Characterization of Thermodynamic‐Fatigue Behavior and Rapid Prediction of Fatigue Limit for Angle‐Ply <scp>CF</scp> / <scp>PAEK</scp> Composites Based on Infrared Thermography

ABSTRACT This study investigates the thermodynamic‐fatigue behavior of angle‐ply thermoplastic composite laminates using infrared thermography and proposes a rapid fatigue limit prediction method. The research first characterizes fatigue mechanisms, including matrix cracking, fiber breakage, and the characteristic thermo‐mechanical coupling damage of thermoplastic composites, and identifies three thermodynamic phases during cyclic loading. A thermographic fatigue experiment is conducted to analyze the effects of loading amplitude and fiber orientation on temperature rising, revealing a nonlinear relationship governed by shear stress and fiber angle. Building upon these findings, a novel prediction method was developed by integrating a piecewise temperature–stress function with an iterative judgment algorithm to efficiently estimate the fatigue limits of laminates with various stacking sequences ([0°/90°] 3s , [±25°] 3s , [±35°] 3s , [±45°] 3s ). The results demonstrate strong agreement with conventional fatigue tests, offering improved accuracy compared to existing approaches while significantly reducing testing time and cost.