COMPRESSION & THERMOSET MOLDING TERMINOLOGY

Nov 4, 2022
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Sutherland News

Like any industry, molding of Composites has a plethora of terminology that can be daunting to someone new to the industry. Below are some of the most common terms used within the compression molding and Resin Transfer molding industry, as well as a brief overview of what they mean. Some of the terms apply to the strength and properties of the reinforcements and the compression or RTM molded components.

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1. Additive

Any substance added to another substance, usually to improve properties, such as plasticizers, initiators, light stabilizers, and flame retardants. See also filler.

2. Adhesion

The state in which two surfaces are held together at an interface by mechanical or chemical forces, interlocking action, or both.

3. Adhesive

A substance capable of holding two materials together by surface attachment. Adhesive can be in film, liquid, or paste form.

4. Air-Bubble Void

Air entrapment within and between the plies of reinforcement or within a bond line or encapsulated area; localized, non-interconnected, spherical in shape.

5. Areal Weight

The weight of fiber per unit area (width x length) of tape or fabric.

6. Aramid

Aromatic polyamide fibers characterized by excellent high-temperature, flame-resistant, and electrical properties.

7. A-Stage

An early stage in the reaction of a thermosetting resin in which the material is still soluble and fusible

8. Balanced Laminate

A composite laminate in which all laminate at angles other than 0¬į and 90¬į occur only in + pairs(not necessarily adjacent) and are symmetrical around the centerline.

9. Barcol Hardness

A hardness value obtained by measuring the resistance to penetration of a sharp steel point under a spring load. The instrument, called the Barcol impressor, gives a direct reading on a 0 to 100scale. The hardness value is often used as a measure of the degree of cure of aplastic.

10. Batch

In general, a quantity of material formed during the same process or in one continuous process and having identical characteristics throughout. Also known as "lo

11. Binder

The resin or cementing constituent (of a plastic compound) that holds the other components together. The agent applied to fiber mat or preforms to bond the fibers before laminating or molding.

12. Bridging

Condition in which fibers do not move into or conform to radii and corners during molding, resulting in voids and dimensional control problems.

13. B-Stage

An intermediate stage in the reaction of a thermosetting resin in which the material melts when heated and dissolves in certain solvents. Materials are usually precured to this stage to facilitate handling and processing prior to final cure.

14. Bulk Factor

The ratio of the volume of a raw molding compound or powdered plastic to the volume of the finished solid piece produced therefrom. The ratio of the density of the solid plastic object to the apparent or bulk density of the loose molding powder.

15. Bulk Molding Compound (BMC)

Thermosetting resin mixed with strand reinforcement, fillers, and so on, into a viscous compound for compression or injection molding. See also sheet molding compound.

16. Carbon Fibers

Fibers produced from pyrolytic degradation of synthetic organic fibers, polyacrylonitrile (PAN) or rayon, which contain about 92-99% carbon content and typically have modulus values up to 75 x 106 psi.

17. Catalyst

A substance that changes the rate of a chemical reaction without itself undergoing permanent change in composition or becoming a part of the molecular structure of the product. A substance that markedly speeds up the cure of a compound when added in minor quantity as compared to the amounts of primary reactants.

18. Caul Plates

Smooth metal, plastic, or rubber plates free of surface defects. A caul plate must be the appropriate size and shape for the composite lay-up with which it will be used. It is used in immediate contact with the lay-up during the curing process to transmit normal pressure and provide a smooth surface on the finished part.

19. Cavity

The space inside a mold in which a resin or molding compound is poured or injected. The female portion of a mold. That portion of the mold that encloses the molded article(often referred to as the die). Depending on the number of such depressions, molds are designated as single cavity or multiple cavities.

20. Coefficient of Thermal Expansion

The fractional change in length of a material for each unit change in temperature.

21. Composite

A material made up of 2 or more individual components whose combined physical strength exceeds their individual properties.

22. 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.

23. Compressive Strength

Ratio of compressive stress to compressive strain below the proportional limit. Theoretically equal to Young's modulus determined from tensile experiments.

24. Core

The central component of a sandwich construction to which the sandwich faces or skins are attached; also, part of a complex mold that forms undercut parts.

25. Core Crush

A collapse, distortion, or compression of the core.

26. Coupon

Usually, a specimen for a specific test, as a tensile coupon.

27. Creep

The dimensional change in a material under physical load over time beyond instantaneous elastic deformation.

28. Cross Laminated

Material laminated so that some of the layers are oriented at various angles to the other with respect to the laminate grain. A cross-ply laminate usually has plies oriented only at 0 and 90 degrees.

29. Cross-Linking

Applied to polymer molecules, the setting-up of chemical links between the molecular chains. When extensive, as in most thermosetting resins, cross-linking makes one infusible super molecule of all the chains.

30. C-Stage

The final stage of the curing of a thermosetting resin in which the material has become infusible and insoluble in common solvents.

31. Cure

To change the properties of a thermosetting resin irreversibly by chemical reaction, i.e., condensation, ring closure, or addition. Cure may be accomplished by addition of curing (cross- linking) agents, with or without catalyst, and with or without heat.

32. Cure Cycle

The time/temperature/pressure cycle used to cure a thermosetting resin system of prepreg.

33. Curing Agent

A catalytic or reactive agent that brings about polymerization when it is added to a resin.

34. Debulking

Compacting of a thick laminate under moderate heat and pressure and/or vacuum to remove most of the air, to ensure seating on the tool, and to prevent wrinkles.

35. Delamination

The separation of a laminated plastic material along the plane of its layers.

36. Draft Angle

The angle of a taper on a mandrel or mold that facilitates removal of the finished part.

37. Drape

The ability of a fabric or prepreg to conform to a contoured surface.

38. E-Glass

"Electrical" glass; the borosilicate glass most often used for the glass fibers in conventional reinforced plastics.

39. Elasticity

That property of materials by virtue of which they tend to recover their original size and shape after removal of a force causing deformation.

40. Elongation

Deformation caused by stretching. The fractional increase in length of a material stressed in tension. (When expressed as percentage of the original gage length, it is called percentage elongation.)

41. Epoxy Plastic

A polymerizable thermoset polymer containing one or more epoxide groups and curable by reaction with amines, alcohols, phenols, carboxylic acids, acid anhydrides, and mercaptans. An important matrix resin in composites and structural adhesive.

42. Exotherm

The liberation or evolution of heat during the curing of a plastic product.

43. Fatigue

The failure or decay of mechanical properties after repeated applications of stess. Fatigue tests give information on the ability of a material to resist the development of cracks, which eventually bring about failure because of many cycles.

44. Fatigue Strength

The maximum cyclical stress a material can withstand for a given number of cycles before failure occurs. The residual strength after being subjected to fatigue.

45. Fiber Content

The amount of fiber presen tin a composite. This is usually expressed as a percentage volume fraction or weight fraction of the composite.

46. Fiber Count

The number of fibers per unit width of ply present in a specified section of a composite.

47. Fiber Direction

The orientation or alignment of the longitudinal axis of the fiber with respect to a stated reference axis.

48. Fiber Orientation

The fiber alignment in a nonwoven or a mat laminate in which most of the fibers are in the same direction, thereby affording higher strength in that direction.

49. Fiber-Reinforced Plastic(FRP)

A general term for a composite that is reinforced with cloth, mat, strands, or any other fiber form.

50. Filament

The smallest unit of a fibrous material. The basic units formed during drawing and spinning, which are gathered into strands of fiber for use in composites. Filaments usually are of extreme length and very small diameter, usually less that 25 mm (1 mil). Normally filaments are not used individually.

Some textile filaments can function as yarn when they are of sufficient strength and flexibility.

51. Filler

A relatively inert substance added to a material to alter its physical, mechanical, thermal, electrical, and other properties or to lower cost or density. Sometimes the term is used specifically to mean particulate additives.

52. Flash

Excess material which forms at the parting line of a mold or die, or which is extruded from a closed mold.

53. 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 fibers of the specimen.

54. Flexural Strength

The maximum stress that can be borne by the surface fibers in a beam in bending. The flexural strength is the unit resistance to the maximum load before failure by bending, usually expressed in force per unit area.

55. Gel

The initial jelly like solid phase that develops during the formation of a resin from a liquid. A semisolid system consisting of a network of solid aggregates in which liquid is held.

56. 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.

57. Gel Time

The time required for a liquid material to form a gel under specified conditions of temperature as measured by a specific test.

58. Glass Cloth

Conventionally woven glass fiber material; certain lightweight glass fabrics are also called scrims.

59. Glass Transition Temperature (Tg)

The approximate mid point of the temperature range over which the glass transition takes place; glass and silica fiber exhibit a phase change at approximately 955¬įC (1750¬įF) and carbon/graphite fibers at 2205¬įC to 2760¬įC (4000¬įF to 5000¬įF).The temperature at which increased molecular mobility results in significant changes in the properties of a cured resin system. Also, the inflection point on a plot of modulus versus temperature. The measured value of Tg depends to some extent on the method of test.

60. Graphite Fibers

A group of carbon fibers which have a carbon content of about 99% and also have high modulus values. This term is used interchangeably with "carbon fibers" throughout the industry.

61. Hardener

A substance used to promote or control curing action by taking part in it; as opposed to catalyst.

62. Hardness

The resistance to surface indentation usually measured by the depth of penetration (or arbitrary units related to the depth of penetration)of a blunt point under a given load using a particular instrument according to a prescribed procedure.

63. Heat Distortion Point

The temperature at which a standard test bar deflects a specified amount under a stated load. Now called deflection temperature.

64. Heat Resistance

The property or ability of plastics and elastomers to resist the deteriorating effects of elevated temperatures.

65. Heat Sink

A contrivance for the absorption or transfer of heat away from a critical element or part. Bulk graphite is often used as a heat sink.

66. Honeycomb

Resin-impregnated material manufactured in (usually) hexagonal cells that serves as a core material in sandwich constructions. Honeycomb may also be metallic or polymer materials in a rigid, open-cell structure.

67. Hybrid

A composite laminate comprised of laminae of two or more composite material systems, e.g., glass and carbon. It also applies to woven fabrics having more than one type of fiber.

68. Impact Strength

A material's ability to withstand shock loading as measured by the work done in fracturing a specimen

69. Impregnate

To saturate the voids and interstices of a reinforcement with a resin.

70. Interface

The boundary or surface between two different, physically distinguishable media. On fibers, the contact area between fibers and sizing or finish. In a laminate, the contact area between the reinforcement and the laminating resin.

71. I-PRESS¬ģ & Automation Control

The most sophisticated, intuitive, and safest press and automation control on the planet. Based on a Rockwell AB hardware and software platform, it is reliable and easy to customize for end users needs.

72. Isotropic

Having uniform properties in all directions. The measured properties of an isotropic material are independent of the axis of testing.

73. Kevlar¬ģ

Registered trademark of E. I. Dupont de Nemours, Inc. for strong organic fibers similar to fiberglass, but having a higher strength-to-weight ratio. When woven into cloth and impregnated with a thermosetting epoxy resin, it produces a material having high impact resistance and low radio frequency attenuation. Generic term: aramid.

74. Laminate

A product made by bonding together two or more layers of material(s).

75. Laminating

Laying up with resin and reinforcing fabric on virtually any surface.

76. Laminate Orientation

The configuration of a cross-plied composite laminate with regard to the angles of cross-plying, the number of laminae at each angle, and the exact sequence of the lamina lay-up.

77. Lay-Up

The reinforcing material placed in position in the mold. The process of placing the reinforcing material in position in the mold. The resin-impregnated reinforcement. A description of the component materials, geometry, and so forth, of a laminate.

78. Lot

A specific amount of material produced at one time using the same process and the same conditions of manufacture, and offered for sale as a unit quantity.

79. Mat

A fibrous reinforcing material comprised of chopped filaments (for chopped-strand mat) or swirled filaments (for continuous-strand mat) with a binder to maintain form; available in blankets of various widths, weights, and lengths.

80. Matrix

A material in which the fiber of a composite is imbedded; it can be plastic, metal, ceramic, or glass.

81. Mil

The unit used in measuring the diameter of glass fiber strands, wire, and so forth (1 mil = 0.001 in.).

82. Modulus

A measure of the ratio of load (stress) applied to the resultant deformation of a material, such as elasticity or shear.

83. Moisture Content

The amount of moisture in a material determined under prescribed conditions and expressed as a percentage of the mass of the moist specimen, that is, the mass of the dry substance plus the moisture present.

84. Mold

The cavity or matrix into which, 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.

85. Molding

Constructing a part within a mold. Sometimes used to denote the finished part.

86. Mold Pressure

The pressure applied to the ram of compression or transfer press to force the softened plastic to fill the mold cavities completely. Fullya djustable via the I-PRESS control system.

87. Mold-Release Agent

A lubricant, liquid, or powder (often silicone oils and waxes),used to prevent sticking of molded articles in the cavity.

88. Nominal Value

A value assigned for the purpose of a convenient designation. A nominal value exists in name only. It is often an average number with a tolerance so as to fit together with adjacent parts.

89. Out Time

The time a prepreg is exposed to ambient temperature, namely, the total amount of time the prepreg is out of the freezer. The primary effects of our time are to decrease the drape and tack of the prepreg while also allowing it to absorb moisture from the air.

90. Parting Line

A mark on a molded piece where the sections of a mold have met in closing.

91. pH

The measure of the acidity or alkalinity of a substance, neutrality being at pH 7. Acid solutions are less than 7, alkaline solutions are more than 7.

92. Platens

The mounting plates of a press, to which the entire mold assembly is bolted. Sutherland offers T- Slotted Platens for ease of clamping and quick die change.

93. Ply

In general, fabrics or felts consisting of one or more layers (laminates, for example). The layers that make up a stack. Yarn resulting from twisting operations (three-ply yarn, for example). A single layer of prepreg. A single pass in filament winding (two plies forming one layer).

94. Polymer

A very large molecule formed by combining a large number of smaller molecules, called monomers, in a regular pattern.

95. Polymerization

A chemical reaction in which the molecules of monomers are linked together to form polymers.

96. Post Cure

The exposure of certain resins to higher than normal curing temperatures after the initial cure cycle. This second stage is necessary to attain the complete cure and desired mechanical properties of the resins involved. The higher temperatures are used separately because they would result in an excessive reaction if applied throughout the entire cure.

97. Pot Life

The length of time a catalyzed thermosetting resin system retains a viscosity low enough for it to be suitable for processing.

98. Preform

A preshaped fibrous reinforcement formed by distribution of chopped fibers or cloth by air, water flotation, or vacuum over the surface of a perforated screen to the approximate contour and thickness desired in the finished part. Also, a preshaped fibrous reinforcement of mat or cloth formed to the desired shape on a mandrel or mock-up before being placed in a mold press.

99. Prepreg, Pre-impregnated

A combination of mat, fabric, nonwoven material, or roving with resin, usually advanced to the B-stage, ready for curing.

100. Press

Two types of press frames are suitable, 4 Post are lower cost and have less accuracy when compared to Gib Guided Straight Sides. The newest technology is Servo Driven Motor to high pressure pumps equipped with the I-PRESS & Automation control allow users to program speeds / velocity and pressure profiles throughout the press cycle. With I-PRESS Connected Enterprise, users can capture and store specific data from part to part.

101. Processing Window

The range of processing conditions, such as stock (melt)temperature, pressure, shear rate, and so on, within which a particular grade of plastic can be fabricated with optimum or acceptable properties by a particular fabricating process.

102. Reinforcement

A material added to the matrix to provide the required properties; ranges from short fibers through complex textile forms.

103. Release Agents

Materials that are used to prevent cured matrix material from bonding to tooling.

104. Resin

A material, generally a polymer, that has an indefinite and often high molecular weight and softening/melting range, and exhibits a tendency to flow when it is subjected to stress. Resins are used as the matrices to bind together the reinforcement material in composites.

105. Resin Content

The amount of resin in a laminate expressed as either a percentage of total weight or total volume.

106. Resin-Rich

Localized area filled with resin but lacking reinforcement fiber.

107. Resin-Starved

Localized area lacking sufficient resin for wet-out of the fibers.

108. Resin-Transfer Molding (RTM)

A molding process in which catalyzed resin is transferred into an enclosed mold into which the fiber reinforcement has been placed; cure normally is accomplished without external heat. RTM combines relatively low tooling and equipment costs with the ability to mold large structural parts.

109. Roving

A number of yarns, strands, tows, or ends collected into a parallel bundle with little or no twist.

110. Sandwich Construction

A composite composed of lightweight core material (usually honeycomb or foamed plastic) to which two relatively thin, dense, high-strength, functional, or decorative skins (also called faces) are adhered.

111. Scrim

A low-cost reinforcing fabric made from continuous filament yarn in an open-mesh construction. Used in the processing of tape or other B-stage material to facilitate handling. Also used as a carrier of adhesive, to be used in secondary bonding.

112. Set Up

To harden, as in curing of a polymer resin.

113. S-Glass

Structural glass; a magnesia/alumina/silicate glass reinforcement designed to provide very high tensile strength.

114. Shear Strength

The maximum shear stress that a material is capable of sustaining. Shear strength is calculated from the maximum load during a shear or torsion test and is based on the original cross-sectional area of the specimen.

115. Sheet Molding Compound(SMC)

A composite of fibers, usually a polyester resin, and pigments, fillers, and other additives that have been compounded and processed into sheet form to facilitate handling in the molding operation.

116. Shelf Life

The length of time a material, substance, product, or reagent can be stored under specified environmental conditions and continue to meet all applicable specification requirements and/or remain suitable for its intended function.

117. Shrinkage

The relative change in dimension from the length measured on the mold when it is cold to the length of the molded object 24 hours after it has been taken out of the mold.

118. Size

Any treatment consisting of starch, gelatin, oil, wax, or other suitable ingredient applied to yarn or fibers at the time of formation to protect the surface and aid the process of handling and fabrication or to control the fiber characteristics. The treatment contains ingredients that provide surface lubricity and binding action but, unlike a finish, contains no coupling agent. Before final fabrication into a composite, the size is usually removed by heat cleaning, and a finish is applied.

119. Sizing Content

The percent of the total strand weight made up by the sizing; usually determined by burning off or dissolving the organic sizing; known as loss on ignition.

120. Skin

A layer of relatively dense material used in a sandwich construction of the surface of the core.

121. Specific Gravity

The density(mass per unit volume) of a material divided by that of water at a standard temperature.

122. Stiffness

A measure of modulus. The relationship of load and deformation. The ratio between the applied stress and resulting strain. A term often used when the relationship of stress to strain does not conform to the definition of Young's modulus.

123. Stops

Metal pieces inserted between die halves. Used to control the thickness of a press-molded part. Not a recommended practice, because the resin will receive less pressure, which can result in voids.

124. Storage Life

The period of time during which a liquid resin, packaged adhesive, or prepreg can be stored under specified temperature conditions and remain suitable for use. Also called shelf life.

125. Strand

Normally an untwisted bundle or assembly of continuous filaments used as a unit, including slivers, tows, ends, and yarn, for example. Sometimes a single fiber or filament is called a strand.

126. Tack

The stickiness of a prepreg.

127. 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.

128. Thermal Conductivity

The ability of a material to conduct heat.

129. Thermoplastic

Capable of being repeatedly softened by an increase of temperature and hardened by an increase in temperature. Applicable to those materials whose change upon heating is substantially physical rather than chemical and that in the softened stage can be shaped by flow into articles by molding or extrusion.

130. Thermoset

A plastic that, when cured by application of heat or chemical means, changes into a substantially infusible and insoluble material.

131. Tow

An untwisted bundle of continuous filaments.

132. Vent

A small hole or shallow channel in a mold that allows air or gas to exit as the molding material enters.

133. Viscosity

The tendency of a material to resist flow.

134. Void Content

Volume percentage of voids, usually less than 1% in a properly cured composite. The experimental determination is indirect, meaning it is calculated from the measured density of a cured laminate and the "theoretical" density of the starting material.

135. Voids

Air or gas that has been trapped and cured into a laminate. Porosity is an aggregation of micro voids. Voids are essentially incapable of transmitting structural stresses or nonradiative energy fields.

136. Volatiles

Materials, such as water and alcohol, in a sizing or a resin formulation, that are capable of being driven off as a vapor at room temperature or at a slightly elevated temperature.

137. Water Jet

Water emitted from a nozzle under high pressure(70 to 410 MPa, or 10 to 60 ksi or higher).Useful for cutting organic composites.

138. Wet-Out

The condition of an impregnated roving or yarn in which substantially all voids between the sized strands and filaments are filled with resin.

139. Working Life

The period of time during which a liquid resin or adhesive, after mixing with catalyst, solvent, or other compounding ingredients, remains usable.

140. Yarn

An assemblage of twisted filaments, fibers, or strands, either natural or manufactured, to form a continuous length that is suitable for use in weaving or interweaving into textile materials.

141. Y-Axis

In composite laminates, the axis in the plane of the laminate that is perpendicular to the x-axis. Contrast with x-axis.

142. Z-Axis

In composite laminates, the reference axis normal to the plane of the laminate.

 

 

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COMPRESSION & THERMOSET MOLDING TERMINOLOGY

Like any industry, molding of Composites has a plethora of terminology that can be daunting to someone new to the industry. Below are some of the most common terms used within the compression molding and Resin Transfer molding industry, as well as a brief overview of what they mean. Some of the terms apply to the strength and properties of the reinforcements and the compression or RTM molded components.

‚Äć

1. Additive

Any substance added to another substance, usually to improve properties, such as plasticizers, initiators, light stabilizers, and flame retardants. See also filler.

2. Adhesion

The state in which two surfaces are held together at an interface by mechanical or chemical forces, interlocking action, or both.

3. Adhesive

A substance capable of holding two materials together by surface attachment. Adhesive can be in film, liquid, or paste form.

4. Air-Bubble Void

Air entrapment within and between the plies of reinforcement or within a bond line or encapsulated area; localized, non-interconnected, spherical in shape.

5. Areal Weight

The weight of fiber per unit area (width x length) of tape or fabric.

6. Aramid

Aromatic polyamide fibers characterized by excellent high-temperature, flame-resistant, and electrical properties.

7. A-Stage

An early stage in the reaction of a thermosetting resin in which the material is still soluble and fusible

8. Balanced Laminate

A composite laminate in which all laminate at angles other than 0¬į and 90¬į occur only in + pairs(not necessarily adjacent) and are symmetrical around the centerline.

9. Barcol Hardness

A hardness value obtained by measuring the resistance to penetration of a sharp steel point under a spring load. The instrument, called the Barcol impressor, gives a direct reading on a 0 to 100scale. The hardness value is often used as a measure of the degree of cure of aplastic.

10. Batch

In general, a quantity of material formed during the same process or in one continuous process and having identical characteristics throughout. Also known as "lo

11. Binder

The resin or cementing constituent (of a plastic compound) that holds the other components together. The agent applied to fiber mat or preforms to bond the fibers before laminating or molding.

12. Bridging

Condition in which fibers do not move into or conform to radii and corners during molding, resulting in voids and dimensional control problems.

13. B-Stage

An intermediate stage in the reaction of a thermosetting resin in which the material melts when heated and dissolves in certain solvents. Materials are usually precured to this stage to facilitate handling and processing prior to final cure.

14. Bulk Factor

The ratio of the volume of a raw molding compound or powdered plastic to the volume of the finished solid piece produced therefrom. The ratio of the density of the solid plastic object to the apparent or bulk density of the loose molding powder.

15. Bulk Molding Compound (BMC)

Thermosetting resin mixed with strand reinforcement, fillers, and so on, into a viscous compound for compression or injection molding. See also sheet molding compound.

16. Carbon Fibers

Fibers produced from pyrolytic degradation of synthetic organic fibers, polyacrylonitrile (PAN) or rayon, which contain about 92-99% carbon content and typically have modulus values up to 75 x 106 psi.

17. Catalyst

A substance that changes the rate of a chemical reaction without itself undergoing permanent change in composition or becoming a part of the molecular structure of the product. A substance that markedly speeds up the cure of a compound when added in minor quantity as compared to the amounts of primary reactants.

18. Caul Plates

Smooth metal, plastic, or rubber plates free of surface defects. A caul plate must be the appropriate size and shape for the composite lay-up with which it will be used. It is used in immediate contact with the lay-up during the curing process to transmit normal pressure and provide a smooth surface on the finished part.

19. Cavity

The space inside a mold in which a resin or molding compound is poured or injected. The female portion of a mold. That portion of the mold that encloses the molded article(often referred to as the die). Depending on the number of such depressions, molds are designated as single cavity or multiple cavities.

20. Coefficient of Thermal Expansion

The fractional change in length of a material for each unit change in temperature.

21. Composite

A material made up of 2 or more individual components whose combined physical strength exceeds their individual properties.

22. 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.

23. Compressive Strength

Ratio of compressive stress to compressive strain below the proportional limit. Theoretically equal to Young's modulus determined from tensile experiments.

24. Core

The central component of a sandwich construction to which the sandwich faces or skins are attached; also, part of a complex mold that forms undercut parts.

25. Core Crush

A collapse, distortion, or compression of the core.

26. Coupon

Usually, a specimen for a specific test, as a tensile coupon.

27. Creep

The dimensional change in a material under physical load over time beyond instantaneous elastic deformation.

28. Cross Laminated

Material laminated so that some of the layers are oriented at various angles to the other with respect to the laminate grain. A cross-ply laminate usually has plies oriented only at 0 and 90 degrees.

29. Cross-Linking

Applied to polymer molecules, the setting-up of chemical links between the molecular chains. When extensive, as in most thermosetting resins, cross-linking makes one infusible super molecule of all the chains.

30. C-Stage

The final stage of the curing of a thermosetting resin in which the material has become infusible and insoluble in common solvents.

31. Cure

To change the properties of a thermosetting resin irreversibly by chemical reaction, i.e., condensation, ring closure, or addition. Cure may be accomplished by addition of curing (cross- linking) agents, with or without catalyst, and with or without heat.

32. Cure Cycle

The time/temperature/pressure cycle used to cure a thermosetting resin system of prepreg.

33. Curing Agent

A catalytic or reactive agent that brings about polymerization when it is added to a resin.

34. Debulking

Compacting of a thick laminate under moderate heat and pressure and/or vacuum to remove most of the air, to ensure seating on the tool, and to prevent wrinkles.

35. Delamination

The separation of a laminated plastic material along the plane of its layers.

36. Draft Angle

The angle of a taper on a mandrel or mold that facilitates removal of the finished part.

37. Drape

The ability of a fabric or prepreg to conform to a contoured surface.

38. E-Glass

"Electrical" glass; the borosilicate glass most often used for the glass fibers in conventional reinforced plastics.

39. Elasticity

That property of materials by virtue of which they tend to recover their original size and shape after removal of a force causing deformation.

40. Elongation

Deformation caused by stretching. The fractional increase in length of a material stressed in tension. (When expressed as percentage of the original gage length, it is called percentage elongation.)

41. Epoxy Plastic

A polymerizable thermoset polymer containing one or more epoxide groups and curable by reaction with amines, alcohols, phenols, carboxylic acids, acid anhydrides, and mercaptans. An important matrix resin in composites and structural adhesive.

42. Exotherm

The liberation or evolution of heat during the curing of a plastic product.

43. Fatigue

The failure or decay of mechanical properties after repeated applications of stess. Fatigue tests give information on the ability of a material to resist the development of cracks, which eventually bring about failure because of many cycles.

44. Fatigue Strength

The maximum cyclical stress a material can withstand for a given number of cycles before failure occurs. The residual strength after being subjected to fatigue.

45. Fiber Content

The amount of fiber presen tin a composite. This is usually expressed as a percentage volume fraction or weight fraction of the composite.

46. Fiber Count

The number of fibers per unit width of ply present in a specified section of a composite.

47. Fiber Direction

The orientation or alignment of the longitudinal axis of the fiber with respect to a stated reference axis.

48. Fiber Orientation

The fiber alignment in a nonwoven or a mat laminate in which most of the fibers are in the same direction, thereby affording higher strength in that direction.

49. Fiber-Reinforced Plastic(FRP)

A general term for a composite that is reinforced with cloth, mat, strands, or any other fiber form.

50. Filament

The smallest unit of a fibrous material. The basic units formed during drawing and spinning, which are gathered into strands of fiber for use in composites. Filaments usually are of extreme length and very small diameter, usually less that 25 mm (1 mil). Normally filaments are not used individually.

Some textile filaments can function as yarn when they are of sufficient strength and flexibility.

51. Filler

A relatively inert substance added to a material to alter its physical, mechanical, thermal, electrical, and other properties or to lower cost or density. Sometimes the term is used specifically to mean particulate additives.

52. Flash

Excess material which forms at the parting line of a mold or die, or which is extruded from a closed mold.

53. 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 fibers of the specimen.

54. Flexural Strength

The maximum stress that can be borne by the surface fibers in a beam in bending. The flexural strength is the unit resistance to the maximum load before failure by bending, usually expressed in force per unit area.

55. Gel

The initial jelly like solid phase that develops during the formation of a resin from a liquid. A semisolid system consisting of a network of solid aggregates in which liquid is held.

56. 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.

57. Gel Time

The time required for a liquid material to form a gel under specified conditions of temperature as measured by a specific test.

58. Glass Cloth

Conventionally woven glass fiber material; certain lightweight glass fabrics are also called scrims.

59. Glass Transition Temperature (Tg)

The approximate mid point of the temperature range over which the glass transition takes place; glass and silica fiber exhibit a phase change at approximately 955¬įC (1750¬įF) and carbon/graphite fibers at 2205¬įC to 2760¬įC (4000¬įF to 5000¬įF).The temperature at which increased molecular mobility results in significant changes in the properties of a cured resin system. Also, the inflection point on a plot of modulus versus temperature. The measured value of Tg depends to some extent on the method of test.

60. Graphite Fibers

A group of carbon fibers which have a carbon content of about 99% and also have high modulus values. This term is used interchangeably with "carbon fibers" throughout the industry.

61. Hardener

A substance used to promote or control curing action by taking part in it; as opposed to catalyst.

62. Hardness

The resistance to surface indentation usually measured by the depth of penetration (or arbitrary units related to the depth of penetration)of a blunt point under a given load using a particular instrument according to a prescribed procedure.

63. Heat Distortion Point

The temperature at which a standard test bar deflects a specified amount under a stated load. Now called deflection temperature.

64. Heat Resistance

The property or ability of plastics and elastomers to resist the deteriorating effects of elevated temperatures.

65. Heat Sink

A contrivance for the absorption or transfer of heat away from a critical element or part. Bulk graphite is often used as a heat sink.

66. Honeycomb

Resin-impregnated material manufactured in (usually) hexagonal cells that serves as a core material in sandwich constructions. Honeycomb may also be metallic or polymer materials in a rigid, open-cell structure.

67. Hybrid

A composite laminate comprised of laminae of two or more composite material systems, e.g., glass and carbon. It also applies to woven fabrics having more than one type of fiber.

68. Impact Strength

A material's ability to withstand shock loading as measured by the work done in fracturing a specimen

69. Impregnate

To saturate the voids and interstices of a reinforcement with a resin.

70. Interface

The boundary or surface between two different, physically distinguishable media. On fibers, the contact area between fibers and sizing or finish. In a laminate, the contact area between the reinforcement and the laminating resin.

71. I-PRESS¬ģ & Automation Control

The most sophisticated, intuitive, and safest press and automation control on the planet. Based on a Rockwell AB hardware and software platform, it is reliable and easy to customize for end users needs.

72. Isotropic

Having uniform properties in all directions. The measured properties of an isotropic material are independent of the axis of testing.

73. Kevlar¬ģ

Registered trademark of E. I. Dupont de Nemours, Inc. for strong organic fibers similar to fiberglass, but having a higher strength-to-weight ratio. When woven into cloth and impregnated with a thermosetting epoxy resin, it produces a material having high impact resistance and low radio frequency attenuation. Generic term: aramid.

74. Laminate

A product made by bonding together two or more layers of material(s).

75. Laminating

Laying up with resin and reinforcing fabric on virtually any surface.

76. Laminate Orientation

The configuration of a cross-plied composite laminate with regard to the angles of cross-plying, the number of laminae at each angle, and the exact sequence of the lamina lay-up.

77. Lay-Up

The reinforcing material placed in position in the mold. The process of placing the reinforcing material in position in the mold. The resin-impregnated reinforcement. A description of the component materials, geometry, and so forth, of a laminate.

78. Lot

A specific amount of material produced at one time using the same process and the same conditions of manufacture, and offered for sale as a unit quantity.

79. Mat

A fibrous reinforcing material comprised of chopped filaments (for chopped-strand mat) or swirled filaments (for continuous-strand mat) with a binder to maintain form; available in blankets of various widths, weights, and lengths.

80. Matrix

A material in which the fiber of a composite is imbedded; it can be plastic, metal, ceramic, or glass.

81. Mil

The unit used in measuring the diameter of glass fiber strands, wire, and so forth (1 mil = 0.001 in.).

82. Modulus

A measure of the ratio of load (stress) applied to the resultant deformation of a material, such as elasticity or shear.

83. Moisture Content

The amount of moisture in a material determined under prescribed conditions and expressed as a percentage of the mass of the moist specimen, that is, the mass of the dry substance plus the moisture present.

84. Mold

The cavity or matrix into which, 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.

85. Molding

Constructing a part within a mold. Sometimes used to denote the finished part.

86. Mold Pressure

The pressure applied to the ram of compression or transfer press to force the softened plastic to fill the mold cavities completely. Fullya djustable via the I-PRESS control system.

87. Mold-Release Agent

A lubricant, liquid, or powder (often silicone oils and waxes),used to prevent sticking of molded articles in the cavity.

88. Nominal Value

A value assigned for the purpose of a convenient designation. A nominal value exists in name only. It is often an average number with a tolerance so as to fit together with adjacent parts.

89. Out Time

The time a prepreg is exposed to ambient temperature, namely, the total amount of time the prepreg is out of the freezer. The primary effects of our time are to decrease the drape and tack of the prepreg while also allowing it to absorb moisture from the air.

90. Parting Line

A mark on a molded piece where the sections of a mold have met in closing.

91. pH

The measure of the acidity or alkalinity of a substance, neutrality being at pH 7. Acid solutions are less than 7, alkaline solutions are more than 7.

92. Platens

The mounting plates of a press, to which the entire mold assembly is bolted. Sutherland offers T- Slotted Platens for ease of clamping and quick die change.

93. Ply

In general, fabrics or felts consisting of one or more layers (laminates, for example). The layers that make up a stack. Yarn resulting from twisting operations (three-ply yarn, for example). A single layer of prepreg. A single pass in filament winding (two plies forming one layer).

94. Polymer

A very large molecule formed by combining a large number of smaller molecules, called monomers, in a regular pattern.

95. Polymerization

A chemical reaction in which the molecules of monomers are linked together to form polymers.

96. Post Cure

The exposure of certain resins to higher than normal curing temperatures after the initial cure cycle. This second stage is necessary to attain the complete cure and desired mechanical properties of the resins involved. The higher temperatures are used separately because they would result in an excessive reaction if applied throughout the entire cure.

97. Pot Life

The length of time a catalyzed thermosetting resin system retains a viscosity low enough for it to be suitable for processing.

98. Preform

A preshaped fibrous reinforcement formed by distribution of chopped fibers or cloth by air, water flotation, or vacuum over the surface of a perforated screen to the approximate contour and thickness desired in the finished part. Also, a preshaped fibrous reinforcement of mat or cloth formed to the desired shape on a mandrel or mock-up before being placed in a mold press.

99. Prepreg, Pre-impregnated

A combination of mat, fabric, nonwoven material, or roving with resin, usually advanced to the B-stage, ready for curing.

100. Press

Two types of press frames are suitable, 4 Post are lower cost and have less accuracy when compared to Gib Guided Straight Sides. The newest technology is Servo Driven Motor to high pressure pumps equipped with the I-PRESS & Automation control allow users to program speeds / velocity and pressure profiles throughout the press cycle. With I-PRESS Connected Enterprise, users can capture and store specific data from part to part.

101. Processing Window

The range of processing conditions, such as stock (melt)temperature, pressure, shear rate, and so on, within which a particular grade of plastic can be fabricated with optimum or acceptable properties by a particular fabricating process.

102. Reinforcement

A material added to the matrix to provide the required properties; ranges from short fibers through complex textile forms.

103. Release Agents

Materials that are used to prevent cured matrix material from bonding to tooling.

104. Resin

A material, generally a polymer, that has an indefinite and often high molecular weight and softening/melting range, and exhibits a tendency to flow when it is subjected to stress. Resins are used as the matrices to bind together the reinforcement material in composites.

105. Resin Content

The amount of resin in a laminate expressed as either a percentage of total weight or total volume.

106. Resin-Rich

Localized area filled with resin but lacking reinforcement fiber.

107. Resin-Starved

Localized area lacking sufficient resin for wet-out of the fibers.

108. Resin-Transfer Molding (RTM)

A molding process in which catalyzed resin is transferred into an enclosed mold into which the fiber reinforcement has been placed; cure normally is accomplished without external heat. RTM combines relatively low tooling and equipment costs with the ability to mold large structural parts.

109. Roving

A number of yarns, strands, tows, or ends collected into a parallel bundle with little or no twist.

110. Sandwich Construction

A composite composed of lightweight core material (usually honeycomb or foamed plastic) to which two relatively thin, dense, high-strength, functional, or decorative skins (also called faces) are adhered.

111. Scrim

A low-cost reinforcing fabric made from continuous filament yarn in an open-mesh construction. Used in the processing of tape or other B-stage material to facilitate handling. Also used as a carrier of adhesive, to be used in secondary bonding.

112. Set Up

To harden, as in curing of a polymer resin.

113. S-Glass

Structural glass; a magnesia/alumina/silicate glass reinforcement designed to provide very high tensile strength.

114. Shear Strength

The maximum shear stress that a material is capable of sustaining. Shear strength is calculated from the maximum load during a shear or torsion test and is based on the original cross-sectional area of the specimen.

115. Sheet Molding Compound(SMC)

A composite of fibers, usually a polyester resin, and pigments, fillers, and other additives that have been compounded and processed into sheet form to facilitate handling in the molding operation.

116. Shelf Life

The length of time a material, substance, product, or reagent can be stored under specified environmental conditions and continue to meet all applicable specification requirements and/or remain suitable for its intended function.

117. Shrinkage

The relative change in dimension from the length measured on the mold when it is cold to the length of the molded object 24 hours after it has been taken out of the mold.

118. Size

Any treatment consisting of starch, gelatin, oil, wax, or other suitable ingredient applied to yarn or fibers at the time of formation to protect the surface and aid the process of handling and fabrication or to control the fiber characteristics. The treatment contains ingredients that provide surface lubricity and binding action but, unlike a finish, contains no coupling agent. Before final fabrication into a composite, the size is usually removed by heat cleaning, and a finish is applied.

119. Sizing Content

The percent of the total strand weight made up by the sizing; usually determined by burning off or dissolving the organic sizing; known as loss on ignition.

120. Skin

A layer of relatively dense material used in a sandwich construction of the surface of the core.

121. Specific Gravity

The density(mass per unit volume) of a material divided by that of water at a standard temperature.

122. Stiffness

A measure of modulus. The relationship of load and deformation. The ratio between the applied stress and resulting strain. A term often used when the relationship of stress to strain does not conform to the definition of Young's modulus.

123. Stops

Metal pieces inserted between die halves. Used to control the thickness of a press-molded part. Not a recommended practice, because the resin will receive less pressure, which can result in voids.

124. Storage Life

The period of time during which a liquid resin, packaged adhesive, or prepreg can be stored under specified temperature conditions and remain suitable for use. Also called shelf life.

125. Strand

Normally an untwisted bundle or assembly of continuous filaments used as a unit, including slivers, tows, ends, and yarn, for example. Sometimes a single fiber or filament is called a strand.

126. Tack

The stickiness of a prepreg.

127. 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.

128. Thermal Conductivity

The ability of a material to conduct heat.

129. Thermoplastic

Capable of being repeatedly softened by an increase of temperature and hardened by an increase in temperature. Applicable to those materials whose change upon heating is substantially physical rather than chemical and that in the softened stage can be shaped by flow into articles by molding or extrusion.

130. Thermoset

A plastic that, when cured by application of heat or chemical means, changes into a substantially infusible and insoluble material.

131. Tow

An untwisted bundle of continuous filaments.

132. Vent

A small hole or shallow channel in a mold that allows air or gas to exit as the molding material enters.

133. Viscosity

The tendency of a material to resist flow.

134. Void Content

Volume percentage of voids, usually less than 1% in a properly cured composite. The experimental determination is indirect, meaning it is calculated from the measured density of a cured laminate and the "theoretical" density of the starting material.

135. Voids

Air or gas that has been trapped and cured into a laminate. Porosity is an aggregation of micro voids. Voids are essentially incapable of transmitting structural stresses or nonradiative energy fields.

136. Volatiles

Materials, such as water and alcohol, in a sizing or a resin formulation, that are capable of being driven off as a vapor at room temperature or at a slightly elevated temperature.

137. Water Jet

Water emitted from a nozzle under high pressure(70 to 410 MPa, or 10 to 60 ksi or higher).Useful for cutting organic composites.

138. Wet-Out

The condition of an impregnated roving or yarn in which substantially all voids between the sized strands and filaments are filled with resin.

139. Working Life

The period of time during which a liquid resin or adhesive, after mixing with catalyst, solvent, or other compounding ingredients, remains usable.

140. Yarn

An assemblage of twisted filaments, fibers, or strands, either natural or manufactured, to form a continuous length that is suitable for use in weaving or interweaving into textile materials.

141. Y-Axis

In composite laminates, the axis in the plane of the laminate that is perpendicular to the x-axis. Contrast with x-axis.

142. Z-Axis

In composite laminates, the reference axis normal to the plane of the laminate.

 

 

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