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F. Golkhosh, Y. Sharma, D.M. Martinez, W. Tsai, L. Courtois, D. Eastwood, P.D.Lee and A.B.Phillion. Synchroton tomographic imaging of softwood paper: A 4D investigation of deformation and failure mechanism. In Advances in Pulp and Paper Research, Oxford 2017, Trans. of the XVIth Fund. Res. Symp. Oxford, 2017, (W.Batchelor and D.Söderberg, eds), pp 611–625, FRC, Manchester, 2018.

Abstract

Fiber pull-out and fiber fracture are the two dominant failure mechanisms of softwood paper. For the first time, 4D synchrotron X-ray tomographic imaging (three spatial directions plus time) was performed to observe these mechanism in-situ during tensile deformation of softwood paper handsheets. The experiments were conducted on three handsheets, produced from pulp that was low consistency refined at 0 k Wh/t and 100 kWh/t and wither air-dried in restraint or freeze-dried. The fibre deformation was found to be highly complex; initially being accommodated via straightening of the fibres resulting in fibre separation and then complete fibre pull-out or fibre fracture. The 3D strain fields, computed by Digital Volume Correlation, revealed increasing out-of =plane deformation in samples with decreasing inter-fibre bonding. Further, the relation between the L2 norms of the out-of-lane strain fields with displacement was computed and found to follow a second order polynomial, with an increasing slope in samples with reduced inter-fibre bonding. It was then shown that the accumulated out-of plane deformations could be used as a metric to quantify the relative contribution of inter-fibre bond breakage, and subsequently, fibre pull-out during tensile deformation of handsheets. The results demonstrate that 4D imaging provides new insights into paper deformation mechanisms.


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