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Air Entrapment: Occlusion of air in a resin or resin glass
system, giving rise to blisters, bubbles or voids in the system.
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Barcol Hardness: A measure of the hardness of a laminate using
a Barber-Coleman spring-loaded indenter.
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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. |
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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.
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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. |
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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. |
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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. |
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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. |
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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. |
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| Kevlar®:
Strong, lightweight aramid fiber trademarked by DuPont, used as a
reinforcement fiber. |
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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. |
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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. |
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Nonwoven Roving: A reinforcement composed
of continuous fiber strands loosely gathered together. |
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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.
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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. |
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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 value.
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.
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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). |
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Unidirectional: Refers to fibers that
are oriented in the same direction, such as unidirectional fabric,
tape or laminate. Often called UD. |
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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. |
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