FDM (Fused Deposition Modelling) is one of the most popular additive manufacturing techniques used to investigate the elastic properties of 3D printed polymer composite structures. The Markforged Two 3D printer is the first commercial FDM-based composite printer developed by Markforged in 2014, offering a print head with two separate extrusion nozzles for polymer and continuous reinforcing fibers [1]. In this work, the tensile strength of the composite made of onyx and carbon fibers will be studied. Onyx is a material produced by the company Mark Forged that is used in 3D printing of composites, and it is actually a thermoplastic filled with carbon fibers that is used in printing solid and rigid parts [2]. Tensile testing according to the ISO 527 standard will be carried out experimentally, and numerical results will be obtained by numerical modeling of the test tube and simulation of the test in Ansys, after which the differences in the results obtained experimentally and numerically will be compared. First, a 3D model of the test sample will be created in NX software, which will be used to obtain an STL file that will be imported into the Eiger cutting software. After it has been imported into Eiger, it is necessary to set the necessary settings for printing, after which the G code that controls the nozzles of the 3D printer is generated. After that, the pattern is printed on the Mark Two printer. Later, the test tube is torn on a tear machine and the experimental results are obtained During modeling in Ansys, it is necessary to adjust the materials, import the geometry modeled in NX (STEP file) and set the boundary conditions and mesh. At the very end, it is necessary to display the results and solve the problem itself.