The subject matter of thesis is determination of properties of composite materials. The introductory part explains composite materials, their application and ways of production, and afterwards micromechanics of composite materials were considered in purpose of estimation of mechanical properties of fiber-reinforced composites. Analytical methods of micromechanics were explained and the expected theoretical ranges of mechanical properties values were calculated using those methods, and then the methods were compared to each other in examples. Within mechanics of composite materials macromechanics of laminas was briefly presented, including various failure criteria of composite materials which were later used in numerical simulations. The continuation of thesis is concerned with experimental methods for determination of mechanical properties of composite materials. Some standards refering to static tensile tests of composite materials were listed and elaborated. Also, the results of tensile test experiments conducted at the Faculty of Mechanical Engineering and Naval Architecture in Zagreb were presented. Then, numerical simulations of tensile experiment were carried out with the purpose of verification and validation of theoretical methods of micromechanics. Before the numarical analysis itself, finite element method was explained and verificaton of finite elements was conducted on composite plate loaded with uniform continuous load example. Verification is required for determination of the most suitable finite elements for numerical analysis. Regarding numerical analysis, there were used Tsai-Hill failure criterion, Tsai-Wu failure criterion and maximum stresses failure criterion. Analysis using theoretically obtained values of mechanical properties was cunducted first and analysis using experimentally obtained properties was conducted afterwards. Validation of numerical solutions was made using avaliable experimental data.