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

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.