Question

1. (15 pts) List five different advantages of composite materials over conventional materials.
2. (15 pts) Calculate the modulus of elasticity of a fiber-reinforced polymer composite under isostrain condition if the composite consists of 35% fibers and 65% polymer by volume. Also, calculate the percentage of load carried by the fibers. The modulus of elasticity of the fibers and the polymer are 345 GPa and 3.5 GPa, respectively .
3. (20 Pts) A fiberglass composite consists of epoxy matrix reinforced with randomly oriented and uniformly distributed E-glass fibers. The modulus of elasticity of the glass fibers and the epoxy are 70 GPa and 6 GPa, respectively. Calculate the modulus of elasticity of the fiberglass if the volume percentage of fibers is (a) 25%, (b) 50%, and (c) 75%. Plot a graph showing the relationship between the modulus of elasticity of the fiberglass and the percent of fibers. Comment on the effect of the percent of glass fibers on the modulus of elasticity of fiberglass.
4. (30 pts) A short reinforced concrete column is subjected to a 1000 kN axial compressive load. The moduli of elasticity of plain concrete and steel are 25 GPa and 207 GPa, respectively, and the cross-sectional area of steel is 2% of that of the reinforced concrete. Considering the column as a structural member made of a composite material and subjected to load parallel to the steel rebars, calculate the following:

a. the modulus of elasticity of the reinforced concrete

b. the load carried by each of the steel and plain concrete

c. the minimum required cross-sectional area of the column given that the allowable compressive stress of plain concrete is 20 MPa and that the allowable compressive stress of plain concrete will be reached before that of steel.

d. Plot the stress-strain behavior for the steel fiber, concrete and composite on the same plot.

Answer 1

Advantage of Composite material over conventional material: Composite material are those, which consists of two or more material with different properities. Different material are bonded together to form a new material. Uses of comosite material is always preferred because of following reasons.

1. High Flextural strength: Uses of composite material over convensional material increase the strength of the section. In case of composite beam, bending stress will be highly increased as compared to conventional one.
2. Light weight material: Uses of composite material in place of conventional material may reduce the weight of section.
3. High performances: Composite material is more heat resistance, corrosion resistance, creep resistance than conventional material.
4. More Durable: Composite material is more durable. So, longibility properities is very high for this material.
5. Lower material cost: Uses of composite material significantly reduce the maetrial cost.

N.B: First question is answered here. As four different questions are asked.