COMPOSITES

Question 1

materials such as wood,
bricks made from straw-reinforced clay, seashells

Answer 1

multiphase materials

Question 2

the recognition of this novel concept of
combining dissimilar materials during manufacture
led to the identification of ______

Answer 2

composites

Question 3

is considered to be any
multiphase material that exhibits a
significant proportion of the properties of
both constituent phases such that a better
combination of properties is realized.

Answer 3

composite

Question 4

It is a multiphase material that is artificially
made, as opposed to one that occurs or
forms naturally

Answer 4

composites

Question 5

a new generation of
extraordinary
materials

Answer 5

composites

Question 6

Most composites have been
created to improve combinations of
mechanical characteristics such as

Answer 6

stiffness, toughness, and ambient and high-temperature strength

Question 7

better
property combinations are
fashioned by the judicious
combination of two or more
distinct materials

Answer 7

PRINCIPLE OF
COMBINED ACTION

Question 8

is continuous and
surrounds the other phase

Answer 8

Matrix phase

Question 9

is continuous and
surrounds the other phase

Answer 9

Matrix phase

Question 10

the one that is being
surrounded by the matrix

Answer 10

Dispersed phase

Question 11

means the shape of the particles
and the particle size, distribution, and
orientation;

Answer 11

Dispersed phase geometry

Question 12

The dispersed phase for particle-reinforced
composites

Answer 12

equiaxed

Question 13

or fiber-reinforced composites, the
dispersed phase has

Answer 13

geometry of a fiber

Question 14

particle
dimensions are approximately the same in all
directions

Answer 14

equiaxed

Question 15

large length to diameter ratio

Answer 15

fiber

Question 16

are multilayered and
designed to have low densities and high
degrees of structural integrity

Answer 16

Structural composites

Question 17

dimensions of the dispersed
phase particles are on the order of
nanometers.

Answer 17

nanocomposites

Question 18

two subclassifications of particle-reinforced
composites.

Answer 18

• Large-particle and dispersion-strengthened composites

Question 19

used to indicate that particle–matrix interactions cannot be
treated on the atomic or molecular level

Answer 19

large

Question 20

For most of these composites, the___________-
harder and stiffer than the matrix.

Answer 20

the particulate phase

Question 21

the degree of reinforcement or improvement of
mechanical behavior depends on strong bonding at the matrix

Answer 21

true

Question 22

Some polymeric materials to which fillers
have been added are

Answer 22

large-particle
composites.

Question 23

modify or
improve the properties of the material and/or
replace some of the polymer volume with a
less expensive material

Answer 23

filler

Question 24

familiar large-particle composite

Answer 24

concrete

Question 25

cement is the

Answer 25

matrix

Question 26

sand and gravel are the

Answer 26

particulates

Question 27

For effective reinforcement, the particles should be small and evenly distributed throughout the matrix

Answer 27

TRUE

Question 28

IT Influences the behavior; mechanical properties are enhanced with increasing particulate content.

Answer 28

VOLUME FRACTION

Question 29

predict that the elastic modulus should fall between an upper bound

Answer 29

rule of mixtures

Question 30

are examples of ceramic–metal composites

Answer 30

cermets

Question 31

the most common cermet

Answer 31

cemented carbide

Question 32

is composed of extremely hard particles of a refractory carbide ceramic such as tungsten carbide

Answer 32

cemented carbide

Question 33

cermets are extensively used in

Answer 33

cutting tools

Question 34

are frequently reinforced with various particulate materials

Answer 34

elastomers and plastics

Question 35

. Use of many modern rubbers would be severely restricted without reinforcing particulate materials such as

Answer 35

carbon black.

Question 36

consists of very small and essentially spherical particles of carbon, produced by the combustion of natural gas or oil in an atmosphere that has only a limited air supp

Answer 36

carbon black

Question 37

When added to vulcanized rubber, this extremely inexpensive material enhances tensile strength, toughness, and tear and abrasion resistance

Answer 37

carbon black

Question 38

implies a composite material consisting of an aggregate of particles

Answer 38

concrete

Question 39

some type of binding medium,

Answer 39

cement

Question 40

The two most familiar concretes are those made with

Answer 40

portland and asphaltic cement

Question 41

is widely used primarily as a paving material

Answer 41

Asphaltic concrete

Question 42

is employed extensively as a structural building mater

Answer 42

Portland cement concrete

Question 43

The ingredients for this concrete are Portland cement, a fine aggregate (sand), a coarse aggregate (gravel), and water.

Answer 43

portland cement concrete

Question 44

act as a filler material to reduce the overall cost of the concrete product because they are cheap,

Answer 44

aggregate particles

Question 45

s a major material of construction, primarily because it can be poured in place and hardens at room temperature and even when submerged in water

Answer 45

Portland cement concrete

Question 46

is relatively weak and extremely brittle

Answer 46

portland cement concrete

Question 47

large concrete structures can experience considerable thermal expansion and contraction with temperature fluctuations

Answer 47

true

Question 48

In addition, water penetrates into external pores, which can cause severe cracking in cold weather as a consequence

Answer 48

freeze–thaw cycles.

Question 49

serves as a suitable reinforcement material

Answer 49

steel

Question 50

its coefficient of thermal expansion is nearly the same as that of concrete

Answer 50

steel

Question 51

steel is not rapidly corroded in the cement environment, and a relatively strong adhesive bond is formed between it and the cured concret

Answer 51

true

Question 52

Portland cement concrete may also be reinforced by mixing fibers of a high- modulus material such as glass, steel, nylon, or polyethylene

Answer 52

true

Question 53

the introduction of residual compressive stresses into the structural member; the resulting material

Answer 53

prestressed concrete

Question 54

Thus, to fracture a prestressed concrete member, the magnitude of the precompressive stress must be exceeded by an applied tensile stress.

Answer 54

true

Question 55

stresses are applied after the concrete hardens

Answer 55

posttensioning

Question 56

the increase in strength may disappear upon heat treatment as a consequence of precipitate growth

Answer 56

precipitation-hardened alloys,

Question 57

thoria (ThO2) as finely dispersed particles; this material

Answer 57

thoria-dispersed (or TD) nickel

Question 58

flakes of aluminum, which are dispersed within an aluminum metal matrix; this material is termed

Answer 58

sintered aluminum powder

Question 59

echnologically, the most important composites are those in which the dispersed phase is in the form of a

Answer 59

fiber

Question 60

Continuous fibers are normally

Answer 60

aligned

Question 61

discontinuous fibers may be

Answer 61

aligned, randomly oriented, or partially oriented

Question 62

the load is applied at a 90° angle to the direction of fiber alignment.

Answer 62

transverse direction

Question 63

The strengths of continuous and unidirectional fibrous composites

Answer 63

highly anisotropic

Question 64

When multidirectional stresses are imposed within a single plane, aligned layers that are fastened together on top of one another at different orientations are frequently used.

Answer 64

laminar composites

Question 65

are very thin single crystals that have extremely large length-to-diameter ratios.

Answer 65

whiskers

Question 66

hey have a high degree of crystalline perfection and are virtually flaw-free, which accounts for their exceptionally high strengths; they are among the strongest known materials.

Answer 66

whiskers

Question 67

include graphite, silicon carbide, silicon nitride, and aluminum oxide

Answer 67

whiskers

Question 68

are either polycrystalline or amorphous and have small diameters; fibrous materials are generally either polymers or ceramics (e.g., the polymer aramids, glass, carbon, boron, aluminum oxide, and silicon carbide).

Answer 68

Fibers

Question 69

used as a radial steel reinforcement in automobile tires, in filament-wound rocket casings, and in wire-wound high-pressure hoses

Answer 69

wires

Question 70

used as a radial steel reinforcement in automobile tires, in filament-wound rocket casings, and in wire-wound high-pressure hoses

Answer 70

Polymer–matrix composites

Question 71

is simply a composite consisting of glass fibers, either continuous or discontinuous, contained within a polymer matrix; this type of composite is produced in the largest quantities

Answer 71

fiberglass

Question 72

is a high-performance fiber material that is the most commonly used reinforcement in advanced (i.e., nonfiberglass) polymer-matrix composites.

Answer 72

carbon

Question 73

are high-strength, high-modulus materials that were introduced in the early 1970s. They are especially desirable for their outstanding strength-to-weight ratios, which are superior to those of metals.

Answer 73

aramid fibers

Question 74

Chemically, this group of materials is known as poly(paraphenylene terephthalamide).

Answer 74

aramid fibers

Question 75

There are a number of aramid materials; trade names for two of the most common are

Answer 75

Kevlar and Nomex

Question 75

There are a number of aramid materials; trade names for two of the most common are

Answer 75

Kevlar and Nomex

Question 76

have been used in military aircraft components, helicopter rotor blades, and sporting goods.

Answer 76

Boron fiber–reinforced polymer composites

Question 77

are used in tennis rackets, circuit boards, military armor, and rocket nose cones

Answer 77

Silicon carbide and aluminum oxide fibers

Question 78

the most widely used and least expensive polymer resins are

Answer 78

the polyesters and vinyl esters.

Question 79

that is, converted into carbon by heating in an inert atmosphere; during pyrolysis, molecular components consisting of oxygen, hydrogen, and nitrogen are driven off, leaving behind large carbon-chain molecules

Answer 79

pyrolyzed

Question 80

which is obtained by using two or more different kinds of fibers in a single matrix

Answer 80

hybrid

Question 81

is used for the manufacture of components having continuous lengths and a constant cross-sectional shape

Answer 81

Pultrusion

Question 82

is the composite industry’s term for continuous-fiber reinforcement preimpregnated with a polymer resin that is only partially cured.

Answer 82

Prepreg

Question 83

a process where tows are then sandwiched and pressed between sheets of release and carrier paper using heated rollers,

Answer 83

calendering

Question 84

spreads the resin into a film of uniform thickness and width.

Answer 84

doctor blade

Question 85

is a process by which continuous reinforcing fibers are accurately positioned in a predetermined pattern to form a hollow (usually cylindrical) shape.

Answer 85

filament winding

Question 86

is a multi-layered and normally low-density composite used in applications requiring structural integrity, ordinarily high tensile, compressive, and torsional strengths and stiffnesses.

Answer 86

structural composites

Question 87

s composed of two- dimensional sheets or panels (plies or laminae) bonded to one another.

Answer 87

laminar composites

Question 88

a class of structural composites, are designed to be lightweight beams or panels having relatively high stiffnesses and strengths.

Answer 88

sandwich panels

Question 89

The material’s world is experiencing a revolution with the development of a new class composite materials

Answer 89

nanocomposites

Question 90

single- and multi-wall carbon nanotubes, graphene sheets and carbon nanofibers

Answer 90

nanocarbons

Question 91

layered silicates; the most common type is montmorillonite clay.

Answer 91

nanoclays

Question 92

inorganic oxides such silica, alumina, zirconia, halfnia, and titania

Answer 92

Particulate nanocrystals

Question 93

Nanocomposite coatings are also used to increase air pressure retention for automobile tires and sports (e.g., tennis, soccer) balls. These coatings are composed of small and exfoliated vermiculite platelets that are embedded in the tire/ sports ball rubber

Answer 93

Gas-barrier coatings