What are necessary material used to make a drivetrain differential casing for formula student race car?

Question

composite material,steel,carbon fibre,glass fibre

Answer 1

A differential experiences very large internal forces due to the geometry of the gears and/or clutch system.  The forces can be on the order of thousands of pounds.

A differential housing made of anything but heat-treated steel would be either too weak (aluminum) or too easily scratched (composites) to function properly.

Answer 2

I have never seen a "heat treated steel" differential casing, I have seen cast iron ones (probably heat treated malleable or ductile iron, but still  a form of cast iron) and I have seen a number of die cast aluminum transaxles and I seem to recall seeing a machined billet aluminum differential casing on a sprint car.

The concentrated stresses and dimensional tolerances probably make this a less than optimum application for composites.

I suppose one could consider titanium, but since you are judged in part on cost it probably won't be the best choice. I suspect Aluminum will be the best material.

At http://www.uwracing.com/comparison.php they say about the differential in the 2007 model (the 2007 Formula SAE champion): "Limited slip, crossed axis helical in custom Alum. housing "