Issue 28

P.Valentino et alii, Frattura ed Integrità Strutturale, 28 (2014) 1-11 ; DOI: 10.3221/IGF-ESIS.28.01 5 (a) (b) Figure 4 : Schematic depictionof sample cross-sections for the two types of dry fabric reinforcements. (a) Twill wave 2/2; (b) Twill weave 1/3. (a) (b) Figure 5 : 3Dmodels of theRVE. (a) Twill weave 2/2; (b) Twill weave 1/3. (a) (b) Figure 6 : Simplifying assumptions for analytical description of the geometry: (a) Sinusoidal spline about centreline of an undulated yarn; (b) Elliptical cross-sectionof a yarn. Starting from the created geometry, the FEMmodel has been generated by using a commercial finite element software. Themesh distribution, with a proper size, has been generated bymeans of an automatic option of the FEM software and a depictionof themeshedRVE for the twill weave 2/2 and twill weave 1/3, respectively, is shown inFig. 7. As a first approach an idealized contact has been obtained by imposing the coincidence of nodes in the matrix-fibres interface, therefore failure mechanisms and friction effects were neglected. Furthermore, this assumption results in no relative displacement between the three different regions, i.e. warp yarns, fill yarns andpurematrix. In order to properly assign the mechanical properties of each component of the RVE, i.e. matrix and fibres tow, two different reference systems have been considered, respectively. Linear elastic properties have been imposed to the yarns, but, in order to simulate the orthotropic behaviour of thematerial two additional reference systems have been introduced: