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A mechanical particle model for analyzing rapid deformations and fracture in 3D fiber materials with ability to handle length effects
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.ORCID iD: 0000-0002-2066-5486
Applied Mechanics, Ångström Laboratory, Uppsala University, Box 534, SE-75121 Uppsala, Sweden.
2014 (English)In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 51, no 11-12, 2244-2251 p.Article in journal (Refereed) Published
Abstract [en]

A mechanical model for analyses of rapid deformation and fracture in three-dimensional fiber materials is derived. Large deformations and fractures are handled in a computationally efficient and robust way. The model is truly dynamic and computational time and memory demand scales linearly to the number of structural components, which make the model well suited for parallel computing. The specific advantages, compared to traditional continuous grid-based methods, are summarized as: (1) Nucleated cracks have no idealized continuous surfaces. (2) Specific macroscopic crack growth or path criteria are not needed. (3) The model explicitly considers failure processes at fiber scale and the influence on structural integrity is seamlessly considered. (4) No time consuming adaptive re-meshing is needed. The model is applied to simulate and analyze crack growth in random fiber networks with varying density of fibers. The results obtained in fracture zone analyses show that for sufficiently sparse networks, it is not possible to make predictions based on continuous material assumptions on a macroscopic scale. The limit lies near the connectivity l(c)/L = 0.1, where is the ratio between the average fiber segment length and the total fiber length. At ratios l(c)/L < 0.1 the network become denser and at the limit l(c)/L -> 0, a continuous continuum is approached on the macroscopic level. (C) 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.

Place, publisher, year, edition, pages
2014. Vol. 51, no 11-12, 2244-2251 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:miun:diva-22032DOI: 10.1016/j.ijsolstr.2014.02.031ISI: 000335272100019ScopusID: 2-s2.0-84897913787OAI: oai:DiVA.org:miun-22032DiVA: diva2:720748
Available from: 2014-06-02 Created: 2014-05-30 Last updated: 2016-11-30Bibliographically approved
In thesis
1. On dynamic crack growth in discontinuous materials
Open this publication in new window or tab >>On dynamic crack growth in discontinuous materials
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis work numerical procedures are developed for modeling dynamic fracture of discontinuous materials, primarily materials composed of a load-bearing network. The models are based on the Newtonian equations of motion, and does not require neither stiffness matrices nor remeshing as cracks form and grow. They are applied to a variety of cases and some general conclusions are drawn. The work also includes an experimental study of dynamic crack growth in solid foam. The aims are to deepen the understanding of dynamic fracture by answering some relevant questions, e.g. What are the major sources of dissipation of potential energy in dynamic fracture? What are the major differences between the dynamic fracture in discontinuous network materials as compared to continuous materials? Is there any situation when it would be possible to utilize a homogenization scheme to model network materials as continuous? The numerical models are compared with experimental results to validate their ability to capture the relevant behavior, with good results. The only two plausible dissipation mechanisms are energy spent creating new surfaces, and stress waves, where the first dominates the behavior of slow cracks and the later dominates fast cracks. In the numerical experiments highly connected random fiber networks, i.e. structures with short distance between connections, behaves phenomenologically like a continuous material whilst with fewer connections the behavior deviates from it. This leads to the conclusion that random fiber networks with a high connectivity may be treated as a continuum, with appropriately scaled material parameters. Another type of network structures is the ordered networks, such as honeycombs and semi-ordered such as foams which can be viewed as e.g. perturbed honeycomb grids. The numerical results indicate that the fracture behavior is different for regular honeycombs versus perturbed honeycombs, and the behavior of the perturbed honeycomb corresponds well with experimental results of PVC foam.

Place, publisher, year, edition, pages
Sundsvall: Mittuniversitetet, 2015. 20 p.
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 223
National Category
Engineering and Technology Natural Sciences
Identifiers
urn:nbn:se:miun:diva-24960 (URN)978-91-88025-26-5 (ISBN)
Public defence
2015-06-16, Sundsvall, 09:15
Opponent
Supervisors
Available from: 2015-05-25 Created: 2015-05-23 Last updated: 2015-05-25Bibliographically approved

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