May 29-June 3, 2016
While most glassy polymers are nominally brittle at macroscopic scales, they are known to exhibit plastic deformation in indentation, scratching, and microcutting when the loaded region is sufficiently small. The same applies to the micrometer size process zone at the tip of a propagating crack. While the presence and approximate size of this microscale plastic zone is well described by the Dugdale model, the prediction of the toughness of these materials is not possible without accounting for the details of the local large strain field and the work hardening behaviour of these polymers, which can be inferred from their response to compressive tests. Strain localization mechanisms such as crazing or shear banding should also be taken into account to properly model toughness. Finally, viscoplastic creep plays a major role in determining the dependence of the toughness on crack propagation velocity, as well as the important difference between the initiation and propagation toughness, which is responsible for the occurrence of a characteristic stick-slip propagation under some loading conditions.
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Matteo Ciccotti, Matthieu George, Yannick Nziakou, Guillaume Fischer, Anne-Caroline Genix, Bruno Bresson, and Stéphane Roux, "Micromechanisms of fracture propagation in glassy polymers" in "International Workshop on the Environmental Damage in Structural Materials Under Static Load/Cyclic Loads at Ambient Temperatures", A.K. Vasudevan, Office of Naval Research (retired), USA Ronald Latanision, Exponent, Inc., USA Henry Holroyd, Luxfer, Inc. (retired) Neville Moody, Sandia National Laboratories, USA Eds, ECI Symposium Series, (2016). http://dc.engconfintl.org/edsm/5