This preview shows page 1. Sign up to view the full content.
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
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...
View Full Document