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[ B ]
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Pressure
Resistance of a material, because of its viscosity, to
continued flow when a mould is closing.
Bag
Molding
A
technique in which the consolidation of the material in the
mould is affected by the application of fluid pressure
through a flexible membrane.
Balanced
Design
In
filament-wound reinforced plastics, a winding pattern so
designed that the stresses in all filaments are equal.
Balanced
Laminate
All
laminate plies, except those at 0°/90°, are placed in
plus/minus pairs (not necessarily adjacent) symmetrically
about the lay-up centreline. This minimises distortion on
demoulding.
Balanced
Twist
An
arrangement of twist in a plied yarn or cord which will not
cause twisting on itself when the yarn of cord is held in
the form of an open loop.
Barcol
Hardness
A
hardness value obtained by measuring the resistance to
penetration of a sharp steel point under a spring load. The
instrument, the Barcol Impressor, gives a direct reading on
a scale of 0 to 100. The hardness value is often used as a
measure of the degree of cure of a plastic.
Bare
Glass
Glass
(yarns, roving or fabrics) from which the sizing or finish
has been removed or before it has been applied.
Barrier
Cream
A cream
used to protect the skin from contact with resins.
Base
The
reinforcing material (glass fibre, paper, cotton, asbestos,
etc.) which is impregnated with resin in the forming of
laminates.
Bearing
Stress
The
applied load divided by the bearing area. (Maximum bearing
stress is the maximum load sustained by the specimen during
the test divided by the original bearing area.)
Benzoyl
Peroxide (BPO)
An
initiator for curing polyester resin. BPO is used with
aniline accelerators or where heat is used to cure the
resin.
Bias
Fabric
A fabric
in which warp and weft fibre are at an angle (usually ±45°)
to the length.
Biaxial
Load
A
loading condition in which a laminate is stressed in at
least two different directions in the plan of the laminate.
Biaxial
Winding
In
filament winding, a type of winding in which the helical
band is laid in sequence, side by side, with no crossover of
fibres.
Bidirectional Laminate
A
reinforced plastic laminate with the fibres oriented in two
directions (usually, but not necessarily, 0/90°) in the
plane of the laminate. (See also Unidirectional Laminate.)
Binder
The
agent applied to glass mat or preforms to bond the fibres
before laminating or moulding.
Bismaleimide
A type
of polyimide resin that cures by an addition reaction,
avoiding formation of volatiles, and has temperature
capabilities between those of epoxy and polyimide.
Bleeder
Cloth
A layer
of woven or non-woven material, not a part of the composite,
that allows excess gas and resin to escape during cure.
Bleedout
The
excess liquid resin that migrates to the surface of a
laminate in any pressure moulding process.
Blister
Undesirable rounded elevation of the surface of a plastic
with boundaries that are more or less sharply defined,
resembling in shape a blister on the human skin.
Block
Copolymer
An
essentially linear copolymer in which there are repeated
sequences of polymer segments of different chemical
structure some of which may be crystalline in nature, others
of which may be amorphous.
Bond
Strength
The
amount of adhesion between bonded surfaces; a measure of the
stress required to separate a layer of material from the
base to which it is bonded. (See also Peel Strength.)
Boron
Fibre
A fibre
usually of a tungsten-filament core with elemental boron
vapor deposited on it to impart strength and stiffness.
Braiding
A
process for assembling fibres into a tubular shape.
Breather
A
usually non-woven material that does not come in contact
with the resin but serves as a continuous vacuum path over a
part in production.
Bridging
A region
of a contoured part which has cured without being properly
compacted against the mould.
B Stage
An
intermediate stage in the reaction of certain thermosetting
resins. The resin in an uncured prepreg or premix is usually
in this stage. (See also A Stage, C Stage.)
Bubble
A
spherical internal void; globule of air or other gas trapped
in a plastic.
Buckling
Crimping
of fibres in a composite material, often occurring in
glass-reinforced thermoset due to resin shrinkage during
cure.
Bulk
Density
The
density of a moulding material in loose form (granular,
nodular. etc.), expressed as a ratio of weight to volume.
Burst
Strength
Hydraulic pressure required to burst a vessel of given
thickness; commonly used in testing filament-wound composite
structures.
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[ C ]
CAD
Computer-aided design.
CAM
Computer-aided manufacturing.
Carbon-carbon
A
composite of carbon fibre in a carbon matrix.
Carbon
Fibre
An
important reinforcing fibre known for its light weight, high
strength, and high stiffness that is produced by pyrolysis
of an organic precursor fibre in an inert atmosphere at
temperatures above 1800°F (982°C). The material may also be
graphitised by heat treating above 3000°F (1649°C).
Casting
The
process of pouring a mixture of resin, fillers and/or fibers
into a mold as opposed to building up layers through
lamination. This technique produces different physical
properties from laminating.
Catalyst
A
substance which changes the rate of a chemical reaction
without itself undergoing permanent change in its
composition; a substance which markedly speeds up the cure
of a compound when added in small quantity compared with 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.
Caulk
An
elastic material used to protect joints or connections from
external elements, particularly moisture.
Caul
Plate
A sheet
the size of the platens used in hot pressing, or other
pressure moulding processes.
Cavity
The
space between a male and female mold set in which the part
is formed. Sometimes used to refer to a female mold.
Centipoise
A unit
of measure used to describe the viscosity of a liquid.
Viscosity is measured with a Brookfield Viscometer for most
polyester resin applications.
Centrifugal Casting
A high
production technique for cylindrical composites, such as
pipe, in which chopped fibre and resin is positioned inside
a hollow mandrel designed to be heated and rotated as resin
is added and cured.
Ceramic
Matrix Composites
Materials consisting of a ceramic or carbon fibre surrounded
by a ceramic matrix, usually silicon carbide.
Chalking
A
surface phenomenon indicating degradation of a cosmetic
surface. Chalking is a powdery film which appears lighter
than the original color.
Charge
The
measurement or weight of material (liquid, preformed, or
powder) used to load a mould at one time or during one
cycle.
Chemical
Vapor Deposition (CVD)
A
process in which desired reinforcement material is deposited
from vapor phase onto a continuous core; boron on tungsten,
for example.
Chill
(1) To
cool a mould by circulating water through it. (2) To cool a
moulding with an air blast or by immersing it in water.
Chopped
Strand Mat
A
fiberglass reinforcement consisting of short strands of
fiber arranged in a random pattern and held together with a
binder. Mat is generally used in rolls consisting of 3/4
oz/ft2 material to 2 oz/ft2 material.
Circuit
In
filament winding (1) one complete traverse of the fibre-feed
mechanism of a winding machine; (2) one complete traverse of
a winding band from one arbitrary point along the winding
path to another point on a plane through the starting point
and perpendicular to the axis.
Circumferential (“circ”) Winding
In
filament-wound reinforced plastics a winding with the
filaments essentially perpendicular to the axis.
Clamping
Pressure
In
injection moulding and transfer moulding the pressure
applied to the mould to keep it closed, in opposition to the
fluid pressure of the compressed moulding material.
Cloth
A
fiberglass reinforcement made by weaving strands of glass
fiber yarns. Cloth is available in various weights measured
in ounces per square yard or Kg/m2.
Co-curing
Simultaneous bonding and curing of components, or dissimilar
materials.
Coefficient of Elasticity
The
reciprocal of Young’s modulus in a tension test.
Coefficient of Expansion
The
fractional change in dimension of a material for a unit
change in temperature. Also called coefficient of thermal
expansion.
Coefficient of Friction
A
measure of the resistance to sliding of one surface in
contact with another surface.
Coefficient of Thermal Expansion
The
change in length per unit length produced by a unit rise in
temperature.
Cohesion
(1) The
propensity of a single substance to adhere to itself. (2)
The internal attraction of molecular particles toward each
other. (3) The force holding a single substance together.
Cohesive
Failure
Failure
of a bonded joint within the adhesive itself.
Cold-setting Adhesive
A
synthetic resin adhesive capable of hardening at normal room
temperature in the presence of a hardener.
Color
Stability
The
ability of a surface coating or pigment to resist
degradation due to environmental exposure.
Co-mingled Yarn
A hybrid
yarn made with two types of materials intermingled in a
single yarn, for example, thermoplastic filaments
intermingled with carbon filaments to form a single yarn.
Composite
A
homogeneous material created by synthetic assembly of two or
more materials (selected filler or reinforcing elements and
compatible matrix binder) to obtain specific characteristics
and properties. Composites are subdivided into the following
classes on the basis of the form of the structural
constituents; fibrous: the dispersed phase consists of
fibers; flake: the dispersed phase consists of flat flakes;
laminar: composed of layers of laminate constituents;
particulate: dispersed phase consists of small particles;
skeletal: composed of a continuous skeletal matrix filled by
a second material.
Compression Molding
A
technique for molding thermoset plastics in which a part is
shaped by placing the fibre and resin into an open mould
cavity, closing the mould, and applying heat and pressure
until the material has cured or achieved its final form.
Compression Molding Pressure
The
pressure applied to the moulding material in the mould.
Compressive Modulus Ec
Ratio of
compressive stress to compressive strain below the
proportional limit. Theoretically equal to Young’s modulus
determined from tensile experiments.
Compressive Strength
(1) The
ability of a material to resist a force that tends to crush.
(2) The crushing load at the failure of a specimen divided
by the original sectional area of the specimen.
Compressive Stress
The
compressive load per unit area of original cross section
carried by the specimen during the compression test.
Condensation Reaction
A
polymerisation reaction in which simple by-products (for
example, water) are formed.
Connection
Where
two panels are attached to each other or a panel is attached
to the building.
Consolidation
A
processing step that compresses fibre and matrix to reduce
voids and achieve a desired density.
Contact
Molding
A
process for molding reinforced plastics in which
reinforcement and resin are placed on an open mould, cure is
at room temperature using a catalyst-promoter system or by
heat in an oven, and no additional pressure is used.
Continuous Filament
An
individual flexible fibre of glass of small diameter and
great or indefinite length.
Continuous-filament Yarn
Yarn
formed by twisting two or more continuous filaments into a
single continuous strand.
Continuous Laminating
An
automated process for forming panels and sheeting in which
fabric or mat is passed through a resin bath, brought
together between covering sheets, and passed through a
heating zone for cure. Squeeze rolls control thickness and
resin content as the various plies are brought together.
Continuous Roving
Parallel
filaments coated with sizing, gathered together into single
or multiple strands, and wound into a cylindrical package.
It may be used to provide continuous reinforcement in woven
roving, filament winding, pultrusion, prepregs, or high
strength moulding compounds, or it may be used chopped.
Cooling
Fixture
A
fixture used to maintain the shape or dimensional accuracy
of a moulding after it is removed from the mould and until
the material is cool enough to hold its shape.
Core
(1) The
central member of a sandwich construction to which the faces
of the sandwich are attached. (2) A channel in a mould for
circulation of heat-transfer media.
Count
(1) For
fabric the number of warp and weft yarns per cm in woven
cloth. (2) For yarn the size based on relation of length and
weight. Basic unit is a tex which is the weight in grammes
of 1000 linear metres of the fibre.
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.
Cowoven
Fabric
A
reinforcement fabric woven with two different types of
fibres in individual yarns, for example, thermoplastic
fibres woven side by side with carbon fibres.
Crazing
Fine
cracks which may extend in a network on or under the surface
of a plastic material.
Creel
A device
for holding the required number of fibre bobbins in the
desired position for unwinding.
Creep
The
change in dimension of a plastic under load over a period of
time not including the initial instantaneous elastic
deformation; at room temperature it is called cold flow.
Crimp
The
waviness of a fibre, particularly in a woven fabric.
Critical
Length
The
minimum length of a fibre necessary for matrix shear loading
to develop fibre ultimate strength by a matrix.
Critical
Strain
The
strain at the yield point.
Crosswise Direction
Refers
to cutting specimens and to application of load. For rods
and tubes, crosswise is the direction perpendicular to the
long axis. For other shapes or materials that are stronger
in one direction than in another, crosswise is the direction
that is weaker. For materials that are equally strong in
both direction, crosswise is an arbitrarily designed
direction at right angles to the length.
Crystallinity
The
quality of having a molecular structure with atoms arranged
in an orderly, three-dimensional pattern.
C Stage
The
final stage in the reaction of certain thermosetting resins
in which the material is relatively insoluble and infusible.
The resin in a fully cured thermoset moulding is in this
stage. (See also A Stage, B Stage.)
Cure
To
change the properties of a resin by chemical reaction, which
may be condensation or addition; usually accomplished by the
action of heat or catalyst, or both, and with or without
pressure.
Curing
Agent
Hardener, a catalytic or reactive agent added to a resin to
cause polymerisation. Curing agents participate in the
polymerisation process. They may be latent - curable only at
elevated temperatures - or they may be activated at room
temperature (25°C).
Curing
Temperature
Temperature at which a cast, moulded, or extruded product, a
resin impregnated reinforcement, an adhesive, etc., is
subjected to curing.
Curing
Time
The
length of time a part is subjected to heat or pressure, or
both, to cure the resin. (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 moulding, the cycle time is the
elapsed time between a certain point in one cycle and the
same point in the next.
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[ D ]
D Glass
A
high-boron-content glass made especially for laminates
requiring precisely controlled dielectric constant.
Damage
Tolerance
A
measure of the ability of structures to retain load carrying
capability after exposure to sudden loads (for example,
ballistic impact).
Damping
(Mechanical)
Mechanical damping gives the amount of energy dissipated as
heat during the deformation of a material. Perfectly elastic
materials have no mechanical damping. Damping also
diminishes the intensity of vibrations.
Daylight
The
distance in the open position between the moving and fixed
tables (platens) of a hydraulic press. For a multidaylight
press, daylight is the distance between adjacent platens.
Debond
An
unplanned nonadhered or unbonded region in an assembly.
Deflection Temperature Under Load
The
temperature at which a simple beam has deflected a given
amount under load (formerly called heat-distortion
temperature).
Deformation Under Load
The
dimensional change of a material under load for a specific
time following the instantaneous elastic deformation caused
by the initial application of the load; also called cold
flow or creep.
Delaminate
To split
a laminated plastic material along the plane of its layers.
(See also Laminate.)
Delamination
Physical
separation or loss of bond between laminate plies.
Denier
A yarn
and filament numbering system in which the yarn number is
equal numerically to the weight in grams of 30,000 ft (9144
m) (used for continuous filaments). The lower the denier the
finer the yarn.
Density
A
comparison of weight per volume, measured in pounds per
cubic foot.
Design
Allowable
A
limiting value for a material property that can be used to
design a structural or mechanical system to a specified
level of success with 95% statistical confidence. B-basis
allowable: material property exceeds the design allowable 90
times out of 100. A-basis allowable: material property
exceeds the design allowable 99 times out of 100.
Dielectric
A
nonconductor of electricity.
Dielectric Constant
(1) The
ratio of the capacity of a capacitor having a dielectric
material between the plates to that of the same capacitor
when the dielectric is replaced by a vacuum. (2) A measure
of the electrical charge stored per unit volume at unit
potential.
Dielectric Strength
The
value of a material as an electrical insulator or the
resistance to the flow of electric current.
Dimensional Stability
Ability
of a plastic part to retain the precise shape to which it
was moulded, cast, or otherwise fabricated.
Displacement Angle
In
filament winding the distance of advance of the winding
ribbon on the equator after one complete circuit.
Distortion
A change
in shape form that which is intended.
Doctor
Roll
A device
for regulating the amount of liquid material on the rollers
of a spreader; also called doctor bar or doctor blade.
Doily
In
filament winding the planar reinforcement applied to a local
area between windings to provide extra strength in an area
where a cutout is to be made, e.g. port openings.
Dome
In
filament winding the portion of a cylindrical container that
forms the integral ends of the container.
Doubler
Localised area of extra layers of reinforcement, usually to
provide stiffness or strength for fastening or other abrupt
load transfers.
Draft
The
taper or slope of the vertical surfaces of a mould designed
to facilitate removal of moulded parts.
Draft
Angle
The
angle between the tangent to the surface at that point and
the direction of ejection.
Drape
The
ability of preimpregnated broad goods or dry fabrics to
conform to an irregular 3-D shape; textile conformity.
Dry
Winding
Filament
winding using preimpregnated roving, as differentiated from
wet winding. (See also Wet Winding.)
Dry
Lay-up
Construction of a laminate by layering preimpregnated
reinforcement in a female or male mould, usually followed by
bag moulding or autoclave moulding.
DSC
Differential scanning calorimeter. Instrumentation for
measuring chemical reactions by observing exothermic or
endothermic (heat output or heat input) reactions of
materials - usually over a programmed temperature cycle.
Dwell
(1) A
pause in the application of pressure to a mould, made just
before the mould is completely closed, to allow gas to
escape from the moulding material. (2) In filament winding
the time the traverse mechanism is stationary while the
mandrel continues to rotate to the appropriate point for the
traverse to begin a new pass. (3) A pause in the temperature
rise of a cure cycle, where the part being cured is held at
a constant temperature for a period.
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[ E ]
Edgewise
Refers
to the application of load. The load is applied edgewise
when it is applied to the edge of the original sheet or
specimen.
E Glass
A
borosilicate glass; the type most used for glass fibres for
reinforced plastics; suitable for electrical laminates
because of its high resistivity. (Also called electric
glass.)
Ejection
Removal
of a moulding from the mould impression by mechanical means,
by hand, or by using compressed air.
Elastic
Deformation
The part
of the total strain in a stressed body which disappears upon
removal of the stress.
Elasticity
The
property of plastics materials by virtue of which they tend
to recover their original size and shape after deformation.
Elastic
Limit
The
greatest stress which a material is capable of sustaining
without permanent strain remaining upon the complete release
of the stress. A material is said to have passed its elastic
limit when the load is sufficient to initiate plastic
(nonrecoverable) deformation.
Elastic
Recovery
The
fraction of a given deformation that behaves elastically.
Elastic
recovery = elastic extension
total
extension
Electroformed Moulds
A mould
made by electroplating metal on the face of a mould.
Elongation
Deformation caused by stretching; the fractional increase in
length of a material stressed in tension. (When expressed as
percentage of the original gauge 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 and a yarn after twist has been
applied): an individual warp yarn, thread, fibre, or roving.
Encapsulating
Completely surrounding an object with resin or a fiber resin
composite.
EpoxyResin
A
polymer resin characterized by epoxide molecule groups.
Even
Tension
The
process whereby each end of roving is kept in the same
degree of tension as the other ends.
Exotherm
The
liberation or evolution of heat during curing of a plastic
product.
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[ F ]
Fabric
A
material constructed of interlaced yarns, fibres, or
filaments, usually planar.
Fabric,
nonwoven
A
material formed from fibres or yarns without interlacing.
Fabric,
woven
A
material constructed of interlaced yarns, fibres, or
filaments.
Fabricating, fabrication
The
manufacture of plastic products from moulded parts, rods,
tubes, sheeting, extrusions, or other form by appropriate
operations such as punching, cutting, drilling, and tapping.
Fabrication includes fastening plastic parts together or to
other parts by mechanical devices, adhesives, heat sealing,
or other means.
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 development of
cracks, which eventually bring about failure as a result of
a large number of cycles.)
Fatigue
Life
The
number of cycles of deformation required to bring about
failure of the test specimen under a given set of
oscillating conditions (pressure/load).
Fatigue
Limit
The
stress below which a material can be stressed cyclically for
an infinite number of times without failure.
Fatigue
Strength
(1) The
maximum cyclic stress a material can withstand for a given
number of cycles before failure occurs. (2) The residual
strength after being subjected to fatigue.
Felt
A
fibrous material made from interlocked fibres by mechanical
or chemical action, moisture, or heat; made from asbestos,
cotton, glass, etc.
Female
Mold
A
concave mold used to precisely define the convex surface of
a molded part.
Fibre-composite Material
A
material consisting of two or more discrete physical phases,
in which a fibrous phase is dispersed in a continuous matrix
phase. The fibrous phase may be macro-, micro-, or
submicroscopic, but must retain its physical identity so
that it can be removed from the matrix intact.
Fibre
Glass
An
individual filament made by extruding fibres from molten
glass.
Fibre
Diameter
The
measurement of the diameter of individual filaments.
Fibre-matrix Interface
The
region separating the fibre and matrix phases, which differs
from them chemically, physically, and mechanically. In most
composite materials, the interface has a finite thickness
(nanometers to thousands of nanometers) because of diffusion
or chemical reactions between the fibre and matrix. Thus,
the interface can be more properly described by the terms
interphase or interfacial zone.
Fibre
Pattern
(1)
Visible fibres on the surface of laminates or mouldings. (2)
The thread size and weave of fabrics.
Fibre
Placement
A
continuous process for fabricating composite shapes with
complex contours and/or cutouts by means of a device that
lays preimpregnated fibres (in tow form) onto a non-uniform
mandrel or tool. It differs from filament winding (below) in
several ways: there is no limit on fibre angles; compaction
takes place online via heat, pressure, or both; and fibres
can be added and dropped as necessary. The process produces
more complex shapes and permits a faster putdown rate than
filament winding.
Filament
Any
fibre whose aspect ratio (length to effective diameter) is
for all practical purposes infinity, i.e. a continuous
fibre.
Filament
Winding
A
process for fabricating a composite structure in which
continuous reinforcements (filament, wire, yarn, tape, or
other) impregnated with a matrix material either previously
or during the winding are placed over a rotating removable
form or mandrel in a prescribed way to meet certain stress
conditions. When the right number of layers has been
applied, the wound form is cured and the mandrel removed.
Fill
(Also
known as weft). Yarn oriented at right angles to the warp in
a woven fabric.
Filler
A
relatively inert material added to a plastic mixture to
reduce cost, modify mechanical properties, serve as a base
for colour effects, or improve the surface texture.
Fillet
A
radiused joint of adhesive between two surfaces being
bonded.
Filling
Yarn
The
transverse threads or fibres in a woven fabric, i.e. fibres
running perpendicular to the warp; also called weft.
Film
Adhesive
A
synthetic resin adhesive in the form of a thin dry film of
resin with or without a carrier.
Finish
A
material applied to the surface of fibres in a fabric used
to reinforce plastics, and intended to improve the physical
properties of the reinforced plastics over those obtained
using reinforcement without finish. Not to be confused with
"size" (q.v.).
Fish Eye
The
effect of surface contamination which causes a circular
separation of a paint or gel coat.
Flame
Resistance
Ability
of a material to not support flame once source of heat is
removed.
Flame
Retardants
Chemicals used to reduce or eliminate the tendency of a
resin to burn.
Flame-retarded Resin
A resin
compounded with certain chemicals to reduce or eliminate its
tendency to burn.
Flammability
A
measure of the extent to which a material will support
combustion.
Flange
An
extension around the perimeter of a mold or part for the
purpose of demolding, stiffening or connecting two
components.
Flash
Point
The
lowest temperature at which a substance gives off enough
vapors to form a flammable mixture.
Flatwise
Refers
to cutting specimens and the application of load. The load
is applied flatwise when it is applied perpendicular to the
flat face of the original sheet or specimen.
Flexural
Modulus
The
ratio, within the elastic limit, of the applied stress on a
test specimen in flexure to the corresponding strain in the
outermost fibres of the specimen.
Flexural
Rigidity
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