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Cohesive crack modelling of paper materials
STFI Packforsk AB.
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).ORCID iD: 0000-0001-8699-7910
2007 (English)In: Proceedings of the 2007 International Paper Physics Conference, 2007, 357-364 p.Conference paper (Other academic)
Abstract [en]

When a notched structure is subjected to sufficiently large tensile loading, it generally exhibits damage evolution in the crack tip region. In paper materials, this damage evolution may reach considerable sizes before ultimate collapse of the structure occurs. Gradual crack growth, characterized by large-scale damage evolution ahead of the crack tip prior to ultimate failure, makes the determination of the initiation of crack growth ill-conditioned and causes the loading in the structure to increase non-proportionally. The applicability of fracture mechanics models that neglect damage evolution, such as classical non-linear fracture mechanics models, therefore becomes questionable for paper materials. The aim of this work was to develop an anisotropic elasticplastic cohesive crack model, i.e. a fracture mechanics model that is capable of accurately describing the anisotropic non-linear constitutive behaviour and the damage behaviour of paper materials. Furthermore, the aim was to use the developed model for studying whether the crack tip state can be characterised by one parameter, as in classical non-linear fracture mechanics models, although large-scale damage evolves. An orthotropic incremental elastic-plastic softening cohesive crack model was formulated. The material parameters of the cohesive crack model were determined for one grade of commercial paper, solely by tensile testing. Short tensile test pieces, allowing for stable post-peak stress behaviour during tensile testing, were used to determine the damage material parameters. The developed cohesive crack model is selfcontained in fracture mechanics applications, i.e. no testing on notched structures was required for calibrating the fracture criterion. The accuracy of the cohesive crack model was investigated by comparing model predictions with experimental data from ordinary tensile tests in different material directions and from tensile testing of notched test pieces with different crack lengths. The calibrated cohesive crack model was shown to predict constitutive behaviour and ultimate failure in excellent agreement with the experiments. The cohesive crack model was further used for examining the crack tip region in more detail. It was demonstrated that the J-integral may accurately characterise the stress and deformation state in the vicinity of the crack tip, although large-scale damage evolves in the crack tip region.

Place, publisher, year, edition, pages
2007. 357-364 p.
National Category
Applied Mechanics
URN: urn:nbn:se:kth:diva-49413ISBN: 9780975746928OAI: diva2:459628
2007 International Paper Physics Conference, May 6-11, 2007, Gold Coast, Qld, Australia
QC 20111128Available from: 2011-11-27 Created: 2011-11-27 Last updated: 2011-11-28Bibliographically approved

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