A numerical investigation of structure–property relations in fibre composite materials V. Sansalone 1 , P. Trovalusci 2 ∗ Abstract A multifield continuous model is adopted to investigate the mechanical behaviour of heterogeneous materials made of short, stiff and tough fibres embedded in a more deformable matrix. This continuum accounts for the presence of internal structure by means of non-standard field descriptors. The constitutive relations, obtained by a multiscale approach linking the material description at different scales, depend on the geometry and the arrangement of the internal phases and include internal scale parameters, which allow taking into account size effects. A multiscale finite element technique has been used for obtaining the numerical solution of the multifield and the corresponding Cauchy model. The numerical results obtained on a sample fibre reinforced composite show the effectiveness of the former in pointing out the influence of the size, the shape and the orientation of the fibres on the gross behaviour of the material. Keywords: Microstructure; Micropolar continua; Multiscale modelling; Composite materials; Homogenization; Finite element method. Introduction The continuous development of engineering applications requires more and more high-performance materials which show, at finer scales, various kinds of hetero- geneities. Among them, polyphase metallic alloy systems, polymer blends, poly- crystalline, textured media, fibre-matrix composites, biocomposite materials, up * Corresponding author 1 Lab. de Biom´ ecanique et Biomat´ eriaux Ost´ eo-Articulaires, CNRS UMR 7052, Universit´ e Paris 12. 61, Av. du G´ en´ eral de Gaulle, 94010 Cr´ eteil Cedex, France. E-mail: vittorio.sansalone@univ-paris12.fr 2 Dip. di Ingegneria Strutturale e Geotecnica, Universit` a La Sapienza. Via Gramsci 53, 00197 Roma, Italy. E-mail: patrizia.trovalusci@uniroma1.it 1