Significance of fracture fatigue entropy in predicting fatigue life across regimes in polymer matrix composites: A review and analysis

Fracture fatigue entropy (FFE) is considered a material property and is widely used for modeling the fatigue life of metals. Because of the simplicity and robustness of the approach in estimating fatigue lives with typically very few fatigue experiments, this methodology is gaining attention in composite investigations. However, the thermal and mechanical properties are entirely different for polymer matrix composites (PMCs) compared to metals. This paper reviews the use of FFE in the literature to predict the fatigue life of composites in different fatigue regimes. The limitation of considering FFE as an independent material property is also reviewed and analyzed. Based on the variation of FFE across different fatigue regimes, the reason for such variation and the appropriate use of FFE to predict fatigue lives are proposed. For composites, FFE can be defined as a range that can reasonably predict the fatigue life of composites with scatter. • Fracture fatigue entropy (FFE) may show variation for polymer matrix composites (PMCs). • FFE must be evaluated solely based on the contribution of irreversible deformation. • FFE range rather than a single value captures scatter in fatigue life of PMCs.