The length to diameter ratio of carbon nanofibers is usually between 100 and 500. Generally, its diameter is 50 to 200nm, and its length ranges from a few microns to tens of microns

Intensity aspect

When the length-diameter ratio of carbon nanofibers increases, its tensile strength tends to increase. This is because a large length-to-diameter ratio means that the fiber has more continuous structure in the length direction and is able to transmit and disperse external forces more effectively. For example, in composite materials, nanocarbon fibers with a large length-to-diameter ratio can act like a "bridge" by transferring externally applied tension along the length of the fiber, making the stress distribution more uniform, thereby improving the overall tensile strength of the material.

Moreover, nanocarbon fibers with a large length-to-diameter ratio are better able to resist these deformations when subjected to bending or torsional forces due to their elongated structure. Just as a long, thin pole is less prone to bending than a short, thick pole, a high aspect ratio of carbon nanofibers can increase the bending and torsional strength of the material.

Toughness aspect

Nanocarbon fiber with large length-diameter ratio is helpful to improve the toughness of the material. When the material is subjected to dynamic loads such as impact, the nano-carbon fiber with large aspect ratio can absorb energy through its own deformation. They can undergo a large degree of stretching and bending before breaking, which effectively prevents the propagation of cracks. For example, in the nanocarbon fiber reinforced polymer composite material, when the crack expansion in the material encounters the nanocarbon fiber, due to its relatively large length and diameter, the fiber can consume the energy of crack expansion through the interaction with the matrix material, such as pulling out, bridging and other mechanisms, so that the material exhibits better toughness.

Elastic modulus

The ratio of length to diameter also has a certain influence on the elastic modulus of carbon nanofibers. The greater the length-diameter ratio, the greater the effect of the nanocarbon fiber on the elastic modulus in the composite. Elastic modulus is a measure of a material's ability to resist elastic deformation. Nanocarbon fibers with large length-to-diameter ratio can form a more effective reinforcement network in the composite material. When the material is subjected to external forces, this network structure can better limit the deformation of the matrix material, thereby improving the elastic modulus of the material. For example, adding nano-carbon fibers with large length-diameter ratio to ceramic matrix composites can make the materials maintain high elastic modulus at high temperatures and improve the structural stability of the materials.