A watt is equal to
a. 746 horsepower
b. one calorie
c. one joule
d. 1 J/s
e. a unit of energy
D
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Carbon-fiber reinforced epoxy is being used as the outer surface material in high-performance aircraft where the surface temperatures are elevated because of the friction with air. The maximum-use temperature for epoxy resin is approximately 260°C. A composite sheet is produced from 75 vol % carbon fiber and 25 vol % epoxy resin. Assume that the epoxy and carbon are stress free at room temperature, and the composite is heated from room temperature (22°C) to 260°C during service. The elastic modulus of the carbon fiber is 380 GPa, the ultimate tensile strength is 2.4 GPa, and the axial thermal expansion coefficient is –0.7×10-6 K-1 . The elastic modulus of the epoxy resin is 4 GPa, the ultimate tensile strength is 0.07 GPa, and the thermal expansion coefficient is 60×10-6 K-1 .
(a) Calculate the thermal stresses, both the magnitude and sign, in the epoxy matrix and in the carbon fibers at 260°C. Assume that each material is elastic at all temperatures, and that there is good interface bonding. (b) Calculate the composite strain in heating from 22°C to 260°C. (c) Is there any component of this design that might cause a problem? Comment on the results in comparison to the data provided. If data is not available on these components, justify your evaluation of this design based upon your knowledge of these materials.
Venus's retrograde spin is not unique among terrestrial planets.
Answer the following statement true (T) or false (F)
A satellite is in a low circular orbit about the Earth (i.e., it just skims the surface of the Earth). How long does it take to make one revolution around the Earth?
What will be an ideal response?
You drop a freely falling body at the equator and at the north pole. The acceleration of the freely falling body at the equator is _______________ the acceleration of the freely falling body at the north pole
Fill in the blank(s) with correct word