Biaxial tension-torsion fatigue tests are carried out on the membrane material Nafion 115 (perfluorosulfonic acid, PFSA). This polymeric material is used in fuel cells as proton exchange membrane, undergoing frequently mechanical loading of tension and torsion during its industrial life. In order to carry out the fatigue tests on this polymeric material a self-designed and self-constructed machine was used, working under the following conditions: from 0 to 50 degrees of torsion, 0 to 60 MPa of initial tensile stresses, from room temperature (22 to 25° C) to 80° C, and two values for relative humidity: environmental and saturated relative humidity. All fatigue tests were carried out at the frequency of 1.2 Hz. This paper presents the first results, which concerns the following testing conditions: constant torsion angle of 50 degrees, 5 initial tensile stress of 60, 55, 50, 45 and 40 MPa, room temperature (22-25° C) and environmental humidity (50 – 60 %). The experimental results show that fatigue endurance decreases noticeably when the tensile stress increases. In the final section are presented the fracture surfaces observed by SEM, in order to investigate the principal trends of crack initiation and propagation under this modality of biaxial fatigue loading.
This work is licensed under a Creative Commons Attribution 4.0 International License.
Authors are allowed to retain both the copyright and the publishing rights of their articles without restrictions.
Open Access Statement
Frattura ed Integrità Strutturale (Fracture and Structural Integrity, F&SI) is an open access journal which means that all content is freely available without charge to the user or his/her institution. Users are allowed to read, download, copy, distribute, print, search, or link to the full texts of the articles in this journal without asking prior permission from the publisher or the author. This is in accordance with the BOAI definition of open access. F&SI operates under the Creative Commons Licence Attribution 4.0 International (CC-BY 4.0). This allows to copy and redistribute the material in any medium or format, to remix, transform and build upon the material for any purpose, even commercially, but giving appropriate credit and providing a link to the license and indicating if changes were made.