## 3 Results and Discussion  
In this section, the SPH solver inside Ansys LS-DYNA is employed to study the low-velocity ice impact over the sandwich structure. The results obtained with the SPH-FEM approach were compared with the traditional impact of the rigid body on a composite plate. The model's accuracy was investigated using the force-time, force-displacement, and energy-time curves. The calculation time was 8 ms, capable enough to capture all the effects during the impact. Generally, the impact starts with an elastic wave propagation from the impact point, where the propagation is influenced by the material damping and the attitude regarding energy diffusion. The response is governed by flexural and shear waves when the impact time becomes longer. The results provided concern a scenario involving an 8 kg mass of ice traveling at a velocity of 10 m/s. In Figure 6a, the overall system's total deformation is illustrated, revealing a noticeable ice impact. Contemporarily, Figure 6b illustrates the deformation, specifically in the Y-direction of 19 mm of the composite plate. On the other side, Figure 7 illustrates the degradation of the ice under identical impact conditions. The maximum principal stresses in the fiber directions of the composite plate are illustrated in Figure 8, while the shear stress can be observed in Figure 9.  
Figure 6: (**a**) Total deformation, (**b**) direction deformation of the composite plate. Figure 7: Ice deformation during the LVI of 8 kg ice mass with velocity of 10 m/s. The impact simulations involving 4 kg of ice revealed distinct variations in the impact energy when subjected to velocities of 5 m/s and 10 m/s. Notably, the impact forces ranged significantly, transitioning from 5.5 kN to 12.8 kN within a mere 1 ms of time difference in peak forces (Figure 10a). Similarly, for a heavier 8 kg piece of ice, the impact forces at 5 m/s were calculated to be 7 kN, whereas at 10 m/s, the force escalated to approximately 15 kN (Figure 10b). It is evident that higher impact velocities result in greater impact forces. The practical observation indicates that a velocity of 5 m/s was without a real peak of strength. Comparing the two different ices under the same impact velocity of 10 m/s, it can be observed that the pic is at the same time of 3.2 ms, with a difference in the impact force of 2 kN (Figure 10c). The data obtained through the smoothed particle hydrodynamics (SPH) method for ice modeling were compared with results from a simulation where the ice was modeled as a rigid body. The higher impact forces observed in the rigid body simulation (Figure 11a) suggest a potential limitation of accurately capturing the internal deformations and interactions within the material. Additionally, Figure 11b illustrates that the rigid body simulation shows significantly greater displacement than the SPH simulation, indicating a potential oversimplification of the material's behavior in the rigid body model. The difference in the ice rebound between the rigid body simulations and SPH simulations (Figure 12) underscores the crucial role of accurately capturing the complex physical phenomena. Rigid body simulations, despite their computational efficiency, fail to account for the nuanced behavior of ice rebound that the SPH simulations capture, highlighting that computational cost alone does not justify the choice of rigid body models when precision is critical. Composite materials, while they offer specific advantages, are inherently susceptible to impact damage due to their brittle nature. Upon impact, composites experience a range of failures including delamination, fiber breakage, matrix cracking, and potentially laminate perforation. The ability to absorb kinetic energy is pivotal to understanding damage; fiber failure generally absorbs a significant amount of energy, whereas matrix cracking and delamination absorb less. During low-velocity impacts, the kinetic energy is absorbed through elastic deformation, resulting in matrix cracking and delamination.