Issue Eur. Phys. J. Appl. Phys. Volume 48, Number 1, October 2009 Article Number 10402 Number of page(s) 13 Section Physics of Organic Materials and Devices DOI 10.1051/epjap/2009121 Published online 08 July 2009

Eur. Phys. J. Appl. Phys. 48, 10402 (2009)
DOI: 10.1051/epjap/2009121

Symmetry considerations on the stiffness and eigen deformations of plant fibers and structures made of them

P.P. Kärenlampi

University of Joensuu, Faculty of Forestry, Box 111, 80101 Joensuu, Finland

petri.karenlampi@joensuu.fi

Received: 9 December 2008 / Received in final form: 27 April 2009 / Accepted: 29 April 2009 / Published online: 8 July 2009

Abstract
Plant fibers with nonzero microfibril angle show no plane reflection symmetries, the groups of spatial symmetry transformations consisting of rotations only. The spatial point symmetry group of any material made of such fibers is of order which is half of the order of the symmetry group of the corresponding orthotropic material. However, materials consisting of fibers show similar degeneracies of stiffness eigenvalues as the non-fibrous materials. Stiffness degeneracies appear to be controlled by the integer exponents of dicycle conditions applied on products of vectors generating symmetry groups. It is found that flat orthotropic sheets always retain their planar shape in eigen deformations, whereas those made of fibers with microfibrils do not. Features of the out-of-plane deformations are clarified. Orthotropic material elements experience normal on-axis eigen strains only, whereas fibrous bodies with orthotropic fiber alignment may experience on-axis shear strains as eigen strains.

Note to the reader:
On page 10402-p12, four mistakes have been corrected on September 7, 2009:
The following commands: "overline{pq}" () and "overline{number}" have been replaced respectively by "overline{p}overline{q}" () and "overline{number}overline{number}".

PACS
87.85.jf - Bio-based materials.
02.20.-a - Group theory.
62.20.de - Elastic moduli.

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