《纺织复合材料》课程参考文献（Composite Materials Handbook，Volume 3）Chapter 2 MATERIALS AND PROCESSES - THE EFFECTS OF VARIABILITY ON COMPOSITE PROPERTIES

MIL-HDBK-17-3F Volume 3,Chapter 2 Materials and Processes-The Effects of Variability on Composite Properties 2.4.1.1.4 Typical properties Typically limitations on the end use for carbon fibers in composite structure depend more on the resin matrix than the fiber.Some exceptions to this are present,however,in which case the oxidative stability, thermal conductivity,coefficient of thermal expansion,or other properties of the fiber must be taken into account.Some key properties for carbon fiber,including cost,are listed in Table 2.4.1.1.4.Typical values for glass,aramid,and boron are shown for comparison.While some carbon fiber properties are fairly uni- versal,different products from different manufacturers can have substantially different properties.Three of the major manufacturers for the US are Amoco,Hercules and Toray.It should be noted that translation of fiber properties to composite properties is dependent on many factors in addition to rule of mixtures. TABLE 2.4.1.1.4 Comparison of carbon and other fiber properties. Tensile Tensile Density, Fiber Cost.$/ Modulus. Strength,ksi g/cm Diameter, Msi micron Carbon(PAN) 30-50 350-1000 1.75-1.90 4-8 20-100 Carbon(Pitch) 25-110 200-450 1.90-2.15 8-11 40-200 Carbon(Rayon)】 6 150 1.6 8-9 5-25 Glass 10-12.5 440-670 2.48-2.62 30 5-40 Aramid 20 410 1.44 25-75 Boron 58 730-1000 2.3-2.6 100-200 100-250 2.4.1.2 Aramid In the early 1970's,Du Pont Company introduced KevlarTM aramid,an organic fiber with high specific tensile modulus and strength.This was the first organic fiber to be used as a reinforcement in advanced composites.Today this fiber is used in various structural parts including reinforced plastics,ballistics, tires,ropes,cables,asbestos replacement,coated fabrics,and protective apparel.Aramid fiber is manu- factured by extruding a polymer solution through a spinneret.Major forms available from Du Pont are continuous filament yarns,rovings,chopped fiber,pulp,spun-laced sheet,wet-laid papers,thermoplastic- impregnated tows,and thermoformable composite sheets. Important generic properties of aramid fibers are:low density,high tensile strength,high tensile stiff- ness,low compressive properties(nonlinear),and exceptional toughness characteristics.The density of aramid is 0.052 Ib/in(1.44 gm/cm).This is about 40%lower than glass and about 20%lower than com- monly used carbon.Aramids do not melt and they decompose at about 900F(500C).Tensile strength of yarn,measured in twisted configuration,can be varied from 500-600 ksi(3.4-4.1 GPa)by choosing different types of aramids.The nominal coefficient of thermal expansion is 3x105 in/in/F (-5x10 m/m/C)in the axial direction.Aramid fibers,being aromatic polyamide polymers,have high thermal stability and dielectric and chemical properties.Excellent ballistic performance and general dam- age tolerance is derived from fiber toughness.Aramid is used,in fabric or composite form,to achieve ballistic protection for humans,armored tanks,military aircraft,and so on. Composite systems,reinforced with aramid,have excellent vibration-damping characteristics.They resist shattering upon impact.Temperature of use,in composite form with polymer matrix,range from-33 to 390F(-36-200C),The nominal tensile properties of composites reinforced with aramid are listed in Table 2.4.1.2(a)-in thermoset(Reference 2.4.1.2(a))and thermoplastic (Reference 2.4.1.2(b))resin ma- trix.At 60%fiber volume fraction,composites of epoxy reinforced with aramid fibers have nominal tensile 2-6

MIL-HDBK-17-3F Volume 3, Chapter 2 Materials and Processes - The Effects of Variability on Composite Properties 2-6 2.4.1.1.4 Typical properties Typically limitations on the end use for carbon fibers in composite structure depend more on the resin matrix than the fiber. Some exceptions to this are present, however, in which case the oxidative stability, thermal conductivity, coefficient of thermal expansion, or other properties of the fiber must be taken into account. Some key properties for carbon fiber, including cost, are listed in Table 2.4.1.1.4. Typical values for glass, aramid, and boron are shown for comparison. While some carbon fiber properties are fairly uni￾versal, different products from different manufacturers can have substantially different properties. Three of the major manufacturers for the US are Amoco, Hercules and Toray. It should be noted that translation of fiber properties to composite properties is dependent on many factors in addition to rule of mixtures. TABLE 2.4.1.1.4 Comparison of carbon and other fiber properties. Tensile Modulus, Msi Tensile Strength, ksi Density, g/cm3 Fiber Diameter, micron Cost, $/# Carbon (PAN) 30-50 350-1000 1.75-1.90 4-8 20-100 Carbon (Pitch) 25-110 200-450 1.90-2.15 8-11 40-200 Carbon (Rayon) 6 150 1.6 8-9 5-25 Glass 10-12.5 440-670 2.48-2.62 30 5-40 Aramid 20 410 1.44 -- 25-75 Boron 58 730-1000 2.3-2.6 100-200 100-250 2.4.1.2 Aramid In the early 1970's, Du Pont Company introduced Kevlar™ aramid, an organic fiber with high specific tensile modulus and strength. This was the first organic fiber to be used as a reinforcement in advanced composites. Today this fiber is used in various structural parts including reinforced plastics, ballistics, tires, ropes, cables, asbestos replacement, coated fabrics, and protective apparel. Aramid fiber is manu￾factured by extruding a polymer solution through a spinneret. Major forms available from Du Pont are continuous filament yarns, rovings, chopped fiber, pulp, spun-laced sheet, wet-laid papers, thermoplastic￾impregnated tows, and thermoformable composite sheets. Important generic properties of aramid fibers are: low density, high tensile strength, high tensile stiff￾ness, low compressive properties (nonlinear), and exceptional toughness characteristics. The density of aramid is 0.052 lb/in3 (1.44 gm/cm3 ). This is about 40% lower than glass and about 20% lower than com￾monly used carbon. Aramids do not melt and they decompose at about 900°F (500°C). Tensile strength of yarn, measured in twisted configuration, can be varied from 500 - 600 ksi (3.4 - 4.1 GPa) by choosing different types of aramids. The nominal coefficient of thermal expansion is 3x10-6 in/in/F° (-5x10-6 m/m/C°) in the axial direction. Aramid fibers, being aromatic polyamide polymers, have high thermal stability and dielectric and chemical properties. Excellent ballistic performance and general dam￾age tolerance is derived from fiber toughness. Aramid is used, in fabric or composite form, to achieve ballistic protection for humans, armored tanks, military aircraft, and so on. Composite systems, reinforced with aramid, have excellent vibration-damping characteristics. They resist shattering upon impact. Temperature of use, in composite form with polymer matrix, range from -33 to 390°F (-36 - 200°C), The nominal tensile properties of composites reinforced with aramid are listed in Table 2.4.1.2(a) - in thermoset (Reference 2.4.1.2(a)) and thermoplastic (Reference 2.4.1.2(b)) resin ma￾trix. At 60% fiber volume fraction, composites of epoxy reinforced with aramid fibers have nominal tensile

MIL-HDBK-17-3F Volume 3,Chapter 2 Materials and Processes-The Effects of Variability on Composite Properties strength (room temperature)of 200 ksi (1.4 GPa)and nominal tensile modulus of 11 Msi (76 GPa). These composites are ductile under compression and flexure.Ultimate strength,under compression or flexure,is lower than glass or carbon composites.Composite systems,reinforced with aramid,are resis- tant to fatigue and stress rupture.In the system of epoxy reinforced with aramid,under tension/tension fatigue,unidirectional specimens (Vr~60%)survive 3,000,000 cycles at 50%of their ultimate stress (Reference 2.4.1.2(a)).Recently,thermoplastic resin composites reinforced with aramid have been de- veloped.These thermoplastic composite systems have exhibited equivalent mechanical properties com- pared to similar thermoset systems (Reference 2.4.1.2(b)).In addition,thermoplastic systems provide potential advantages in economical processing (Reference 2.4.1.2(c)),bonding,and repair.A unique thermoformable sheet product,in thermoplastic matrix reinforced with aramid fibers,is available (Refer- ence 2.4.1.2(d)).These composite systems are also used to achieve low coefficient of thermal expansion or high wear resistance.They are non-conductive and exhibit no galvanic reaction with metals.Aramid fibers are available in several forms with different fiber modulus (Table 2.4.1.2(b)).KevlarTM29 has the lowest modulus and highest toughness (strain to failure~4%).These fibers are used mostly in ballistics and other soft composite systems such as cut-and slash-resistance protective apparel,ropes,coated fabric,asbestos replacement,pneumatic tires,etc.These are also used for composites where maximum impact and damage tolerance is critical and stiffness is less important.KevlarTM49 is predominantly used in reinforced plastics-both in thermoplastic and thermoset resin systems.It is also used in soft compos- ites like core of fiber optic cable and mechanical rubber good systems(e.g.,high pressure flexible hose, radiator hose,power transmission belts,conveyor belts,etc.).An ultra-high modulus Type 149 has been made available recently.It has 40%higher modulus than KevlarTM49.KevlarTM29 is available in fiber yarn sizes and two rovings sizes.KevlarTM49 is available in six yarn and two rovings sizes.KevlarTM149 is available in three yarn sizes.Yarn sizes range from the very fine 55 denier(30 filaments)to 3000 den- ier(1300 filaments).Rovings are 4560 denier(3072 filaments)and 7100 denier(5000 filaments).Com- posite thermoplastic tows,several types of melt-impregnated thermoplastic reinforced with different Kev- larTM yarns and deniers,are also available. TABLE 2.4.1.2(a)Nominal composite properties reinforced with aramid fiber(V~60%). Thermoset (epoxy) Thermoplastic(J2) Tensile Units unidirectional fabric unidirectional fabric' Property Modulus Msi(GPa) 11(68.5) 6(41) 10.5-11.5(73-79) 5.1-5.8(35-40) Strength ksi(GPa) 200(1.4) 82(0.56) 180-200(1.2-1.4) 77-83(0.53-0.57 1 Normalized from Vr=40%;fabric style S285 Aramid composites were first adopted in applications where weight savings were critical-for exam- ple,aircraft components,helicopters,space vehicles,and missiles.Armor applications resulted from the superior ballistic and structural performance.In marine recreational industries,light weight,stiffness, vibration damping,and damage tolerance are valued.Composites reinforced with aramids are used in the hulls of canoes,kayaks,and sail and power boats.These same composite attributes have led to use in sports equipment.Composite applications of aramid continue to grow as systems are developed to capitalize on other properties.The stability and frictional properties of aramids at high temperatures have led to brake,clutch,and gasket uses;low coefficient of thermal expansion is being used in printed wiring boards;and exceptional wear resistance is being engineered into injection-molded thermoplastic indus- trial parts.Melt-impregnated thermoplastic composites,reinforced with aramids,offer unique processing advantages-e.g.,in-situ consolidation of filament-wound parts.These can be used for manufacturing thick parts where processing is otherwise very difficult(Reference 2.4.1.2(e)). 2-7

MIL-HDBK-17-3F Volume 3, Chapter 2 Materials and Processes - The Effects of Variability on Composite Properties 2-7 strength (room temperature) of 200 ksi (1.4 GPa) and nominal tensile modulus of 11 Msi (76 GPa). These composites are ductile under compression and flexure. Ultimate strength, under compression or flexure, is lower than glass or carbon composites. Composite systems, reinforced with aramid, are resis￾tant to fatigue and stress rupture. In the system of epoxy reinforced with aramid, under tension/tension fatigue, unidirectional specimens (Vf ~ 60%) survive 3,000,000 cycles at 50% of their ultimate stress (Reference 2.4.1.2(a)). Recently, thermoplastic resin composites reinforced with aramid have been de￾veloped. These thermoplastic composite systems have exhibited equivalent mechanical properties com￾pared to similar thermoset systems (Reference 2.4.1.2(b)). In addition, thermoplastic systems provide potential advantages in economical processing (Reference 2.4.1.2(c)), bonding, and repair. A unique thermoformable sheet product, in thermoplastic matrix reinforced with aramid fibers, is available (Refer￾ence 2.4.1.2(d)). These composite systems are also used to achieve low coefficient of thermal expansion or high wear resistance. They are non-conductive and exhibit no galvanic reaction with metals. Aramid fibers are available in several forms with different fiber modulus (Table 2.4.1.2(b)). Kevlar™29 has the lowest modulus and highest toughness (strain to failure ~ 4%). These fibers are used mostly in ballistics and other soft composite systems such as cut- and slash- resistance protective apparel, ropes, coated fabric, asbestos replacement, pneumatic tires, etc. These are also used for composites where maximum impact and damage tolerance is critical and stiffness is less important. Kevlar™49 is predominantly used in reinforced plastics - both in thermoplastic and thermoset resin systems. It is also used in soft compos￾ites like core of fiber optic cable and mechanical rubber good systems (e.g., high pressure flexible hose, radiator hose, power transmission belts, conveyor belts, etc.). An ultra-high modulus Type 149 has been made available recently. It has 40% higher modulus than Kevlar™49. Kevlar™29 is available in fiber yarn sizes and two rovings sizes. Kevlar™49 is available in six yarn and two rovings sizes. Kevlar™149 is available in three yarn sizes. Yarn sizes range from the very fine 55 denier (30 filaments) to 3000 den￾ier (1300 filaments). Rovings are 4560 denier (3072 filaments) and 7100 denier (5000 filaments). Com￾posite thermoplastic tows, several types of melt-impregnated thermoplastic reinforced with different Kev￾lar™ yarns and deniers, are also available. TABLE 2.4.1.2(a) Nominal composite properties reinforced with aramid fiber (Vf ~ 60%). Thermoset (epoxy) Thermoplastic (J2) Tensile Property Units unidirectional fabric1 unidirectional fabric1 Modulus Msi (GPa) 11 (68.5) 6 (41) 10.5-11.5 (73-79) 5.1-5.8 (35-40) Strength ksi (GPa) 200 (1.4) 82 (0.56) 180-200 (1.2-1.4) 77-83 (0.53-0.57) 1 Normalized from Vf = 40%; fabric style S285 Aramid composites were first adopted in applications where weight savings were critical - for exam￾ple, aircraft components, helicopters, space vehicles, and missiles. Armor applications resulted from the superior ballistic and structural performance. In marine recreational industries, light weight, stiffness, vibration damping, and damage tolerance are valued. Composites reinforced with aramids are used in the hulls of canoes, kayaks, and sail and power boats. These same composite attributes have led to use in sports equipment. Composite applications of aramid continue to grow as systems are developed to capitalize on other properties. The stability and frictional properties of aramids at high temperatures have led to brake, clutch, and gasket uses; low coefficient of thermal expansion is being used in printed wiring boards; and exceptional wear resistance is being engineered into injection-molded thermoplastic indus￾trial parts. Melt-impregnated thermoplastic composites, reinforced with aramids, offer unique processing advantages - e.g., in-situ consolidation of filament-wound parts. These can be used for manufacturing thick parts where processing is otherwise very difficult (Reference 2.4.1.2(e))

MIL-HDBK-17-3F Volume 3,Chapter 2 Materials and Processes-The Effects of Variability on Composite Properties TABLE 2.4.1.2(b)Nominal properties of aramid fiber. Tensile Property Units Type of Kevlar TM 29 49 149 Modulus Msi(GPa) 12(83) 18(124) 25(173) Strength ksi(GPa) 525(3.6) 525-600(3.6-4.1) 500(3.4) Aramid fiber is relatively flexible and tough.Thus it can be combined with resins and processed into composites by most of the methods established for glass.Yarns and rovings are used in filament wind- ing,prepreg tape,and in pultrusion.Woven fabric prepreg is the major form used in thermoset compos- ites.Aramid fiber is available in various weights,weave patterns,and constructions;from very thin (0.0002 in.,0.005mm)lightweight(275 gm/m2)to thick(0.026 in.,0.66 mm)heavy (2.8 gm/m)woven roving.Thermoplastic-impregnated tows can be woven into various types of fabrics to form prepregs. These composites demonstrate good property retention under hot and humid conditions (Reference 2.4.1.2(f)).Chopped aramid fiber is available in lengths from 6 mm to 100 mm.The shorter lengths are used to reinforce thermoset,thermoplastic,and elastomeric resins in automotive brake and clutch linings, gaskets,and electrical parts.Needle-punched felts and spun yarns for asbestos replacement applica- tions are made from longer fiber staple.A unique very short fiber(0.08-0.16 in.,2-4 mm)with many attached fibrils is available(aramid pulp).It can provide efficient reinforcement in asbestos replacement uses.Aramid short fibers can be processed into spun-laced and wet-laid papers.These are useful for surfacing veil,thin-printed wiring boards,and gasket material.Uniform dispersion of aramid short fiber in resin formulations is achieved through special mixing methods and equipment.Inherent fiber toughness necessitates special types of tools for cutting fabrics and machining aramid composites. 2.4.1.3 Glass Glass in the forms used in commerce has been produced by many cultures since the early Etruscan civilization.Glass as a structural material was introduced early in the seventeenth century and became widely used during the twentieth century as the technology for flat pane was perfected.Glass fibrous us- age for reinforcement was pioneered in replacement of metals and used for both commercial and military uses with the advent of formulation control and molten material which is die or bushing pulled into con- tinuous filaments.These events lead to a wide range of aerospace and commercial high performance structural applications still in use today. 2.4.1.3.1 Chemical description Glass is derived from one of our most abundant natural resources--sand.Other than for,possibly, transport and the melting process,it is not petro-chemical dependent.For purposes of this handbook the typical glass compositions are for electrical/Grade"E"glass,a calcium aluminoborosilica composition with an alkali content of less than 2%,chemical resistant "C"glass composed of soda-lime-borsilicates and high strength S-2 glass which is a low-alkali magnesi-alumina-silicate composition(See Table 2.4.1.3.1). Surface treatments(binders/sizing)can be applied directly to the filaments during the pulling step.Or- ganic binders,such as starch oil,are applied to provide optimum weaving and strand protection during weaving of fabrics or"greige goods".These type binders are then washed and heat cleaned off the fab- rics for finishing or sizing at the weaver with coupling agents to improve compatibility with resins.(See 2-8

MIL-HDBK-17-3F Volume 3, Chapter 2 Materials and Processes - The Effects of Variability on Composite Properties 2-8 TABLE 2.4.1.2(b) Nominal properties of aramid fiber. Tensile Property Units Type of Kevlar™ 29 49 149 Modulus Msi (GPa) 12 (83) 18 (124) 25 (173) Strength ksi (GPa) 525 (3.6) 525-600 (3.6-4.1) 500 (3.4) Aramid fiber is relatively flexible and tough. Thus it can be combined with resins and processed into composites by most of the methods established for glass. Yarns and rovings are used in filament wind￾ing, prepreg tape, and in pultrusion. Woven fabric prepreg is the major form used in thermoset compos￾ites. Aramid fiber is available in various weights, weave patterns, and constructions; from very thin (0.0002 in., 0.005mm) lightweight (275 gm/m2 ) to thick (0.026 in., 0.66 mm) heavy (2.8 gm/m2 ) woven roving. Thermoplastic-impregnated tows can be woven into various types of fabrics to form prepregs. These composites demonstrate good property retention under hot and humid conditions (Reference 2.4.1.2(f)). Chopped aramid fiber is available in lengths from 6 mm to 100 mm. The shorter lengths are used to reinforce thermoset, thermoplastic, and elastomeric resins in automotive brake and clutch linings, gaskets, and electrical parts. Needle-punched felts and spun yarns for asbestos replacement applica￾tions are made from longer fiber staple. A unique very short fiber (0.08 - 0.16 in., 2 - 4 mm) with many attached fibrils is available (aramid pulp). It can provide efficient reinforcement in asbestos replacement uses. Aramid short fibers can be processed into spun-laced and wet-laid papers. These are useful for surfacing veil, thin-printed wiring boards, and gasket material. Uniform dispersion of aramid short fiber in resin formulations is achieved through special mixing methods and equipment. Inherent fiber toughness necessitates special types of tools for cutting fabrics and machining aramid composites. 2.4.1.3 Glass Glass in the forms used in commerce has been produced by many cultures since the early Etruscan civilization. Glass as a structural material was introduced early in the seventeenth century and became widely used during the twentieth century as the technology for flat pane was perfected. Glass fibrous us￾age for reinforcement was pioneered in replacement of metals and used for both commercial and military uses with the advent of formulation control and molten material which is die or bushing pulled into con￾tinuous filaments. These events lead to a wide range of aerospace and commercial high performance structural applications still in use today. 2.4.1.3.1 Chemical description Glass is derived from one of our most abundant natural resources--sand. Other than for, possibly, transport and the melting process, it is not petro-chemical dependent. For purposes of this handbook the typical glass compositions are for electrical/Grade "E" glass, a calcium aluminoborosilica composition with an alkali content of less than 2%, chemical resistant "C" glass composed of soda-lime-borsilicates and high strength S-2 glass which is a low-alkali magnesi-alumina-silicate composition (See Table 2.4.1.3.1). Surface treatments (binders/sizing) can be applied directly to the filaments during the pulling step. Or￾ganic binders, such as starch oil, are applied to provide optimum weaving and strand protection during weaving of fabrics or "greige goods". These type binders are then washed and heat cleaned off the fab￾rics for finishing or sizing at the weaver with coupling agents to improve compatibility with resins. (See

MIL-HDBK-17-3F Volume 3,Chapter 2 Materials and Processes-The Effects of Variability on Composite Properties Figure 2.4.1.3.1)The exception to this process for fabrics is when they are heat treated or"caramelized", which converts the starch to carbon(0.2-0.5%).Glass roving products (untwisted)type yarns are most often directly finished with the final coupling agents during the filament manufacturing step.Therefore the products will be identified with the glass manufacturer's product codes and the desizing step is not necessary as common with fabric"greige goods"forms.Heat cleaned products are also available where the product is essentially pure glass.These products,which are subject to damage,are commonly util- ized for silicone laminates.Another finish designation is applicable to the heat cleaned product when it is followed with a demineralized water wash(neutral pH).More common for structural applications are the coupling agents which are applied for use with standard organic polymers.During the 1940's Volan'fin- ishes were introduced.Since then,many variations/improvements identified with various company desig- nations have appeared.Perhaps the most recognized is Volan A.This finish provides good wet and dry strength properties in use with polyester,epoxy,and phenolic resins.Prior to the application of this finish the clean(ed)glass is saturated with methacrylate chromic chloride so that the chrome content of the fin- ish is between 0.03%and 0.06%.This addition enhances wet-out of the resin during cure.Perhaps more typically called out for use,but not limited to,with epoxy are the silane finishes.Most all are formulated to enhance laminate wet-out.Some also produce high laminate clarity or good composite properties in aqueous environments.Others improve high-pressure laminating,or resist adverse environment or chemical exposures.Although other finishes are used in combination with matrix materials other than epoxy,finishes may have proprietary formulations or varied designations relative to the particular glass manufacturer or weaver,it is believed the compositions are readily available to the resin compounders (prepreggers)to determine compatibility and end use purposes.Note that,non-compatible finishes are purposely applied for ornament applications. 2.4.1.3.2 Physical forms available Due to the high quantity of commercial applications for glass products,there are many product forms available.For purposes of this publication glass forms will be limited to continuous filament product forms.These forms fall into four major categories.They are continuous rovings,yarn for fabrics or braid- ing.mats,and chopped strand.(See Figure 2.4.1.3.2 and ASTM Specification D 579,Reference 2.4.1.3.2(a)for information on glass fabrics.Further discussion of fabrics may be found in Section 2.5.1 on fabrics and preforms.)They are available with a variety of physical surface treatments and finishes Most structural applications utilize fabric,roving,or rovings converted to unidirectional tapes.Perhaps the most versatile fiber type to produce glass product forms is "E"glass."E"glass is identified as such for electrical applications.This type or grade of glass has eight or more standardized filament diameters available.These range from 1.4 to 5.1 mils(3.5 to 13 micrometers).(See Table I,ASTM Specification D 578,Reference 2.4.1.3.2(b).)This facilitates very thin product forms.The "S"glasses are identified as such to signify high strength.The S-2 type glasses are available with but one filament diameter.This does not limit the availability of basic structural fabric styles for S-2 glass however.Although there are more "E"roving products,as to yields,available,this has not noticeably restricted the use of S-2 type rov- ing products or roving for unidirectional tape.S-2 type rovings are available in yields of 250,750,and 1250 yards per lb(500,1500,and 2500 m/kg).Although woven rovings may be considered a fabric product form it should be noted for its importance for military applications.Also,there are glass product forms which could be considered as complimentary products for advanced structures.These would in- clude milled fibers and chopped strand. E.I.Du Pont de Nemours 2-9

MIL-HDBK-17-3F Volume 3, Chapter 2 Materials and Processes - The Effects of Variability on Composite Properties 2-9 Figure 2.4.1.3.1) The exception to this process for fabrics is when they are heat treated or "caramelized", which converts the starch to carbon (0.2 - 0.5%). Glass roving products (untwisted) type yarns are most often directly finished with the final coupling agents during the filament manufacturing step. Therefore, the products will be identified with the glass manufacturer's product codes and the desizing step is not necessary as common with fabric "greige goods" forms. Heat cleaned products are also available where the product is essentially pure glass. These products, which are subject to damage, are commonly util￾ized for silicone laminates. Another finish designation is applicable to the heat cleaned product when it is followed with a demineralized water wash (neutral pH). More common for structural applications are the coupling agents which are applied for use with standard organic polymers. During the 1940's Volan1 fin￾ishes were introduced. Since then, many variations/improvements identified with various company desig￾nations have appeared. Perhaps the most recognized is Volan A. This finish provides good wet and dry strength properties in use with polyester, epoxy, and phenolic resins. Prior to the application of this finish the clean(ed) glass is saturated with methacrylate chromic chloride so that the chrome content of the fin￾ish is between 0.03% and 0.06%. This addition enhances wet-out of the resin during cure. Perhaps more typically called out for use, but not limited to, with epoxy are the silane finishes. Most all are formulated to enhance laminate wet-out. Some also produce high laminate clarity or good composite properties in aqueous environments. Others improve high-pressure laminating, or resist adverse environment or chemical exposures. Although other finishes are used in combination with matrix materials other than epoxy, finishes may have proprietary formulations or varied designations relative to the particular glass manufacturer or weaver, it is believed the compositions are readily available to the resin compounders (prepreggers) to determine compatibility and end use purposes. Note that, non-compatible finishes are purposely applied for ornament applications. 2.4.1.3.2 Physical forms available Due to the high quantity of commercial applications for glass products, there are many product forms available. For purposes of this publication glass forms will be limited to continuous filament product forms. These forms fall into four major categories. They are continuous rovings, yarn for fabrics or braid￾ing, mats, and chopped strand. (See Figure 2.4.1.3.2 and ASTM Specification D 579, Reference 2.4.1.3.2(a) for information on glass fabrics. Further discussion of fabrics may be found in Section 2.5.1 on fabrics and preforms.) They are available with a variety of physical surface treatments and finishes. Most structural applications utilize fabric, roving, or rovings converted to unidirectional tapes. Perhaps the most versatile fiber type to produce glass product forms is "E" glass. "E" glass is identified as such for electrical applications. This type or grade of glass has eight or more standardized filament diameters available. These range from 1.4 to 5.1 mils (3.5 to 13 micrometers). (See Table I, ASTM Specification D 578, Reference 2.4.1.3.2(b).) This facilitates very thin product forms. The "S" glasses are identified as such to signify high strength. The S-2 type glasses are available with but one filament diameter. This does not limit the availability of basic structural fabric styles for S-2 glass however. Although there are more "E" roving products, as to yields, available, this has not noticeably restricted the use of S-2 type rov￾ing products or roving for unidirectional tape. S-2 type rovings are available in yields of 250, 750, and 1250 yards per lb (500, 1500, and 2500 m/kg). Although woven rovings may be considered a fabric product form it should be noted for its importance for military applications. Also, there are glass product forms which could be considered as complimentary products for advanced structures. These would in￾clude milled fibers and chopped strand. 1 E. I. Du Pont de Nemours

MIL-HDBK-17-3F Volume 3,Chapter 2 Materials and Processes-The Effects of Variability on Composite Properties TABLE 2.4.1.3.1 Typical chemical compositions of glass fiber. %(wt) E-Glass S-2 Glass HR Glass(B) (Nominals) Silicon Dioxide(SiO2) 52-56(A) 65 63.5-65.0 Aluminum Oxide(Al2O3) 12-16(A) 25 24.0-25.5 Boron Oxide(B2O3) 5-10(A) Calcium Oxide(CaO) 16-25(A) <0.5 Magnesium Oxide(MgO) 0-5(A) 10 9.5-10.5 Lithium Oxide(Li2O) Potassium Oxide(K2O) 0.c 0.0-0.2 Sodium Oxide(Na2O) 0.c. 0-2 Titanium Oxide (TiO2) O.C. 0-1.5 Cerium Oxide(CeO2) Zirconium Oxide (Zr2O2) Beryllium Oxide(BeO) Iron Oxide(Fe2O3) 0.c 0.0-0.8 Fluorine(F2) 0.c 0.0-0.1 Sulfate (SO2) Alkaline Oxides PPG 0.5-1.5 Calcium Fluoride(CAF) PPG 0.0-0.8 Finishes/Binders 0.5/3.0 2-10

MIL-HDBK-17-3F Volume 3, Chapter 2 Materials and Processes - The Effects of Variability on Composite Properties 2-10 TABLE 2.4.1.3.1 Typical chemical compositions of glass fiber. %(wt) E-Glass S-2 Glass (Nominals) HR Glass (B) Silicon Dioxide (SiO2) 52-56 (A) 65 63.5 - 65.0 Aluminum Oxide (Al2O3) 12-16 (A) 25 24.0 - 25.5 Boron Oxide (B2O3) 5-10 (A) Calcium Oxide (CaO) 16-25 (A) <0.5 Magnesium Oxide (MgO) 0-5 (A) 10 9.5 - 10.5 Lithium Oxide (Li2O) Potassium Oxide (K2O) O.C. 0.0-0.2 Sodium Oxide (Na2O) O.C. 0-2 Titanium Oxide (TiO2) O.C. 0-1.5 Cerium Oxide (CeO2) Zirconium Oxide (Zr2O2) Beryllium Oxide (BeO) Iron Oxide (Fe2O3) O.C. 0.0-0.8 Fluorine (F2) O.C. 0.0-0.1 Sulfate (SO2) Alkaline Oxides PPG 0.5-1.5 Calcium Fluoride (CAF) PPG 0.0-0.8 Finishes/Binders 0.5/3.0