The Behavior of Fabrics in Shear

Abstract

A new instrumental method for the analysis of the stress-strain behavior of fabrics in shear has been designed which utilizes the Instron and its automatic recording. It is similar in principle to the laboratory method previously employed by Treloar. A cotton and a spun viscose fabric were investigated for their dependence of shear properties on specimen shape and normal stress. The range of variables previously investigated by Treloar has been extended to include specimen shapes corresponding to length: width ratios of 1:1 to 20: 1, and normal stresses of 0 to 120 g/cm. It was found that the properties of the long, narrow specimen in shear were much less sensitive to the normal stress than were those of the square specimen, particularly at the important lower values of the normal stress. The more favorable wrinkling behavior of the long, narrow specimen enables one to extend the range of test conditions beyond those of the square specimen. It is further shown that Behre's theory for the incidence of wrinkling could not be experimentally corroborated.

The Behavior of Fabrics in Shear

“…Behre [1 ] applied the small-strain theory to these two tests and observed the considerable importance of the test conditions in determining the results. However, he employed a rather unadvantageous square specimen in simple shear [8,9], and his results may be subject to some uncertainty for that reason. In an attempt to define theoretically the planar stress-strain relationships of woven fabrics, Weissenberg [10] introduced the trellis type of mechani-. cal model, with the assumptions of inflexible and inextensible threads, pinpointed at their nodal points, with lines of zero elongation.…”

The Behavior of Fabrics in Shear

“…Data were obtained for ten filament samples from each of the .two specimens, and a comparison of the results showed that heat-setting caused the filaments to contract by approximately 5.5%. ' Effect of Setting-Temperature Oil the Shear Properties of the Fabric All shear measurements on the fabrics were made on the instrument and by the method described in an earlier paper [ 15 ] . The shear parameters employed in this earlier work will also be continued here.…”

“…Values of tan 91 and tan d2 were used, tan 91 being obtained from the known initially applied shear strain and tan 62 calculated from the resulting mean decrement. The values of cyclical energy loss were then compared with the cyclical energy loss obtained in experiments by the sf atic method 15 ] Table IV is a summary of the cyclical energy loss values obtained by the two methods and for the unset and heat-set specimens investigated. Two values of normal stress for the heat-set specimen are presented, while only the higher of the two for the unset specimen as its greater energy loss and damping make accurate recording difbcult at lower normal stresses.…”

“…In the case of multifilament yarns, whose flexural rigidity is very much lower than that of monofilaments of comparable linear density, the contribution of yarn rigidity ,to the shearing resistance of the .fabric will be correspondingly diminished, and is likely to be negligible, compared with the frictional forces, for specimens of the dimensions considered above. This is borne out by an examination of the deformed yarns in the types of fabric considered in the previous paper [ 15 ] . These showed no evidence of visible curvature in the neighborhood of the clamps.…”

“…A new device has been designed which will yield a simple and direct measurement of the cyclical frictional loss of the fabric in shear, and a comparison of the loss thus obtained has been made with the cyclical f rictional loss obtained by the static method [15] ] used in all other shear investigations reported in this work.…”