Exam 3 Flashcards
Which material would you expect to have the highest % elongation to failure?
Elastomer
Properties of composites depend upon
The constituent phases, relative amounts of each phase, geometry of the dispersed phase
Which of the following is greater for polymers than for metals?
%EL
If a ceramic material is denoted as an AX structure, what meaning does this have?
AX specifies the stoichiometry
A semicrystalline polymer will exhibit____
glass transition temp, a melting temp, and amorphous regions
A possible structure for an ionic ceramic can be determined from
charge neutrality and radius ratio
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?
Continuous, longitudinal force
Which of the following are not a characteristic of a thermoplastic polymer?
Network or crosslinked structure
Frenkel defect involves what?
Cation interstitial, cation vacancy
Schottky defect involves what?
One cation and anion vacancy
Composites can be classified as what?
Fiber-reinforced, particle-reinforced, and structural
Compared to ceramic materials, ceramic-matrix composites have better
Fracture toughness
What defects can occur in an ionic ceramic?
substitutional impurity cation, substitutional anion, a single missing positive ion and an interstitial positive ion.
Si coordination in silicate materials would best be described as
tetrahedral
Tempered glass resists fracture because
the material contains residual stresses
In a covalently-bonded ceramic material, such as SiC, what effect is most likely to determine the structure?
Bond hybridization
Forming cross-links between amorphous polymer chains causes what effect for the elastic modulus
a decrease
Elastomers have
moderate amount of crosslinking between chains, very low modulus of elasticity, high recoverable elastic strains
A semi-crystalline polymer will exhibit a
glass transition temp, melting temp, supercooled liquid of amorphous regions
Which kind of bond is responsible for the flexibility of polymer chains
C-C
The deformation behavior of a thermoplastic becomes increasingly brittle as
temperature decreases
The purpose of the matrix phase is to
transfer stress to other phases
As the temperature is decreased below that for a phase transition, the
rate of nucleation increases, critical cluster radius decreases, free energy barrier for nucleation decreases
Which of the following eutectoid microstructures is the most ductile?
spheroidite
