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Monday | Salon 10 | 01:30 PM–01:50 PM
#15708, Evaluation of Mechanical Heterogeneity of Thin Web Materials
Mechanical heterogeneity of thin web materials affects their processibility and performance. Thin web materials, like paper and paperboard, are printed and converted at high speeds and web breaks incur significant material loss. If the web survives printing, mechanical heterogeneity may cause print mis-registration and blurry images. In heavier materials, like paperboard, glue skips may occur during corrugating that dramatically reduce box strength. The objective of this work is to quantify the stiffness heterogeneity of paper and paperboard. This type of heterogeneity involves the local identification of the anisotropic 2D stiffness tensor. A drumhead load frame was fabricated to activate the local strain states required for identification. The examined circular specimen had 26 cm diameter and was stretched by eight motion-controlled grips symmetrically located at 45 degree intervals. Each gripping location could be controlled in active or passive mode to apply various loading conditions to produce the necessary strain fields. Experiments were conducted with feedback control to maintain static equilibrium and prevent any wrinkling within the web matrix. Surface deformations were monitored with digital image correlation. A heterogeneous form of the virtual fields methods was used to identify local stiffness. Effectiveness of identification was evaluated with equilibrium analysis.