How Hard Is Carbon Fiber?

[OAdriel]

Carbon fiber is an ultra-hard material that is 10 times harder than ordinary steel, second only to diamond in hardness. Here is a detailed introduction to carbon fiber: 1. Composition of Carbon Fiber: Carbon fiber is formed by stacking organic polymer fibers with extremely high carbon content along the fiber bundle direction. However, the currently recognized high hardness and exceptional shear resistance are not entirely due to the material properties. A decisive factor is the critical void. When the stacking between fibers is below a certain critical value, the void index between the fibers determines the hardness, shear resistance, and tensile strength of the fiber. 2. Reasons for Hardness Reduction: The critical porosity that causes a decline in material mechanical properties is 1%-4%. When the void volume content is within the range of 0-4%, for every 1% increase in void volume content, the interlaminar shear strength decreases by approximately 7%. Moreover, higher porosity leads to larger void sizes, significantly reducing the area of interlaminar interfaces in the laminate. When the material is under stress, it is prone to failure along the interlaminar direction, which is why interlaminar shear strength is relatively sensitive to porosity.