molding

RTM Light: see Vacuum Molding

RTP: Sometimes used to distinguish reinforced thermoplastic from reinforced thermosetting

plastic.

Rule-of-Mixtures:A composites properties are the combination of properties in its twoconstituent materials. The composite property equals the amount of fiber property multiplied by

the volume percentage of fiber, plus the amount of matrix property multiplied by the volume

percentage of matrix.

Run-Out: The process of pulling glass from the doff to the chopper.

Runner: The channel through which thermoplastic material moves through a mold.

S

SAN: Styrene Acrylonitrile (Thermoplastic Resin).

S Glass: A family of magnesium-alumina-silicate glasses with a certified chemical composition

that conforms to an applicable material specification and produces high mechanical strength.


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Sandwich Constructions: Panels composed of a lightweight core material, such as honeycomb

or foamed plastic, to which two relatively thin, dense, high-strength or high-stiffness faces or

skins are adhered.

Scrim: Light woven or non-woven fabric with relatively large openings between the yarns, used

to reinforce paper and other products.

Secton Beam: Flanged cylinder onto which yarn is drawn and accumulated from yarn bobbins or

packages.

Serving: Wrapping of yarn around a product in one or more layers to form a protective covering.

Set-Up: To harden, as in curing.

Sewing Thread: Flexible small diameter yarn or strand, usually treated with a surface coating

and/or lubricant, used to stitch one or more pieces of material together or stitch an object to a

material.

Shear: Engineering term referring to force normally applied to the surface of a given material.

The movement between plies of a laminate is referred to as interlaminate shear.

Shear Edge: Cut-off edge of the mold.

Sheet Molding Compound (SMC): Composite of fibers, usually polyester resin, pigments,

fillers and other additives, that have been compounded and processed into sheet form to facilitate

handling in the molding operation.

Shelf Life: Allowable storage time before a product must be used.

Shore Hardness:A materials resistance to indentation from a spring-loaded indenter. Higher

numbers indicate materials with greater resistance.

Shrinkage: The relative change in dimension between the length measured on the mold when it

is cold and the length of the molded object 24 hours after it has been taken out of the mold.

Single Yarn: The simplest strand of textile material suitable for weaving, knitting and otheroperations.

Sink Mark: A shallow depression or dimple on the surface of an injection molded part due to itssurface collapsing from local internal shrinkage after the gate seals; an incipient short shot.

Size: Treatment applied to glass fiber that allows resin and glass to adhere to one another. Also

allows glass fiber to be conveniently handled.

Skein: A loose coil of roving or strands generally used as a Quality Control sample.


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Skin Coat: First layer of laminate next to the gel coat.

Slashing: Applying size to a width of warp yarns on a continuous basis.

Slink: Glass bundles thrown off the chopper or cot during chopping.

Sliver: A term describing the geometry of fibrous glass reinforcement in the forming operation.

For example, 2K37 S/2 means a configuration that makes a nominal fiber diameter in the "K"range (3700 yards to a pound) and is split into two discrete bundles in the forming cake.

Sluffing:see Doff Collapse

SMC:see Sheet Molding Compound

Snarl:see Birdnest

Soft Glass: A roving product whose sizing is moderately soluble in acetone or styrene, resultingin bundles that tend to open readily or filamentize the matrix resin. The size is generally between

50% and 80% soluble in acetone.

Solid: The amount of sizing on glass expressed as a percentage of the total weight.

Solvent Resistance: The non-swelling of a material; also, a materials ability to resist being

dissolved by a particular solvent.

Specific Gravity:A materials weight in relation to the weight of an equal volume of water. For

example, a material with a Specific Gravity of 2.0 weighs twice as much as an equal volume of

water. Because specific gravity is a ratio of values for two materials, there are no units. Highernumbers indicate heavier materials.

Specific Heat (Thermal Capacity): The amount of heat needed to raise the temperature of onepound of material one degree Fahrenheit (F). Units are measured in BTUs per pound per degree

(BTA/LB/F) - Joules/Kilogram Kelvin (J/KgK). Higher numbers indicate more input heat

energy is needed to raise the temperature of a material.

Specimen: An individual piece or portion of a sample used for a specific test; also, of specificshape and dimensions.

Splice : Joining two ends of yarn by intertwining, knotting, overlapping or adhering themtogether.

Split: One bundle.

Split Mold: A mold whose cavity is formed of two or more components held together by an

outer chase. The components are known as splits.


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Spray-Up: Technique in which a spray gun is used as an applicator tool. In reinforced plastics,

for example, fibrous glass and resin can be simultaneously deposited in a mold.

Sprue: Connector between the runner and nozzle in an injection-molding machine.

Splitting Efficiency: Ratio of the actual number of ends divided by the theoretical number ofends in a roving doff, expressed as a percentage.

Staple: Filaments produced in short lengths from the bushing (usually less than 17 inches)

gathered into strands or sliver.see Continuous Filament

Starved Area: Portion of a plastic part without sufficient resin to completely wet out the

reinforcement. Usually due to improper wetting, impregnation or excessive molding pressure.

Static: Buildup of an electrical charge causing the chopper roving to "cling" or stick to the

chopper, line and/or people. The static level is quantified by measuring the electrical field

strength in kilovolts per inch.

Sticker:see Trapped End

Stiffness: The relationship of load to deformation; a term often used when the relationship of

stress to strain does not conform to the definition of Young's modulus.

Strand: In the roving process or shop, a primary group of bundles gathered together in a creel. A

strand is that which is pulled out of a doff; also a plurality of drawn and elongated individual

filaments combined together to form an individual strand. Strands are held together and protectedby sizing.

Strand Count: According to the U.S. Yardage System, the length in hundreds of yards of asingle strand having a mass of one pound. In the European TEX System, the mass in grams of a

strand 1000 meters in length.

Strand Integrity:The sizes ability to keep all filaments in a bundle stuck together during

chopping. Good strand integrity is required for good flow in or wet-through and wet-out on the

mold.

Strength, Flexural: Maximum stress that can be borne by surface fibers in a beam in bending.

Flexural strength is the unit resistance to maximum load prior to failure by bending, usually

expressed in pounds per square inch.

Stress-Strain: Stiffness, expressed in pounds per square inch or kilograms per square

centimeter, at a given strain.

Stress-Strain Curve: Simultaneous readings of load and deformation, converted to stress and

strain, plotted as ordinates and abscissa to obtain a stress-strain diagram.


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Structural Reaction Injection Molding (S-RIM): Evolution of two other plastic molding

processes, RIM and RTM. S-RIM uses the fast polymerization reactions of RIM-type polymers,

its intensive resin mixing procedures and its rapid resin injection rates. S-RIM also employspreforms like RTM to obtain composite mechanical properties.

Styrene/Acetone Solubility: Percentage of sizing on glass fiber dissolved off the strand instyrene or acetone after soaking in the solvent.

Styrene Monomer: A water-thin liquid monomer used to thin polyester resins and act as thecross-linking agent.

Surfacing Mat: Very thin mat, usually 180 to 510 mm (7 to 20 mil) thick, used primarily to

produce a smooth, resin-rich surface on a reinforced plastic laminate, or for precise machining or

grinding.see Veil

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.

T

Tack: Surface stickiness.

Tack Free: Surface which is not sticky after cure.

Tangent Modulus: Slope of the line at a predefined point on a static stress-strain curve,

expressed in force per unit area per unit strain. This is the tangent modulus at that point in shear,tension or compression, as the case may be.

Tape: A narrow fabric whose mass per unit area is less than 0.5 kg/m 2 (0.1 LB/ft2) for each25.4 mm (1 in.) of width; used primarily for utilitarian purposes.

Tenacity: Term used in yarn manufacture and textile engineering to denote the strength of a yarnor filament of a given size. Numerically, it is expressed as 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: Engineering term referring to the amount of stretch a sample experiencesduring tensile strain.

Tensile Load: Lo ad applied away from and to opposite ends of a given sample.

Tensile Modulus: When a bar is pulled in tension, it gets longer. Tensile modulus calculates

how much longer it will get when a certain load is applied. Units are normally millions of pounds


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per square inch. (10 6 psi) - Giga Pascals (gPa). Higher numbers indicate materials that do not

elongate as much as others under equal tensile loading conditions.

Tensile Strength: The amount of nonmoving load a bar can withstand before it breaks due to

elongation. Units are normally thousands of pounds per square inch. (103 psi) - Mega Pascals

(mPa). Higher numbers indicate materials that can withstand a stronger pull before breaking.

Tensile Stress: Normal stress caused by forces directed away from the plane on which they act.

Tension Device: A mechanical or magnetic device that controls tension.

TEX: A unit for expressing linear density, equal to the mass in grams of 1 km of yarn, filament,

fiber or other textile strand.

Texturized Glass Yarn: Yarn processed from continuous filaments that have been disoriented,

adding bulk.

Thermal Coefficient of Expansion: Measures how much the length of a material will change

when it is heated or cooled. The value given is based on the inch as a unit. The number given

shows how much one-inch of material will increase if its temperature is raised one degreeFahrenheit. Units are expressed in inches per inch per degree Fahrenheit (in/in/F) -

Meters/Meter/C. Higher numbers mean that the material will expand or lengthen more for each

degree that its temperature increases. Smaller numbers indicate relative stability to changes intemperature.

Thermal Conductivity (K factor): The amount of heat transferred by conduction; i.e., how

much heat is transferred from one side of a plate to the other. It is measured as BTUs (units of

heat in the English system) per hour per unit area (square feet) for a thickness of one inch and atemperature difference of one degree Fahrenheit between both sides of the plate. Units are

expressed as BTU/hr/sq/F/inch. - Watt/(Meter Deg Kelven) W/MK. Higher numbers mean thatthe material will absorb more energy before it is broken by a moving weight.

Thermoplastic: Capable of being repeatedly softened by an increase of temperature andhardened by a decrease in temperature. Applicable to those materials whose change upon heating

is substantially physical rather than chemical, and that in the softened stage, they can be shaped

by flow into articles by molding or extrusion.

Thermoplastic Polyesters: Class of thermoplastic polymers in which the repeating units are

joined by ester groups. The two important types are (1) polyethylene terephthalate (PET), whichis widely used as film, fiber and soda bottles; and (2) polybutylene terephthalate (PBT),

primarily a molding compound.

Thermoset: A material that undergoes a chemical reaction caused by heat, catalyst or other

condition, which results in the formation of a solid. Once it becomes a solid, it cannot be

reformed.


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Thermosetting Polyesters: Class of resins produced by dissolving unsaturated, generally linear,

alkyd resins in a vinyl-type active monomer such as styrene, methyl styrene, or diallyl phthalate.

Cure is effected through vinyl polymerization using peroside catalysts and promoters or heat toaccelerate the reaction. The two important commercial types are (1) liquid resins that are cross-

linked with styrene and used either as impregnants for glass or carbon fiber reinforcements in

laminates, filament-wound structures and other built-up constructions, or as binders for chopped-fiber reinforcements in molding compounds, such as sheet molding compound (SMC), bulkmolding compound (BMC) and thick molding compound (TMC); and (2) liquid or solid resins

cross-linked with other esters in chopped-fiber and mineral-filled molding compounds (for

example, alkyd and diallyl phthalate).

Theoretical End Count: The maximum number of bundles in a roving doff; for example, a

roving doff made with 18 forming cakes in the creel that were "split out" 4 ways in forming willhave 64 theoretical ends.

Thickeners: Material added to resin to thicken it or raise its viscosity index so that it will not

flow as readily.

Thixotropic: The property of becoming a gel at rest, but liquefying again on agitation.

Tooling Gel Coat: Gel coat formulated for mold surfaces.

Transfer: The smooth and successful transition from one roving doff to another during

processing.

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

Trapped End: A loop embedded into a doff during the roving process that gets stuck duringrun-out with such tenacity that it prevents the entire strand from running freely to the chopper.

Tube Stoppage or Plug: The failure of glass to run through metal tubes or guide-eyes from the

creel to the chopper. Usually caused by a large knot or small birdnest becoming stuck inside the

tube or guide-eye.

Tur

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