## 1 Introduction
This level of precision is particularly beneficial for CFRP components used in aerospace, automotive, and other high-performance industries, where tight tolerances and detailed geometries are often required [3; 29]. The AWJ produces clean and smooth edges on CFRP components. The narrow left width of AWJC results in minimal waste of material. This is particularly important for expensive materials like  
Figure 1: The AWJ process applied for CFRP machining: (**a**) The AWJ process; (**b**) the CFRP delamination mechanism. CFRP, for which reducing waste can lead to significant cost savings and more efficient use of resources [11]. The main process is AWJ cutting, in which internal and external contours are precisely machined [1,30]. The initial step is AWJ piercing, which creates entry holes in the material to facilitate further cutting and shaping operations. AWJ piercing is very challenging due to the high energy applied to the material. This high-energy impact can lead to issues such as delamination if not properly controlled. Delamination refers to the separation of the layers within the composite material, which can significantly compromise the structural integrity and performance of the CFRP component (Figure 1b) [14,31]. Avoiding CFRP delamination is especially important when cutting expensive parts, like airplane components (the fuselage, wings, and tail) [2] and car body components (the cockpit, doors, hood, and bumpers) [3]. Delamination can compromise the structural integrity and functionality of the CFRP workpiece, leading to significant quality issues. This not only affects the performance of the final product but also results in additional costs due to the need for rework or the replacement of the damaged workpiece. Proper parameter optimization and control ensure precise AWJ piercing in CFRP components. AWJ piercing parameters such as water pressure, standoff distance, abrasive mass flow, delay time, material thickness, orifice diameter, and focusing tube diameter can significantly influence CFRP delamination [17,32]. The water jet pressure significantly impacts CFRP delamination during piercing [14,17,31]. Higher pressures increase the impact force of the AWJ on the processed material, which can lead to greater delamination [14]. [PERSON] et al., in their experimental studies, observed that decreasing the water pressure from 350 to 100 MPa resulted in reduced delamination [17]. [PERSON] et al. recommended using a pressure below 148 MPa for the piercing phase to minimize delamination and then increasing the pressure for the cutting process [32]. Another important parameter of the piercing process is the distance between the cutting head and the workpiece, called standoff distance. A decrease in standoff distance was shown to reduce delamination, with recommended values between 0.5 and 4 mm [17]. Increasing the abrasive mass flow was shown to slightly reduce delamination [14]. Ensuring the homogeneity of the abrasive water jet during the initial stages of the piercing process can also prevent delamination. The abrasive start must synchronize with the water jet start [17]. There are three main types of piercing methods used in AWJ machining: stationary piercing, dynamic piercing, and drilling [17,32]. Drilling a starter hole can prevent the delamination of composite materials. Some AWJ machines can be fitted with an additional spindle for drilling, though this can lead to increased machining time and costs [32]. The development of mathematical models based on physical phenomena occurring inside the AWJ piercing process is a very complicated task because of the process complexity and the large number of variables involved [20,23,33]. Artificial neural networks (ANNs) are computational models inspired by the neural networks of the human brain and are particularly suited for modeling complex processes [34,35,36]. They consist of interconnected layers of nodes or \"neurons,\" which process input data and learn patterns through training [34,37,38,39].