###### Abstract
The results demonstrated that this novel embedding technique enables real-time ultrasonic inspection of carbon fiber-reinforced plastic (CFRP) composites. In another study by [PERSON] et al. [24] the detection and classification of surface-mounted artificial damage and BVID were investigated in GFRP composites with embedded PZT transducers. The researchers achieved a detection rate above 90% and an acceptable ratio of false-positive indications below 3%. These results indicate the feasibility of using embedded PZT transducers for damage detection in the early stages of SHM system development. Furthermore, [PERSON] et al. [24] proposed a novel Bayesian approach for damage classification. The Bayesian approach yielded a damage detection rate above 93% and a false rate below 3%. This suggests that the Bayesian approach is effective in accurately classifying different types of damage. Overall, this study demonstrates the effectiveness of embedded PZT transducers in detecting and classifying damage in composite structures. The novel embedding technique with electrical insulation and the utilization of advanced techniques such as second harmonic generation, nonlinear modulation, LDV, and Bayesian approaches contribute to the improved capabilities of the SHM system. These findings further support the potential of embedded PZT transducers for real-time ultrasonic inspection and reliable monitoring of composite structures. In the field of embedding PZT transducers into composite laminates, two common methods are typically used: the direct insertion method [25; 26; 27; 28] and the use of Stanford Multi-Actuator Receiver Transduction (SMART) LayerTM [29; 30; 31]. However, both methods have certain drawbacks that need to be addressed. The direct insertion method, while effective, can significantly increase the weight of the host structure due to the additional traditional wires used for connection [32]. On the other hand, the SMART LayerTM approach involves adding a relatively thick layer to the composite, which can contribute to its degradation [32]. Moreover, during the manufacturing process, the exposed embedded circuits using above methods can affect the trim of the composites after curing, making it impractical for industrial fabrication and subsequent higher assembly steps. To overcome these challenges, the authors presented a novel edge cut-out method [33] that involves embedding diagnostic films and phase-array PZT transducers into composites using inkjet printing techniques. This method offers several advantages over the traditional approaches. Firstly, the use of diagnostic films can reduce the weight of the extra cables by one-third [34]. Secondly, the active sensing capabilities of the embedded PZT transducers remain stable even after fatigue testing, ensuring long-term performance [35]. Additionally, the reduction in tensile and compressive modulus resulting from the embedding process remains acceptable, even in worst-case scenarios [35]. Furthermore, the diagnostic films used in this novel approach exhibit excellent performance during low- and high-temperature changes under cyclic loading, aligning with the operational and environmental conditions experienced by regional aircraft [36]. The author of this paper recently conducted a study on the thickness effect of UGWs by mounting diagnostic films with phased-array PZT transducers on the surface of CFRP composites [21]. However, the research mentioned in the previous discussions [21; 33] did not specifically investigate the influence of thickness on ultrasonic guided waves (UGWs) and damage detection and localization using embedded PZT transducers in composite laminates. Building upon the author's previous work, this paper aims to provide an in-depth investigation into the influence of thickness on UGW propagation properties, as well as its impact on the reliability of damage detection and localization using embedded PZT transducers in composite laminates.