## 1 Introduction
[PERSON] [13] conducted a localization impact study on a 3 mm thick graphite fiber epoxy resin composite structure by incorporating angle variation into triangulation and genetic algorithms. [PERSON] [14] monitored damage in carbon fiber composite materials with a thickness of 2.24 mm under energy impacts of 3 J, 5 J, and 10 J. As a representative algorithm for armor SHM, the time-reversal focusing method is instrumental in overcoming challenges by enabling self-focusing of signals with minimal prior knowledge of the monitored structures. [PERSON] [15] proposed a new adaptive time-reversal method with a damage-imaging algorithm for calculating damage index values through local adaptive analysis of Lamb wave time-reversal signals. [PERSON]. [PERSON] [16] investigated an improved time-reversal method to mitigate the effects of the time-reversal operator by modulating the response signal in the forward path and the reconstructed signal in the time-reversed path. [PERSON] [17] proposed a method combining the time-reversal method with a spectral element method for structural damage detection. To reduce economic burden and simplify installation, [PERSON] [18] developed a small number of transducers equipped with a concrete-adapted time-reversal imaging algorithm using implantable technology. [PERSON] [19] introduced a nonlinear Lamb wave time-reversing method and highlighted the differences between the physical nonlinear time-reversed method and the conventional virtual time-reversed algorithm for detecting and quantifying fatigue cracks. In summary, all the aforementioned composite structures have small thicknesses and consist of a single layer. Although the above research using materials with small thicknesses can cause complex signal multi-modality and dispersion phenomena, the time-reversal method can overcome the attenuation of Lamb wave signals and locate damage exactly. However, there is currently limited research on the time-reversal method for the health monitoring of multiple multi-layer and large-thickness composite structures. Therefore, it is worth exploring the proposed method on armor composite structure. In this paper, to address the issue of inaccurate localization resulting from the multi-modality and dispersion of Lamb wave signals in large-thickness composite structures, this research proposes and verifies a time-reversal algorithm for damage detection in armor composite structures. The arrival time of Lamb waves in a sandwich armor composite, comprising alumina ceramic, T700 Carbon Fiber, and TC4 titanium alloy, is calculated using wavelet transform. Time reversal is employed to mitigate differences caused by propagation paths and the influence of armor composite anisotropy, thereby enhancing imaging resolution. This approach facilitates damage monitoring and visualization under virtual loading. The structure of this study is organized as follows: Section 2 elucidates the principles of time-reversal algorithms, and Section 3 introduces the imaging method. Section 4 details the selection of materials for each layer. Finally, single-damage and multi-damage impact localization and imaging validation experiments are conducted on an armor composite plate.