I always prepare my new mini quad frames by chamfering the edge using a file or piece of sand paper, which is good for your carbon fibre frame.
Why prepare new carbon fibre frames?
Cheap carbon fibre frames can come with very sharp edges that might cut electrical wires and battery strap in a crash. Sometimes they are even sharp enough to cut your fingers when holding the quad in your hand.
Furthermore, chamfered carbon fibre edges hold their structural integrity better in a crash and reduces the chance of becoming delaminated.
More and more frame manufacturers start providing chamfered edges as a frame feature by charging customers more. But it only takes 15 mins to polish those frame edges by yourself, and you will get a more reliable frame that feels great in your hands. :)
Where to buy the tools?
How to file frame edges?
Get a bucket full of water, dip both the frame and the file/sandpaper in the water, place the file 45 degree against the edge, and start sanding off material.
We do this underwater to avoid breathing in dust from the carbon fibre, which is extremely bad for your lung.
You can try changing the angle slightly during the process, until you get a round, smooth edge.
Here is an example of a prepared arm with rounded edges (on top) while the other unprepared arm has very sharp edges (bottom).
Try not to over-do it though, you can weaken the frame strength by removing too much material.
Repeat this on both sides of the frame plates and arms.
Note that I only do this for the edges that I can touch and are exposed to crashes. E.g. on the Martian frame, I only do the outer edges marked by the red lines in the following diagram, but of course this is entirely up to you.
Glue the frame edges
You can go even further and apply Epoxy or CA glue on the edges of the frame, this will hold the carbon fibre layers even stronger together against crashes and delamination. But I am just too lazy for that right now :)