Cadfil Filament Winding Glossary
Aging: The process of exposing materials to an environment for an interval of time, usually for testing purposes.
Angle of winding: The angle at which the fibre is laid with respect to the mandrel axis of rotation, where winding along the length of the mandrel is 0° and winding around the circumference is 90°. See also Wind angle
Anisotropic: Not isotropic, when tested along axes in different directions, different material properties are given.
Aramid: Aramid fibres are a class of heat-resistant and strong synthetic fibres. They are used in aerospace and military applications, they include Kevlar and Nomex. See also Kevlar
A-stage: An 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 also B-stage and C-stage.
Axial winding: A winding path where the filaments are parallel to the axis (0° helix angle).
Axsym: A Cadfil software package for all axisymmetric mandrels. see Cadfil Axsym.
Balanced design: In filament-wound reinforced plastics, a winding pattern so designed that the stresses in all filaments are equal.
Band density: In filament winding, the quantity of fibreglass reinforcement per inch of band width, expressed as strands (or filaments) per inch.
Band width: In filament winding, the width of the reinforcement as it is applied to the mandrel (measured perpendicular to the band).
Bismaleimide (BMI): A type of polyimide that cures by an addition rather than a condensation reaction (thus avoiding problems with volatiles formation), which is produced by a vinyl-type polymerization of a prepolymer terminated with two maleimide groups. They are intermediate in temperature capability between epoxy and polyimides. BMI Resins are typically used in higher temperature applications than Epoxy resins.
Bleedout: In filament winding, the excess liquid resin that migrates to the surface of a winding.
Boss: Commonly referred to as polar boss or end fitting. It is a metal fitting located in the centre of each dome that describes the pole about which winding bands are wrapped.
Bottle winds: These combine a helical wind section with a geodesic, or near-geodesic, wind pattern to generate a stable fibre path over the end domes of the part. These are typically used for pressure vessels.
B-stage: An intermediate stage in the reaction of certain thermosetting resins in which the material swells when in contact with certain liquids and softens when heated, but may not entirely dissolve or fuse; sometimes referred to as resitol. The resin in an uncured prepreg or premix is usually in this stage. See also A-stage and C-stage.
Bulk factor: Reciprocal of fibre volume. Used to calculate lamina thickness.
Burst strength: Hydraulic pressure required to burst a vessel of given thickness. Commonly used in testing filament-wound composite structures.
Carbon/Graphite fibre: Fibre produced by the pyrolysis of organic precursor fibres, such as rayon, polyacrylonitrile (PAN), and pitch, in an inert environment. The term is often used interchangeably with the term graphite; however, carbon fibres and graphite fibres differ. The basic differences lie in the temperature at which the fibres are made and heat treated, and in the amount of elemental carbon produced. Carbon fibres typically are carbonized in the region of 2400 °F (1315 °C) and assay at 93 to 95% C, while graphite fibres are graphitized at 3450 to 4500 °F (1900 to 2480 °C) and assay at more than 99% elemental carbon.
Catalyst: A substance that changes the rate of a chemical reaction without itself undergoing a 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 a minor quantity is added, compared to the amounts of primary reactants.
Chain winds: see Combined Winding.
Circuit: One complete traverse back and forth of the fibre-feed mechanism of a winding machine.
Circumferential (“Circ”) winding: In filament wound reinforced plastics, a winding with the filaments essentially perpendicular to the horizontal mandrel axis (90° or hoop winding).
Coefficient of variation: The ratio of the standard deviation to the mean.
Combined Winding: The user can combine individual winds to form multiple layers of a more complex wind.
Compaction: In reinforced plastics and composites, the application of a temporary press bump cycle, or vacuum, to remove trapped air and compact the lay-up. Pressure exerted on previously wound, uncured layers by high angle or circumferential windings.
Composite material: A combination of two or more materials (reinforcing elements, fillers, and composite matrix binder) differing in form or composition on a macroscale. The constituents retain their identities: They do not dissolve or merge completely into one another although they act in concert. Normally, the components can be physically identified and exhibit an interface between one another.
Continuous filament: An individual rod of small-diameter fibre that is flexible and of great or indefinite length.
Continuous filament yarn: Yarn formed by twisting two or more continuous filaments into a single, continuous strand.
Creel: A device for holding the required number of roving balls or supply packages in a desired position for unwinding onto the mandrel when filament winding.
C-stage: The final stage in the reaction of certain thermosetting resins in which the material is practically insoluble and infusible. Sometimes referred to as resite. The resin in a fully cured thermoset molding is in this stage. See also A-stage and B-stage.
Cure: To irreversibly change the properties of a thermosetting resin by chemical reaction (that is, condensation, ring closure, or addition). Cure may be accomplished by addition of curing (cross-linking) agents, with or without heat and pressure.
Cure cycle: The time/temperature/pressure cycle used to cure a thermosetting resin system.
Delamination: The separation of a laminate along the plane of its layers. Also the separation of bonded insulation within the adhesive layer or at the adhesive interface.
Denier: A yarn and filament numbering system in which the yarn number is equal to the weight in grams of 9000 m. Used for continuous filaments. The lower the denier, the finer the yarn.
Diameters: Outside diameter: The outside major diameter of a cylindrical part. Inside diameter: The inside major diameter of a cylindrical part. This would correspond to the outside diameter of the mandrel. Mean diameter: The diameter halfway between the outside and inside diameters. Major diameter: The largest diameter of a tapered or nonuniform mandrel or part. Minor diameter: The smallest diameter of a tapered or nonuniform mandrel or part. Pole diameter: The minimum diameter at the end of a closed-end vessel. Sprocket diameter: The pitch diameter of the carriage drive sprocket. Eye diameter: The inside diameter of round or semicircular deliver eyes. The inside surface is usually toroidal in shape.
Doctor blade (or Bar): A straight piece of material (usually smooth metal) used to spread and control the amount of resin applied to the roving, tow tape, or fabric.
Doily: A planar reinforcement applied to local areas (usually around port openings) to provide additional strength.
Dome: In a cylindrical container, the portion that forms the integral ends of the container
Doubler: A local area with extra wound reinforcement, wound integrally with the part or wound separately and fastened to the part.
Dry winding: A process in which preimpregnated B-staged fibres are used in the winding.
E-glass: A borosilicate glass, the type most used for glass fibres for reinforced plastics.
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 and a yarn after twist has been applied); an individual warp yard, thread, fibre, or roving.
End count: An exact number of ends supplied on a ball or roving.
Epoxide equivalent weight (EEW): The weight of a resin in grams that contains one gram equivalent of epoxy.
Equator: In a pressure vessel, the juncture plane between the cylindrical portion and the end dome. Also called the tangent line.
Even tension: Describes the process whereby each end of roving is kept in the same degree of tension as the other ends making up that ball of roving.
Extractor: A machine used to pull off the mandrel through a small hole, stripping the part that was wet-wound onto the mandrel. A method of part removal.
Eye height: The distance between the delivery eye and the mandrel surface (measured in a radial direction from the mandrel axis).
Fatigue: The failure or decay of mechanical properties after repeated applications of stress. Fatigue tests give information on the ability of a material to resist the loss of strength from repetitive loading.
Fibre: A general term used to refer to filamentary materials. Often, fibre is used interchangeably with filament. It is a general term for a filament with a finite length that is at least 100 times its diameter, which is typically 0.004 to 0.005 in. (0.10 to 0.13 mm). (In most cases, it is prepared by drawing from a molten bath, spinning, or deposition on a substrate. Fibres can be continuous or specific short lengths, that is, discontinuous, normally no less than 1⁄8 in., or 3.2 mm).
Fibreglass: An individual filament made by attenuating molten glass. A continuous filament in a glass fibre of great or indefinite length.
Filaments: Individual fibres of indefinite length.
Filament winding: A process for fabricating a composite structure in which continuous reinforcements (filament, wire, yarn, tape, or other), previously impregnated with a matrix material or impregnated during the winding, are placed over a rotating and removable form or mandrel in a previously prescribed way to meet certain stress conditions. Generally, the shape is a surface of revolution and may or may not include end closures. When the right number of layers is applied, the wound form is cured and the mandrel removed.
Finish: A material applied to the surface of fibres in a roving or fabric used to reinforce plastics and intended to improve the physical properties of such reinforced plastics over that obtained using reinforcement without finish.
Finite element analysis/method (FEM/FEA): Structural analysis of a wound part by subdividing the system into smaller, simpler parts that are called finite elements. This is achieved by a particular space discretisation in the space dimensions, which is implemented by the construction of a mesh of the object, which has a finite number of points
Flow: The movement of resin under pressure, allowing it to fill all parts of a mold; the gradual but continuous distortion of a material under continued load, usually at high temperature. Also known as creep.
Fracture toughness: A measure of the damage tolerance of a material containing initial flaws or cracks. G1c and G2c are the critical strain energy release rates in the 1 and 2 directions.
Fuzz: Accumulation of loose, broken filaments (usually the result of abrasion).
G1c, G2c: See fracture toughness.
Gap (filament winding): The space between successive windings, which are usually intended to lay next to each other.
Gel: A semisolid system consisting of a network of solid aggregates in which liquid is held; the initial gellike solid phase that develops during the formation of a resin from a liquid.
Gel coat: A quick-setting resin applied to the surface of a mold and gelled before lay-up. The gel coat becomes an integral part of the finished laminate and is usually used to improve surface appearance and bonding.
Geodesic: The shortest distance between two points on a surface.
Geodesic-isotensoid contour: In a filamentwound reinforced plastic pressure vessel, a dome contour in which the filaments are placed on geodesic paths so that the filaments, when wet, will not slip on the mandrel surface and will exhibit uniform tension throughout their length under pressure loading.
Glass: An inorganic product of fusion that has cooled to a rigid condition without crystallizing. (Glass is typically hard and relatively brittle and has a conchoidal fracture.)
Graphite fibre: A fibre made from a precursor by an oxidation, carbonization, and graphitization process (which provides a graphitic structure). See also Carbon/Graphite fibre.
Hardener: A substance or mixture added to a plastic composition to promote or control the curing action by taking part in it.
Helical winding: In filament-wound items, a winding in which a filament band advances along a helical path, not necessarily at a constant angle, except in the case of a cylinder.
Hoop winding: Parallel winding at nearly 90° to the mandrel axis of rotation.
Hoop stress.: The circumferential stress in a material of cylindrical form subjected to internal or external pressure.
Hybrid: A composite laminate consisting of laminae of two or more composite material systems. A combination of two or more different fibres, such as carbon and glass or carbon and aramid, in a structure. Tapes, fabrics, and other forms may be combined; usually only the fibres differ. See also interply hybrid and intraply hybrid.
Impregnate: In reinforced plastics, the saturation of the reinforcement with a resin.
Interlaminar shear: Shearing force tending to produce a relative displacement between two laminae in a laminate along the plane of their interface.
Interpenetrating network (IPN): A combination of two polymers in a network in which at least one (or both) is synthesized and/or cross linked in the presence of the other
Interply hybrid: A reinforced plastic laminate in which adjacent laminae are composed of different materials.
Intraply hybrid: A reinforced plastic laminate in which different materials are used within a specific layer or band.
Isotropic: Having uniform properties in all directions. The measured properties of an isotropic material are independent of the axis of testing.
Joining path: The Cadfil software will also generate transitions in order to join one layer to the next. Requires user input in some cases, but is calculated automatically in pipewinder.
Joint: The location at which two adherends are held together. The general area of contact for a bonded, bolted, or riveted structure.
Joint lap: A joint made by cutting away similar angular segments of two adherends and bonding them with the cut areas fitted together.
Kevlar: An organic polymer, in fibre form, composed of aromatic polyamides having a paratype orientation (parallel chain with bonds extending from each aromatic nucleus).
Knuckle radius: The area of transition between the cylinder and dome in a filament wound vessel; for examples of vessel geometry, see the Vessel with Endcaps page, where knuckle radius is defined as R2 for a torispherical endcap.
Lamina: A single ply or layer in a laminate. A flat or curved surface containing fabric or unidirectional fibres.
Laminate (noun): A product made by lamination.
Laminate (verb): To unite sheets of material by a bonding material, usually with pressure and heat.
Lap: In filament winding, the amount of overlay between successive windings, usually intended to minimize gapping.
Lap joint: A joint made by placing one adherend partly over another and bonding the overlapped portions.
L/D ratio: A term to define a pressure vessel; denotes the ratio of chamber length to chamber diameter.
Liner: In a filament-wound pressure vessel, the continuous, usually flexible coating on the inside surface of the vessel, used to protect the laminate from chemical attack or to prevent leakage under strain. Pressure vessel liners are often metal, rubber, or thermoplastic.
Lite: A Cadfil software package for all parametrically defined vessels and pipes. see Cadfil Lite.
Longos: Low-angle helical or longitudinal windings. Also called longitudinals.
Mandrel: The form (usually cylindrical) around which resin-impregnated fibre is wound to form pipes, tubes, or vessels.
Mat: A sheet formed by filament winding a single-hoop ply of fibre on a mandrel, cutting across its width and laying out a flat sheet.
Matrix: See resin.
Mechanical properties: The properties of a material, such as modulus and compressive and tensile strengths, that are associated with elastic and inelastic reaction when force is applied. The individual relationship between stress and strain.
Moisture absorption: The pickup of water vapor from air by a material. It relates only to vapor withdrawn from the air by a material and must be distinguished from water absorption, which is the gain in weight due to the takeup of water by immersion.
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-release agent: A liquid or powder used to prevent sticking to the mandrel.
Monofilament: A single fibre or filament of indefinite length generally produced by extrusion; a continuous fibre of sufficient size to serve as yarn in normal textile operations. Also called monofil.
Multifilament yarn: A multitude of fine, continuous filaments (often 5 to 100 individual filaments), usually with some twist in the yarn to facilitate handling. Sizes range from 5 to 10 denier up to a few hundred denier. Individual filaments in a multifilament yarn are usually approximately 1 to 5 denier.
Multi-pipe: A Cadfil software package. See Pipewinder.
Netting analysis: The analysis of filament wound structures that assumes the stresses induced in the structure are carried entirely by the filaments; the strength of the resin is neglected. It also assumes that the filaments possess no bending or shearing stiffness and carry only the axial tensile loads.
NOL ring: A parallel filament- or tape-wound hoop test specimen developed by the Naval Ordnance Laboratory (NOL, now the Naval Surface Weapons Laboratory) for measuring various mechanical strength properties of the material, such as tension and compression, by testing the entire ring or segments of it.
Non-destructive inspection (NDI): A process or procedure, such as ultrasonic or radiographic inspection, for determining the quality or characteristics of a material, part, or assembly without permanently altering the subject or its properties. Used to find internal anomalies in a structure without degrading its properties. Also considered synonymous with nondestructive evaluation (NDE).
One-circuit winding: See Single-circuit winding.
Orthotropic: Having three mutually perpendicular planes of elastic symmetry.
Overtravel: The additional carriage or eye travel beyond the ends of the part mandrel that is necessary to provide laydown of the fibre on the mandrel.
Package: Yarn, roving, and so forth in the form of units capable of being unwound and suitable for handling, storing, shipping, and use.
Peel ply: A layer of open-weave material, usually fiberglass or heat-set nylon, applied directly to the surface of a prepreg lay-up. The peel ply is removed from the cured laminate immediately before bonding operations, leaving a clean, resin-rich surface that needs no further preparation for bonding, other than application of a primer where one is required.
Permeability: The passage or diffusion (or rate of passage) of a gas, vapor, liquid, or solid through a barrier without physically or chemically affecting it.
Pin ring: A ring that sits around the end of a mandrel, containing protruding pins, which fibres can wrap around to allow a short turning zone while avoiding the fibre slipping.
Plastic: A material that contains as an essential ingredient an organic polymer of large molecular weight, as well as hardeners, fillers, reinforcements, and so forth; is solid in its finished state; and, at some stage in its manufacture or its processing into finished articles, can be shaped by flow. A plastic may be either thermoplastic or thermoset.
Ply: A single layer of prepreg. A single pass in filament winding (two plies forming one layer).
PMR polyimides: A novel class of high-temperature-resistant polymers. PMR represents in situ polymerization of monomer reactants.
Polar winding: A winding in which the filament path passes tangent to the polar opening at one end of the chamber and tangent to the opposite side of the polar opening at the other end. Also known as planar winding.
Polyesters: Thermosetting 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 peroxide catalysts and promoters, or heat, to accelerate the reaction. The resins are usually furnished in solution form, but powdered solids are also available.
Polyetheretherketone (PEEK): A linear aromatic crystalline thermoplastic. A composite with a PEEK matrix may have a continuous use temperature as high as 480 °F (250 °C).
Polymer: A high-molecular-weight organic compound, natural or synthetic, whose structure can be represented by a repeated small unit, the mer, for example, polyethylene, rubber, and cellulose. Synthetic polymers are formed by addition or condensation polymerization of monomers. Some polymers are elastomers, some are plastics. When two or more monomers are involved, the product is called a copolymer
Pipewinder: A Cadfil software package for all parametrically defined pipes. see Cadfil Pipewinder.
Postcure: Additional elevated-temperature cure, usually without pressure, to improve final properties and/or complete the cure, or decrease the percentage of volatiles in the compound. 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.
Post processor:A Post Processor is a unique "driver" specific to a CNC machine, in Cadfil the post processor software changes the program output to suit a specific machine using an .sm file.
Pot life: The length of time that a catalysed thermosetting resin system retains a viscosity low enough to be used in processing. Also called working life.
Preimpregnation: The practice of mixing resins and reinforcement and effecting partial cure before use or shipment to the user. See also prepreg.
Prepreg: Ready-to-wind material in roving form that is impregnated with resin and stored for use. The resin generally is partially cured to a B-stage and supplied to the fabricator, who winds the finished shape and completes the cure with heat. A wet prepreg contains resin that is not pre-advanced and is subject to the same viscosity changes as a wet-wound resin system.
Quasi-isotropic: A material having isotropic properties, but only in-plane. In other words, the strength and stiffness are equal in all directions within the plane of the part.
Reinforced plastics: Molded, formed, filament-wound, tape-wrapped, or shaped plastic parts consisting of resins to which reinforcing fibres, mats, fabrics, and so forth have been added before the forming operation to provide some strength properties greatly superior to those of the base resin.
Reinforcement: A strong material bonded into a matrix to improve its mechanical properties. Reinforcements are usually long fibres, chopped fibres, whiskers, particulates, and so forth. The term should not be used synonymously with filler.
Release agent: A material that is applied in a thin film to the surface of a mold to keep the resin from bonding to the mandrel.
Resin: A solid, semisolid, or pseudosolid organic material that has a variable (often high) molecular weight, exhibits a tendency to flow when subjected to stress, usually has a softening or melting range, and usually fractures conchoidally. Most resins are polymers. In reinforced plastics, the material used to bind together the reinforcement material; the matrix.
Roving: A collection of bundles of continuous filaments either as untwisted strands or as twisted yarns. Rovings may be lightly twisted, but they generally are wound as bands or tapes with as little twist as possible.
Roving ball: A term used to describe the supply package offered to the winder. It consists of a number of ends or strands wound to a given outside diameter onto a length of cardboard tube.
S-glass: A magnesium aluminosilicate glass specially designed to provide very high-tensile-strength glass filaments. S-glass and S-2 glass fibres have the same glass composition but different finishes (coatings). S-glass is made to more demanding specifications, and S-2 is considered the commercial grade.
Single-circuit winding: A winding in which the filament path makes a complete traverse of the component, after which the following traverse lies immediately adjacent to the previous one. See also polar winding.
Size: A treatment applied to fibre to protect its surface.
Skein: A continuous filament, strand, yard, roving, and so on wound up to some measurable length.
Specific properties: Material properties divided by material density.
Spun roving: A heavy, low-cost glass fibre strand consisting of filaments that are continuous but doubled back on each other.
Stacking sequence: A description of a laminate that details the ply orientations and their sequence in the laminate. Also known as winding sequence.
Stiffness: The relationship of load and deformation; a term often used when the relationship of stress to strain does not conform to the definition of Young’s modulus.
Strain gage: Device to measure strain in a stressed material based on the change in electrical resistance.
Strand: An assembly of continuous filaments, without twist. When used as a unit, may include tows, ends, yarn, and denier.
Stress: The internal force per unit area that resists a change in size or shape of a body. Expressed in force per unit area.
Tangent line: The axial distance from the outside of the pressure vessel at the nearest dome to the intersection of the dome and the cylinder
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, or gpd). The yarn is usually pulled at the rate of 12 in./min. Tenacity equals breaking strength (grams) divided by denier.
Tensile strength: The maximum load or force per unit cross-sectional area, within the gage length, of the specimen. The pulling stress required to break a given specimen.
Tex: A metric term used to classify fibres, it refers to grams per 1000m of material (g/km).
Thermoplastic: Capable of being repeatedly softened by an increase in temperature and hardened 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, can be shaped by flow into articles by molding or extrusion.
Thermoset: A plastic that, when cured by application of heat or chemical means, changes into a substantially infusible and insoluble material.
Torsion: Twisting stress. In filament wound tubes winding at +/-45 degrees has maximum resistance to torsion
Toughness: A property of a material for absorbing work. The actual work per unit volume or unit mass of material that is required to rupture it. Toughness is proportional to the area under the load-elongation curve from the origin to the breaking point.
Tow: An untwisted bundle of continuous filaments. Commonly used in referring to manmade fibres, particularly carbon and graphite but also glass and aramid. A tow designated as 12K has 12,000 filaments.
Towpreg: Preimpregnated tow or strands for filament winding. It differs from typical prepreg tape in that the tow is wound onto the roving core without a separator sheet. The tow matrix has been adjusted in tack so that it unwinds freely. Also, the tow can have more lateral displacement on a mandrel than an equivalent-width tape because the individual tows can slip relative to the rest of the band.
Turns per inch (tpi): A measure of the amount of twist produced in a yarn, tow, or roving during its processing history. Also, the lead rate of a hoop layer at a specified band width.
Transition winds: see Joining path.
Unidirectional (UD) Composite: This is a composite in which all the fibres run in one direction only. Sometime woven fabrics are called UD when a small amount of fibre or other material may run in other directions to hold the primary fibres in position. UD material properties are often used to calculate the properties of a laminate made up of several layers at different orientations
Virgin filament: An individual filament that is in the same condition as when it was spooled, that is it has not been in processed in an way.
Viscosity: The property of resistance to flow exhibited within the body of a material, expressed in terms of relationship between applied shearing stress and resulting rate of strain in shear. Viscosity is usually taken to mean Newtonian viscosity, in which case the ratio of shearing stress to the rate of shearing strain is constant. In non-Newtonian behavior, which is the usual case with plastics, the ratio varies with the shearing stress. Such ratios are often called the apparent viscosities at the corresponding shearing stresses. In wet winding we normal want low viscosity to aid impregnation of the fibres and reduce friction on guides but sometimes higher viscosity to stop dripping and fibre slippage.
Voids: Air or gas that has been trapped and cured into a laminate. Porosity is an aggregation of microvoids. Voids are essentially incapable of transmitting structural stresses.
Volatiles: Materials in a sizing or a resin formulation that are capable of being driven off as a vapor at room, or slightly elevated, temperature.
Wafer: A reinforcement for port openings.
Wet-out: The condition of an impregnated roving or yarn wherein substantially all voids between sized strands and filaments are filled with resin.
Wet winding: A process in which the fibre reinforcement is coated with resin just prior to wrapping on the mandrel.
Wind angle: The angular measure in degrees between the direction parallel to the filaments and an established reference. In filament winding it is the convention to have zero degrees in the axial direction and 90 degrees in the hoop/circumferential direction.
Winding pattern: A regularly recurring pattern of the filament path after a certain number of mandrel revolutions, leading to the eventual complete coverage of the mandrel.Often referred to as the band pattern
Winding tension: In filament winding, the amount of tension on the reinforcement as it makes contact with the mandrel. Winding tension can influence resin content, propensity to slip at a specific wind angle, and residual stress, among others.
Xylophone: A musical instrument in the percussion family that consists of wooden bars struck by mallets. Irrelevant to filament winding, but begins with the letter 'x'.
Yarn: An assemblage of twisted filaments, fibres, or strands, either natural or manufactured, to form a continuous length that is suitable for use in weaving or interweaving into textile materials.
Yield: An English term used to classify glass; it refers to nominal yards of material per pound.
Young’s modulus: The ratio of normal stress to corresponding strain for tensile or compressive stresses less than the proportional limit of the material.
Zero-degree winds: Specialty winds for generating zero-angle winds that run the length of cylinders (generally combined with the use of specialized mandrels to catch the fibre at the ends of the part and prevent slippage).