Issue 47

M. Peron et alii, Frattura ed Integrità Strutturale, 47 (2019) 425-436; DOI: 10.3221/IGF-ESIS.47.33 425 Focussed on “Crack Paths” Assessment of tensile and fatigue behavior of PEEK specimens in a physiologically relevant environment Mirco Peron, Jan Torgersen, Filippo Berto Department of Mechanical and Industrial Engineering, Norwegian University of Science and Technology (NTNU), Richard Birkelands vei 2b, 7034, Trondheim, Norway. mirco.peron@ntnu.no, jan.torgersen@ntnu.no, filippo.berto@ntnu.no A BSTRACT . In the last decades the necessity of implant devices is continuously increasing. The researchers have thus focused their attentions on the development of new biocompatible materials, in particular polymers. Among them, polyetheretherketone (PEEK) has gained wide interest in load- bearing applications such as spinal cages due to its yielding behavior and its superior corrosion resistance. Since such applications are characterized by notches and other stress concentrators weakening the implant resistance, a design tool for assessing their tensile and fatigue behavior, in the presence of such discontinuities, is highly claimed. To this aim, tensile and fatigue data available in literature related to neat and differently notched PEEK samples, experimentally tested in a phosphate-buffered saline (PBS) at 37 °C have been analyzed using the strain energy density (SED) approach. The method is shown to provide accurate results regardless of the different notch geometries, both in terms of tensile and fatigue behavior. Concerning the former, the tensile strength was in fact estimated with an error lower than ±10%, whereas for the latter the SED approach was able to summarize the experimental fatigue data in a single narrow scatter band, independently from the notch geometry. K EYWORDS . PEEK; Tensile; Fatigue; Notch; SED Citation: Peron, M., Torgersen, J., Berto, F., Assessment of tensile and fatigue behavior of PEEK specimens in a physiologically relevant environment, Frattura ed Integrità Strutturale, 47 (2019) 425-436. Received: 19.11.2018 Accepted: 02.12.2018 Published: 01.01.2019 Copyright: © 2019 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION n recent years, the need of surgical procedures, and consequently the necessity of implant devices, have continuously increased [1]. These implants are generally used for applications that ensure a substantial improvement in patients’ quality of life, such as orthopedics, pacemakers, cardiovascular stents, defibrillators, neural prosthetics and drug delivery systems [2–5], but load-bearing implants are characterized by the highest annual growth rate [6] and, posing significant challenges, they have attracted large scale researcher efforts [4,7,8]. For example, artificial limbs have to fit I