Exam 3

Question 1

Which material would you expect to have the highest % elongation to failure?

Answer 1

Elastomer

Question 2

Properties of composites depend upon

Answer 2

The constituent phases, relative amounts of each phase, geometry of the dispersed phase

Question 3

Which of the following is greater for polymers than for metals?

Answer 3

%EL

Question 4

If a ceramic material is denoted as an AX structure, what meaning does this have?

Answer 4

AX specifies the stoichiometry

Question 5

A semicrystalline polymer will exhibit____

Answer 5

glass transition temp, a melting temp, and amorphous regions

Question 6

A possible structure for an ionic ceramic can be determined from

Answer 6

charge neutrality and radius ratio

Question 7

For a ceramic fiber-strengthened polymer matrix composite with a fixed volume fraction (Vf), which combination of fiber type and applied stress direction would result in the highest elastic modulus?

Answer 7

Continuous, longitudinal force

Question 8

Which of the following are not a characteristic of a thermoplastic polymer?

Answer 8

Network or crosslinked structure

Question 8

Frenkel defect involves what?

Answer 8

Cation interstitial, cation vacancy

Question 9

Schottky defect involves what?

Answer 9

One cation and anion vacancy

Question 10

Composites can be classified as what?

Answer 10

Fiber-reinforced, particle-reinforced, and structural

Question 11

Compared to ceramic materials, ceramic-matrix composites have better

Answer 11

Fracture toughness

Question 12

What defects can occur in an ionic ceramic?

Answer 12

substitutional impurity cation, substitutional anion, a single missing positive ion and an interstitial positive ion.

Question 13

Si coordination in silicate materials would best be described as

Answer 13

tetrahedral

Question 14

Tempered glass resists fracture because

Answer 14

the material contains residual stresses

Question 15

In a covalently-bonded ceramic material, such as SiC, what effect is most likely to determine the structure?

Answer 15

Bond hybridization

Question 16

Forming cross-links between amorphous polymer chains causes what effect for the elastic modulus

Answer 16

a decrease

Question 17

Elastomers have

Answer 17

moderate amount of crosslinking between chains, very low modulus of elasticity, high recoverable elastic strains

Question 18

A semi-crystalline polymer will exhibit a

Answer 18

glass transition temp, melting temp, supercooled liquid of amorphous regions

Question 19

Which kind of bond is responsible for the flexibility of polymer chains

Answer 19

C-C

Question 20

The deformation behavior of a thermoplastic becomes increasingly brittle as

Answer 20

temperature decreases

Question 21

The purpose of the matrix phase is to

Answer 21

transfer stress to other phases

Question 22

As the temperature is decreased below that for a phase transition, the

Answer 22

rate of nucleation increases, critical cluster radius decreases, free energy barrier for nucleation decreases

Question 23

Which of the following eutectoid microstructures is the most ductile?

Answer 23

spheroidite

Question 24

TTT diagrams are useful for which purpose?

Answer 24

determining how quickly to cool a material to obtain a desired microstructure