Very high cycle fatigue of fiber‐reinforced polymer composites: Uniaxial ultrasonic fatigue

This review explores uniaxial ultrasonic fatigue (USF) testing as a common and dependable method for quantifying the extended fatigue life of fiber-reinforced polymer (FRP) composites. The objective is to explain the complexities governing the fatigue life behavior of FRPs, particularly in the realm of very high cycle fatigue (VHCF) where the number of loading cycles exceeds 107. To this end, this review encompasses the analysis of VHCF behavior, including the derivation and interpretation of stress–life (S–N) data, the evaluation of various fatigue damage mechanisms (i.e., controlling mechanisms of crack initiation and propagation) exhibited in FRP composites, and a thorough investigation of the frequency-dependent effects on fatigue responses. Furthermore, this review tries to analyze the microscopic intricacies intrinsic to the VHCF failure of FRP composites, encompassing aspects such as fiber-matrix de-bonding, matrix cracking, and delamination, unveiling their modes and effects in a detailed manner. This review also underscores the pivotal integration of simulations, machine learning, and modeling techniques, emphasizing their crucial role in explaining both macroscopic and microscopic interactions governing the VHCF of FRPs.