The air permeability of carbon fiber paper increases with the increase of thickness. The air permeability of carbon fiber paper with a thickness of 110μm is 3.5s; when its thickness is 170μm, the air permeability becomes 8.5s, and the air permeability decreases by nearly 60%. This shows that the thickness of carbon fiber paper is an important parameter affecting its permeability. This is because as the thickness of carbon fiber paper increases, the pores grow, and because the carbon fiber paper contains multiple parts such as carbon fibers, resin carbon and pores, the pore formation is complex. Therefore, the proportion of pore growth is different from the proportion of thickness growth, and most of the pore growth proportions are greater. Although the volume density is the same, the channel structure of thick carbon fiber paper and thin carbon fiber paper is basically the same, but the channel for gas to penetrate thick carbon fiber paper becomes longer, and the curvature of the channel may also increase.
