Composites

Question 1

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 1

Composite

Question 2

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

Answer 2

Composite

Question 3

According to this principle, better property combinations are fashioned by the judicious combination of two or more distinct materials

Answer 3

PRINCIPLE OF COMBINED ACTION

Question 4

Two Phases of Composite Materials

Answer 4

Matrix phase
Dispersed phase

Question 5

which is continuous and surrounds the other phase

Answer 5

Matrix phase

Question 6

the one that is being surrounded by the matrix.

Answer 6

Dispersed phase

Question 7

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

Answer 7

Dispersed phase geometry

Question 8

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

Answer 8

Structural composites

Question 9

two subclassifications of particle-reinforced composites

Answer 9

Large-particle and dispersion-strengthened composites

Question 10

The term _____ is used to indicate that particle–matrix interactions cannot be treated on the atomic or molecular level; rather, continuum mechanics is used.

Answer 10

large

Question 11

Some polymeric materials to which fillers have been added are

Answer 11

large-particle composites

Question 12

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

Answer 12

Filler

Question 13

composed of cement (the matrix) and sand and gravel (the particulates).

Answer 13

Cement

Question 14

predict that the elastic modulus should fall between an upper bound & lower bound

Answer 14

rule-of-mixtures equations

Question 15

Large-particle composites are used with all three material types

Answer 15

(metals, polymers, and ceramics

Question 16

composed of extremely hard particles of a refractory carbide ceramic such as tungsten carbide (WC) or titanium carbide (TiC) embedded in a matrix of a metal such as cobalt or nickel.

Answer 16

cemented carbide

Question 17

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 supply.

Answer 17

Carbon black

Question 18

a common large-particle composite in which both matrix and dispersed phases are ceramic materials

Answer 18

Concrete

Question 19

The two most familiar concretes are those made with

Answer 19

Portland and asphaltic cements

Question 20

widely used primarily as a paving material

Answer 20

Asphaltic concrete

Question 21

employed extensively as a structural building material.

Answer 21

Portland cement concrete

Question 22

act as a filler material to reduce the overall cost of the concrete product because they are cheap, whereas cement is relatively expensive

Answer 22

aggregate particles

Question 23

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

Answer 23

Portland cement concrete

Question 24

The strength of Portland cement concrete may be increased by additional reinforcement. This is usually accomplished by means of _________ which are embedded into the fresh and uncured concrete.

Answer 24

steel rods, wires, bars (rebar), or mesh

Question 25

serves as a suitable reinforcement material because its coefficient of thermal expansion is nearly the same as that of concrete

Answer 25

Steel

Question 26

Another reinforcement technique for strengthening concrete involves the introduction of residual compressive stresses into the structural member; the resulting material is called

Answer 26

prestressed concrete

Question 27

Another technique, in which stresses are applied after the concrete hardens, is appropriately called

Answer 27

posttensioning

Question 28

The high-temperature strength of nickel alloys may be enhanced significantly by the addition of about 3 vol% thoria (ThO2) as finely dispersed particles; this material is known as

Answer 28

thoria-dispersed (or TD) nickel.

Question 29

A very thin and adherent alumina coating is caused to form on the surface of extremely small (0.1 to 0.2μm thick) flakes of aluminum, which are dispersed within an aluminum metal matrix; this material is termed

Answer 29

sintered aluminum powder (SAP)

Question 30

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

Answer 30

Fiber

Question 31

The mechanical characteristics of a fiber-reinforced composite depend not only on the _______, but also on the __________

Answer 31

properties of the fiber, degree to which an applied load is transmitted to the fibers by the matrix phase.

Question 32

With respect to orientation, two extremes are possible:

Answer 32

(1) a parallel alignment of the longitudinal axis of the fibers in a single direction, and (2) a totally random alignment.

Question 33

The strengths of continuous and unidirectional fibrous composites are highly ______, and such composites are normally designed to be loaded along the high strength, longitudinal direction.

Answer 33

anisotropic

Question 34

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. These are termed

Answer 34

laminar composites

Question 35

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

Answer 35

Whiskers

Question 36

On the basis of diameter and character, fibers are grouped into three different classifications:

Answer 36

whiskers, fibers, and wires

Question 37

Materials that are classified as ______ are either polycrystalline or amorphous and have small diameters; materials are generally either polymers or ceramics

Answer 37

fibers

Question 38

Have relatively large diameters; are used as a radial steel reinforcement

Answer 38

Wires9

Question 39

consist of a polymer resin as the matrix and fibers as the reinforcement medium.

Answer 39

Polymer–matrix composites (PMCs)

Question 40

a composite consisting of glass fibers, either continuous or discontinuous, contained within a polymer matrix

Answer 40

Fiberglass

Question 41

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

Answer 41

Carbon

Question 42

Are high-strength, high-modulus materials that were introduced in the early 1970s.

Answer 42

Aramid fibers

Question 43

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

Answer 43

Boron fiber–reinforced polymer composites

Question 44

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

Answer 44

Silicon carbide and aluminum oxide fibers

Question 45

The most widely used and least expensive polymer resins are the

Answer 45

polyesters and vinyl esters

Question 46

the matrix is a ductile metal. These materials may be used at higher service temperatures than their base-metal counterparts

Answer 46

metal-matrix composites (MMCs)

Question 47

(CMCs)—particulates, fibers, or whiskers of one ceramic material that have been embedded into a matrix of another ceramic.

Answer 47

Ceramic-matrix composites (CMCs)

Question 48

have low coefficients of thermal expansion and relatively high thermal conductivities; these characteristics, coupled with high strengths, give rise to a relatively low susceptibility to thermal shock

Answer 48

carbon fiber–reinforced carbon-matrix composite, often termed a carbon–carbon composite

Question 49

molecular components consisting of oxygen, hydrogen, and nitrogen are driven off, leaving behind large carbon chain molecules.

Answer 49

pyrolysis

Question 50

Obtained by using two or more different kinds of fibers in a single matrix; have a better all-around combination of properties than composites containing only a single fiber type.

Answer 50

hybrids

Question 51

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

Answer 51

Pultrusion

Question 52

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

Answer 52

Prepreg

Question 53

tows are then sandwiched and pressed between sheets of release and carrier paper using heated rollers

Answer 53

calendering.

Question 54

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

Answer 54

doctor blade

Question 55

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

Answer 55

Filament winding

Question 56

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 56

structural composite

Question 57

composed of two-dimensional sheets or panels bonded to one another

Answer 57

laminar composite

Question 58

there are four classes of laminar composites:

Answer 58

unidirectional, cross-ply, angle-ply and multidirectional

Question 59

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

Answer 59

Sandwich panels

Question 60

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

Answer 60

the nanocomposites.

Question 61

are composed of nanosized particles (or nanoparticles) that are embedded in a matrix material.

Answer 61

Nanocomposites

Question 62

Two factors account for these size-induced properties of nanoparticles:

Answer 62

(1) the increase in ratio of particle surface area to volume; and (2) particle size.

Question 63

Most of today’s commercial nanocomposites use three general nanoparticle types:

Answer 63

• Nanocarbons • Nanoclays - layered silicates • Particulate nanocrystals - inorganic oxides

Question 64

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 64

Gas-barrier coatings

Question 65

Graphene nanocomposites are used in anodes for lithium-ion rechargeable batteries—batteries that store electrical energy in hybrid electric vehicles.

Answer 65

Energy storage

Question 66

Thin coatings composed of multi-walled carbon nanotubes dispersed in silicone matrices exhibit outstanding flame barrier characteristics

Answer 66

Flame-barrier coatings

Question 67

High-strength and lightweight polymer nanocomposites are produced by the addition of multi-walled carbon nanotubes into epoxy resins

Answer 67

Mechanical strength enhancements

Question 68

The motion of highly flammable fuels in automotive and aircraft polymer fuel lines can lead to the production of static charges.

Answer 68

Electrostatic dissipation