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Determining Fiber Orientation in Nonwovens by Digital Quantification of Microscopic Images

Wilton R. Goynes and Kathryn H. Pusateri


Measurement of physical properties of nonwovens can be difficult. Strength parameters, for example, are different in nonwovens and in woven fabrics. Strength in woven fabrics depends on several factors. Measurement of strength is generally made in two directions, the warp and fill, of the fabric because the yarns are oriented in perpendicular directions. Strength and dimensional stability are thus greater in directions of the warp and fill yarns, and not on the fabric bias. Fibers in many nonwoven fabrics are not highly oriented but lie in many different angles in the plane of the fabric. Although nonwoven fabrics may be engineered for specific use and thus with intended fiber orientations, strength measurements are more difficult than in woven fabrics. With nonwovens blended of more than one fiber type, fiber order may become even more random, depending on the nature of the blend of the fibers. It thus becomes difficult to consistently determine the strength of the fabric since degree of fiber orientation is not certain. When a product of specific strength is needed and natural and synthetic fibers are blended, determination of fiber orientation can be of great importance. This work describes exploratory use of a procedure for determining degree of fiber orientation within nonwovens in any given direction. A computer program has been used to assign pixel grey-value increments to angles from 0 to 359º in an image of a nonwoven surface. Pixel orientations are grouped in 1.4º segments, and the data giving the counted pixel grey value within that angle can be grouped into any angle range. The percentage of pixels within a given angle range represents the fiber segments oriented at that angle. The procedure has been applied to several nonwoven fabric patterns, and data evaluated to determine whether fiber orientation measurements could be discerned successfully in fabrics of various fiber orientations using this method.

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Document last modified 04/27/04