1. A unidirectional E-Glass fiber-epoxy composite material contains 61% by volume E-Glass fibers stressed under isostrain conditions. The E-Glass fibers have a tensile modulus of 10 x 106 psi, and a tensile strength of 0.35 x 106 psi. The epoxy matrix has a tensile modulus of 0.45 x 106 psi, and a tensile strength of 9.0 x 103 psi. What is the strength of the composite material and what fraction of the load is carried by the E-Glass fibers?
2. A simple plate capacitor can store 6.5 x 10-5 C at a potential of 10,000 V. What dielectric constant must the material between the plates have if their area is 6.0x10-5 m2 and they are 0.16 mm apart?
3. It is desired to produce 5 cubic yards of concrete with a ratio of 1:1.8:3.5 (by weight) of cement, sand, and gravel. What are the required amounts of the components if 5.5 gallons of water per sack of cement is to be used? Assume the free moisture contents of the sand and gravel are 3% and 0.75% respectively. The specific gravities of the cement, sand, and gravel are 3.15, 2.65, and 2.65 respectively. (1 sack of cement weighs 94lb, and 1ft3 of water=7.48 gallons). Give the answere for cement in sacks, the sand and gravel in pounds, and the water in gallons.