Mechanics of Winding Laminate Webs and the Prediction of Machine Direction Curl
Abstract
Winding models that describe the residual stresses due to winding single layer webs at the end of roll-to-roll manufacturing machines began development over 50 years ago. These models have been used to reduce or avoid defects that are due to winding. Many products that are wound can have considerable thickness. Laminates formed from webs are joined to form yet thicker composite webs where the properties of each layer provide unique functionality. The winding models developed previously have focused on determining membrane stresses in the tangential and axial directions and the radial pressure as a function of radius, web material properties and winder operating conditions. These models have considered the web to be a thin homogenous layer. While bending strains result from any web being wound at a radius of curvature into a roll, these bending stains are largest for the thicker homogeneous webs and laminates. Many webs are viscoelastic at some level. Creep will result from the bending strains. When the web material is unwound and cut into discrete samples some residual curvature will remain. This curvature, called curl, is the inability for the web to lie flat at no tension. Curl is an undesirable web defect that causes loss of productivity in a subsequent web process. The goal of this research is to develop tools by which process engineers can explore and mitigate curl in homogenous and laminated webs. Findings and conclusions: laminated winding models and predictive models for curl based upon viscoelastic material characterization were developed. Tests were performed to confirm the accuracy of these models.
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- OSU Dissertations [11222]