PSI - Issue 77

Jafar Amraei et al. / Procedia Structural Integrity 77 (2026) 207–214 Author name / Structural Integrity Procedia 00 (2026) 000–000

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range (e.g., 100 MPa), highlighting the critical influence of self-heating on the degradation process of the composite structure. These findings confirm that the entropy-based framework enables physically based prediction of the thermomechanical fatigue response of polymer-matrix composites, offering a practical alternative to experimental testing that would otherwise be prohibitively time-consuming and costly across such a wide frequency domain.

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Fig. 4. Predicted fatigue life of the tested composites using the fracture fatigue entropy concept for different loading frequencies.

4. Conclusions This study has broadened the application of the FFE approach to the prediction of fatigue life in polymer-matrix composites across a wide range of loading frequencies between 10 and 100 Hz. Building upon the previous work of Amraei and Katunin (2025), where the trilinear model was introduced for selected frequencies, the present study extended the methodology by explicitly separating the damage-induced heat dissipation from the total energy release and by systematically extending the model to a wide frequency range that was not experimentally investigated. The exponential decrease of fatigue strength with frequency was identified, demonstrating the key role of self-heating in accelerating the transition from friction-dominated to damage-dominated fatigue mechanisms. Furthermore, the relationship between absolute temperature rise and applied stress was determined not only from direct experimental observations at selected frequencies but also through controlled interpolation and extrapolation. This approach provided an extended and physically consistent thermal response across the entire frequency spectrum from 10 to 100 Hz. Incorporating these results into the fracture fatigue entropy framework enabled reliable predictions of fatigue life and demonstrated a pronounced reduction in lifetime at higher frequencies. The outcomes of this work highlight the potential of the FFE concept as a rapid and effective tool for predicting the fatigue life of composites under conditions where experimental testing would be prohibitively time-consuming and costly. The proposed methodology, therefore, represents a comprehensive and promising step towards efficient structural integrity assessment of polymer-matrix composites in demanding engineering applications. Acknowledgements The first author gratefully acknowledges funding through the rector's pro-quality grant under the Excellence Initiative – Research University Program of the Silesian University of Technology, with grant no. 32/014/RGJ25/2032, year 2024.