## 2 Experimental Research  
### Methodology  
During the experiment, hybrid composite panels reinforced with aramid and carbon fabrics were used. Aramid will weave fabric used in the experiment with weight of 300 g/m\({}^{2}\) was made from Twaron 2200 fibers. The second material used as a reinforcement was carbon twweight of 200 g/m\({}^{2}\). It was made from Pyrofil TR30 S fibers. Mechanical properties of used fibers [47; 48] are shown in Table 1.  
Hybrid panels consisted of 14 layers of reinforcing fabrics. They were arranged in the following combination: four layers of aramid fabric, one layer of carbon fabric, four layers of aramid fabric, one layer of carbon fabric, and four layers of aramid fabric. Epoxy resin LG285 was used as a matrix. The dedicated by manufacturer HG285 curing agent was mixed with resin with a 100:40 weight ratio. The epoxy matrix's properties declared by the manufacturer [49] are shown in Table 2.  
The composite panels were manufactured by the hand-laminating method with vacuum support (\(-68\) kPa of vacuum pressure). On the basis of the literature [6; 16], four striker geometries were developed. Geometries of those strikers are shown in Figure A1. The adopted geometries allow the strikers to maintain a constant mass and to simulate the impact of various splinters. The required repeatability of the strikers' impact kinetic energy can be achieved because of this. This repeatability is important because the researchers' main goal is to determine the destruction images depending on the geometry of the strikers. They could be compared only when the impact energy was the same. Steel strikers with a mass of 49 g are shown in Figure 2.  
The tests were realized using a hybrid electromagnetic launcher with a pneumatic support [26; 50]. Initial air pressure value in an air tank and air valves were set up using a control panel. The test stand is shown in Figure 3.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Unit** & **Twaron 2200** & **Pyrofil TR30 S** \\ \hline Elongation at break [\%] & \% & 2.9 & 1.8 \\ Tensile strength [MPa] & MPa & 2930 & 4120 \\ Tensile modulus & GPa & 102 & 235 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Mechanical properties of used reinforcing fibers.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Unit** & **Value** \\ \hline Flexural modulus & MPa & 2700–3300 \\ Tensile strength & MPa & 75–85 \\ Compressive strength & MPa & 130–150 \\ Elongation at break & \% & 5–6.5 \\ Hardness in Shore D scale & - & 85 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Properties of epoxy resin LG285 with HG285 curing agent.  
Figure 2: Strikers used in experiment: A—ogival striker, B—blunt striker, C—hemispherical striker, D—conical striker.  
The striker velocity was measured using an optical gate connected to the oscilloscope. When the striker breaks the optical beam, the voltage spike could be observed on the oscilloscope. The next voltage spike is observed when the striker ends, breaking the optical beam. The experiments were carried out with 23.5 J of impact kinetic energy. This energy refers to sub ballistic velocities of the impact--such as collisions with fast moving elements [16]. The samples were glued to the 10 mm polyethylene base plate and hit three times by each striker. The polyethylene plate was exchanged with each composite sample. There is no deformation and destruction in the polyethylene plates after impact.