A Resonance-Based Inductive-Capacitive Dual Modality Sensing Method for Detecting CFRP Composites

With the increasing use of carbon fiber reinforced polymer (CFRP) composites in fields such as aerospace, automotive, and rail transportation, ensuring their structural health and integrity has become a critical concern that attracts growing attention. Nondestructive testing (NDT) methods, such as ultrasonic testing, X-ray, and infrared thermography, are widely used in industry to detect defects in CFRP composites. However, traditional NDT methods often struggle to effectively perform in-situ detection and identification of complex defects within multi-thin-layer CFRP materials due to their complex structures and heterogeneous permittivity and conductivity, which remains a significant challenge. This paper proposes a resonance-based inductive-capacitive dual-modality sensing method that effectively integrates capacitive sensing and eddy current sensing, thereby leveraging their complementary advantages to enhance overall sensing capability for detecting CFRP composites. A synchronous dual-modality detection is achieved at the designed resonant working point by integrating the coplanar electrode sensor and eddy current sensor within the same circuit. Then, the sensitivity and efficiency are achieved by integrating the complementary characteristics of capacitive and eddy current signals, making this sensing method optimal for the detection of complex defects in multi-layer CFRP composites. The sensing principle of resonance-based dual-modality method is introduced, and the finite-element-method (FEM) simulation modeling work is presented. Finally, the experimental validation is carried out using the developed dual-modality sensing system. The results show that the developed dual-modality sensor can effectively detect defects in insulating layers and complex defects in CFRP composites. Furthermore, the findings indicate that the two sensing modalities complement each other, thereby enhancing detection accuracy and efficiency compared with the single-modality methods, which proves the effectiveness of the resonance-based dual-modality sensing method in assessing defects under complex conditions.