Expression And Fractal Simulation Of Morphologic Structures Of Nonwovens

Nonwovens are fiber materials which are based on nonwoven technologies. Nonwoven technology embodies both quite old and the very new processing techniques. From a fairly modest beginning with only a limited variety of raw materials, processes, and end uses, the nonwoven industry has reached a state of enormous diversity. Their most advantages are that the processing technologies and forming methods for the products can be designed scientifically according to their end-use. So that the resources can be used most adequately and the satisfactory products be obtained. The applications of nonwovens in industry, agriculture, civil construction, sanitary, home-use and so on, are wider and wider. They can be used as various kinds of filters, adsorbents, geotextiles, insulation materials of heat, sound and electricity, culture medium of farm produces, etc.. Meanwhile, they also can be used as fundus for composite materials. Whether they are used as single or composite materials, their properties are related to their porosity structures, such as pore shape, pore size, pore quantity and pore size distribution and so on. And the porosity structures are related to fiber diameter, fiber crimp, fiber orientation, fiber quantity and the forming method of the fiber aggregations. Therefore, it is important for both manufactory and end-use to obtain the parameters which can be used to express the structure of nonwovens conveniently, and furthermore to find out the relationships between structures parameters and produce methods and properties of products. But for the complexity and randomness of nonwovens structures, it is difficult to express their structures effectively using classical geometry. With the enlargement of their applications, it is urgent to find a way to express their structures quantitatively. Fractal geometry give us a new idea and a powerful tools to study on irregularity ofgeometric objects. Therefore, we studied on the morphologic structures of real nonwovens using fractal geometry combined with computer image processing technology first. The result shows that the pore size distribution in nonwovens is fractal, and the rule of pore size distribution can be expressed by fractal dimension. Fractal dimension, combined with compactness and roughness which are related to pore shape, and fiber orientation function, is found to be capable of express the irregular morphologic structures of nonwovens in the round.Then, on the basis of studying on fractal character of crimped morphology of routine fibers, we simulated the crimped fibers using fractal curve through programming with Visual Basic Language. Furthermore, we simulated various kinds of nonwovens made up of crimped fibers.Finally, a large series of simulated nonwovens were generated through changing the fiber diameter, fiber crimp, fiber orientation and fiber quantity in the program, so as to study the effect of those fiber parameters mentioned above on fractal dimension of pore size distribution and pore shape.The study on real nonwovens indicates that the fractal dimension of pore size distribution is related to nonwovens permeability; and the results from simulated nonwovens show that fiber diameter, fiber crimp, fiber orientation and web density influence the fractal dimension of pore size distribution prominently, and the latter three also influence the pore shape obviously. Accordingly, we know that to express and simulate the morphologic structures of nonwovens will provide the theoretics foundation for revealing the relationships between manufacture, structure and properties of nonwovens in a deep level.