Analysis of Fabric Deformation in a Roll-Making Operation Part III: Effect of Viscoelasticity

Abstract

The relationship between various parameters of roll making, fabric properties, and the resultant stresses developed within a fabric roll has been discussed in Pans I and I1 of this scries. A discrete continuum modcl was used to describe fabric deformation during roll making. In the present model, the fabric is assumed to be in plane stress state and the effect in the filling direction is entirely neglected. The fabric is considered as anisotropic in warp and thickness directions. The effect of fabric viscoclasticity in the warp direction is also considered. A simple two-term Maxwell viscoelastic model is used to describe the fabric viscoelastic behavior. The stress relaxation process within fabric rolls during and after roll formation is discussed through numerical examples.We studied fabric deformation in a roll-making operation as both static and dynamic processes in Parts I and 11, respectively [I, 21. In those two studies, the fabric was assumed as an elastic sheet material, whose elastic moduli in the deformation process would not change with time. However, most textile fabrics are really viscoelastic in nature, and thcir responses to applied loads are rate or timc dependent. At any timc, the state of stress within a roll depends on the entire winding and subsequent history of the roll up to that point. Thus, without considering the viscoelastic properties of the fabric, it is impossible to understand the stress relaxation process within the fabric roll during and after the roll-making operation. Considering the most fabric rolls are stored for significant periods of time before actual usc in apparel or other manufacturing operations, this knowledge can be important for the purposc of precluding possible slippage between fabric layers and buckling of sections within the roll,. thereby assuring fabric quality in rolls after storage for a pcriod of timc.The viscoelastic analysis of a fabric roll-making operation has not been reported so far in the textile or related literature, but xveral authors have investigated a similar problem dealing with the viscoelastic winding mechanics of magnetic tape systems. Tnmposch 15, 61 considered the viscoelastic relaxation of the internal stress field arising from an initial elastic stress state in the complete roll. Recently, Lin and Westmann [4] presented an excellent viscoclastic analysis of tape systems composed of rate-dependent material. The methodology and numerical procedures used in their study can be readily applied to general windinglunwinding problems. Their mathematical modcl is based on a linear isotropic tape material. In our study, fabric properties arc assumed to be linear but anisotropic. In a sense, our study may be viewed as a further development of Lin and Westmann's analysis.AS a common practice, the viscoelastic properties of fabrics in any one oftheir main directions (warp, filling, or thickness) can be characterized by using either a relaxation function [ 3 ] or a creep function [4]. A generalized Maxwell modcl may be employed to represent either one...

Prediction of Stress Relaxation of Fabrics with Increased Elasticity

“…With different combinations of these basic elements we can obtain a number of variations of the basic models such as linear and nonlinear models. The linear models represent the linear relation between the stress and the strain by loading, whereas the nonlinear models show nonlinear or disproportionate relationships [9,10].…”

A study of the relaxation phenomena in the fabrics containing elastane yarns

“…This can be seen after manually unwinding the first layer of the fabric roll, as there is no change of length of the cut layer after particular relaxation time (Šajn et al , 2003). On the contrary, the stresses in the radial direction from the outside to the inner part of the roll increase (Ghosh et al , 1992). The behaviour of the fabric in the roll as a viscoelastic material is described using the mechanical models, which consist of the basic model of the spring and the dashpot.…”

Stress distribution of the nonwoven fabric package during winding

“…Batra et al 6 investigated the state of stress in a warp beam through isotropic and anisotropic continuum models, which could be estimated by the anisotropy parameters, such as the wind-thickness, slip-factor, and Poisson's ratio of the material. Ghosh et al [7][8][9][10] identified a discrete continuum model for simulating fabric deformation in the static case. The torque and dynamic factor were applied to the equation of motion of the wound package in the dynamic case.…”

“…Ghosh et al. 7–10 identified a discrete continuum model for simulating fabric deformation in the static case. The torque and dynamic factor were applied to the equation of motion of the wound package in the dynamic case.…”