2 Materials Major constituents in a fiber-reinforced composite material are the reinforcing fibers and a matrix,which acts as a binder for the fibers.Other constituents that may also be found are coupling agents,coatings,and fillers.Coupling agents and coatings are applied on the fibers to improve their wetting with the matrix as well as to promote bonding across the fiber-matrix interface.Both in turn promote a better load transfer between the fibers and the matrix.Fillers are used with some polymeric matrices primarily to reduce cost and improve their dimensional stability. Manufacturing of a composite structure starts with the incorporation of a large number of fibers into a thin layer of matrix to form a lamina(ply).The thickness of a lamina is usually in the range of 0.1-1 mm (0.004-0.04 in.).If continuous(long)fibers are used in making the lamina,they may be arranged either in a unidirectional orientation (i.e.,all fibers in one direction,Figure 2.1a), in a bidirectional orientation (i.e.,fibers in two directions,usually normal to each other,Figure 2.1b),or in a multidirectional orientation (i.e.,fibers in more than two directions,Figure 2.1c).The bi-or multidirectional orientation of fibers is obtained by weaving or other processes used in the textile industry.The bidirectional orientations in the form of fabrics are shown in Appendix A.1. For a lamina containing unidirectional fibers,the composite material has the highest strength and modulus in the longitudinal direction of the fibers.How- ever,in the transverse direction,its strength and modulus are very low.For a lamina containing bidirectional fibers,the strength and modulus can be varied using different amounts of fibers in the longitudinal and transverse directions. For a balanced lamina,these properties are the same in both directions. A lamina can also be constructed using discontinuous (short)fibers in a matrix.The discontinuous fibers can be arranged either in unidirectional orientation (Figure 2.1c)or in random orientation (Figure 2.1d).Disconti- nuous fiber-reinforced composites have lower strength and modulus than continuous fiber composites.However,with random orientation of fibers (Figure 2.le),it is possible to obtain equal mechanical and physical properties in all directions in the plane of the lamina. The thickness required to support a given load or to maintain a given deflection in a fiber-reinforced composite structure is obtained by stacking several laminas in a specified sequence and then consolidating them to form a laminate.Various laminas in a laminate may contain fibers either all in one 2007 by Taylor&Francis Group.LLC
2 Materials Major constituents in a fiber-reinforced composite material are the reinforcing fibers and a matrix, which acts as a binder for the fibers. Other constituents that may also be found are coupling agents, coatings, and fillers. Coupling agents and coatings are applied on the fibers to improve their wetting with the matrix as well as to promote bonding across the fiber–matrix interface. Both in turn promote a better load transfer between the fibers and the matrix. Fillers are used with some polymeric matrices primarily to reduce cost and improve their dimensional stability. Manufacturing of a composite structure starts with the incorporation of a large number of fibers into a thin layer of matrix to form a lamina (ply). The thickness of a lamina is usually in the range of 0.1–1 mm (0.004–0.04 in.). If continuous (long) fibers are used in making the lamina, they may be arranged either in a unidirectional orientation (i.e., all fibers in one direction, Figure 2.1a), in a bidirectional orientation (i.e., fibers in two directions, usually normal to each other, Figure 2.1b), or in a multidirectional orientation (i.e., fibers in more than two directions, Figure 2.1c). The bi- or multidirectional orientation of fibers is obtained by weaving or other processes used in the textile industry. The bidirectional orientations in the form of fabrics are shown in Appendix A.1. For a lamina containing unidirectional fibers, the composite material has the highest strength and modulus in the longitudinal direction of the fibers. However, in the transverse direction, its strength and modulus are very low. For a lamina containing bidirectional fibers, the strength and modulus can be varied using different amounts of fibers in the longitudinal and transverse directions. For a balanced lamina, these properties are the same in both directions. A lamina can also be constructed using discontinuous (short) fibers in a matrix. The discontinuous fibers can be arranged either in unidirectional orientation (Figure 2.1c) or in random orientation (Figure 2.1d). Discontinuous fiber-reinforced composites have lower strength and modulus than continuous fiber composites. However, with random orientation of fibers (Figure 2.1e), it is possible to obtain equal mechanical and physical properties in all directions in the plane of the lamina. The thickness required to support a given load or to maintain a given deflection in a fiber-reinforced composite structure is obtained by stacking several laminas in a specified sequence and then consolidating them to form a laminate. Various laminas in a laminate may contain fibers either all in one 2007 by Taylor & Francis Group, LLC
Constituents Fibers matrix+ coupling agent or fiber surface coating fillers and other additives Lamina (thin ply or layer) (a)Unidirectional continuous fibers (b)Bidirectional continuous fibers (c)Multidirectional continuous fibers (d)Unidirectional discontinuous fibers (e)Random discontinuous fibers A Laminate (consolidated stack of many layers) FIGURE 2.1 Basic building blocks in fiber-reinforced composites. direction or in different directions.It is also possible to combine different kinds of fibers to form either an interply or an intraply hybrid laminate.An interply hybrid laminate consists of different kinds of fibers in different laminas, whereas an intraply hybrid laminate consists of two or more different kinds of fibers interspersed in the same lamina.Generally,the same matrix is used throughout the laminate so that a coherent interlaminar bond is formed between the laminas. Fiber-reinforced polymer laminas can also be combined with thin aluminum or other metallic sheets to form metal-composite hybrids, commonly known as fiber metal laminates (FML).Two such commercial metal composite hybrids are ARALL and GLARE.ARALL uses alternate layers of aluminum sheets and unidirectional aramid fiber-epoxy laminates 2007 by Taylor Francis Group,LLC
direction or in different directions. It is also possible to combine different kinds of fibers to form either an interply or an intraply hybrid laminate. An interply hybrid laminate consists of different kinds of fibers in different laminas, whereas an intraply hybrid laminate consists of two or more different kinds of fibers interspersed in the same lamina. Generally, the same matrix is used throughout the laminate so that a coherent interlaminar bond is formed between the laminas. Fiber-reinforced polymer laminas can also be combined with thin aluminum or other metallic sheets to form metal–composite hybrids, commonly known as fiber metal laminates (FML). Two such commercial metal–composite hybrids are ARALL and GLARE. ARALL uses alternate layers of aluminum sheets and unidirectional aramid fiber–epoxy laminates Constituents Fibers + matrix + coupling agent or fiber surface coating + fillers and other additives Lamina (thin ply or layer) (a) Unidirectional continuous fibers (b) Bidirectional continuous fibers (c) Multidirectional continuous fibers (d) Unidirectional discontinuous fibers (e) Random discontinuous fibers Laminate (consolidated stack of many layers) FIGURE 2.1 Basic building blocks in fiber-reinforced composites. 2007 by Taylor & Francis Group, LLC
2 Nominal thickness =1.3mm Construction of a 3/2 ARALL Layers 1,3,and 5:Aluminum alloy sheet(each 0.3 mm thick) Layers 2 and 4:Unidirectional aramid fiber/epoxy laminate (each 0.2 mm thick) FIGURE 2.2 Construction of an ARALL laminate. (Figure 2.2).GLARE uses alternate layers of aluminum sheets and either unidirectional or bidirectional S-glass fiber-epoxy laminates.Both metal- composite hybrids have been primarily developed for aircraft structures such as wing panels and fuselage sections. 2.1 FIBERS Fibers are the principal constituents in a fiber-reinforced composite material. They occupy the largest volume fraction in a composite laminate and share the major portion of the load acting on a composite structure.Proper selection of the fiber type,fiber volume fraction,fiber length,and fiber orientation is very important,since it influences the following characteristics of a composite laminate: 1.Density 2.Tensile strength and modulus 3.Compressive strength and modulus 4.Fatigue strength as well as fatigue failure mechanisms 5.Electrical and thermal conductivities 6.Cost A number of commercially available fibers and their properties are listed in Table 2.1.The first point to note in this table is the extremely small filament diameter for the fibers.Since such small sizes are difficult to handle,the useful form of commercial fibers is a bundle,which is produced by gathering a large number of continuous filaments,either in untwisted or twisted form.The untwisted form is called strand or end for glass and Kevlar fibers and tow for carbon fibers (Figure 2.3a).The twisted form is called yarn (Figure 2.3b). Tensile properties listed in Table 2.1 are the average values reported by the fiber manufacturers.One of the test methods used for determining the tensile properties of filaments is the single filament test.In this test method,designated as ASTM D3379,a single filament is mounted along the centerline of a slotted 2007 by Taylor&Francis Group.LLC
(Figure 2.2). GLARE uses alternate layers of aluminum sheets and either unidirectional or bidirectional S-glass fiber–epoxy laminates. Both metal– composite hybrids have been primarily developed for aircraft structures such as wing panels and fuselage sections. 2.1 FIBERS Fibers are the principal constituents in a fiber-reinforced composite material. They occupy the largest volume fraction in a composite laminate and share the major portion of the load acting on a composite structure. Proper selection of the fiber type, fiber volume fraction, fiber length, and fiber orientation is very important, since it influences the following characteristics of a composite laminate: 1. Density 2. Tensile strength and modulus 3. Compressive strength and modulus 4. Fatigue strength as well as fatigue failure mechanisms 5. Electrical and thermal conductivities 6. Cost A number of commercially available fibers and their properties are listed in Table 2.1. The first point to note in this table is the extremely small filament diameter for the fibers. Since such small sizes are difficult to handle, the useful form of commercial fibers is a bundle, which is produced by gathering a large number of continuous filaments, either in untwisted or twisted form. The untwisted form is called strand or end for glass and Kevlar fibers and tow for carbon fibers (Figure 2.3a). The twisted form is called yarn (Figure 2.3b). Tensile properties listed in Table 2.1 are the average values reported by the fiber manufacturers. One of the test methods used for determining the tensile properties of filaments is the single filament test. In this test method, designated as ASTM D3379, a single filament is mounted along the centerline of a slotted Nominal thickness = 1.3 mm 1 3 5 2 4 Construction of a 3/2 ARALL Layers 1, 3, and 5: Aluminum alloy sheet (each 0.3 mm thick) Layers 2 and 4: Unidirectional aramid fiber/epoxy laminate (each 0.2 mm thick) FIGURE 2.2 Construction of an ARALL laminate. 2007 by Taylor & Francis Group, LLC
2007 by Taykr&Francis Group. TABLE 2.1 Properties of Selected Commercial Reinforcing Fibers Coefficient of Typical Tensile Tensile Thermal Diameter Density Modulus Strength Strain-to-Failure Expansion Poisson's Fiber (μm)2 (g/cm) GPa (Msi) GPa(ksi) (%) (10-6/C) Ratio Glass E-glass 10(round) 2.54 72.4(10.5) 3.45(500) 4.8 5 0.2 S-glass 10 (round) 2.49 86.9(12.6 4.30(625) 5.0 2.9 0.22 PAN carbon T-300° 7(round) 1.76 231(33.5) 3.65(530) 1.4 -0.6 (longitudinal) 0.2 7-12 (radial) AS-1d 8(round) 1.80 228(33) 3.10(450) 1.32 AS-44 7 (round) 1.80 248(36) 4.07(590) 1.65 T.40f 5.1 (round) 1.81 290(42) 5.65(820) 1.8 -0.75 (longitudinal) IM-7d 5(round) 1.78 301(43.6) 5.31(770) 1.81 HMS-44 8 (round) 1.80 345(50) 2.48(360) 0.7 GY-70 8.4 (bilobal) 1.96 483(70) 1.52(220) 0.38 Pitch carbon P.55 1 2.0 380(55) 1.90(275) 0.5 -1.3 (longitudinal) P.100 10 2.15 758(110) 2.41(350) 0.32 -1.45 (longitudinal) Aramid Kevlar 49 11.9 (round) 1.45 131(19) 3.62(525) 2.8 -2 (longitudinal) 0.35 59 (radial) Kevlar 149 1.47 179(26) 3.45(500) 1.9 Technoras 139 70(10.1) 3.0(435) 4.6 -6 (longitudinal)
TABLE 2.1 Properties of Selected Commercial Reinforcing Fibers Fiber Typical Diameter (mm)a Density (g=cm3) Tensile Modulus GPa (Msi) Tensile Strength GPa (ksi) Strain-to-Failure (%) Coefficient of Thermal Expansion (106=8C)b Poisson’s Ratio Glass E-glass 10 (round) 2.54 72.4 (10.5) 3.45 (500) 4.8 5 0.2 S-glass 10 (round) 2.49 86.9 (12.6) 4.30 (625) 5.0 2.9 0.22 PAN carbon T-300c 7 (round) 1.76 231 (33.5) 3.65 (530) 1.4 0.6 (longitudinal) 0.2 7–12 (radial) AS-1d 8 (round) 1.80 228 (33) 3.10 (450) 1.32 AS-4d 7 (round) 1.80 248 (36) 4.07 (590) 1.65 T-40c 5.1 (round) 1.81 290 (42) 5.65 (820) 1.8 0.75 (longitudinal) IM-7d 5 (round) 1.78 301 (43.6) 5.31 (770) 1.81 HMS-4d 8 (round) 1.80 345 (50) 2.48 (360) 0.7 GY-70e 8.4 (bilobal) 1.96 483 (70) 1.52 (220) 0.38 Pitch carbon P-55c 10 2.0 380 (55) 1.90 (275) 0.5 1.3 (longitudinal) P-100c 10 2.15 758 (110) 2.41 (350) 0.32 1.45 (longitudinal) Aramid Kevlar 49f 11.9 (round) 1.45 131 (19) 3.62 (525) 2.8 2 (longitudinal) 0.35 59 (radial) Kevlar 149f 1.47 179 (26) 3.45 (500) 1.9 Technorag 1.39 70 (10.1) 3.0 (435) 4.6 6 (longitudinal) 2007 by Taylor & Francis Group, LLC
Extended chain polyethylene Spectra 900h 38 0.97 117(17) 2.59(375) 3.5 Spectra 1000h 27 0.97 172(25) 3.0(435) 2.7 Boron 140 (round) 2.7 393(57) 3.1(450) 0.79 5 0.2 Taykr&Francis Group.LLC. SiC Monofilament 140(round) 3.08 400(58) 3.44(499) 0.86 1.5 Nicalon'(multifilament) 14.5 (round) 2.55 196(28.4) 2.75(399) 1.4 A03 Nextel 610 10-12 (round) 3.9 380(55) 3.1(450) 8 Nextel 720 10-12 3.4 260(38) 2.1(300) 6 A1203-Si03 Fiberfrax(discontinuous) 2-12 2.73 103(15) 1.03-1.72 (150-250) 41μm=0.0000393in. bm/m per C =0.556 in./in.per F. e Amoco. d Hercules. e BASF. f DuPont. 8 Teijin. h Honeywell. i Nippon carbon. j3-M
Extended chain polyethylene Spectra 900h 38 0.97 117 (17) 2.59 (375) 3.5 Spectra 1000h 27 0.97 172 (25) 3.0 (435) 2.7 Boron 140 (round) 2.7 393 (57) 3.1 (450) 0.79 5 0.2 SiC Monofilament 140 (round) 3.08 400 (58) 3.44 (499) 0.86 1.5 Nicaloni (multifilament) 14.5 (round) 2.55 196 (28.4) 2.75 (399) 1.4 Al2O3 Nextel 610j 10–12 (round) 3.9 380 (55) 3.1 (450) 8 Nextel 720j 10–12 3.4 260 (38) 2.1 (300) 6 Al2O3–SiO2 Fiberfrax (discontinuous) 2–12 2.73 103 (15) 1.03–1.72 (150–250) a 1 mm ¼ 0.0000393 in. b m=m per 8C ¼ 0.556 in.=in. per 8F. c Amoco. d Hercules. e BASF. f DuPont. g Teijin. h Honeywell. i Nippon carbon. j 3-M. 2007 by Taylor & Francis Group, LLC