Fractal character forecast of down fiber assembly microstructure

Down fiber assemblies are used widely in thermal products in winter because of their excellent heat-insulating abilities. These consist of down fibers and air, and belong to a typical kind of porous material. The internal microstructures involved fiber arrangement and pore distribution affects assembly heat conduction greatly. In this article, the micro computer tomography as a nondestructive observing technique to assembly microstructure is introduced, and the mathematical method of "local fractal" is applied to forecast and characterize the fractal characteristics of the down fiber assembly microstructure. The parameter "local fractal dimension" quantifies the geometric complexity of both the fiber arrangement and the pore distribution in the assemblies.