Hello everyone,
We are building a formula student car and this is our first time. I have no prior experience in carbon fiber fabrication. I have decided to do vacuum infusion. How to decide the number of layers needed? I've already calculated the required thickness for the strength I need but there are few things which make me confused,
- If 3K 200GSM 2/2 twill fabrics are used, how to know the thickness of 3 layers with resin? 
- If a core material is used could I reduce the number of carbon fiber layers? 
- Any suggestions on the fabric type, number of layers and core material combinations to get 'good' strength so that it won't fail when hit on a cone, rock or something hard (I mean a rule of thumb from your experience)?
Thanks!!

A composites analyses with only thickness as parameter isn't a proper analyses. This would include fibre orientations, as well as the distance of each layer to the neutral plane, for which you would already need the thickness of each layer. And the use of a sandwich (and the understanding how it works) should be taken into consideration before the first iteration too.
The substitution of an isothropic material with an orthopic one (or many orthopic layers) may change the load paths significantly. An isothropic fem isn't suited for composites.