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Unformatted text preview: Main Menu | Textbook Table of Contents pg609 [R] G13 7-27060 / IRWIN / Schaffer iq Chapter 14 13.01.98 plm QC2 rps MP Composite Materials 609 b. Boron
c. Oriented polyethylene
18. Suggest an appropriate application for each of the following ﬁber types:
c. Al2 O3
19. Suppose you need to achieve certain mechanical properties in a composite. What is the
principal basis for selecting the matrix material? For example, why choose epoxy rather
than aluminum? SECTION 14.4
Systems 26. Using the data in Tables 14.3–1 and 14.3–2 calculate the following properties of composite materials:
a. The isostrain modulus of epoxy reinforced with 60 volume % for
(i) B ﬁber
(ii) C ﬁber
b. The isostress modulus of the composites in part a
c. The isostrain modulus of Al reinforced with 60 volume % for
(i) B ﬁber
(ii) C ﬁber
d. The isostress modulus of the composites in part c
e. Estimate the maximum achievable strength of the composites described in parts a and c.
Note that the composite may not reach this strength due to the presence of defects.
27. The elastic modulus of magnesium is about 50 GPa, and its density is 1.74 g/cm3. Find
the volume fraction of SiC whiskers all aligned in one direction that must be added to a
magnesium-based alloy to increase its speciﬁc elastic modulus by 50%.
28. The shear strength of an aluminum alloy is 150 MPa. This alloy is under consideration for
being reinforced by SiC whiskers, which have a tensile strength of 8 GPa. Estimate the
critical aspect ratio to achieve ﬁber strengthening assuming (a) the interface strength is
larger than the matrix shear strength and (b) the interface strength is only half of the matrix shear strength.
29. Compare the advantage of 2024-T4 Al (tensile strength 400 MPa), Ti–6Al–4V (tensile
strength 1100 MPa), and 300 grade maraging steel (tensile strength 2000 MPa) for
use as matrix materials for SiC whisker-reinforced composites in which the whiskers are
randomly oriented. SECTION 14.5
Prediction of Composite
Properties | v v 20. Why is it necessary to thoroughly clean the surfaces of glass ﬁbers to achieve a strong
bond with epoxy?
21. Explain why a strong interface is a detriment to the properties of ceramic-matrix composites.
22. List two applications that favor the use of
a. Metal-matrix composites
b. Ceramic-matrix composites
c. Polymer-matrix composites
23. Which class of composites (CMCs, MMCs, or PMCs) is generally the least expensive class?
24. What is generally considered to be the most serious problem associated with the use of
CMCs? How is this problem addressed?
25. Discuss the advantages and disadvantages of carbon-carbon composites over traditional
PMCs. | e-Text Main Menu | Textbook Table of Contents pg610 [V] G12 7-27060 / IRWIN / Schaffer Part III 13.01.98 plm QC2 rps MP Properties 30. How does Equation 14.5–9 depend on ﬁber length?
31. Show that in 1 cm3 of a composite containing 50 - m -diameter ﬁbers in a square array w...
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