Term
T or F
Viscoelastic deformation is instantaneous, which means that total deformation occurs the instant the stress is applied or released. 

Definition
F
Elastic deformation is time independent while Viscoelastic deformation is time dependent.



Term
What is the relaxation modulus?
What is it's associated formula?
(hint: it's time dependent) 

Definition
The stress necessary to maintain a predetermined strain level in a viscoelastic material.
[image]
Where σ(t) is the measured timedependent stress
ε_{0 }is the strain level. 


Term
T or F
1. The higher the temprature of a viscoelastic specimen, the lower the Relaxation Modulus.
2. The temperature dependence for an almost totally crystalline material the more pronounced glass region it will exibit.


Definition
1. True
2. False  The greater the crystallinity of a specimen the less pronounced the drop in temprature at T_{g} 


Term
T or F
1. As a general rule the susceptibility to creep decreases as the degree of crystallinity increases.
2. The creep modulus is also temperature sensitive and increases with increasing temperature. 

Definition
1. True  (this means Creep modulus E_{c}(t) will increase)
2. False  Creep Modulus is temprature dependant, but will diminish as temprature increases. 


Term
As a general rule, the mode of fracture in thermosetting polymers is brittle. Why? 

Definition
Thermosetting polymers have heavily crosslinked networks which prevent plastic deformation. 


Term
T or F
The onset of elastic deformation for semicrystalline polymers results from chain molecules in crystalline regions elongating in the direction of the applied tensile stress. 

Definition
False  chain molecules in amophous regions allow elongation. 


Term
What are some factors that affect the Tensile Strength of polymers?
How can a polymer be modified such that TS is improved? 

Definition
1. •Average Molecular Weight  The higher the AMW the higher the TS.
. •Degree of Crystallinity  for semicrystaline polymers increasing the DoC increases TS, but makes brittle.
2. •Predeformation by Drawing  Tensile modulus in the direction of drawing is increased by orienting chains.
•Heat Treating  (increases degree of crystallinity) 


Term
In what material does the modulus of elasticity increases with increasing temperature, which is opposite to the behavior found in other materials? 

Definition


Term
Fraction crystallized y is a function of time according to the Avrami equation: 

Definition


Term
T or F
Vulcanization can occur on any carbon in a repeat unit. 

Definition
False  It can occur on any carbon sharing a double bond. 


Term
Tor F
For most composites, the particulate phase is harder and stiffer than the matrix. 

Definition


Term
Upper Bound composite equation for elastic moduli:
When is this used? 

Definition
[image]
Used when force is parallel to fiber alignment. 


Term
Lower Bound composite equation for elastic moduli:
When is this used? 

Definition
[image]
Used when force is perpendicular to fiber alignment. 


Term
A fiber is continuous when?
A fiber is discontinuous when? 

Definition
1. l > 15 x l_{c}
2. l < 15 x l_{c} 


Term

Definition
stress on composite matrix when fiber fails. 


Term
What is Ohm's Law?
Describe it's components in detail. 

Definition
V = IR
V is Voltage (potential difference) » Volts (J/C)
I is Current » Amperes (C/s)
R is Resistance » Ohms (V/A) (A is amperes)
C is Charge » Coulomb (A*s) 


Term
Resistivity:
1. Description
2. Relation to Conductivity
3. Formula 

Definition
1.A measure of how strongly a material opposes the flow of an electric current.
2. Inverse.
3. ρ=RA/l
where: R is resistance.
A is the crosssectional area perpendicular to the direction of the current.
l is the distance between the two points at which the voltage is measured 


Term
The electrical properties of a solid material are a consequence of:


Definition
...the arrangement of the outermost electron bands and the way in which they are filled with electrons.



Term

Definition
For a metal, the energy corresponding to the highest
filled electron state at 0 K.



Term
Definition:
free electrons


Definition
Electrons with energies greater than the Fermi energy
may be acted on and accelerated in the presence of an
electric field.These are the electrons that participate in the conduction process.



Term
T or F
For metals, empty states adjacent to the top of the filled valence band are not available. 

Definition
False  Such is the case for
insulators and semiconductors



Term
Drift Velocity:
1. Description
2. Formula 

Definition
1. The average electron velocity in the direction of the force imposed by the applied field.
2. V_{d} = ξ μ_{e}
where μ_{e }_{is the the electron mobility constant.(m2/Vs)}
_{ξ is is the electric field intensity (V/m)}
(or the voltage difference between two points divided by the distance separating them)



Term

Definition
σ = neμ_{e}
where n is the number of free or conducting electrons per unit volume.
e is the absolute magnitude of the electrical charge on an electron (constant value of 1.6 x 10^{19} C)
μ_{e} is the the electron mobility. 


Term
What is Matthiessen’s rule? 

Definition
The total resistivity of a metal is the sum of the contributions from thermal vibrations, impurities, and plastic deformation.
ρ_{total} = ρ_{t} + ρ_{i} + ρ_{d} 


Term
Influences on Resistivity:
1. Temprature
2. Impurities
3. Deformation 

Definition
1. ρ_{t} = ρ_{0} + aT
where ρ_{0 }& a_{ }are constants for each particular metal.
2. Given on Test
where c_{i} is the impurity concentration & A is a constant regarding both the impurity and host metals.
or for a 2phase alloy consisting of α & β
ρ_{i }= ρ_{α}V_{α} _{+} ρ_{β}V_{β}
3. Plastic deformation also raises the electrical resistivity as a result of increased numbers of electronscattering dislocations



Term
Conductivity of a pure intrinsic semiconductor. 

Definition
σ = n_{i}e(μ_{e} + μ_{h})
where n_{i} is the # of holes = free electrons
μ_{e }is the electron mobility
μ_{h }is the hole mobility
e is the absolute magnitude of the electrical charge on an electron (constant value of 1.6 x 10^{19} C) 


Term
Conductivity of a ntype extrinsic semiconductor. 

Definition
σ ≈ neμ_{e}
where n is the # of free electrons
μ_{e }is the electron mobility
e is the absolute magnitude of the electrical charge on an electron (constant value of 1.6 x 10^{19} C) 


Term
Conductivity of a ptype extrinsic semiconductor. 

Definition
σ ≈ peμ_{h}
where p is the # of holes
μ_{h }is the hole mobility
e is the absolute magnitude of the electrical charge on an electron (constant value of 1.6 x 10^{19} C) 


Term
What is the degree of polymerization?
What is the equation? 

Definition
1.the average number of repeat units in a polymer chain.
2. DP = M_{n}/m
Where M_{n} is the number average molecular weight. and m is the molecular weight of the repeated unit. 


Term
Define:
Isotactic
&
Syndiotactic


Definition
1.A type of polymer chain configuration (stereoisomer) wherein all side groups are positioned on the same side of the chain molecule.
2. A type of polymer chain configuration (stereoisomer) in which side groups regularly alternate positions on opposite sides of the chain. 


Term
How do you calculate the degree of polymerization for a copolymer? 

Definition
Σ (molefraction_{i}*molecularweight_{i}) 


Term
4 criteria for a polymer to be elastomeric: 

Definition
1. Amorphus
2.Chain Bonds free to rotate
3. Cross Linking
4. must be above its glass transition temperature 


Term
Explain the change of specific volume (1/ρ) with regards to increased temperature for glasses, semicrystalline, and crystalline polymers. 

Definition
SV goes up linearly with increasing temperature until it meets the glass temperature. At this point the slope increases. For a glass, the change in slope is large, for a semicrystalline polymer, the change is small, for a crystalline polymer, it is negligible. 


Term
T or F
the properties of a composite having its fibers aligned are highly anisotropic, that is, dependent on the direction in which they are measured. 

Definition


Term
T or F
Isostrain conditions correspond to the "lower limit" or traverse strain behaviors for fiber and matrix phases. 

Definition
False  Isostrain condition corresponds with the "upper limit" or longitudinal strain behaviors. 


Term
How does the elastic modulus differ for a radndom oriented fiber composite than that of an aligned? 

Definition
A constant K is added to the Fiber term where K is the fiber efficiency constant and depends on V_{f} 


Term
1.What is capacitance?
2. What is the general formula?
3.What is the formula for a parallel capacitor separated by a vacuum? 

Definition
1. the magnitude of charge stored on either plate divided by the applied voltage.
2. C = Q/V
Where Q is the quantity of charge stored on either plate & V is the voltage applied across the capacitor.
3. ε_{0}A/l



Term
1. What is electric field intensity ξ?
2. How does it relate to current density? 

Definition
1.voltage difference between two points divided by the distance separating them: ξ = V/l
2. current density J = ξσ
units of current per unit of area 


Term
1. What is the dielectric constant?
2. What is it used for? 

Definition
1. it is the ratio of permittivity of a dielectric medium to permittivity of a vacuum.
ε_{r} = ε/ε_{o}
2. ε can be used in place of ε_{o }if there is not a vacuum between a parallel capacitor. 


Term
1. Equation relating frequency to wavelength for electromagnetic radiation.
2. How is energy related? 

Definition
1. c = λv
where λ is wavelength & v is frequency
2. E = hv
where h is plank's constant (6.63 * 10^34 Js) 


Term
1. Equation for the intensity of the beam incident to the surface of the solid medium.
2.Alternate form? 

Definition
1. I_{0} = I_{T} + I_{A} + I_{R}
(intensities of the transmitted, absorbed, and reflected beams)
2. T + A + R = 1
where X = I_{X}/I_{0}



Term
1. index of refraction n:
2. also equals
3.which approximates 

Definition
1. n = c/v
where v = velocity of light in medium
2. (ε_{r}μ_{r})^{1/2}
3. (ε_{r})^{1/2}
where ε_{r }is the dielectric constant 


Term
T or F
Energy excitations with the accompanying absorption can take place only if the photon energy is greater than that of the band gap E_{g}? 

Definition


Term
transmitted intensity I_{T} is given by the formula: 

Definition
[image]
Where I_{0} is incident beam of intensity
l is the specimen of thickness
β is absorption coefficient
& R is is the reflectance 

