Velocidad De Corte

Solutions for Fundamentals of Modern Manufacturing, 3/e (published by Wiley) © MPGroover 2007

9 COMPOSITE MATERIALS
Review Questions
9.1

What is a composite material?
Answer. A composite material is a materials system consisting of two or more distinct phases whose
combination results in properties that differ from those of its constituents.

9.2

Identify some of thecharacteristic properties of composite materials.
Answer. Typical properties include (1) high strength-to-weight and stiffness-to-weight ratios; (2)
good fatigue properties and toughness; (3) anisotropic properties in many cases; and (4) other
properties and features that are difficult or impossible to obtain with metals, ceramics, or polymers
alone.

9.3

What does the term anisotropic mean?
Answer.Anisotropic means that the properties of a material vary depending on the direction in which
they are measured.

9.4

How are traditional composites distinguished from synthetic composites?
Answer. Traditional composites have been used for decades or centuries; some of them are obtained
from sources in nature, such as wood. Synthetic composites are manufactured.

9.5

Name the threebasic categories of composite materials.
Answer. Metal matrix composites (MMCs), ceramic matrix composites (CMCs), and polymer matrix
composites (PMCs).

9.6

What are the common forms of the reinforcing phase in composite materials?
Answer. The forms are: (1) fibers, (2) particles and flakes, and (3) an infiltrated phase in skeletal
structures.

9.7

What is a whisker?
Answer. Awhisker is a thin, hairlike crystal of very high strength.

9.8

What are the two forms of sandwich structure among laminar composite structures? Briefly describe
each.
Answer. The two forms are (1) foamed-core sandwich, in which the core is polymer foam between
two solid skins; and (2) honeycomb, in which the core is a honeycomb structure sandwiched between
two solid skins.

9.9

Givesome examples of commercial products which are laminar composite structures.
Answer. Examples given in Table 9.2 are automotive tires, honeycomb sandwich structures, fiber
reinforced polymer structures such as boat hulls, plywood, printed circuit boards, snow skis made
from fiber reinforced polymers, and windshield glass.

9.10 What are the three general factors that determine the propertiesof a composite material?
Answer. Three factors are given in the text: (1) the component materials; (2) the geometric shapes of
the constituents - the reinforcing phase in particular - and the resulting structure of the material; and
(3) the interaction of the phases.
9.11 What is the rule of mixtures?
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Solutions for Fundamentals of Modern Manufacturing, 3/e (publishedby Wiley) © MPGroover 2007

Answer. The rule of mixtures applies to certain properties of composite materials; it states that the
property value is a weighted average of the property values of the components, the weighting being
by proportions of the components in the composite.
9.12 What is a cermet?
Answer. A cermet is a composite material consisting of a ceramic and a metal. In the text,it is
defined as a composite consisting of ceramic grains imbedded in a metallic matrix.
9.13 Cemented carbides are what class of composites?
Answer. A cemented carbide is a cermet; although the cemented carbide industry does not generally
think of cemented carbides as cermets, they fit within the definition.
9.14 What are some of the weaknesses of ceramics that might be corrected in...