Which ber is stronger pound for pound 12 give an

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Unformatted text preview: fiber-reinforced composites consist of three “parts”: the fibers, the matrix, and the interfaces. Describe the major functions of each of these “parts.” 2. Briefly describe each of the following composite classes: a. Unidirectional fiber-reinforced composite b. Pseudo-isotropic composite c. Particulate composite d. Transversely isotropic composite 3. Explain why composites are common in the aerospace industry. 4. Define the terms specific strength and specific modulus. 5. Give examples of composite materials in the home. Provide a reason why these products contain composite materials. 6. Compare the following strengthening mechanisms: oxide strengthening of nickel alloys, precipitation hardening in aluminum alloys, and dispersion strengthening in concrete. 7. Discuss the advantage of reinforcing mud bricks with straw. 8. Using the data in Tables 14.3–1 and 14.3–2, estimate the percentage weight savings in the robotic arm in Example 14.2–1 if it were to be made from 304 stainless steel, epoxy resin, Ti–6Al–4V, (Al/B)–0.50Vf composite, and (Ti–6Al–4V/SiC)–0.35Vf composite. Use 304 stainless steel as your reference material. 9. What are the advantages of producing fibers with small diameters? 10. Equation 14.3–2 shows the effect of the relationship between fiber properties and matrix properties on the critical length required to achieve maximum effective reinforcement. a. What occurs when 1 d does not equal or exceed f u 2 my ? b. If a particularly good fiber is available in two diameters, large and small, and two corresponding lengths, long and short, respectively, which fiber do you select for use in a composite? c. If the fiber is inadvertently sprayed with a very thin layer of lubricant, what will be the effect on composite properties? 11. Calculate the specific strength (strength/density) and specific modulus, (elastic modulus/density) of stainless steel, Kevlar, and Spectra fibers. Which fiber is stronger, pound for pound? 12. Give an example of fibrous material for which a decrease in diameter will result in an increase in strength. Give an example of a fiber for which you would expect a correlation between modulus and diameter. 13. Explain in your own words the principle behind mechanical bonding. Suggest a means by which you can improve the interfacial strength in steel-reinforced concrete. 14. Explain what is meant by the term chemical bonding as it relates to a fiber-matrix interface. 15. Table 14.3–1 does not give the cost of fibers, which is important in manufacturing of composites. If boron fiber cost $400/lb, carbon fiber costs $50/lb, and oxide glass fiber costs $2/lb, which is the best choice for: a. High specific strength in a cost-critical application? b. High specific modulus in a cost-critical application? 16. What is a lamina? Describe the stacking sequence of laminae in a laminated composite that has good tensile properties in 0 and 90 orientations and also has good shear stress resistance. What design modification would you suggest if shear resistance is not required. 17. Suggest an appropriate matrix to be used with each of the following fiber types: a. E-glass | v v SECTION 14.3 General Concepts | e-Text...
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This note was uploaded on 02/25/2013 for the course PHYS 2202 taught by Professor Sowell during the Spring '10 term at Georgia Institute of Technology.

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