Carbon vs aluminium commuter for 50km per day Is it worth it to purchase a carbon bike for commuting daily 50km. I'm thinking I would be faster and also be able to train on weekends for my first iron man this year.
I don't have the funds to purchase two bikes and wondering whether it's better to have just one good bike? 

Located in Vancouver Canada
It depends on your budget and circumstances. A relatively cheap bike for commuting can have a few advantages compared to an expensive time trial bike:


Lower maintenance and replacement costs, especially in winter.
Less fragile (especially if you compare steel to some high-end carbon components). [Per Weiwen Ng’s comment] 
Ability to fit wider tires for bad roads, light off-road use, winter etc.
Wheels with shallow rims for better cross wind performance.
(Hub dynamo powered) lights.
Luggage rack in case you want to go shopping or bring stuff to/from work.
Less likely to get stolen (and if it gets stolen the financial damage is lower).
More relaxed seating position, better for riding in traffic.
Better brakes (less true with hydraulic disc brakes on modern time trial bikes).


Of course if your budget is barely large enough for a decent road bike it makes more sense to get that instead of two cheap bikes where neither will be great to race or commute with.

I commute on a 1200€ aluminium cyclocross bike with good, street-legal lights and mostly use the 3000€ carbon road bike with power meter for fun&amp;training only.