PSI - Issue 72

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ScienceDirect

Procedia Structural Integrity 72 (2025) 141–148

12th Annual Conference of Society for Structural Integrity and Life (DIVK12) Random vibration-driven prediction of residual fatigue life and strength of thermoplastic coupons: an experimental and numerical approach Niki Tsivouraki a,b , Konstantinos Tserpes a, *, Spilios Fassois b a Laboratory of Technology & Strength of Materials, Department of Mechanical Engineering & Aeronautics, University of Patras, Patras, 26504, Greece b Stochastic Mechanical Systems and Automation Laboratory, Department of Mechanical Engineering & Aeronautics, University of Patras, Patras, 26504, Greece Abstract A methodology for predicting the residual fatigue life and strength of thermoplastic coupons using random vibration signals, established through both experimental and numerical methods, is proposed. Initially, tension-tension fatigue tests with a stress ratio of 0.1 were conducted on quasi-isotropic PAEK/T700 coupons. Fatigue tests were interrupted every 10,000 cycles (fatigue state) to perform random vibration tests using white noise random excitation. In parallel, additional fatigue tests were carried out on coupons, which were subsequently subjected to quasi-static tensile loading at each fatigue state. This process was applied to a sufficiently large sample of coupons to account for uncertainty effects. Fatigue damage progression was identified from the vibration signals using various damage metrics. By correlating residual properties and damage metrics with fatigue states, the residual properties of the coupons were linked to their fatigue states. To minimize or even eliminate the need for extensive experiments, especially in complex structures, this process was replicated through numerical modeling. The numerical framework incorporated a fatigue delamination model to simulate fatigue damage progression, a static progressive damage model to predict residual strength, and a random vibration model to simulate the vibration response of the coupons. All models were validated against experimental data. This methodology holds potential for online life and strength prognosis of vibrating structures, such as aircraft wings or wind turbine blades, provided that vibration signal measurements are available. © 2026 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of Aleksandar Sedmak, Branislav Djordjevic, Simon Sedmak Dr. Simon Sedmak, ssedmak@mas.bg.ac.rs, Innovation Center of Faculty of Mechanical Engineering, Belgrade, Serbia

Keywords: Random vibration; Thermoplastics; Life prognosis; Fatigue; Finite element analysis

* Corresponding author. Tel.: +30 2610 969498. E-mail address: kitserpes@upatras.gr

2452-3216 © 2026 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of Aleksandar Sedmak, Branislav Djordjevic, Simon Sedmak Dr. Simon Sedmak, ssedmak@mas.bg.ac.rs, Innovation Center of Faculty of Mechanical Engineering, Belgrade, Serbia 10.1016/j.prostr.2025.08.085