Theoretical modeling and influencing factor analysis for the temperature and damage dependent fatigue strength of fiber-reinforced polymer composites

As aviation and space technology advances rapidly, fiber-reinforced polymer (FRP) composites are finding growing applications under extreme service conditions, particularly under high-thermal environments. Assessing the fatigue resistance of FRP composites across different temperature ranges has become a major concern. By applying the Force-Heat Equivalent Energy Density (FHEED) principle and damage failure analysis, a temperature and damage dependent fatigue strength model (TDDFS) was established for FRP composites, grounded in physical mechanisms. The TDDFS model considers the comprehensive influence of temperatures, evolution of constituent properties, load level, layup configurations, especially the damage evolution with temperature on the fatigue strength. The well comparisons between model predictions and experimental data demonstrate the reliability and reasonability of TDDFS model. The study also analyzed the fatigue performance and temperature-related damage evolution of FRP composites. These insights contribute to a reliable theoretical approach for TDDFS prediction and deepen the understanding of fatigue degradation and damage mechanisms in FRP materials at elevated temperatures.