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Fakulteta za strojništvo, Ljubljana (FSLJ)
  • Influence of viscoelastic behavior on curl of paper
    Lu, Wentao ; Carlsson, Leif A.
    The influence of viscoelastic stress relaxation on the curl response of paper subjected to transient humidity changes was investigated numerically and experimentally. We considered asymmetric two-ply ... paper sheets consisting of low (L) and high (H) anisotropy plies bonded together. Experiments were conducted at room temperature at various constant relative humidities (RH) to obtain the mechanical properties, moisture content, moisture expansion coefficients, and stress relation curves of the constituent plies. The time-dependent curl response of an unconstrained sheet was analyzed using finite-element analysis. Geometrically linear analysis predicted a double curvature shape of the sheets while geometrically nonlinear analysis predicted a cylindrical (single-curvature) shape with the axis in the direction of the major stiffness (MD). The analysis revealed that viscoelasticity has little influence on curling in dry conditions. With increased humidity, the moisture absorbed softens the material, reduces the relaxation time, and the curvature response becomes highly viscoelastic. Predicted time-dependent curvature response was in reasonable agreement with experimental measurements, although it was observed that the analysis under predicted the curvature change during the increasing phase of the moisture loading. Such a deviation is attributed to the assumption of uniform through-thickness distribution of moisture in the analysis.
    Vir: Mechanics of time-dependent materials : an international journal devoted to the time-dependent behaviour of materials and structures. - ISSN 1385-2000 (Vol. 5, no. 1, 2001, 79-100)
    Vrsta gradiva - članek, sestavni del
    Leto - 2001
    Jezik - angleški
    COBISS.SI-ID - 4859419

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