A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
A
Abrasion
The wearing away of materials by friction. Particles become detached by a combined cutting, shearing and tearing action.
Absorbed Moisture
Moisture that has entered a solid by absorption and has physical properties not substantially different from ordinary water at the same temperature and pressure.
Accelerated Test
A test procedure in which conditions are increased in magnitude to reduce the time required to obtain a result. To reproduce in a short time the deteriorating effect obtained under normal service conditions.
Accelerator
A material which, when mixed with a catalyzed resin, will speed up the chemical reaction between the catalyst and resin. Also known as 'promoter'.
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 that 100%.)
Additive
A constituent component that may be added to the composite matrix to modify its properties and in general, enhance its performance. Additives include catalysts, colorants, flame retardants and other ingredients that expand and improve the capabilities of the matrix. See also filler.
Adherend
A body that is held to another body, usually by an adhesive. A detail or part prepared for bonding.
Adhesion
The state in which two surfaces are held together at an interface by mechanical or chemical forces or interlocking action or both.
Adhesion Promoter
A coating applied to a substrate before it is coated with an adhesive, to improve the adhesion of the plastic. Also called primer.
Adhesive
The method of joining two substrates using either paste, liquid or film.
Adhesive Failure
Rupture of an adhesive bond such that the separation appears to be at the adhesive-adherend interface.
Adhesive Film
A synthetic resin adhesive, with or without a film carrier fabric, usually of the thermosetting type, in the form of a thin film of resin, used under heat and pressure as an interleaf in the production of bonded structures.
Adhesive Strength
Strength of the bond between an adhesive and an adherend.
Aging
The effect on materials of exposure to an environment for an interval of time. The process of exposing materials to an environment for an interval of time.
Air Entrapment
Occlusion of air in a resin or resin glass system, giving rise to blisters, bubbles or voids in the system.
Air Splice
The coupling between two roving doffs which is made by a jet of air entwining/snarling the two strands together. The air splice is used instead of a knot.
Air Vent
Small outlet, to prevent entrapment of gases.
Air-Bubble Void
Air entrapment within and between the plies of reinforcement or within a bond line or encapsulated area; localized, non interconnected, spherical in shape.
Anisotropy
The tendency of a material to exhibit different along the directions parallel to the length or width into the lamination planes; or parallel to the thickness into the planes perpendicular to the lamination.
Anti-Static Agents
Agents which, when added to the molding material or applied on the surface of the molded object, make it less conducting (thus hindering the fixation of dust).
Antioxidant
A substance that when added in small quantities to the resin, prevents its oxidative degradation and contributes to the maintenance of its properties.
Aramid
Aromatic polyamide fibers characterized by excellent high-temperature, flame-resistance, and electrical properties. Sometime refer to as AFRP.
Areal Weight
The weight of fiber per unit area (width x length) of tape or fabric.
Ash Content
The solid residue remaining after a reinforcing substance has been incinerated (or strongly heated).
Aspect Ratio
The ratio of length to diameter of a fiber.
Autoclave
A closed vessel that permits application of pressure and heat used for processing composite materials.
Axial Winding
A type of filament winding in which the filaments are parallel to the axis.
B
Bag Molding
A process in which the consolidation of the material in the mold is effected by the application of fluid or gas pressure through a flexible membrane.
Bag Side
The side of the part that is cured against the vacuum bag.
Bagging
Applying an impermeable layer of film over an uncured part and sealing the edges so that a vacuum can be drawn.
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 lateral directions.
Balanced Laminate
A composite laminate in which all laminate at angles other than 0o and 90o occur only in + pairs (not necessarily adjacent) and are symmetrical around the centerline.
Bare Glass
The glass as it flows from the bushing in fiber form, before a binder or sizing is applied.
Bearing Strength
The maximum bearing stress that can be sustained. Also, the bearing stress at that point on the stress-strain curve where the tangent is equal to the bearing stress divided by n% of the bearing hole diameter.
Bearing Stress
The applied load in pounds sustained by a specimen divided by the bearing area.
Bias Fabric
A fabric in which warp and fill fibers are at an angle to the length.
Biaxial Winding
A type of filament winding in which the helical band is laid in sequence, side by side, with no crossover of the fibers.
Bi-Directional Laminate
A reinforced laminate in which the fibers are oriented in 2 directions.
Binder
A coating applied to the surface of a chopped glass mat or preform which is then cured. The binder holds the previously sized glass bundles or ends together in the roving operation into a stable shape or form.
Bisphenol A
A condensation product formed by 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.
Bladder
An elastomeric lining for the containment of pressurization medium in filament-wound structures, or for the manufacture of composite structures
Bleeder Cloth
A nonstructural layer of material used in the manufacture of composite parts to allow the escape of excess gas and resin during cure. The bleeder cloth is removed after the curing process is complete and is not part of the final composite.
Bleedout
The excess liquid resin appearing at the surface primarily occurring during filament winding.
Blister
Undesirable rounded elevation of the surface of a plastic, whose boundaries may be more or less sharply defined, resembling in shape a blister on the human skin. The blister may burst and become flattened.
Bobbin
The spool or shipping package on to which textile yarns are wound.
Bond
The adhesion and grip of a material to other surfaces against which it is placed.
Bond Area
The nominal area of interface between two elements across which adhesion develops or may develop
Bond Strength
The measurement of the stress needed to separate two bonded surfaces calculated using the load/bond area.
Bond Stress
The force per unit area necessary to rupture a bond
Braid/Braider
A narrow tubular or flat fabric produced by intertwining a single set of yarns according to a definite pattern.
Breather
A loosely woven material, such as glass fabric, which serves as a continuous vacuum path over a part but does not come in contact with the resin. The breather is removed after the curing process is complete and is not part of the final composite.
Bridging
Condition in which fibers do not move into or conform to radii and corners during molding, resulting in voids and dimensional control problems.
C
Cabled Yarn
Yarn that is plied more than once; yarn made by plying two or more previous plied yarns.
Cake
A term applied to the glass package that is produced in the forming department. Also used as forming cake package, forming cake and cake package. All terms are synonymous.
Carbon
An element common to all organic substances. Graphite is one of the forms under which carbon occurs in nature (as is diamond)
Carbon/Carbon
A composite of carbon fiber in a carbon matrix.
Carbon Fiber
An important reinforcing fiber known for its light weight, high strength, and high stiffness that is commonly produced by pyrolysis of an organic precursor fiber (often polyacrylonitrile (PAN) or rayon) in an inert atmosphere.
Casting
The process of pouring the resin and fillers (and possibly fibers) into a mold.
Catalyst
A substance that changes the rate of a chemical reaction without itself undergoing permanent change in composition or becoming a part of the molecular structure of the product. A substance that markedly speeds up the cure of a compound when added in minor quantity as compared to the amounts of primary reactants.
Catenary
A measure of the difference in length of the strands in a specified length of roving as a result of unequal tension; the tendency of some strands in a taut horizontal roving to sag lower than the others.
Caul Plates
Smooth metal, plastic, or rubber plates free of surface defects, used in contact with the lay-up during the curing process to transmit normal pressure and provide a smooth surface on the finished part. A caul plate must be the appropriate size and shape for the composite lay-up with which is will be used.
Cavity
The space inside a mold in which a resin or molding compound is poured or injected. The female portion of a mold. That portion of the mold that encloses the molded article (often referred to as the die). Depending on the number of such depressions, molds are designated as single cavity or multiple cavity.
Cell
In honeycomb core, a cell is a single honeycomb unit, usually in a hexagonal shape.
CFRP
Carbon fiber-reinforced plastic
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.
Chopped Strand
Continuous roving that is chopped into short lengths for use in mats, spray-up or molding compounds.
Chopped Strand Mat
A fiberglass reinforcement that utilizes continuous rovings that are cut into short strands, arranged in a random pattern and held together with a binder.
Co-Cured
Cured and simultaneously bonded to another prepared surface.
Coefficient of Thermal Expansion (CTE)
The change in length (or volume) per unit length (or volume) produced by one degree Celsius rise in temperature.
Cohesion
The propensity of a single substance to adhere to itself. The internal attraction of molecular particles toward each other. The force holding a single substance together.
Compaction
The application of a temporary vacuum bag and vacuum to remove trapped air and compact the lay-up.
Composite
A homogeneous material created by the synthetic assembly of two or more materials (a selected filler or reinforcing elements and compatible matrix binder) to obtain specific characteristics and properties. Composites are subdivided into classes on the basis of the form of the structural constituents; Laminar - Composed of layer or laminar constituents; Particular -The dispersed phase consists of small particles; Fibrous -The dispersed phase consists of fibers; Flake -The dispersed phase consists of flat flakes; Skeletal -Composed of a continuous skeletal matrix filled by a second material.
Compression Mold
A mold which is open when the material is introduced and which shapes the material by heat and by the pressure of closing.
Compound
An admixture of a polymer with other ingredients such as reinforcements, fillers, and additives. A thermoset compound normally consists of the necessary ingredients for the finished product.
Compression Molding
A technique for molding thermoset plastics in which a part is shaped by placing the fiber and resin into an open mold cavity, closing the mold, and applying heat and pressure until the material has cured or achieved its final form.
Compressive Strength
The ability of a material or structure to resist a crushing or buckling force. The maximum compressive load sustained by the material or structure divided by the original cross-sectional area of the material or structure.
Conditioning
Subjecting a material to a prescribed environmental and/or stress history before testing.
Conformability
Ability of the mat to conform to difficult shapes without causing wrinkles or leaving excessively resin-rich or glass-rich radii, which may craze.
Contact Molding
A process for molding reinforced plastics in which reinforcement and resin are placed on a mold, cure is either at room temperature using a catalyst-promoter system or by heat in an oven and no additional pressure is used.
Continuous Filament
An individual, small-diameter reinforcement that is flexible and indefinite in length.
Continuous Roving
Parallel filaments coated with sizing, gathered together in single or multiple strands and wound into a cylindrical package. It can be used to provide continuous reinforcement in woven roving, filament winding, pultrusion, prepregs or high-strength molding components. It also can be chopped (see Chopped Strand).
Conventional Roving
Roving that is assembled from several forming packages using a creel and a roving winder. Typical characteristics are multiple ends, 3-inch diameter centers, a tube core and some catenary.
Core
The central component of a sandwich construction to which the sandwich faces or skins are attached; also, part of a complex mold that forms undercut parts.
Corrosion Resistance
The ability of a material to withstand contact with ambient natural factors or those of a particular artificially created atmosphere, without degradation or change in properties.
Count
For fabric, number of warp and filling yarns per inch in woven cloth. For yarn, size based on relation of length and weight.
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; a bonding link.
Co-Woven Fabric
A reinforcement fabric woven with two different types of fibers in individual yarns; for example, thermoplastic fibers woven side by side with carbon fibers.
Crazing
Fine cracks that may extend in a network on or under the surface of a plastic material.
Creel
A device for holding the required number of roving balls or supply packages in desired position for unwinding onto the next processing step.
Creep
The change in dimension of a material under sustained load over a period of time, not including the material's initial elastic deformation. The time-dependent part of strain resulting from an applied load.
Crimp
A fiber's waviness, which determines the capacity of the fiber to cohere.
Cross Laminated
Material laminated so that some of the layers are oriented at various angles to the other with respect to the laminate grain. A cross-ply laminate usually has plies oriented only at 0/90 degrees.
Cure
To change the properties of a thermosetting resin irreversibly by chemical reaction, i.e., condensation, ring closure, or addition. Cure may be accomplished by addition of curing (cross-linking) agents, with or without catalyst, and with or without heat.
Cure Cycle
The time/temperature/pressure cycle used to cure a thermosetting resin system of prepreg.
Cure Stress
A residual internal stress produced during the curing cycle of composite structures. Normally, these stresses originate when different components of a wet lay-up have different thermal coefficients of expansion.
Curing Agent
A catalytic or reactive agent that brings about polymerization when it is added to a resin.
Curing Temperature
Temperature at which a cast, molded, or extruded product, a resin-impregnated reinforcement, an adhesive, etc., is subjected to curing.
Curing Time
The period of time during which a part is subjected to heat or pressure, or both, to cure the resin; interval of time between the instant of cessation of relative movement between the moving parts of a mold and the instant that pressure is released. (Further cure may take place after removal of the assembly from the conditions of heat or pressure.)
Cycle
The complete, repeating sequence of operations in a process or part of a process. In molding, the cycle time is the period (or elapsed time) between a certain point in one cycle and the same point in the next.
D
Debonding
The separation of bonded surfaces, usually unplanned.
Debulking
Compacting of a thick laminate under moderate heat and pressure and/or vacuum to remove most of the air, to ensure seating on the tool, and to prevent wrinkles.
Deformation
A change in dimension or shape due to stress.
Delaminate
To split a laminated plastic material along the plane of its layers. Physical separation or loss of bond between laminate plies.
Denier
A numbering system for yarn and filament in which yarn number is equal to weight in grams of 9000 meters of yarn.
Dimensional Stability
Ability of a part to retain the precise shape to which it was molded, cast, or otherwise fabricated.
Direct-Sized Yarn
Specially formulated sizings on textile yarns that allow them to be resin compatible.
Draft
The tape or slope of the vertical surfaces of a mold designed to facilitate removal of molded parts.
Drape
A property indicating the stiffness of a product. The stiffness of a mat, for example, determines the ease of conformity to molded surfaces during initial processing.
Dry Laminate
A laminate containing insufficient resin for complete bonding of the reinforcement.
Dry Lay-Up
Construction of a laminate by the layering of preimpregnated reinforcement (partly cured resin) in a female mold or on a male mold, usually followed by bag molding or autoclave molding.
Dry Loft
Height of the bed of chopped fibers.
Dry Winding
A filament winding operation in which resin is not used.
Durability
The ability of a material to resist weathering action, chemical attack, abrasion, and other conditions of service. Also, the capability of a structure or its components to maintain serviceability over a designed period of time in a specified environment.
E
E-Glass
A family of glasses with a calcium alumina borosilicate composition and a maximum alkali content of 2.0%. A general-purpose fiber that is most often used in reinforced plastics, and is suitable for electrical laminates because of its high resistivity.
Ejection / Demolding
The process of removing a molding from the molding impression; by mechanical means, by hand, or by the use of compressed air.
Ejection Plate
A metal plate used to operate ejector pins; designed to apply a uniform pressure to them in the process of ejection.
Elasticity
The ability of a material to recover to its original size and shape after the removal of a force causing deformation.
Elongation
The increase in length of a material
Elongation at Break
Elongation recorded at the moment of rupture of the specimen, often expressed as a percentage of the original length.
End
A strand of roving consisting of a given number of filaments gathered together. The group of filaments is considered an "end" or strand before twisting, a "yarn" after twist has been applied. An individual warp yarn, thread, fiber, or roving.
End Count
The number of strands contained in a roving.
Epoxy
A polymerizable thermoset polymer containing one or more epoxide groups and curable by reaction with amines. alcohols, phenols carboxylic acids, acid anhydrides, and mercaptans.
Exotherm
The liberation or evolution of heat during the curing of a plastic product.
Extenders
An inert material added to provide economical extension of resins without lessening of properties.
F
Fabric
Arrangement of fibers held together in two dimensions. A fabric may be woven, nonwoven, or stitched.
Fabric, Nonwoven
A material formed from fibers or yarns without interlacing (e.g., stitched bonded, nonwoven broadgoods).
Fabric, Woven
A material constructed of interlaced yarns, fibers or filaments produced by the weaving process.
Fabrication
The process of making a composite part or tool.
Fatigue
The lessening or failure of mechanical properties after repeated applications of stress.
Fatigue Life
The number of cycles of deformation required to bring about failure of the test specimen under a given set of oscillating conditions (stresses and strains).
Fatigue Strength
The maximum cyclical stress a material can withstand for a given number of cycles before failure occurs. Also the residual strength after being subjected to fatigue.
Feathered Edge
A fabric edge that tapers down in weight instead of abruptly ending.
Fiber
A general term used to refer to filamentary materials. Often, fiber is used synonymously with filament.
Fiber Architecture
The design of a fibrous part in which the fibers are arranged in a particular way to achieve the desired result. This can include braided, stitched or woven fabrics, or mats, rovings or carbon tows.
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 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 Direction
The orientation or alignment of the longitudinal axis of the fiber with respect to a stated reference axis.
Fiber Orientation
The fiber alignment in a nonwoven or a mat laminate in which most of the fibers are in the same direction, thereby affording higher strength in that direction.
Fiber Pattern
Visible fibers on the surface of laminates or moldings; the thread size and weave of glass cloth.
Fiber Prominence
The appearance of reinforcement fibers in the surface of a molded part. Can also be termed pattern print-through, strike-through or fiber pattern.
Fiber Reinforced Plastics (Frp)
A general term for composite materials or parts that consist of a resin matrix that contains reinforcing fibers such as glass or fiber and have greater strength or stiffness than the resin. FRP is most often used to denote glass fiber-reinforced plastics.
Fiberglass
Primarily means glass in fiber form. However, "fiber glass" is also used to describe composite processing and applications. Examples of usage: fiber glass molding plant, fiber glass car.
Fiberglass Reinforcement
Major material used to reinforce plastic. Available as a mat, roving, fabric, etc.
Filament
The smallest unit of a fibrous material. The basic units formed during drawing and spinning, which are gathered into strands of fiber for use in composites. Filaments usually are of extreme length and very small diameter, usually less than 25 micron. Normally filaments are not used individually. Some textile filaments can function as yarn when they are of sufficient strength and flexibility.
Filament Winding
A process for fabricating a composite structure in which continuous reinforcements (filament, wire, yarn, tape, or other), either previously impregnated with a matrix material or impregnated during the winding, are placed over a rotating and removable form.
Fill
That part of a woven fabric in which the strands are perpendicular to the main direction of the fabric (warp), the strands running from selvage to selvage . Also called weft.
Filler
A relatively inert substance added to a material to alter its physical, mechanical, thermal, electrical, and other properties or to lower cost or density. Sometimes the term is used specifically to mean particulate additives.
Film Adhesive
An adhesive in the form of a thin, dry, resin film with or without a carrier, commonly used for adhesion between layers of laminates.
Finish
A mixture of materials that is applied to fibers that improve the bonding characteristics of the resin to the fiber.
Flame Retardants
Certain chemicals that are used to reduce or eliminate a resin's tendency to burn.
Flange
A flat area of a mold that extends perpendicularly from the edge of the molding surface.
Flash
Excess material which forms at the parting line of a mold or die, or which is extruded from a closed mold.
Flexural Strength
The property of a material or a structural member that indicates its ability to resist failure in bending. A unit of resistance to the maximum load before failure by bending.
Flow
The movement of resin under pressure, allowing it to fill all parts of a mold; flow the gradual but continuous distortion of a material under continued load, usually at high temperature.
Flow Line
A mark on a molded piece made by the meeting of two flow fronts during molding. (Also, 'striae', or 'weld-mark,' or 'weld-line.')
Fly
Loose filaments of fiber that have broken from their parent strand during processing and are freely floating in the air.
Fracture
The separation of a body. Defined both as a rupture of the surface without complete separation of the laminate or as a complete separation of a body because of external or internal forces.
FRP
Acronym for fiber glass-reinforced or fiber-reinforced plastic, polymer or polyester.
FRP Composite
A polymer matrix, either thermoset or thermoplastic, reinforced with a fiber or other material with a sufficient aspect ratio (length to thickness) to provide a discernable reinforcing function in one or more directions (see composites).
G
Gate
Where molten thermoplastic or liquid thermoset resin enters the cavity in a tool.
Gel
A partial cure of plastic resins; a semi-solid, jelly-like state similar to gelatin in consistency.
Gel Coat
A resin applied to the surface of a mold and gelled prior to lay-up. The gel coat becomes an integral part of the finished laminate, and is usually used to improve surface appearance and protect the laminate from the environment.
Gel Point
The stage at which a liquid begins to exhibit pseudoelastic properties. (This stage may be conveniently observed from the inflection point on a viscosity-time plot). Also, 'gel time.'
Gel Time
Time required to change a flowable liquid resin into a non-flowing gel.
GFRP
Glass fiber-reinforced plastic, polymer or polyester.
Glass Cloth
Conventionally woven glass fiber material; certain lightweight glass fabrics are also called scrims.
Glass Content
Percentage of glass in the compound.
Glass Fiber
Reinforcing fiber made by drawing molten glass through bushings. The predominant reinforcement for polymer matrix composites, it is known for good strength, processability and low cost.
Glass Fiber, types
Alkali resistant (AR-glass)
General Purpose (E-glass)
High Strength (S-glass)
Glass Resin Ratio
The amount of glass by weight compared to the amount of resin by weight in a finished laminate or molding.
Glass Rich
An area of molded part that has an overabundance of glass reinforcement. The reinforcement may appear dry and unwet with the resin.
Glass-Transition Temperature
The midpoint of the temperature range over which an amorphous material changes from (or to) a brittle, vitreaous state to (or from) a plastic state.
Glint
A visual defect in a fiber glass reinforced cured organic (usually corrosion resistant resin) panel. The defect appears as many small visible unwet or foreign substances; a salt and pepper effect. The defect is not visible before cure but appears at exotherm of the panel.
Graphite Fibers
This term is used interchangeably with carbon fibers throughout the industry.
Green Strength
The strength of a freshly molded part that hasn't completely cured.
GRP
Glass-reinforced plastic, polymer or polyester.
Gun Roving
A special type of roving reinforcement designed for use in a gun or chopper gun.
H
Hand Lay-Up
A fabrication method in which reinforcement layers are placed in mold by hand, saturated with resin and then cured to the formed shape.
Hardener
A substance or mixture added to a plastic composition to promote or control the curing action by taking part in it.
Honeycomb
Lightweight, cellular structure made from either metallic sheet materials or non-metallic materials (e.g., resin-impregnated paper or woven fabric) and formed into hexagonal nested cells, similar in appearance to the cross section of a beehive, that serves as a core material in sandwich constructions. Honeycomb may also be metallic or polymer materials in a rigid, open-cell structure.
Hybrid
A composite laminate comprised of laminae of two or more composite material systems, e.g., graphite and glass. It also applies to woven fabrics having more than one type of fiber.
I
Impact Strength
The ability of a material to withstand shock loading.
Impregnate
In reinforced plastics, the saturation of the reinforcement with a resin.
Inclusion
A physical and mechanical discontinuity occurring within a material or part, usually consisting of solid, encapsulated foreign material. Inclusions are often capable of transmitting some structural stresses and energy fields, but in a noticeably different manner from the parent material.
Inhibitor
A substance that retards a chemical reaction. Also used in certain types of monomers and resins to prolong storage life.
Injection Molding
Method of forming a plastic to the desired shape by forcibly injecting the polymer into the mold.
Insert
An integral part of a plastics molding consisting of metal or other material which may be molded into position or pressed into the molding after the molding is completed.
Interface
The boundary or surface between two different, physically distinguishable media. On fibers, the contact area between fibers and sizing or finish. In a laminate, the contact area between the reinforcement and the laminating resin.
Interlaminar
Existing or occurring between two or more adjacent laminae.
Isotropic
Having uniform properties in all directions. The measured properties of an isotropic material are independent of the axis of testing.
J
K
Kevlar®
Registered trademark of E.I. Dupont de Nemours, Inc. for a strong organic fibers with high strength-to-weight ratio. Often used for applications requiring high impact resistance. Generic term aramid.
Knitted Fabric
A textile structure produced by interlooping one or more ends of yarn or comparable material.
L
Laminate
A product made by bonding together two or more layers of material or materials. Primarily means a composite material system made with layers of fiber reinforcement 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.
Laminate Orientation
The configuration of a cross-plied composite laminate with regard to the angles of cross-plying, the number of laminae at each angle, and the exact sequence of the lamina lay-up.
Laminate Ply
One layer of a laminated product.
Lay-Up
The reinforcing material placed in position in the mold. The process of placing the reinforcing material in position in the mold. The resin-impregnated reinforcement. A description of the component materials, geometry, and so forth, of a laminate.
Low Profile
Resin compounds formulated for low or zero shrinkage during molding.
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 or without application of heat from external source, to form a structure possessing definite physical properties.
M
Mandrel
The core around which paper-, fabric-, or resin-impregnated glass is wound to form pipes, tubes, or vessels; in extrusion, the central finger of a pipe or tubing die.
Mat
A fibrous reinforcing material comprised of chopped filaments (for chopped-strand mat) or swirled filaments (for continuous-strand mat) with a binder to maintain form; available in blankets of various widths, weights, and lengths.
Mat Binder
Resin applied to glass fiber and cured during the manufacture of mat, to hold the fibers in place and maintain the shape of the mat.
Mat Strength
Ability of the mat to resist being pulled apart under tension during impregnation and molding.
Matched Metal Molding
A reinforced plastics manufacturing process in which matching male and female metal molds are used (such as compression molding) to form the part, as opposed to low pressure laminating or spray-up.
Matrix
The material in which the fiber reinforcements of a composite system are embedded. Thermoplastic and thermoset resin systems can be used, as well as metal and ceramic.
Mechanical Properties
The properties of a material such as compressive and tensile strengths and modulus that are associated with elastic and inelastic reaction when force is applied. The relationship between stress and strain.
Metal-Matrix Composites
Materials in which continuous carbon, silicon carbide, or ceramic fibers are embedded in a metallic matrix material.
Microcracking
The cracks formed when exerted stress exceeds the strength of the matrix.
Milled Fiber
Continuous glass strands hammer milled into very short glass fibers. Useful as inexpensive filler or anticrazing reinforcing fillers for adhesives.
Modulus
The ratio of stress to strain. A high modulus indicates a stiff material.
Modulus of Elasticity
The ratio of normal stress to corresponding strain for tensile or compressive stresses below the proportional limit of the material.
Mold
The cavity or matrix into or on which the plastic composition is placed and from which it takes form. To shape plastic parts or finished articles by heat and pressure. The assembly of all the parts that function collectively in the molding process.
Mold Shrinkage
The immediate shrinkage which a molded part undergoes when it is removed from a mold and cooled to room temperature; the difference in dimensions, expressed in inches per inch between a molding and the mold cavity in which it was molded (at normal temperature measurement); the incremental 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.
Mold Surface
The side of a laminate that faced the mold (tool) during cure.
Molding
The forming of a polymer or composite into a solid mass of prescribed shape and size by the application of pressure and heat for given times. Sometimes used to denote the finished part.
Molding Compounds
Plastics in a wide range of forms to meet specific processing requirements. Granules or pellets are popular forms.
Molding Cycle
The period of time occupied by the complete sequence of operations on a molding press requisite for the production of one set of moldings; the operations necessary to produce a set of moldings without reference to the time taken.
Molding Pressure, Compression
The unit pressure applied to the molding 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. The unit pressure is calculated by dividing the total force applied by this projected area, and is expressed in pounds per square inch.
Mold-Release Agent
A lubricant, liquid, or powder (often silicone oils and waxes), used to prevent sticking of molded articles in the cavity.
Monomer
A simple molecule which is capable of reacting with like or unlike molecules to form a polymer; the smallest repeating structure of a polymer; for addition polymers, this represents the original unpolymerized compound.
Multifilament
A yarn consisting of many continuous filaments.
Multiple-Cavity Mold
A mold with two or more mold impressions; that is, a mold which produces more than one molding per molding cycle.
N
Nanocomposite
Polymer compound containing dispersed nanofillers. Nanocomposites have shown improvements in both mechanical, thermal and physical properties such as enhanced transparency and barrier properties.
Nanofiller
Very small particulate, with at least one dimension in the nanometer range (10-9m). Used as an additive or reinforcement for polymer systems to provide the materials with enhanced properties.
Nanotube (or Carbon Nanotubes)
Long cylinders of carbon with a wall thickness in the nanometer range (10-9m). Carbon nanotubes exhibit remarkable tensile strength and provide a broad range of electrical properties.
Nol Ring
A parallel filament wound test specimen used for measuring various mechanical strength properties of the material by testing the entire ring, or segments of it.
Nomex
See Aramid
Non-Woven Fabric
A textile structure produced by bonding or interlocking of fibers, or both, accomplished by mechanical, chemical, thermal, or solvent means and combinations thereof.
O
Open Molding
The general term used to describe composites manufacture whereby resin and reinforcement are placed on an open mold. See also hand lay up and spray-up.
One-Part Resin System
A resin system (often used in resin transfer molding) in which the neat resin and catalyst are mixed together by the material supplier as part of the resin production operation.
Orange Peel
An uneven surface somewhat resembling that of an orange peel; said of moldings that have unintentionally ragged surfaces.
Oriented Materials
Composites whose constituents are aligned in a particular way.
Orthotropic
A material that has six different sets of moduli and Poisson's ratios.
Out Time
The time a prepreg is exposed to ambient temperature, namely, the total amount of time the prepreg is out of the freezer. The primary effects of our time are to decrease the drape and tack of the prepreg while also allowing it to absorb moisture from the air.
Outgassing
The release of solvents and moisture from composite parts under a vacuum.
Oxidation
Combining or increasing the proportion of oxygen.
P
Pan Fibers
Carbon reinforcement fiber derived from the controlled pyrolysis of poly(acrylonitrile) fiber.
Parting Line
A mark on a molded piece where the sections of a mold have met in closing.
PBT
Polybuthlene Therephthalate (Thermoplastic Polyester Resin).
Peel Ply
Layer of material applied to a prepreg layup surface that is removed from the cured laminate prior to bonding operations and leaves a clean resin-rich surface ready for bonding.
Peel Strength
Adhesive bond strength, as in pounds per inch of width, obtained by a stress applied in a peeling mode.
Permeability
The passage or diffusion rate of a gas, vapor, liquid or solid through a barrier without physically or chemically affecting it.
PET
Polyethylene Terephthalate (Thermoplastic Polyester Resin).
Phenolic
A thermosetting resin produced by the condensation of an aromatic alcohol particularly based on phenol (carbolic acid) and formaldehyde.
Pinhole
A tiny hole in the surface of, or through, a plastic material; usually occurring in multiples.
Pit
Small regular or irregular crater in the surface of a plastic, usually with width approximately of the same order of magnitude as its depth.
Pitch
A Residual Petroleum Product Used In The Manufacture Of Certain Carbon Fibers.
Plain Weave
A weaving pattern in which the warp and fill fibers alternate; that is, the repeat pattern is warp/fill/warp/fill, and so on. Both faces of a plain weave are identical. Properties are significantly reduced relative to a weaving pattern with fewer crossovers.
Plastic
A material that contains as an essential ingredient an organic substance of large molecular weight, is solid in its finished state, and, at some stage in its manufacture or its processing into finished articles, can be shaped by flow; made of plastic.
Platens
The mounting plates of a press, to which the entire mold assembly is bolted.
Pleat
A fold made by doubling the vacuum bag upon itself and pressing it together with sealant tape to form a tight seal
Ply
In general, fabrics or felts consisting of one or more layers (laminates, and so forth). The layers that make up a stack. Yarn resulting from twisting operations (three-ply yarn, and so forth). A single layer of prepreg. A single pass in filament winding (two plies forming one layer).
Polyacrylonitrile (Pan)
A product used as a base material in the manufacture of certain carbon fibers.
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.
Polyesters
Thermosetting resins, produced by dissolving unsaturated, generally linear, alkyd resins in a vinyl-type active monomer such as styrene, methyl styrene, and diallyl phthalate. Cure is effected through vinyl polymerization using peroxide catalysts and promoters, or heat, to accelerate the reaction. The resins are usually furnished in solution form, but powdered solids are also available.
Polymer
A very large molecule formed by combining a large number of smaller molecules, called monomers, in a regular pattern.
Polymerization
A chemical reaction in which the molecules of monomers are linked together to form polymers.
Porosity
The presence of visible voids within a solid material into which either air or liquids can pass.
Positive Mold
A mold designed to apply pressure to a piece being molded with no escape of material.
Post-Cure
Additional elevated temperature cure, usually without pressure, to improve final properties and/or complete the cure. In certain resins, complete cure and ultimate mechanical properties are attained only by exposure of the cured resin to higher temperatures than those of curing.
Pot Life
The length of time a catalyzed thermosetting resin system retains a viscosity low enough for it to be suitable for processing.
Ppo
Polyphenylene Oxide (Thermoplastic Resin).
Pps
Polyphenylene Sulfide (Thermoplastic Resin).
Precursor
For carbon fibers, the rayon, PAN, or pitch fibers from which carbon fibers are made.
Preform
A preshaped fibrous reinforcement formed by distribution of chopped fibers by air, water flotation, or vacuum over the surface of a perforated screen to the approximate contour and thickness desired in the finished part. Also, a preshaped fibrous reinforcement of mat or cloth formed to 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 of uniformity of charges for mold loading.
Preform Binder
A resin applied to the chopped strands of a preform, usually during its formation, and cured so that the preform will retain its shape and can be handled.
Premix
A molding compound prepared prior to and apart from the molding operations and containing all components required for molding resin, reinforcement, fillers, catalysts, release agents, and other compounds.
Prepreg
Ready-to-mold material in sheet form which may be cloth, mat, or paper pre-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 finished shape and completes the cure with heat and pressure.
Pressure Bag Molding
A process for molding reinforced plastics in which a tailored, flexible bag is placed over the contact lay-up on the mold, sealed, and clamped in place. Fluid pressure, usually provided by compressed air or water, is placed against the bag, and the part is cured.
Pressure Intensifier
A layer of flexible material (usually a high-temperature rubber) used to ensure the application of sufficient pressure to a location, such as a radius, in a lay-up being cured.
Primer
A coating applied to a surface, before the application of an adhesive, lacquer, enamel, and so forth, to improve the adhesion performance or load-carrying ability of the bond.
Processing Window
The range of processing conditions, such as stock (melt) temperature, pressure, shear rate, and so on, within which a particular grade of plastic can be fabricated with optimum or acceptable properties by a particular fabricating process.
Promoter
A chemical that reduces the activation energy required for a given initiator.
Pultrusion
An automated, continuous process for manufacturing composite rods, tubes and structural shapes having a constant cross section. Roving and other reinforcements are saturated with resin and continuously pulled through a heated die, where the part is formed and cured. The cured part is then cut to length.
Q
Quality Assurance
Actions taken by an owner or his representative to provide assurance that what is being done and what is being provided are in accordance with the applicable standards of good practice for the work.
Quasi-Isotropic
Approximating isotropy by orientation of plies in several directions.
R
Reinforcement
A material added to the matrix to provide the required properties; ranges from short fibers through complex textile complex textile forms.
Release Agents
Materials that are used to prevent cured matrix material from bonding to tooling.
Release Film
An impermeable layer of film that does not bond to the resin being cured. See also separator.
Resin
A material, generally a polymer that has an indefinite and often high molecular weight and a softening or melting range and exhibits a tendency to flow when it is subjected to stress. Resins are used as the matrices to bind together the reinforcement material in composites.
Resin Content
The amount of resin in a laminate expressed as either a percent of total weight or total volume.
Resin Rich
Localized area filled with excess resin as compared to consistent resin/fiber ratio.
Resin-Starved
Areas of insufficient resin, usually identified by low gloss, dry spots or fiber show.
Resin-Transfer Molding (Rtm)
A molding process in which catalyzed resin is transferred into an enclosed mold into which the fiber reinforcement has been placed; cure normally is accomplished without external heat. RTM combines relatively low tooling and equipment costs with the ability to mold large structural parts.
Roll-Out
A process used in spray-up and hand lay-up procedures where the resin and glass reinforcement are compacted to a uniform laminate with rollers.
Roving
A number of yarns, strands, tows, or ends collected into a parallel bundle with little or no twist.
RP
Reinforced plastic, polymer or polyester.
RTP
Sometimes used to distinguish reinforced thermoplastic from reinforced thermosetting plastic.
Rule-Of-Mixtures
When combined, the properties of the composite material is some combination of the properties of the two constituent materials. The composite property equals the amount of the fiber property multiplied by the volume percentage of fiber, plus the amount of matrix property multiplied by the volume percentage of matrix.
S
S Glass
A family of magnesium-alumina-silicate glasses with high mechanical strength.
SAN
Styrene Acrylonitrile (Thermoplastic Resin).
Sandwich Construction
A composite composed of lightweight core material (usually honeycomb or foamed plastic) to which two relatively thin, dense, high strength, functional, or decorative skins (also called faces) are adhered.
Sandwich Panel
Panels composed of a lightweight core material, such as honeycomb, balsa, foamed plastic, and so forth to which two relatively thin, dense, high strength of high stiffness faces or skins adhered.
Scrim
A low-cost reinforcing fabric made from continuous filament yarn in an open-mesh construction. Used in the processing of tape or other B-stage material to facilitate handling. Also used as a carrier of adhesive, to be used in secondary bonding.
Scrimp
Seamann Composite Resin Infusion Molding Process.
Secondary Bonding
The joining together, by the process of adhesive bonding, of two or more already cured composite parts, during which the only chemical or thermal reaction occurring is the curing of the adhesive itself.
Separator
A permeable layer that also acts as a release film. Porous Teflon-coated fiberglass is an example. Often placed between lay-up and bleeder to facilitate bleeder system removal from laminate after cure.
Set Up
To harden, as in curing of a polymer resin.
Shear
An action or stress resulting from applied forces which causes or tends to cause two contiguous parts of a body to slide relative to each other in a direction parallel to their plane of contact. Inter laminar Shear (ILS). The plane of contact is composed of resin only.
Shear Edge
The cut-off edge of the mold.
Shear Reinforcement
Reinforcement designed to resist shear or diagonal tension stresses.
Shear Strength
The maximum shear stress that a material is capable of sustaining. Shear strength is calculated from the maximum load during a shear or torsion test and is based on the original cross-sectional area of the specimen.
Sheet Molding Compound (SMC)
A ready-to-mold glass fiber reinforced polyester material primarily used in compression molding.
Shelf Life
The length of time a material, substance, product, or reagent can be stored under specified environmental conditions and continue to meet all applicable specification requirements and/or remain suitable for its intended function.
Short Beam Shear (SBS)
A flexural test of a specimen having a low test span-to-thickness ratio (for example, 4:1), such that failure is primarily in shear.
Shrinkage
The relative change in dimension between the length measured on the mold when it is cold and the length on the molded object 24 hours after it has been taken out of the mold.
Silicon Carbide Fiber
A reinforcing fiber with high strength and modulus; density is equal to that of aluminum. It is used in organic metal-matrix composites.
Single Yarn
The simplest strand of textile material suitable for operations such as weaving, knitting, etc.
Sink Mark
A shallow depression or dimple on the surface of an injection molded part due to collapsing of the surface following local internal shrinkage after the gate seals; an incipient short shot.
Sizing
The treatment applied to the glass fiber to allow the resin and glass to adhere to one another. Also allows glass fiber to be conveniently handled.
Skin
A layer of relatively dense material used in a sandwich construction of the surface of the core.
Soft Glass
A roving product whose sizing is moderately soluble in acetone or styrene, which results in the tendency of the bundles to open readily or filamentize the matrix resin. The size is generally between 50% and 80% soluble in acetone.
Solvent
A liquid in which another substance may be dissolved.
Specimen
An individual piece or portion of a sample used to make a specific test; of specific shape and dimensions.
Splice
The joining of two ends of yarn by intertwining, knotting, overlapping or adhering them together.
Split Mold
A mold in which the cavity is formed of two or more components held together by an outer chase. The components are known as splits.
Spray Pattern
In connection with the spray-up process (see below), it refers to the width and uniformity of the fan of resin and glass while it is travelling between the gun and the mold.
Spray-Up
Techniques in which a spray gun is used as the processing tool. In reinforced plastics, for example, fibrous glass and resin can be simultaneously deposited in a mold. In essence, roving is fed through a chopper and ejected into a resin stream, which is directed at the mold by either of two spray systems. In foamed plastics, very fast-reacting urethane foams or epoxy foams are fed in liquid streams to the gun and sprayed on the surface. On contact, the liquid starts to foam.
Stacking Sequence
A description of a laminate that details the ply orientations and their sequence in the laminate.
Starved Area
An area in a plastic part that has an insufficient amount of resin to wet out the reinforcement completely. This condition may be due to improper wetting or impregnation or excessive molding pressure.
Stiffness
A measure of modulus or a material's ability to resist bending. The relationship of load and deformation.
Storage Life
The period of time during which a liquid resin or packaged adhesive can be stored under specified temperature conditions and remain suitable for use. (Also 'shelf life.')
Strand
Normally an untwisted bundle or assembly of continuous filaments used as a unit, including slivers, tows, ends, yarn, and so forth. Sometimes a single fiber or filament is called a strand.
Strand Count
The number of strands in a plied yarn; the number of strands in a roving. U.S. Yardage System; the length, in hundreds of yards, of a single strand having a mass of one pound. European TEX System; the mass, in grams, of a strand 1000 meters in length.
Strand Integrity
Relating to the ability of the size to keep all the filaments of a bundle stuck together during chopping. Good strand integrity is required for good flow in or wet-through and wet-out on the mold.
Stress
The internal force per unit area that resists a change in size or shape of a body as expressed in force per unit area.
Stress Crack
An internal and/or external fissure caused by tensile stresses to a part.
Structural Adhesive
Adhesive used for transferring required loads between adherends exposed to service environments typical for the structure involved.
Structural Bond
A bond that joins basic load-bearing parts of an assembly. The load may be either static or dynamic.
Styrene Monomer
A water-thin liquid monomer used to thin polyester resins and act as the crosslinking agent.
Substrate
A material or part that can be bonded or coated for any purpose.
Surface Preparation
Physical and/or chemical preparation of an adherend to make it suitable for adhesive bonding.
Surfacing Mat
A very thin mat, usually 7 to 20 mils thick, of highly filamentized fiber glass used primarily to produce a smooth surface on a reinforced plastic laminate.
T
Tack
Stickiness of an adhesive or filament reinforced resin prepreg material.
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 Reinforcement
Reinforcement designed to carry tensile stresses. Can be internal reinforcement of the product or external reinforcement such as a composite repair material placed on an existing structure.
Tensile Strength
Maximum unit stress that a material is capable of resisting under axial tensile loading; based on the cross-sectional area of the specimen before loading.
Textile
Fabric, usually woven.
Thermal Conductivity
The property of a particular body or assembly to transfer heat.
Thermal Contraction
Contraction caused by the decrease in temperature.
Thermal Expansion
Expansion caused by by an increase in temperature.
Thermoplastic
Capable of being repeatedly softened by an increase of temperature and hardened by an increase in temperature. Applicable to those materials whose change upon heating is substantially physical rather than chemical and that in the softened stage can be shaped by flow into articles by molding or extrusion.
Thermoset
A material that will undergo a chemical reaction caused by heat, catalyst, etc., leading to the formation of a solid. Once it becomes a solid, it cannot be reformed.
Thickeners
Material added to the resin to thicken it or raise the viscosity index of the resin so that it will not flow as readily.
Thixotropic, Thixotropy
Concerning materials that are gel-like at rest but fluid when agitated
Thread Count
The number of yarns (threads) per inch in either the lengthwise (warp) or crosswise (fill or weft) direction of woven fabrics.
Tool (Tooling)
The mold onto which the composite material is placed to in order to fabricate the composite part. The mold itself may or may not be made of composite materials, it may be one or two sided and may be open or closed.
Tow
An untwisted bundle of continuous filaments (usually carbon) usually designated by a number followed by K, indicating multiplication by 1,000 (for example, 12K tow has 12,000 filaments).
Tracer
A fiber, tow, or yarn added to a prepreg for verifying fiber alignment and, in the case of woven materials, for distinguishing warp fibers from fill fibers.
Twist
The spiral turns about its axis per unit of length in a yarn or other textile strand.
U
Ultrasonic Testing
A nondestructive test applied to materials for the purpose of locating internal flaws or structural discontinuities by the use of high-frequency reflection or attenuation (ultrasonic beam).
Unidirectional
Refers to fibers that are oriented in the same direction, such as unidirectional fabric, tape, or laminate, often called UD.
Unidirectional Laminate
A reinforced plastic laminate in which substantially all of the fibers are oriented in the same direction.
V
Vacuum Bag Molding
A process in which a sheet of flexible transparent material plus bleeder cloth and release film are placed over the lay-up on the mold and sealed at the edges. A vacuum is applied between the sheet and the lay-up. The entrapped air is mechanically worked out of the lay-up and removed by the vacuum, and the part is cured with temperature, pressure, and time. Also called bag molding.
Vacuum-Assisted Resin Transfer Molding (VARTM)
An infusion process where a vacuum draws resin into a one-sided mold. A cover, either rigid or flexible, is placed over the top to form a vacuum-tight seal.
Veil
An ultra thin mat similar to a surface mat, often composed of organic fibers as well as glass fibers.
Vent
A small hole or shallow channel in a mold that allows air or gas to exit as the molding material enters.
Vinyl Esters
A class of thermosetting resins containing ester of acrylic and/or methacrylic acids, many of which have been made from epoxy resin.
Viscosity
The property of a body of material to resist a change to its shape: internal friction.
Void
A physical and mechanical discontinuity occurring within a material or part which may be two-dimensional (e.g., disbonds, delaminations) or three-dimensional (e.g., vacuum-, air-, or gas-filled pockets). Porosity is an aggregation of micro-voids. Voids are essentially incapable of transmitting structural stresses or nonradiative energy fields. (See Inclusion.)
Void Content
Volume percentage of voids, usually less than 1% in a properly cured composite. The experimental determination is indirect, that is, calculated from the measured density of a cured laminate and the "theoretical" density of the starting material.
Volatiles
Materials, such as water and alcohol, in a sizing or a resin formulation, that are capable of being driven off as a vapor at room temperature or at a slightly elevated temperature.
W
Warp
The yarn running lengthwise in a woven fabric. A group of yarns in long lengths and approximately parallel. A change in dimension of a cured laminate from its original molded shape.
Weave
Pattern by which a fabric is formed from interlacing yarns. In a plain weave, the warp and fill fibers alternate to make both fabric faces identical. In a satin weave, the pattern produces a satin appearance with the warp roving crossing over several fill rovings and under the next one (e.g., eight-harness satin would have warp roving over seven fill rovings and under the eighth).
Weft
The system of yarns running crosswise in a fabric. Also known as fill.
Wet Lay-Up
A method of making a reinforced product by applying the resin system as a liquid when the reinforcement is put in place.
Wet-Out
The degree and/or rate at which each individual filament is "wet" or encapsulated by the matrix polymer resin in a composite sheet. Relates to the ability of the polymer matrix resin system to move through the glass fiber bed and to attain complete encapsulation of each individual filament. A measure of the wetability of the sized glass fiber surface.
Working Life
The period of time during which a liquid resin or adhesive, after mixing with catalyst, solvent, or other compounding ingredients, remains usable.
Woven Fabric
A material constructed by interlacing yarns, fibers or filaments to form specific fabric patterns.
Woven Roving
A heavy glass fiber fabric made by the weaving of roving.
Wrinkle
A surface imperfection in laminated plastics that has the appearance of a crease or fold in one or more outer sheets of the paper, fabric, or other base, which has been pressed in. Also occurs in vacuum bag molding when the bag is improperly placed, causing a crease.
X
X-Axis
The axis in the plane of the laminate used as 0-degree reference; the Y-axis is the axis in the plane of the laminate perpendicular to the X-axis; the Z-axis is the reference axis normal to the laminate plane in composite laminates.
Y
Y-Axis
In composite laminates, the axis in the plane of the laminate which is perpendicular to the x-axis.
Yardage
Similar to Yield (see) but used to describe the linear density of "bare glass" or an unsized product. Yardage specifies the number of yards of glass required to weigh one pound. It is measured in hundreds. For example, K18 is a K fiber diameter that has 1800 yards in one pound of glass.
Yarn
An assemblage of twisted filaments, fibers, or strands, either natural or manufactured, to form a continuous length that is suitable for use in weaving or interweaving into textile materials.
Yield
Yield refers to the linear density of a roving or yarn and is measured as the number of yards per pound.
Yield Strength
The stress at the yield point. The stress at which a material exhibits a specified limiting deviation from the proportionality of stress to strain.
Young's Modulus
The ratio of normal stress to the corresponding strain for tensile or compressive stresses less than the proportional limit of the material.
Z
Z-Axis
In composite laminates, the reference axis normal to the plane of the laminate.
Zero Bleed
A procedure that prohibits the loss of resin during the cure of a laminate.
