fundamentals of engineering supplied-reference handbook - Ventech!

COMPOSITE MATERIALS
ρc = Σ fiρi
Cc = Σ fici
⎡ ⎤
⎢ ⎥
⎣ ⎦
−1
fi
∑ ≤ E ≤ f E
c ∑ i i
Ei
ρc = density of composite,
Cc = heat capacity of composite per unit volume,
Ec = Young's modulus of composite,
fi = volume fraction of individual material,
ci = heat capacity of individual material per unit
volume, and
Ei = Young's modulus of individual material.
Also, for axially oriented long fiber reinforced composites,
the strains of the two components are equal.
∆L =
(∆L/L)1 = (∆L/L)2
change in length of the composite,
L = original length of the composite.
HALF-LIFE
N = Noe –0.693t/τ , where
No = original number of atoms,
N = final number of atoms,
t = time, and
τ = half-life.
Material
Aluminum
Steel
Magnesium
Glass
Polystyrene
Polyvinyl Chloride
Alumina fiber
Aramide fiber
Boron fiber
Beryllium fiber
BeO fiber
Carbon fiber
Silicon Carbide fiber
Density
ρ
Mg/m 3
2.7
7.8
1.7
2.5
1.05
1.3
3.9
1.3
2.3
1.9
3.0
2.3
3.2
Young's Modulus
E
GPa
70
205
45
70
2
< 4
400
125
400
300
400
700
400
E/ρ
N⋅m/g
26,000
26,000
26,000
28,000
2,700
< 3,500
100,000
100,000
170,000
160,000
130,000
300,000
120,000
85
COMPRESSIVE STRENGTH, PSI
AVERAGE 28-DAY COMPRESSIVE
STRENGTH, PSI
6,000
5,000
4,000
3,000
2,000
MATERIALS SCIENCE/STRUCTURE OF MATTER (continued)
CONCRETE
Portland Cement Concrete
Concrete is a mixture of Portland cement, fine aggregate,
coarse aggregate, air, and water. It is a temporarily plastic
material, which can be cast or molded, but is later converted
to a solid mass by chemical reaction.
Water-cement W/C ratio is the primary factor affecting the
strength of concrete. The figure below shows how W/C,
expressed as a ratio by weight, affects the compressive
strength for both air-entrained and non-air-entrained
concrete. Strength decreases with an increase in W/C in both
cases.
♦
8,000
6,000
NO ADDED AIR
4,000
2,000
1,000
RECOMMENDED
PERCENT
ENTRAINED AIR
0.40 0.60 0.80 1.00
W/C BY WEIGHT
Concrete strength decreases with increase in watercement
ratio for concrete with and without entrained air.
(From Concrete Manual, 8th ed., U.S. Bureau of Reclamation, 1975.)
Water Content affects workability. However, an increase in
water without a corresponding increase in cement reduces
the concrete strength. Air entrainment is the preferred
method of increasing workability.
♦
IN AIR AFTER 28 DAYS
IN AIR AFTER 7 DAYS
IN AIR AFTER 3 DAYS
IN AIR AFTER 14 DAYS
STORED CONTINUOUSLY IN LABORATORY AIR
CONTINUOUSLY MOIST CURED
1,000
03
7 14 28 90
AGE, DAYS
180
Concrete compressive strength varies with moist-curing conditions.
Mixes tested had a water-cement ratio of 0.50, a slump of 3.5 in.,
cement content of 556 lb/yd 3 , sand content of 36%, and air content of 4%.
♦ Merritt, Frederick S., Standard Handbook for Civil Engineers, 3rd ed.,
McGraw-Hill, 1983.