The article is devoted to study mechanical properties of unidirectional fiberglass rods of circular cross section, using the method of buckling. The annex to this problem considered data from the literature devoted to the study of deformation of thin linearly elastic rods in the supercritical region of loading. It is shown close correspondence of the real behavior of fiberglass and the ideal linear-elastic rod buckling. The methods of testing and results processing. Proposed expressions for calculating the tensile strength, ultimate strain and modulus of elasticity of the sample data obtained when buckling. The results of tests of unidirectional fiberglass rods in a wide range of lengths and diameters of the samples. It is shown that the test results are in good agreement with the calculated data obtained by the rule of mixtures.