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《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

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MIL-HDBK-17-3F Volume 3,Chapter 2 Materials and Processes-The Effects of Variability on Composite Properties Available almost exclusively in filament or epoxy matrix prepreg form,boron fiber has been used for aerospace applications requiring high strength and/or stiffness,and for selective reinforcement in sporting goods.The most notable use of this fiber is the stabilizer sections of the F-14 and F-15 military aircraft, dorsal longeron of the B-1B bomber,and the repair of metallic airframe structures.High modulus(HM)or high strength(HS)carbon/epoxy composites can match either the tensile modulus or strength of boron composites at a more economical price,but boron/epoxy composites offer twice the composite strength. Additional information can be found in References 2.4.1.4(a)through(g). TABLE 2.4.1.4 Typical end-use properties of a unidirectional boron/epoxy laminate (Vr=0.5). Value,ksi (MPa) Moduli Tensile,longitudinal 30(207) Tensile,transverse 2.7(19) Strength Tensile,longitudinal 192(1323) Tensile,transverse 10.4(72) Compressive,longitudinal 353(2432) 2.4.1.5 Alumina Continuous polycrystalline alumina fiber is ideally suited for the reinforcement of a variety of materials including plastics,metals,and ceramics.Alumina is prepared in the form of continuous yarn containing a nominal 200 filaments.It is supplied in bobbins containing continuous filament yarn,and alu- mina/aluminum and alumina/magnesium plates.Alumina staple is also available for short fiber reinforce- ment. Fibers that are more than 99%purity a alumina have excellent chemical resistance,and have higher modulus and temperature capabilities than ceramic fibers containing silica.The high modulus of 55 Msi (380 GPa)is comparable to that of boron and carbon.The average filament tensile strength is 200 ksi (1.4 GPa)minimum.Since alumina is a good insulator,it can be used in applications where conducting fibers cannot.Nominal properties of alumina are listed in Table 2.4.1.5(a).Cost projections for alumina are competitive with carbon. Alumina,in continuous form,offers many advantages for composite fabrication including ease of han- dling,the ability to align fibers in desired directions,and filament winding capability.The fact that alumina is an electrical insulator combined with its high modulus and compressive strength make it of interest for polymer matrix composite applications.For example,alumina/epoxy and aramid/epoxy hybrid compos- ites reinforced with alumina and aramid fibers have been fabricated and are of potential interest for radar transparent structures,circuit boards,and antenna supports.Typical properties of unidirectional compos- ites are listed in Table 2.4.1.5(b). 2-17

MIL-HDBK-17-3F Volume 3, Chapter 2 Materials and Processes - The Effects of Variability on Composite Properties 2-17 Available almost exclusively in filament or epoxy matrix prepreg form, boron fiber has been used for aerospace applications requiring high strength and/or stiffness, and for selective reinforcement in sporting goods. The most notable use of this fiber is the stabilizer sections of the F-14 and F-15 military aircraft, dorsal longeron of the B-1B bomber, and the repair of metallic airframe structures. High modulus (HM) or high strength (HS) carbon/epoxy composites can match either the tensile modulus or strength of boron composites at a more economical price, but boron/epoxy composites offer twice the composite strength. Additional information can be found in References 2.4.1.4(a) through (g). TABLE 2.4.1.4 Typical end-use properties of a unidirectional boron/epoxy laminate (Vf = 0.5). Value, ksi (MPa) Moduli Tensile, longitudinal 30 (207) Tensile, transverse 2.7 (19) Strength Tensile, longitudinal 192 (1323) Tensile, transverse 10.4 (72) Compressive, longitudinal 353 (2432) 2.4.1.5 Alumina Continuous polycrystalline alumina fiber is ideally suited for the reinforcement of a variety of materials including plastics, metals, and ceramics. Alumina is prepared in the form of continuous yarn containing a nominal 200 filaments. It is supplied in bobbins containing continuous filament yarn, and alumina/aluminum and alumina/magnesium plates. Alumina staple is also available for short fiber reinforcement. Fibers that are more than 99% purity α alumina have excellent chemical resistance, and have higher modulus and temperature capabilities than ceramic fibers containing silica. The high modulus of 55 Msi (380 GPa) is comparable to that of boron and carbon. The average filament tensile strength is 200 ksi (1.4 GPa) minimum. Since alumina is a good insulator, it can be used in applications where conducting fibers cannot. Nominal properties of alumina are listed in Table 2.4.1.5(a). Cost projections for alumina are competitive with carbon. Alumina, in continuous form, offers many advantages for composite fabrication including ease of handling, the ability to align fibers in desired directions, and filament winding capability. The fact that alumina is an electrical insulator combined with its high modulus and compressive strength make it of interest for polymer matrix composite applications. For example, alumina/epoxy and aramid/epoxy hybrid composites reinforced with alumina and aramid fibers have been fabricated and are of potential interest for radar transparent structures, circuit boards, and antenna supports. Typical properties of unidirectional composites are listed in Table 2.4.1.5(b)

MIL-HDBK-17-3F Volume 3,Chapter 2 Materials and Processes-The Effects of Variability on Composite Properties 2.4.1.6 Silicon carbide Various super-refractory fibers were first produced in the early 1950's based upon work by the Arthur D.Little Co.by various production methods.The primary of these based upon: 1.Evaporation for polycrystalline fiber process. 2.HITCO continuous process for polycrystalline fibers. 3.Vapor deposition of aluminum oxide single crystals(Reference 2.4.1.6(a)). The most recent advances in the CVD type process in use by AVCO consist of substrate wires drawn through glass reaction tubes at high temperature. Silicon carbide fibers are produced with a nominal 0.0055 in.(140 um)filament diameter and are characteristically found to have high strength,modulus and density.Fiber forms are oriented toward the strengthening of aluminum or titanium alloys for both longitudinal and transverse properties.Additional forms are also produced as polycrystalline fiber whiskers of varying length and diameters (Reference 2.4.1.6(b) Several systems for describing the material morphology exist,the alpha and beta forms designated by Thibault and Lindquist being the most common(Reference 2.4.1.6(c)). Practically all silicon carbide monofilament fibers are currently produced for metal composite rein- forcement.Alloys employing aluminum,titanium,and molybdenum have been produced (Reference 2.4.1.6(b)ù General processing for epoxy,bisimide,and polyimide resin can be either via a solvated or solvent- less film impregnation process,with cure cycles equivalent to those provided for carbon or glass rein- forced products.Organic matrix silicon carbide impregnated products may be press,autoclave,or vac- uum bag oven cured.Lay-up on tooling proceeds as with carbon or glass composite products with all bleeding,damming,and venting as required for part fabrication.General temperature and pressure ranges for the cure of the selected matrix resins used in silicon carbide products will not adversely affect the fiber morphology. Silicon carbide ceramic composites engineered to provide high service temperatures (in excess of 2640F or 1450C)are unique in several thermal properties.The overall thermal resistance is determined by the through conductivity,thermal expansion,thermal shock and creep resistance.Thermal conductivi- ties of silicon carbide ceramics have a range in Btu-in/s-ft2-F of 0.12 at room temperature to 0.09 at 1470F(W/m-K of 60 at room temperature to 48 at 800C).Expansion values range,in percentage of original dimension,from 0.05 at 390F(200C)to 1470F(0.30%at 800C).The creep resistance of the silicon carbide ceramic will vary as the percentage of intra-granular silicon phase increases.In general, the creep rate is very low when compared to aluminum oxide or zirconium oxide materials. Mechanical properties of silicon carbide materials are shown in Table 2.4.1.6(a).Fracture toughness as measured by double torsion analysis has reported literature values for Ki ranging from 0.55 ksi Jm (0.6 MPa m for monocrystalline SiC/Si to 5.5 ksi Jm(6.0 MPa Jm)for hot pressed SiC ceramics(Ref- erence 2.4.1.6(g)).Corrosion resistance,of consideration in advanced structural material design,has been evaluated with a variety of mineral acids on the basis of corrosive weight loss as shown in Table 2.4.1.6(b). General cost ranges for the CVD processed fibers are currently in the $100.00 per Ib.,with the control in crystalline form requiring additional expense(Reference 2.4.1.6(e)). 2-19

MIL-HDBK-17-3F Volume 3, Chapter 2 Materials and Processes - The Effects of Variability on Composite Properties 2-19 2.4.1.6 Silicon carbide Various super-refractory fibers were first produced in the early 1950's based upon work by the Arthur D. Little Co. by various production methods. The primary of these based upon: 1. Evaporation for polycrystalline fiber process. 2. HITCO continuous process for polycrystalline fibers. 3. Vapor deposition of aluminum oxide single crystals (Reference 2.4.1.6(a)). The most recent advances in the CVD type process in use by AVCO consist of substrate wires drawn through glass reaction tubes at high temperature. Silicon carbide fibers are produced with a nominal 0.0055 in. (140 µm) filament diameter and are characteristically found to have high strength, modulus and density. Fiber forms are oriented toward the strengthening of aluminum or titanium alloys for both longitudinal and transverse properties. Additional forms are also produced as polycrystalline fiber whiskers of varying length and diameters (Reference 2.4.1.6(b)). Several systems for describing the material morphology exist, the alpha and beta forms designated by Thibault and Lindquist being the most common (Reference 2.4.1.6(c)). Practically all silicon carbide monofilament fibers are currently produced for metal composite reinforcement. Alloys employing aluminum, titanium, and molybdenum have been produced (Reference 2.4.1.6(b)). General processing for epoxy, bisimide, and polyimide resin can be either via a solvated or solventless film impregnation process, with cure cycles equivalent to those provided for carbon or glass reinforced products. Organic matrix silicon carbide impregnated products may be press, autoclave, or vacuum bag oven cured. Lay-up on tooling proceeds as with carbon or glass composite products with all bleeding, damming, and venting as required for part fabrication. General temperature and pressure ranges for the cure of the selected matrix resins used in silicon carbide products will not adversely affect the fiber morphology. Silicon carbide ceramic composites engineered to provide high service temperatures (in excess of 2640°F or 1450°C) are unique in several thermal properties. The overall thermal resistance is determined by the through conductivity, thermal expansion, thermal shock and creep resistance. Thermal conductivities of silicon carbide ceramics have a range in Btu-in/s-ft2 -°F of 0.12 at room temperature to 0.09 at 1470°F (W/mxK of 60 at room temperature to 48 at 800°C). Expansion values range, in percentage of original dimension, from 0.05 at 390°F (200°C) to 1470°F (0.30% at 800°C). The creep resistance of the silicon carbide ceramic will vary as the percentage of intra-granular silicon phase increases. In general, the creep rate is very low when compared to aluminum oxide or zirconium oxide materials. Mechanical properties of silicon carbide materials are shown in Table 2.4.1.6(a). Fracture toughness as measured by double torsion analysis has reported literature values for KIc ranging from 0.55 ksi Jm (0.6 MPa m ) for monocrystalline SiC/Si to 5.5 ksi Jm (6.0 MPa Jm) for hot pressed SiC ceramics (Reference 2.4.1.6(g)). Corrosion resistance, of consideration in advanced structural material design, has been evaluated with a variety of mineral acids on the basis of corrosive weight loss as shown in Table 2.4.1.6(b). General cost ranges for the CVD processed fibers are currently in the $100.00 per lb., with the control in crystalline form requiring additional expense (Reference 2.4.1.6(e))

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