## 1 Introduction  
There is a rapid increase in the use of carbon-fiber-reinforced composite materials in the aerospace industry over the last decade [1, 2]. The main advantage includes low weight, high static and fatigue strength, and the possibility to manufacture large integral shell structures. In present time, commercial aircraft contain such composites for primary and secondary wing and fuselage components. However, the main drawback of carbon fiber/epoxy is that these are inherently brittle and usually exhibit a linear elastic response up to failure with little or no plasticity. This makes composite structures very vulnerable to impact damage and must therefore satisfy certification procedures for high-velocity impact from runway debris or bird strike. Impact damage is considered to be a serious damage mechanism in composite structures, which limits performance and reliability for further use. The problem with impact damage is that it may not be visible from the surface of the material, and even so, small scratches at the surface may hide severe damages underneath the impacted surface. Indeed, the impact generates a shock wave whose mechanical energy propagates deep inside the material, thus causing different types of damage along its path. Generally, impact damage occurs during in-service applications or as a result of handling during manufacturing. Very common examples of impact events include tool drops during the manufacturing, preparation or storage of the structure, or during in-service use, e.g., birds' collisions for aeronautic components, hail impact, volcanic ash, runway debris etc. Meanwhile, it is also well known that mechanical properties of composite materials can be severely degraded by the initiation and propagation of structural damages (fiber breakage, delamination, matrix cracking, etc. ), which may appear during the components' life cycles [1]. Since impacts can locally cause crack-like defects, they also may lead to local decays in material properties, i.e., in the vicinity of the impacted zone [1; 3; 4; 5]. It is therefore necessary to reliably detect and evaluate impact damages, as well as their effects on residual resistance of the structure. The use of non-destructive techniques to evaluate defects, such as the ones based on ultrasonic waves, is therefore suitable because the tested component remains available either for tests, as mentioned above, or for reuse in the whole structure. In particular, ultrasonic guided waves are very advantageous because they can finely interrogate the whole thickness of the material and be used for imaging internal hidden defects when appropriate post-processing is applied. Several authors have worked on locating the point of impact in composite plates [5; 6; 7; 8]. [PERSON] and [PERSON] [9] investigated the directivity of the A\({}_{0}\) Lamb mode scattered at a crack-like notch defect in an isotropic plate. [PERSON] et al. [10; 11] analytically and numerically discussed the scattering of guided waves partly through thickness and/or flat bottom cavities with irregular shapes in plates. [PERSON] et al. [12] studied the sensitivity of phased array techniques to detect internal damage caused by impacts at different energy levels on unidirectional and multidirectional laminates depending on the stacking sequence. The problem of impact damage evolution and penetration within thick-section composites was investigated by [PERSON] and [PERSON] [13] using explicit finite element (FE) analysis in 3D. Various studies on modeling guided waves in composite plates have been performed by [PERSON] and his coworkers [14]. Agreement between modelling and experimental data is, in general, achieved for the signals, which are less affected by the damage scattered waves. This is mainly due to the complexity of the involved phenomena during the scattering of ultrasonic guided waves in the presence of point impact damage in composites [15].