A reconsideration of the relationship between structural features and mechanical properties of carbon fibers

The relationship between mechanical properties and micro-structures of carbon fibers was reconsidered based on the "elastic unwrinkling" model and Griffith microcracks theory. Experimental results showed, stress relaxation and elastic unwrinkling process could both be observed in non-graphitic fibers, the tensile deformation of which was suitable to be described by "elastic unwrinkling" model. However, elastic unwrinkling process was not so obvious in graphitic fibers since the recrystallization of the crystalline structure had changed the shear compliance of the carbon lattice. A correction towards the compliance was proposed in this case based on the surface fractal of the graphitic fibers. On the other hand, the relationship between tensile strength and the void's parameter of carbon fibers was found generally follow the Griffith equation. In addition, some factors besides of voids, e.g., the local density fluctuation etc., were also found indirectly related to the tensile fracture process of carbon fibers, while a complete exposition of the influencing mechanism remained to be further explored.