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Tongue-tear tests were made on samples of acetate fabrics, varying certain controlled factors: weave, texture, yarn twist, and yarn structure. An analysis of the resulting experimental data showed certain relationships between these fabric factors and tear strength. A qualitative discussion was made of tearing action—the influence on tear strength of various types of fabric distortion at or near the tear such as yarn pull-out force, crimp, cover factors, and dimensional stability in the plane of the fabric. Then the relationships between these types of distortion and the variable fabric factors were examined. The actual "mechanism of tear" in the tongue-tear test was theoretically investigated from the nature of the frequency distribution of load drops through the geometry of the tear structure to the synthesis of the tear diagram. Then the effects of the tails and the untorn fabric were studied; finally, all components were studied together.

Stress-analysis methods for textile materials are illustrated through a study of the forces pro duced when a continuous-filament yarn is stressed in tension. It is shown that the effects of yarn twist and yarn size on the tensile properties of singles continuous-filament yarns depend upon the stress distribution. Mathematical formulas are derived to express variations in tensile character istics, both for one-time loading to rupture and repeated stress, as a function of yarn geometry. The influence of fiber inherent properties is described and illustrated by experimental data ob tained for viscose rayon, acetate rayon, and nylon of various singles geometry.

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This report is concerned with the study of the mechanical properties of cordage yarns. The relationship between fiber properties and yarn performance is expressed mathematically by a method involving a generalized extension of the work of Hamburger [2] and Philipp [7]. The mathematical formulas representing the mechanical behavior of cordage yarns are shown to be useful by a comparison between theoretically calculated and experimentally obtained data.The validity and accuracy of the mathematical analysis is further tested by a detailed examination of the range of possible error due to unforeseen discrepancies between reality and the two assumptions: (a) a normal distribution of fiber properties, thus permitting the application of standard statistical treatment; and (b) no fiber slippage during the application to yarns of loads to rupture.The results of the mathematical analysis are shown graphically over a range of fiber properties in excess of those evidenced by cordage fibers. Thus, if the assumptions made hold for all textile fibers, the behavior of other fibers than those normally used for cordage can be predicted for the case of yarns of cordage type.Work is in progress covering further aspects of the research—namely, applying similar mathematical analysis to the translation of yarn properties into strand, plied yarn, and rope structures. the exploration of the factors which are responsible for the properties of the yarns in terms of fiber properties and yarn geometry.