Question 1
A composite material consists of 35% parallel carbon fibres of Young's modulus 420GPa in a matrix of epoxy resin with a Young's modulus of 3GPa.
Calculate the Young's modulus of the composite in the directions parallel and perpendicular to the direction of the fibres.
Start writing down the value of your unique data for the cabon fibre Young's modulus.
Question 2
Aluminium 6061 is widely used in the aircraft industry and high tech industry. With the suitable heat treatment can be used in welded structures as bicycle frames. In the laboratory some probes of Aluminium 6061T6 are going to be tested against fatigue failure. Two experiments have been performed already, the probe have failed after 107 cycles and 105 cycles at 92 MPa and 113 MPa stress range respectively.
a) Applying Basquin's law, estimate the stress range that will make the probe fail at 104 cycles.
b) Applying Goodman's rule, estimate the stress range that will make the probe fail at 107 cycles if the probe is subjected to a mean continuous tensile stress of 70 MPa. (σTS=0.25 GPa)
Start writing down the unique data for your stress ranges.
Question 3
Explain, with aid of a diagram, the physical failure of a bolt under, evaluate the accuracy of the assumptions you take for the calculations:
a) Single shear where the forces are parallel and opposing and applied atright angles to the longest axis.
b) Double shear where the forces are parallel and opposing and applied at right angles to the longest axis.
[Hint] You will need to understand engineering drawings, top view, front view, side view. You will need to assume and estimate the area of all possible failed sections.
Question 4
The figure below shows the copper-antimony Cu-Sb phase diagram.
Figure: copper-antimony Cu-Sb phase diagram
a) Find the chemical formula for the compound marked X (atomic weights of Cu and Sb are 63.54 and 121.75 respectively).
b) The Cu-Sb system contains 2 eutectics, 1 eutectoid, 1 peritectic and 1 peritectoid. Mark them all on the figure, write down the temperature and composition of each point, and identify the phases involved in each reaction, on cooling.
c) An alloy containing 53wt% Sb is cooled slowly to room temperature from the melt. Explain the phase changes that occur during cooling, using schematic sketches of the microstructure at key temperatures to illustrate your answer. Start writing down the unique data for weight percentage of Sb.
d) Sketch a temperature-time curve for the 95 wt% Sb alloy over the range 650 to 450oC and account for the shape of the curve.
Question 5
"To reduce wear on a steel component, a hard wear resistant ceramic coating is applied"
(a) Explain using suitable examples, what is meant by this statement.
why using ceramic coatings on steel
(b) With the aid of diagrams, illustrate three different techniques by which this could be done. Explain how a ceramic coating can be applied and discuss the advantages of the three techniques. You may use appropriate examples and references.