The influence of void size on the micropolar constitutive properties of model heterogeneous materials

Affan Waseem, Andrew James Beveridge, Marcus Wheel, David Nash

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25 Citations (Scopus)
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In this paper the mechanical behaviour of model heterogeneous materials consisting of regular periodic arrays of circular voids within a polymeric matrix is investigated. Circular ring samples of the materials were fabricated by machining the voids into commercially available polymer sheet. Ring samples of differing sizes but similar geometries were loaded using mechanical testing equipment. Sample stiffness was found to depend on sample size with stiffness increasing as size reduced. The periodic nature of the void arrays also facilitated detailed finite element analysis of each sample. The results obtained by analysis substantiate the observed dependence of stiffness on size. Classical elasticity theory does not acknowledge this size effect but more generalized elasticity theories do predict it. Micropolar elasticity theory has therefore been used to interpret the sample stiffness data and identify constitutive properties. Modulus values for the model materials have been quantified. Values of two additional constitutive properties, the characteristic length and the coupling number, which are present within micropolar elasticity but absent from its classic counterpart have also been determined. The dependence of these additional properties on void size has been investigated and characteristic length values compared to the length scales inherent within the structure of the model materials.
Original languageEnglish
Pages (from-to)148-157
Number of pages10
JournalEuropean Journal of Mechanics - A/Solids
Issue numberJuly-August
Early online date4 Feb 2013
Publication statusPublished - Jul 2013


  • micropolar elasticity
  • Cosserat elasticity
  • heterogeneous material
  • size effect


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