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The goal of this study is to acquire an understanding of the manner in which cotton yam properties (including structure) contribute to the tear resistance of woven fabrics as measured by the tongue tear test. Our approach to this overall goal is a three step process. First, we examined samples during and after failure to identify the important phenomena that contribute to tearing strength, termed the subcomponents of tear. Next, we designed tests to observe the isolated contributions of pull-in (of yams into the del zone), pull-ahead (of yams towards the untorn fabric), and yam tenacity. Finally, in Part II of this paper, we will describe a model based on a mechanical spring analogy that will allow us to predict load-displacement responses of woven fabrics being torn.Whereas tensile strength might be seen as a minimum strength requirement that ensures the quality of raw materials and finishing processes, tearing strength can be considered an assessment of the serviceability of a fabric [ I 0 ] .Tearing strength (in conjunction with abrasion resistance) should be a concern of potential buyers as an indication of the useful life they should expect from their purchase. Although there are a variety of ways to measure the strength of a fabric that is tearing, predicting these results from a knowledge of more basic constituent yarn and fabric properties is key. This is not a trivial matter, especially when one considers the number of variables to be considered. Beyond the weave texture adjustments, which can be made in the mill by appropriate loom adjustments, are the &dquo;microscopic&dquo; properties such as compaction, bending rigidity, and frictional properties of yarns, all of which depend on the spinning technology used to form them. These factors, in turn, influence in-fabric behavior such as crimp interchange, shear transfer, interyarn normal forces, and the like. The goal of this work is not to derive a completely predictive model of tear, but rather to isolate the primary factors that contribute to the resistance to fabric tear. These factors can then be analyzed, assessed for relevance, and integrated into a predictive model. Past modeling attempts have not been successful in the jump from yarn / fabric structure and behavior to tear strength prediction. The approach we have taken here is put forth as a first step toward developing a completely predictive model. '

This paper is a study of the geometry of fabric interstices as related to air flow through cloth structures. It assumes that textile yarns act as flexible, inextensible, circular cylinders. Modes of thread interlacing are classified, and minimum horizontal pore areas for each type of intermesh are calculated. Minimum pore areas are then related to the air permeabilities of both open-and close-weave fabrics. Considerable attention is devoted to the elements of fabric structure which complicate geometric calculations of pore-sectional areas. These include crimp balance and yarn flattening and ballooning. Further attention is given to the relative importance of interfiber spacings and to the interaction between yarn and fabric structures. Finally, this study emphasizes the significance of the primary and secondary structural features of woven fabrics in the design of materials which must satisfy air-permeability requirements.Pore Shapes

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