ScienceDirect Available online at www.sciencedirect.com www.elsevier.com/locate/procedia Procedia Structural Integrity 3 (2017) 18–24 Copyright © 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the Scientifc Committee of IGF Ex-Co. 10.1016/j.prostr.2017.04.004 Copyright © 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the Scientifc Committee of IGF Ex-Co. Keywords: Fracture Mechanics; Polymer network; Fracture toughness; Damage tolerance 1. Introduction Fracture toughness is an important property to be taken into account for defect tolerance-based design of structural components. Such a property quantifies the ability of a material to reduce the effect of flaws on the global strength of the structures. In this paper, we present the results of some experimental tests performed on flawed specimens made by a common silicone-based polymer. This material has a particular stress-strain curve, which is nearly hyperelastic up to failure, with a negligible effect of plasticity or internal damage until the final brittle failure occurs (Brighenti 2016). * Corresponding author. Tel.: +39 0521 905910; fax: +39 0521 905924. E-mail address: brigh@unipr.it XXIV Italian Group of Fracture Conference, 1-3 March 2017, Urbino, Italy Fracture toughness of highly deformable polymeric materials Roberto Brighenti a *, Andrea Carpinteri a , Federico Artoni a a Dept. of Engineering & Architecture – University of Parma, Parco Area delle Scienze 181/A, 43124 Parma, Italy Abstract A fundamental requirement for safety design of structural components is flaw tolerance. In this field, the soft materials have a unique ability to bear external loads despite the presence of defects, due to their pronounced deformability. Unlike traditional materials, which have an enthalpic elasticity, the mechanical response of a polymer-based material is governed by the state of internal entropy of a molecular network which has a great ability to rearrange the material structure and shape so to minimize the local detrimental effect of flaws. For a correct estimation of the fracture toughness of these materials, a proper knowledge of this entropic effect is needed. In the present research, the mechanical behaviour up to failure of silicone-based cracked plates is examined by taking into account the time-dependent effects. Experimental and theoretical aspects are discussed in order to understand the defect tolerance of such materials. © 2017 The Authors. Published by Elsevier B.V.