Issue 28

P. Valentino et alii, Frattura ed Integrità Strutturale, 28 (2014) 1-11; DOI: 10.3221/IGF-ESIS.28.01 4 Figure 2 : Typical composite plate after cutting usingwater jet inorder toproduce tensile test samples. Figure 3 : Side viewof the tensile test specimenswith tabs according toGerman standardDINEN 2747 [7]. Experimental tensile tests, in order to evaluate the mechanical properties of the fabric composites, in terms of stiffness and strength, have been carried out according to [7]. Each test has been performed using a universal servo-hydraulic testing machine (Instron 8500), at room temperature T=298 K and the strain has been measured by a resistance extensometer with a gauge lengthof 20mm. F INITE -E LEMENT -A NALYSES representative volume element (RVE) of the fabric composite has been geometrically defined and numerically modelled. In order to evaluate the geometric dimensions of the RVE, top view of the dry fabric and side view of a cross- section of the test panels have been investigated using an optical microscope. Information about length and width have beenobtained and they have beenproperlymatchedwith the geometric dimensions provided in the data sheet. Fig. 4 shows a depiction of the cross-section of a single lamina for both of the analysed structures. The height of theRVE has been simply obtained by dividing the thickness of the test panel by the number of constituent laminas. The geometry of the RVE has been carefully modelled, in different steps, by using a commercial CAD software as follows: 1. Modeling of warp and fill yarn (corresponds to the dry fabric); 2. Separatelymodeling of the surroundingmatrix; 3. Assembling of the fabric andmatrix inorder to get the final geometricmodel of theRVE. Fig. 5 shows a 3-dimensional depiction, inwireframe, of the final obtainedRVEs for bothof the fabric reinforcements. According to [5], inorder tobetter simulate the real shape of the fabric composite, the trend of thewarp and fill yarnhave beenmodelled using a sinusoidal shapewhich canbe expressed as [5, 14] 2 cos x y A c         (2) where A is the amplitude, and c is the pitch of the tow path curve, Fig. 6(a). An elliptical shape has been assumed to model the cross-sections of thewarp and fill yarn [15, 16]. A