## 1 Introduction
With the help of experimental measurements, the mechanical properties for a fixed ratio of fibers and matrix with a set of specimens fabricated in a single process can be determined. To determine the mechanical properties of fibrous composites with various fiber-matrix ratios, a wide range of specimens are fabricated in separate batches. For this reason, experimental measurements of the mechanical properties of fibrous materials with different fiber ratios become challenging in terms of time and cost which represent a major limitation. To address this issue, semi-empirical and theoretical methods have been developed to predict the mechanical properties of unidirectional fiber-reinforced composites [2]. [PERSON] and [PERSON] conducted a study to maximize the fracture toughness of particle-matrix composites [3]. In addition, evolutionary topology optimization and a phase method were combined and applied to the composites to evaluate their fracture toughness. The results of this study showed an increase in fracture toughness. Similar studies [4; 5] have focused on the enhancement of failure strain and fracture toughness using topology opti  
Figure 1: Schematic representation of a unidirectional fiber-reinforced composite. mization techniques on composite materials. [PERSON] and [PERSON] [6] used methods derived from variational material modeling for topology optimization problems. For an aircraft, the main landing gear takes most of the landing load upon landing which causes it to be a highly stressed area. The landing gear stores versatile energy that is easily convertible into another form upon landing. Therefore, the material used for the manufacture of landing gear struts must be capable of withstanding and absorbing this versatile energy. High mechanical stiffness, a high strength-to-weight ratio and high energy storage and damping capacity are key attributes that the main landing gear should possess [7]. The leaf spring is the oldest, but still one of the most frequently used, suspension systems in aerial vehicles. The amount of energy that is absorbed upon landing of an aircraft depends on the stiffness of the leaf spring. Therefore, key features, such as strength and stiffness, must be considered simultaneously during the design phase. Currently, both the automobile and aerospace industries are devoting effort to replacing metallic suspension systems with composite solid spring systems due to their enhanced structural strength and low weight. [PERSON] et al. designed and analyzed glass-fiber-reinforced composite material and steel leaf spring suspension systems and compared their results [8]. Pro-E(r) was used for the design and modeling of the spring while ANSYS 10.0(r) was used for the analysis.The results of the analysis showed that the deflection of composite leaf spring was lower than that of steel leaf spring. However, an 84.4% weight reduction was achieved using the composite leaf spring. [PERSON] et al. published work related to simplified flexible multi-body dynamics for a main landing gear using flexible leaf spring [9]. Generally, the coupled rigid-flexible body model consumes extensive computational resources. In the same context, a new method based on modal analysis and the linear theory of elastodynamics was proposed to ensure the accuracy of results with reduced computational power. The same model was applied to landing gear systems during a computational drop test of an unmanned aerial vehicle (UAV) and the results were compared for the drop test. These results showed that error caused by linear approximation was in the acceptable range with fast and stable computational analysis. Unmanned aerial vehicles (UAVs) are now widely used, with applications in military areas, structural inspections, weather monitoring and festival demonstrations, etc. For safe take-off and landing of a UAV, the landing gear is a critical element, for which high-strength and lightweight struts play a vital role. Composite struts are a promising solution for this purpose. A study performed by [PERSON] et al.