Determining the mechanical properties of materials at simple and multiaxial loading is of great importance since most of the engineering structures are subjected to the complex loading regimes during their exploitation. The aim of the experimental investigation is to identify the mechanical parameters of the material in order to describe material response in a more reliable way and consequently evaluate the lifetime of the constructions. The existing experimental methods for mechanical investigation when the sample is subjected under shear loading have been constantly modified in the last few years because an additional out of plane bending effect was noted. The most known methods of mechanical shear testing are conducted on the Iosipescu and Arcan rigs. The latter test methods use butterfly specimen with two symmetrical V notches in order to achieve an uniform shear state. Furthermore, in order to access the material behaviour under shear loading regime can be achived by applying torsion to the circular or rectangular bars. In this work, the experimental investigation was performed on butterfly samples. The mechanical tests have been conducted on the uniaxial Beta 50-5 testing machine (Messphysik Austria). The shear laoding was carried on the test sample via modified multiaxial Arcan rig. The aim of this thesis is to determine the out of plane displacements and strains occurring on the butterfly specimens with different thicknesses. For the proposed investigation, samples with 1, 2, 3 and 4 mm thicknesses were made of DC01 constructional steel. The displacement and strain fields were measured by digital image correlation method on the surface of the sample. A stereo optical measuring system Aramis was used to measure the out of plane displacements. The proposed comercial measuring system compares the image of the region of interest taken in the reference configuration with a series of images captured in the deformed configuration. Aramis measuring system is based on the correlation algorithm. The displacement and strain fields of the observed, between the two V notches, were calculated using the proposed mechanical and optical setup. Shear strain field, change of thickness of the sample or (i.e. the material wrinkling ) and the displacement field in the perpendicular direction of the observed surface region were measured and analyzed for the four test samples. Shear stress and strain relation was determined coupling the data reported on the uniaxial testing machine and the measured displacement and strain fields is determined. Moreover, the relation of the change of thickness and shear stress are reported for the characteristic measuring points.