In stead of using CNC milling machine, you can try cutting by laser.

Hello Reza Pourazizi

Prepare a mold of 150x150x3mm from this prepare composite slab. this slab can be cut into pieces of standard dimensions for tensile, flexural, impact tests etc by using laser cutter.

Good luck

PVR

I would recommend against using a laser to cut carbon fiber. The thermal conductivity of the fiber will alter the physical characteristics of the binder.

I had to do this to prepare lab samples in the Aerospace industry. I used a CNC and slowly spiraled down through the sample at depth of 1/3 the diameter of the reinforcement fiber per cut. This takes a while but the results were clean cut edges. Calculate the feed rate so it is grinding the material away not making chips ~0.00001in/flute or smaller. Use a CVD diamond coated carbide end mill and If possible cut past the bottom of the sample using a ball nosed cutter so the sharp edges will not have the tendency to "grab" the fibers.

This process also works well on brittle materials like Iron Ferrite for electrical cores.

Good luck

Frank

The issue of the extended heat affected zone, mentioned by @ Frank Borke, is very important.

However, the careful selection of the processing parameters can solve this issue. Please refer to :

https://doi.org/10.1016/j.promfg.2017.09.026

https://doi.org/10.1016/j.compositesa.2012.02.012

and many other papers.

Thank you Imad Disher Frank Borke and P Venkateshwar Reddy for your helps.

Additionally to the answers you were given already (laser cutter) you could take circular saw blade (e.g. diamond coated) or water jet cutting into account. CNC is also an option, but the operator must be experienced with such samples as yours, otherwise, as he mentioned, delamination may occure. So if you have material to spare you could try it anyway to find satisfying milling parameters. We're using small circular saw blades in case we have just couple samples to make. Otherwise water jet. It doesn't affect the thermal properties at at the cutting edge, makes a clear cut and does not cause delamination if properly set.

If you want to avoid effects of any machining/cutting operation, the best idea would be to build the specimen to required shape. You need to apply your brain to develop a nice mold.

For the correct recommendations it is necessary to know an ultimate goal of your researches and structure of a sample - unidirectional it or not. For the simplest researches to you will be rather diamond disk similar to disks for cutting of ceramics but with water. For more difficult it is necessary the CNC or the hydroabrasive machine. But your problem of 1,2 mm is very simple. You will have more problems in fastening of samples in hijacking in testing equipment

The use diamond cutter and suitable files will most economical way to give desired shape to your CFRC.