###### Abstract  
The paper presents results obtained by experimental and numerical research focusing on the influence of the strikers' geometry at the images of the destruction created in hybrid composite panels after applying impact load. In the research, the authors used four strikers with different geometry. The geometries were designed to keep the same weight for each of them. The composite panels used in the experiment were reinforced with aramid and carbon fabrics. An epoxy resin was used as a matrix. The experiments were carried with an impact kinetic energy of 23.5 J. The performed microscopy tests allowed for determination of destruction mechanisms of the panels depending on the geometry of the striker. The numerical calculations were performed using the finite element method. Each reinforcement layer of the composite was modeled as a different part. The bonded connection between the reinforcement layers was modeled using bilateral constraints. That approach enabled engineers to observe the delamination process during the impact. The results obtained from experimental and numerical investigations were compared. The authors present the impact of the striker geometry on damage formed in a composite panel. Formed damage was discussed. On the basis of the results from numerical research, energy absorption of the composite during impact depending on the striker geometry was discussed. It was noted that the size of the delamination area depends on the striker geometry. It was also noted that the diameter of the delamination area is related to the amount of damage in the reinforcing layers. Keywords:hybrid composite; damage; aramid fiber; carbon fiber; finite element method; delamination +
Footnote †: journal: Applied  
Polymer composites in addition to high strength are also characterized by a low weight and high value of specific strength [4; 10]. Depending on the application, composite shields can be subjected to the impacts of stones, hail, birds, bullets, or explosive debris. Therefore, resistance to impact loads perpendicular to the plane of laminate reinforcement layers is particularly important. Composite energy absorbing panels in the military application are used in various types of solutions. They are used both in personal protective equipment in the form of bulletproof vests or helmets [11; 12; 13], as well as in special purpose vehicles [9; 12; 14; 15]. In the case of combining a polymer composite material with a ceramic material [7; 11], the ceramic layer is responsible for defragmenting the striker and changing its trajectory, as a result of which a large part of the impact energy is absorbed. The layer made of fiber composite is designed to capture the remains of the striker, the defragmented ceramic layer, and the striker's inhibition. In the case where a multilayer panel with fiber reinforcement is used individually, it must stop the striker and absorb all of the impact energy. Impact loads cause exceeding the strength of the polymer matrix in the form of shear and bending. A delamination process is initiated between successive layers of reinforcing fabrics [16]. This is also a disadvantage of fibrous composites, consisting of the loss of connection between adjacent layers of reinforcing material, which leads to decreasing of the composite strength. During the continuous operation of composite products, this is particularly important because, in combination with fatigue strength [17], it leads to a significant weakening of the material. Delamination in the multilayered composites could be located using, for example, the wave propagation method [18; 19]. The material susceptibility for delamination depends on many factors. Some of them could be mentioned, for example, the material used as an reinforcement, its properties, or bond quality between the fiber and the matrix [20]. Material delamination occurs because the energy threshold initiating this process is much lower than the energy threshold causing destruction of the composite reinforcement fibers [21].