PSI - Issue 8

A. Pantano et al. / Procedia Structural Integrity 8 (2018) 517–525 A. Pantano, B. Zuccarello / Structural Integrity Procedia 00 (2017) 000–000

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The polymer matrix, considered constituted by a green epoxy resin of the type SUPERSAP (refer to Technical Data Sheet INH Hardener with Super Sap CLR system), was modeled as a continuous isotropic with linear elastic behavior; its mechanical properties have been borrowed from Mancino et al. (2017) where the results of specific traction tests are reported: Young module E m = 2.58 GPa and traction resistance σ m,R =50 MPa. Agave fibers considered are fibers of the sisalan variety ( sisal in Anglo Saxon literature), also characterized in [17]: Young modulus E f = 39.5 GPa and failure stress σ f,R =690 MPa. Volumes were meshed with finite elements having quadratic displacement function. The dimension of the side of the elements varies from 0.05 mm to 0.3 mm, for a number of average elements for the various models of about 4 million. The simulations performed are linear and assume a perfect matrix fiber adhesion. Fig. 4a, 4b and 4c show the maps of the displacements (Fig. 4a, 4b) and the stress (Fig. 4c) obtained from numerical simulations for the finite element model characterized by the following parameters: a/l = 0.05 and V f = 0.2. In particular, Fig. 4a shows the variation of the vertical displacements in the U 2 direction along the surface of the model, as the displacement imposed is 1.75 mm so as to determine a deformation in the direction of traction equal to ε = 0.01. Traction results in a sectional reduction not uniform in the transverse direction, as shown in Fig. 4b, due to the presence of fibers ending along the two thin lateral edges. Fig. 4c shows the distribution of von Mises's stress on the surface of the model. By neglecting very localized stress peaks, which occur at the ends of the fibers ending alon g the two thin lateral edges, it is noted that, for ε = 0.01, the fibers are subject to loads in the range of 359 -474 MPa, lower than the failure stress.

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Fig. 4. Maps of (a) vertical displacements U 2 , (b) horizontal displacements U1, (c) Von Mises stress, for a biocomposite with a/l = 0.05 and V f =0.2.

The following Fig. 5 provides the variation of the E L /E m ratio between the longitudinal Young's modulus of the E L biocomposite and the Young's modulus of the polymeric matrix E m as function of the volume fraction V f of the agave fibers. There is a essentially linear dependence between the longitudinal modulus of the biocomposite and the