A Air Entrapment Occlusion of air in a resin or resin glass system, giving rise to blisters, bubbles or voids in the system. B Barcol Hardness A measure of the hardness of a laminate using a Barber-Coleman spring-loaded indenter. C 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. Catenary A term describing the uniformity of strand length in a specified length of roving stretched under tension. Poor catenary means some strands in the roving length are longer than others. Chopability A term describing the ease with which a reinforcement can be cut. Chopper Gun A special piece of equipment used in the manufacture of reinforced plastic parts, which chops glass and sprays resin and catalyst simultaneously onto a molded surface. Chopped Strand Continuous roving that is chopped into short lengths for use in mats, spray-up or molding compounds. Composite A material that combines fiber and bonding matrix to maximize specific performance properties. Neither element merges completely with the other. 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. 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, prepegs 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. Creel Pack A type of packaging wherein many rovings are connected in a continuous sequence, allowing full pallet run-out before stopping to splice in a new pallet. D Delaminate The physical separation or loss of bond between laminate plies or layers. Dielectric Nonconductor of electricity. The ability of a material to resist the flow of an electrical current. Direct Wound Roving A roving made directly at the bushing that does not go through a roving process. Typical characteristics are: single-end roving, coreless, 6-inch diameter centers and no catenary. 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 Chop Chopping a roving without the simultaneous admixture of resin and catalyst. Dry Spot An area of incomplete coating film on laminated plastics; in reinforcements, an area in which the interlayer and the glass are not bonded. Dry Strength The strength of a test specimen in the completely cured state determined in a standard laboratory atmosphere. Dry Winding A filament winding operation in which resin is not used. Durometer Hardness: The hardness of a material determined by Shore durometer. E Ease of Rollout The relative facility with which a sprayed admixture of chopped glass and resin can be compacted by rolling. Elasticity The property of materials by virtue of which they tend to recover their original shape and size at room temperature after deformation. Elastic Deformation The part of the total strain in a material under stress that recovers upon removal of the stress. Elastic Limit The greatest stress a material is capable of sustaining without permanent strain remaining after complete release of the stress. Elongation The fractional increase in length of a material stressed in tension. When expressed as a percentage of the original length, it is called percentage elongation. 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. End Count The number of strands contained in a roving. F 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. Fan Pattern A term denoting the dispersion of chopped glass when being used as a gun roving. A wide fan pattern is indicative of good dispersion. Feathered Edge In reference to chopped strand mat, this is a mat whose edge was not trimmed during production. Consequently, the edge 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 Amount of fiber in a composite expressed as a ratio to the matrix. The most desirable fiber content is a 60:40 ratio, or 60 percent fiber to 40 percent matrix resin. Fiber Diameter A term used to denote the diameter of continuous glass filaments. Their diameter can vary depending on the purpose for which they are to be used. Can be expressed in letter designation, microns or inches. Fiber Prominence The appearance of reinforcement fibers in the surface of a molded part. Can also be termed pattern print-thru, strike-thru 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. Filament A single glass fiber that is drawn from one tip of a bushing. Filamentization A phenomenon in which a coated strand breaks up into loose individual filaments. Filamentize The process whereby a glass strand breaks up into loose filaments. Filament Winding An automated process for fabricating composites in which continuous roving, either preimpregnated with resin or drawn through a resin bath, are wound around a rotating mandrel. Fill That part of a woven fabric in which the strands are perpendicular to the main direction of the fabric. Also called weft. Filler Material added to the mixed resin to increase viscosity, improve appearance and/or lower the density and cost. Flexural Strength The strength of a material in bending expressed as the stress of a bent test sample at the instant of failure. Usually expressed in force per unit area. Fly Loose filaments of fiber that have broken from their parent strand during processing and are freely floating in the air. Fracture A rupture of the surface of a laminate due to external or internal forces; may or may not result in complete separation. Fuzz Detached and broken glass fiber that has collected on processing equipment. G 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 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. Green Strength The strength of a freshly molded part that hasn't completely cured. 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. Hang-Up Fiber accumulations in a preform hood or other surface caused by static electricity. Heat Term used colloquially to indicate any temperature above ambient (room) temperature, to which a part or material is or will be subjected. Heat-Distortion Temperature (HDT) Temperature at which a test bar deflects a certain amount under specified temperature and stated load. 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. Hybrid Composite A composite made with two or more types of reinforcing fibers in a gun or chopper gun. I Impact Strength The energy required to break a standard-size specimen using a weighted pendulum. Impregnate To saturate the voids and interstices of a reinforcement with a resin. Impregnated Resin See Prepeg. Injection Molding Method of forming a plastic to the desired shape by forcibly injecting the polymer into the mold. K Kevlar® Strong, lightweight aramid fiber trademarked by DuPont, used as a reinforcement fiber L Laminate To unite layers with a bonding material, usually with pressure and heat. Laminate Ply One fabric/resin or fiber/resin layer that is bonded to adjacent layers in the curing process. Lay-Up Placement of layers of reinforcement in the mold. Linear Coefficient of Thermal Expansion The change in length per unit length produced by a one degree change in temperature. Loft The height of the glass lay-down either dry (as in chopping SMC glass) or wet (as in the height of the glass/resin mixture in a spray-up on the mold before roll-out). Low Profile Resin compounds formulated for low or zero shrinkage during molding. M Mat A finished product composed of chopped fiberglass strands uniformly distributed in a random fashion and bonded together, usually with a powdered polyester resin to form an integral blanket of glass fiber. 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. Milled Fiber Continuous glass or carbon strands hammermilled into very short fibers. Modulus The physical measurements of stiffness in a material, which equals the ratio of applied load (stress) to the resultant deformation of a material, such as elasticity or shear. A high modulus indicates a stiff material. Modulus of Elasticity The ratio of stress applied to the strain produced in a material that is elastically deformed. Multifilament A yarn consisting of many continuous fibers. P Plastic A high molecular weight thermoplastic or thermosetting polymer that can be molded, cast, extruded or laminated into objects. A major advantage of plastics is that they can deform significantly without rupturing. Plastic Deformation The change in dimensions of an object under load that is not recovered when the load is removed; opposed to elastic deformation. Porosity The presence of visible voids within a solid material into which either air or liquids can pass. Positive End Count An end count or count of strands in a roving that does not deviate from a specified number of strands. Preform A process in the manufacture of reinforced plastic parts wherein the glass reinforcement is processed into a predetermined shape approximating the mold cavity to be used in molding the final product. Prepeg Resin-impregnated fibers, fabric or mat in flat form that is preimpregnated with resin before being stored for later use in molds and in hand lay-up. 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. R Resin A solid or pseudosolid material with indefinite and often high molecular weight and a softening or melting range that exhibits a tendency to flow when subjected to stress. As composite matrices, resins bind together reinforcement fibers. Resin Rich Localized area filled with excess resin as compared to consistent resin/fiber ratio. Resin Starved Localized areas lacking sufficient resin for fiber wet-out. Resin Transfer Molding (RTM) A molding process in which catalyzed resin is pumped into a two-sided, matched mold where a fibrous reinforcement has been placed. The mold and/or resin may or may not be heated. Ribbonization A phenomenon occurring in a finished roving on which the individual strands have "blocked" or bonded together to give a ribbon of strands. 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 specified number of single strands wound up in parallel to give a spool of glass fibers. S SCRIMP Seamann Composite Resin Infusion Molding Process. Sheet Molding Compound (SMC) A ready-to-mold glass fiber reinforced polyester material primarily used in compression molding. Shore Hardness A measure of the resistance of a material to indentation by a spring-loaded indenter. The degree of rebound by the indenter is measured on a graduated scale. The harder the material, the greater the rebound of the indenter and the higher the numerical ＆#118alue. Sizing A water-based resin coating that is applied to fiberglass strands. The coating not only protects the strands and makes them easy to handle, but it also determines, in part, the process for which the strand can be used and the compatibility with particular resin systems. 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 traveling between the gun and the mold. Spray-Up Technique in which continuous strand roving is fed into a chopper gun, which chops the roving into predetermined lengths. The gun sprays the chopped fiber, along with a measured amount of resin and catalyst, onto an open mold. Static The tendency of the glass reinforcement to acquire charge during chopping with the result that the chopped fiber clings to equipment, operators and so on, having relatively less or opposite polarity. Stop Motion A device on a creel that quickly stops the winder when a strand breaks so that the strand can be repaired/replaced for further winding. Strand A group of filaments coated and gathered together in a bundle. Strand Integrity A term indicating degree of bonding between the filaments in a glass fiber strand. Generally, a higher degree of bonding results in more integrity in the strand. Stress Internal resistance to change in size or shape, expressed in force per unit area. Stress Crack External or internal cracks in a composite caused by tensile stresses; cracking can be present internally, externally or in combination. T Tensile Strength Maximum strength sustained by composite specimen before it fails in a tension test. Thermal Stress Cracking Crazing and cracking of some thermoplastic resins from overexposure to elevated temperatures. 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). U Unidirectional Refers to fibers that are oriented in the same direction, such as unidirectional fabric, tape or laminate. Often called UD. V Vacuum Bag Molding Molding technique wherein the part is cured inside a layer of film from which entrapped air is removed by vacuum. 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.