DISCRETE MODELS FOR NONWOVEN FABRICS (COMPUTER SIMULATION, GEOMETRY, FIBER WEBS, VOID SPACE DISTRIBUTION).

摘要

Nonwoven fabrics (or nonwovens) are three-dimensional structures consisting of a web of randomly placed individual fibers which can be bonded in a variety of ways. Understanding the characteristics of nonwovens requires knowledge of the constituent fibers, their orientation or geometry as a collective unit, and the method of bonding. A sequence of three-dimensional models of nonwovens was developed to describe their geometry. The final model developed considers fibers as a set of line segments, joined at their endpoints, whose projections onto the x-y plane are all on the same line. The determination of the z-coordinate of a fiber is made by restricting the degree to which a fiber can bend.; The model was tested against 28 sample fabrics that differed in terms of fabric weight, fiber orientation, and the mixture of fiber deniers included. In order to validate the model, the fabric properties of thickness, cover factor, and void space distribution were chosen. With regard to thickness and cover factor, fabric weight was found to be a major factor in both, and the model only modestly improved the prediction capabilities over that obtained by considering the weight alone. However, fabric weight did not provide a good predictor of void space distribution. For validation of the model's predicted void space distribution, a filtration test was used. This is a test of the amount of a contaminant that a filter removes from an airstream. The size of the voids in a fabric determines its ability to trap these particles. The model predicted this quantity well. Though the results are not entirely conclusive, largely because of the small sample size, the model appears to predict the above geometric properties that previously had not been calculated directly.; A portion of the validation of the void space calculation required the solving of the problem of inscribing a circle in a polygon. An O(n log(n)) algorithm was developed for finding the largest inscribed circle in a convex polygon. Similar geometric problems have been solved by the use of Voronoi diagrams. Inscribing a circle in a polygon is a problem that can be solved by the use of the dual of the Voronoi diagram.