Rapid fatigue limit estimation of smart polymer-matrix composite under self-heating bending tests using an innovative automatic approach: Knee method

In recent years, Polymer-Matrix Composites (PMCs) have gained increasing attention across various sectors. With this growing interest and usage, accurately determining their mechanical properties, including the fatigue properties, has become crucial. Traditional methods for these evaluations are both time-consuming and costly, prompting the development of easier and more cost-effective methods for rapidly estimating the fatigue limits of materials. Among these methods, the self-heating test has emerged as notable. The first innovation of this study lies in determining the fatigue limit through the capacitance measurements of in-situ piezoceramic transducers during the four-point self-heating bending test. This determination was validated using the classical temperature measurement methods. Additionally, a novel method called the "knee method"was developped and employed, representing the second originality of this study, and it has shown very promising results.