Matrix Dependent Cryogenic Damage Mechanisms in CFRPs : Unraveling the Interface Behavior via In Situ Acoustic Emission

ABSTRACT While carbon fiber‐reinforced polymers (CFRPs) are pivotal for cryogenic applications, precisely monitoring their complex, temperature‐dependent micro‐damage evolution remains a critical challenge. In this study, the cryogenic damage evolution of CFRPs with cyanate ester (CE) and epoxy (EP) matrices was investigated at 300 and 77 K, using an in situ acoustic emission (AE) mechanical testing system designed for cryogenic conditions. By integrating macroscopic stress–strain behavior and AE signal characteristics, the damage process was divided into three stages, while a clustering analysis of AE amplitude and peak frequency classified the failure modes into matrix cracking, interface damage, and fiber fracture. Results indicate that cryogenic embrittlement exacerbates residual thermal stresses, triggering an earlier onset and a higher occurrence of all damage modes. Compared to the EP matrix, the CE matrix exhibits superior thermomechanical compatibility and interfacial stability, effectively suppressing premature interface degradation. Consequently, this enhanced interfacial integrity preserves stress transfer efficiency, enabling the CF/CE composite to achieve outstanding tensile strengths of 2098.7 MPa at 300 K and 1828.4 MPa at 77 K—outperforming the CF/EP composite by 51.8% and 47.0%, respectively. These findings not only elucidate the matrix‐ and temperature‐dependent damage kinetics of cryogenic CFRPs but also provide a robust, data‐driven diagnostic tool for assessing the structural reliability of advanced composites in extreme environments.