Exam 4 ENGR31
For an aligned fibrous composite, when a stress is applied perpendicular to the fibers, what is the reinforcement efficiency? (a)0, (b)1/5, (c)3/8, (d)3/4, (e)1.
(a)0,
What is the viscosity value corresponding to the melting point of glass? (a)10 Pa-s, (b)10^3Pa-s, (c)5×10^13Pa-s, (d)10^12Pa-s, (e)3×10^13Pa-s.
(a)10 Pa-s,
A Frenkel defect is composed with a pair of which of the following? (a)A cation interstitial and a cation vacancy, (b)A cation interstitial and an anion interstitial, (c)Acation vacancy and an anion vacancy, (d)An anion interstitial and an anion vacancy, (e)None ofthe above.
(a)A cation interstitial and a cation vacancy,
In order for a polymer to behave as an elastomer, which of the following are necessary? (a)It must not crystallize easily; chain bond rotations must be relatively free; the polymer must be above its glass transition temperature. (b)It must not crystallize easily; chain bond rotations must not be relatively free; the polymer must be below its glass transition temperature. (c)It must not crystallize easily; chain bond rotations must be relatively free; the polymer must be below its glass transition temperature. (d)It must not crystallize easily; chain bond rotations must not be relatively free; the polymer must be above its glass transition temperature. (e)None of the above.
(a)It must not crystallize easily; chain bond rotations must be relatively free; the polymer must be above its glass transition temperature.
The crystal structure for NiO is: (a)Sodium Chloride, (b)Cesium Chloride, (c)Zinc Blende, (d)Fluorite, (e)None of the above.
(a)Sodium Chloride,
What is the viscosity value corresponding to the working point of glass? (a)10 Pa-s, (b)10^3Pa-s, (c)5×10^13Pa-s, (d)10^12Pa-s, (e)3×10^13Pa-s.
(b)10^3Pa-s,
What is the viscosity value corresponding to the annealing point of glass? (a)10 Pa-s, (b)10^3Pa-s, (c)5×10^13Pa-s, (d)10^12Pa-s, (e)3×10^13Pa-s.
(d)10^12Pa-s,
Which of the following are the most common coordination numbers for ceramic materials? (a)2 and 3, (b)6 and 12, (c)6, 8, and 12, (d)4, 6, and 8, (e)none of the above.
(d)4, 6, and 8,
Which of the following are the two primary constituents of clays? (a)Alumina (Al2O3) and limestone (CaCO3), (b)Limestone (CaCO3) and cupric oxide (CuO), (c)Sil-ica (SiO2) and limestone (CaCO3), (d)Alumina (Al2O3) and silica (SiO2), (e)None of the above.
(d)Alumina (Al2O3) and silica (SiO2),
Fiber reinforced composites are very well known for (a)high specific strength, (b)high specific stiffness, (c)high specific density, (d)both A andB, (e)none of above.
(d)both A and B, (high specific strength and high specific stiffness,)
The type of material that will usually possess the best ductility is (a)metals, (b)ceramics, (c)plastics, (d)elastomers, (e)none of the above.
(d)elastomers, (because it stretches, hence elastic)
What is the viscosity value corresponding to the strain point of glass? (a)10 Pa-s, (b)10^3Pa-s, (c)5×10^13Pa-s, (d)10^12Pa-s, (e)3×10^13Pa-s.
(e)3×10^13Pa-s.
Which of the following is (are) composite(s)? (a)Wood, (b)Bone, (c)Concrete, (d)Carbon fiber-reinforced epoxy, (e)All of the above.
(e)All of the above.
APF=?
APF= Volume of ions/Volume unit cell
P=?
P=(n(W_a+W_c))/(V_c+N_A)
Cation-Anion Radius Ratio?
R_c/R_a
TS= TS_∞ - (A/M_n)
TS=Tensile Strength, A=Constant, M_n=avg molecular weight
*How are continuous fibers typically oriented in fibrous composites? a) aligned b) partially oriented c) randomly oriented d) all e) none
a) aligned
*Glass rods are fabricated by which of the following techniques? a) drawing b) pressing c) blowing d) casting e) none
a) drawing
*Which of the following properties is NOT a characteristic of ceramics? a) good electrical conductivity b) high hardness c) high melting temperature d) good corrosion resistance e) none
a) good electrical conductivity
*For fiber applications, a polymer should be: a) highly crystalline b) semicrystalline c) noncrystalline d) none
a) highly crystalline
*The aspect ratio of a reinforcing fiber is defined as its a) length/diameter b) strength/stiffness c) strength/density d) stiffness/density e) none
a) length/diameter
*Isotropic properties (uniform in ALL directions) are expected in ALL composites are a) particle reinforced b) fiber reinforced c) laminates d) sandwich panels e) none
a) particle reinforced
*As the porosity of refractory ceramic bricks increases: a) strength decreases, chemical resistance decreases, and thermal insulation increases b) strength increases, chemical resistance increases, and thermal insulation decreases c) strength decreases, chemical resistance increases, and thermal insulation decreases d) strength increases, chemical resistance increases, and thermal insulation increases e) none
a) strength decreases, chemical resistance decreases, and thermal insulation increases
rock salt crystal structure formula for a?
a=2(r_c+r_c)
APF for zinc sulfide crystal structure?
a=2*sqrt(2)R_a V=a^3=16*sqrt(2)*R_a^3 APF=(4*(4pi/3)(R_a^3_R_c^3))/(16*sqrt(2)*R_a^3)
*Which of the following can NOT be true for the crystal structure of SiC? a) Structure name=Zinc Sulfide b) Structure type=AX_2 c) Anion packing=FCC d) Coordination number=4 e) none
b) Structure type=AX_2
*Which of the following is NOT a ceramic material? a) glass b) diamond c) cement d) abrasives e) none
b) diamond
*The type of polymer that can be easily recycles is: a) thermosetting polymer b) thermoplastic polymer c) both A and B d) elastomer e) none
b) thermoplastic polymer
*Which types of bonds are found between atoms within hydrocarbon molecules? a) ionic bonds b) hydrogen bonds c) covalent bonds d) van der Waals bonds e) metallic bonds
c) covalent bonds
Which of the following property combinations is required for abrasive ceramics? (a)High melting temperature, high hardness, and high ductility. (b)High fracture toughness, high melting temperature, and high hardness. (c)High fracture toughness, high hardness, and low co-efficient of thermal expansion. (d)High melting temperature, high ductility, and low coefficient of thermal expansion. (e)None of the above.
c)High fracture toughness, high hardness, and low co-efficient of thermal expansion.
*What is the coordination number for a ceramic material with R_C/R_A=0.8? a) 2 b) 4 c) 6 d) 8 e) 12
d) 8
*Carbon fiber-reinforced composites have which of the following properties? a) relatively high strengths b) relatively high stiffnesses c) high service temperatures (>200degC) d) all e) A and C
d) all
Most ceramic materials a) are strong but brittle b) are compounds between metallic and nonmetallic elements, c) have a high hardness d) all e) none
d) all
σ_c=σ_m*V_m+σ_f*V_f=σ_m(1-V_f)+σ_f*V_f
f=fiber m=matrix σ_c=stress
l_c=σ*_f(d)/2t_c
l_c=critical length σ*_f=fiber tensile strength d=diameter t_c=min(fiber matrix bond strength or matrix shear yield strength)
