Graphite products have a certain degree of inertness, and they will lose their proper protection mechanism in a short time, then cracks will appear, and then lose their luster and cracks. For example, if the wood is dried in the air for a long time, it will inevitably deform. This is similar to cracking, and graphite is also similar.

Go to Baidu Graphite Bar to have a look, people there also like to say this

I heard that the structural and mechanical strength of graphite particles is higher than that of ordinary materials

This is a good question, and a physics major should answer it. After studying thermology in high school, I think so. For those who are specialized in materials or processing technology, graphite has good ductility when cutting at high temperatures. Ordinary materials are thermally destroyed, and the strength is very slow, which is very similar to the difference between conductors and semiconductors. Because of the diameter of graphite particles, high temperature is difficult to damage. Graphite is just like: copper wire maximum thickness of 10mm

The short-distance contact force area is also tiny.

At the speed of 3w-4w, there is no difference between the conventional graphite sheet and the metal sheet. The cracks are mainly composed of internal voids. The trials have the following conditions: 1. The arrangement of graphite atoms is not uniform; 2. The distance between atoms is too small; 3. The plate is stretched and shrunk too fast due to material defects, or the addition of nitrogen and other loose material factors.

The properties of this material are not known

Why is the bookmark not so long on this picture and this picture on the picture

It should be that the thermal conductivity and mechanical strength are relatively low. Conventional materials can make a small hole, and the thermal conductivity and mechanical strength can be increased by increasing the gap through pressure at the small hole. But graphite can't do that, and the speed shrinkage causes the smooth surface to break down.

Thank you. I think that there are two main reasons for graphite cracking: 1. The graphite particles break due to friction when they contact thin paper.  2. The surface of graphite particles is entangled and bonded due to the attachment of various substances (wood fiber, resin, etc.). Woody ones add fiber, and resinous ones add thickening. You can refer to the metal aluminum graphite sheet. The above pictures are all made according to the effect shown in the figure.