I am a new cyclist who is on my 2nd year of biking. I bought a cheapo Schwinn MTB at Walmart to start with but now I want a real road bike. I currently have $2k saved up and am looking into a Specialized Secteur Exprt Disc which is aluminum. I did pick up a carbon frame bike at the shop and although it is lighter, not by much. How sturdy are these carbon frames? From what I've read they can crack if you get in a tumble, and at that point you are done. Vs an aluminum frame will more likely than not be OK. I'd have to spend over $1000 more to get a carbon frame and as good components (Shimano 105 or above) so I don't know if its worth it or not. I'm just a casual cyclist who likes to go on long solo rides for fitness/fun.
There's no reason to worry about carbon fibre durability. I'm riding on a 20 year old Specialized Epic Allez (CF tubes with Al lugs), and it's just as light and stiff as it was when new.
If you have a serious accident CF may break in a non-repairable way, but the same is more-or-less true about aluminium as well, although it may take more of a tumble to break it. (In theory Al can be welded, but you have to be very careful, as the welding will wreck the heat treatment.)
At the same time, CF is more expensive. If I would buy a new bike today I would probably get a decent aluminium frame and instead spend more money on the components, rather than an expensive frame with sub-par groupset.
For a 2k budget, you can get either a mediocre new carbon frame, or a high-quality aluminium frame like a Cannondale CAAD 10.
Newer aluminium frames ride significantly better than their predecessors of even as recently as 5 years ago. The best aluminium frames can rival their carbon counterparts on weight and ride quality, while providing (in most cases) upgraded components.
I'd recommend buying a new aluminium bike over a lower-end carbon bicycle any day.