A numerical study on the thermal expansion coefficients of fiber
A numerical study on the thermal expansion coefficients of fiber A numerical study on the thermal expansion coefficients of fiber
13 proportion of the applied load. This load partitioning depends on the ratio of fiber and matrix elastic moduli, E f /E m . In nonceramic matrix composites, this ratio can be very high, while in CMCs, it is rather low and can be as low as unity. Another distinctive point regarding CMCs is that because of limited matrix ductility and generally high fabrication temperature, thermal mismatch between components has a very important bearing on CMC performance. The problem of chemical compatibility between components in CMCs is similar to those in MMCs (Chawla, 1998). CMCs are highly advanced materials and their use is restricted to applications where high strength or high toughness is required at high temperatures. The high cost of producing CMCs has restricted their use to applications in the power generation and aerospace applications. Silicon carbide and boron nitride and other ceramic fibers are used to reinforce ceramics matrices, such as aluminum oxide and silicon carbide. 2.2.2 Fibers Fiber is a general term for a filament with a finite length that is at least 100 times its diameter (typically 0.10 to 0.13 mm). They are the most commonly used reinforcing materials in high performance composites as the load bearing component. They must have high thermal stability and should not contract or expand much with temperature. Defects can be placed on the surface to allow the fiber to interact with the matrix, however; bulk defects should be low. In most cases, fibers are prepared by drawing from a molten bath, and spinning or deposition on a substrate. The term fiber is often used synonymously with filament. Some short fibers are called whiskers which are short single-crystal fibers or filaments made from a variety of materials ranging from 1 to 25 microns and aspect ratios between 100 and 15,000. There are many types of fibers used in industrial applications. The most used ones are described below. A comparison of some important characteristics of fiber reinforcement fibers is in Table 2.1.
14 Table 2.1 Properties of reinforcement fibers (Chawla, 1998). Property 1 High modulus 2 Heat stabilized 3 Trademark of Du Pont 4 Chemical vapor deposition 5 Trademark of Nippon Carbon Co. PAN-Based Carbon Kevlar 3 49 E-Glass HM 1 HS 2 SiC CVD 4 Nicalon 5 Al 2 O 3 Boron Diameter (µm) 7 – 10 7.6 - 8.6 12 8 - 14 100 - 200 10 - 20 20 100 - 200 Density (g/cm 3 ) 1.95 Young’s modulus (GPa) 1.75 1.45 2.55 3.3 2.6 3.95 2.6 Parallel to fiber axis 390 250 125 70 430 180 379 385 Perpendicular to fiber axis 12 20 – 70 – – – – Tensile Strength (GPa) 2.2 2.7 2.8 - 3.5 1.5 - 2.5 3.5 2 1.4 3.8 Strain to fracture (%) 0.5 1 2.2 - 2.8 1.8 - 3.2 – – – – Coefficient of thermal expansion (10 -6 /K) Parallel to fiber axis –0.5 – 0.1 –0.5 - 0.1 –2 - –5 4.7 5.7 – 7.5 8.3 Perpendicular to fiber axis 7 – 12 7 - 12 59 4.7 – – – – 14
- Page 1 and 2: DOKUZ EYLÜL UNIVERSITY GRADUATE SC
- Page 3 and 4: M.Sc THESIS EXAMINATION RESULT FORM
- Page 5 and 6: A NUMERICAL STUDY ON THE THERMAL EX
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- Page 25 and 26: 16 2.2.2.2 Carbon Fibers Carbon is
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- Page 41 and 42: 32 3.3.1 Mechanical Dilatometry Thi
- Page 43 and 44: 34 absolute accuracy of about ± 0.
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- Page 47 and 48: 38 • The composite is macroscopic
- Page 49 and 50: 40 3.4.1.3 Equation of Van Fo Fy In
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14<br />
Table 2.1 Properties <strong>of</strong> reinforcement <strong>fiber</strong>s (Chawla, 1998).<br />
Property<br />
1 High modulus<br />
2 Heat stabilized<br />
3<br />
Trademark <strong>of</strong> Du P<strong>on</strong>t<br />
4<br />
Chemical vapor depositi<strong>on</strong><br />
5 Trademark <strong>of</strong> Nipp<strong>on</strong> Carb<strong>on</strong> Co.<br />
PAN-Based Carb<strong>on</strong><br />
Kevlar 3 49 E-Glass<br />
HM 1 HS 2<br />
SiC<br />
CVD 4 Nical<strong>on</strong> 5 Al 2 O 3 Bor<strong>on</strong><br />
Diameter (µm) 7 – 10 7.6 - 8.6 12 8 - 14 100 - 200 10 - 20 20 100 - 200<br />
Density (g/cm 3 ) 1.95<br />
Young’s modulus (GPa)<br />
1.75 1.45 2.55 3.3 2.6 3.95 2.6<br />
Parallel to <strong>fiber</strong> axis 390 250 125 70 430 180 379 385<br />
Perpendicular to <strong>fiber</strong> axis 12 20 – 70 – – – –<br />
Tensile Strength (GPa) 2.2 2.7 2.8 - 3.5 1.5 - 2.5 3.5 2 1.4 3.8<br />
Strain to fracture (%) 0.5 1 2.2 - 2.8 1.8 - 3.2 – – – –<br />
Coefficient <strong>of</strong> <strong>the</strong>rmal<br />
expansi<strong>on</strong> (10 -6 /K)<br />
Parallel to <strong>fiber</strong> axis –0.5 – 0.1 –0.5 - 0.1 –2 - –5 4.7 5.7 – 7.5 8.3<br />
Perpendicular to <strong>fiber</strong> axis 7 – 12 7 - 12 59 4.7 – – – –<br />
14
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