Molecular dynamics simulation of mechanical properties in carbon fibers: a quantitative study on orientation, porosity, and amorphous microstructures

Guided by experimental data, we constructed a series of CF models incorporating varying y-axis orientations(0°–26°), pore characteristics (content and orientation), crystalline/amorphous structures (content and graphitization degree), and their coexistence using large-scale ReaxFF molecular dynamics simulations.

Nonlinear regression was employed to relate structural features to mechanical properties quantitatively. Results indicate that the axial Young’s modulus is primarily governed by axial stress and sp2 carbon content, while tensile strength is dictated by the combined contributions of sp2 and sp/sp3 hybridized carbons. Both tensile strength and modulus decrease with increasing porosity up to 25%; at a given porosity, pores aligned perpendicular to the fiber axis are more detrimental than axially aligned ones.