## 1 Introduction  
Within the framework of biomechanical research on external fixators, great attention is paid to examining the structural parameters influencing the stability of the fixator, such as the rigidity of the fixator, the value of the maximum von Mises stresses at controlled points in the system, and the bearing capacity of the pin-bone connection. Numerous experimental biomechanical studies of different types of fixators have been performed. [PERSON] (2003) experimentally investigates and compares the mechanical properties of a pinless external fixator applied to the lower leg with AO tubular and Ultra-x fixators. The study concludes that AO tubular fixators outperform the other two fixators in terms of stability under all test loads. [PERSON] et al. [PERSON] et al. (2003) compare the biomechanical properties of four external fixators: Ortofix, the M20 fixator, the Charnley fixator, and the Iliazov fixator. The results are obtained through the examination of 3D finite element method (FEM) models of the fixators, physical models, and clinical investigations. [PERSON] et al. [PERSON] et al. (2003) perform biomechanical tests to analyze the influence of the location and number of pins and needles on the stiffness of the hybrid fixator according to axial load and bending in two planes. [PERSON] et al. [4] analyze the influence of the number of pins and trusses as well as the position of the connectors on the pins on the stiffness of the [PERSON] unilateral, uniplanar fixator. The rigidity of the fixator construction is evaluated according to loads that simulate conditions during normal walking. In the last few years, researchers, in addition to conducting experimental tests, increasingly use the advantages of 3D modeling and numerical analysis to obtain a more complete picture of the behavior of a fixator and its components during loading. Thus, [PERSON] et al. [5], [PERSON] et al. [6], [PERSON] et al. [7], and many others have developed FEM models for biomechanical testing of the analyzed fixators. These models are used to determine the displacement values of bone segments at the fracture site and the stiffness values of the system under observed loads. Additionally, the FEM models provide information on the maximum von Mises stress values at characteristic locations, such as the pin-bone contact and the bone segment interfaces. The results obtained through the finite element analysis are validated through experimental testing of the analyzed fixators. With the development of new biomaterials such as polymers and composites, research into the possibility of their application in orthopedics begins [8; 9; 10]. The term composite materials refers to materials made up of two or more components that differ both in chemical composition and other properties. The development of these materials has emerged from the need to achieve higher strength and rigidity while reducing weight in many structures. Essentially, composites consist of a matrix and reinforcing materials (fibers or particles). The matrix, which binds the reinforcing materials together into a unified whole, is typically made of polymer resins (such as epoxy, polyester, phenolic), but can also be ceramic, metal, and other materials. The reinforcing fibers can be glass, carbon, aramid, boron, and other materials, while particles can include wood, stone, and other substances. [11]. [PERSON] et al. [12] conduct numerical and experimental investigations on the stiffness of the Iizarov fixator ring made of different materials (steel, aluminum, Kevlar, and carbon), as well as its radiotransparency. [PERSON] et al. [13] perform numerical and experimental tests on the C-ring of the Iizarov fixator, which is made of a carbon fiber-reinforced composite material. [PERSON] et al. [14] perform numerical investigations on the elastic modulus of implants made from (HA)/epoxy composite reinforced with carbon fibers. [PERSON] et al. [15] conduct tests on the mechanical properties of a hybrid composite material used for manufacturing bone fracture fixation plates.