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The purpose of the experiment was to determine the distribution of shear stresses in the measurement area of a natural and modified wood sample. Previous wood shear tests conducted on a typical Iosipescu specimen have shown that a complex stress state exists at the bottom of the notch. With transverse loading of the samples, flexure occurs and normal stresses arise from the bending moment and thus fibers are deformed. For the investigations oriented on shear, shear with stretching, and shear with compression, a special specimen was prepared which differed by notch geometry from a typical Iosipescu specimen. A new test machine is described in the article, which is equipped with special specimen holders to perform investigations in complex stress conditions. Crack patterns recorded for natural and modified wood are presented. For all tests, numerical finite element model simulations were performed to obtain stress distributions inside the specimens. The calculated stress distributions were visualized as contour line projections for natural and modified wood. Transverse shear strength values for the modified Iosipescu sample were found to exceed the magnitude of previously published ASTM D1037-87 test results. The test results proved that the strength properties of anisotropic materials in a complex state of stress can be assessed with great accuracy. This is very important in engineering applications.

Composite materials are used in many industries. Their mechanical and physical properties as well as their low weight make them suitable for use in many constructions. Their wide application generates a problem with their disposal. Therefore, it is necessary to design new materials based on waste from polyester–glass laminates in order to introduce a closed circuit in the composite production process. The article presents research aimed at determining solid material composites with polyester–glass recyclate, in order to use these materials for modeling the structure. The aim of this study was to determine the effect of the addition of recyclate to the polyester–glass composite on the deformation and the value of the Poisson number of the material. During the study, samples from composites with the addition of polyester–glass recyclate were used. Samples made in accordance with the standard for plastics PN-EN ISO 527-4_2000P were subjected to static tensile test on a universal testing machine, with variable load parameters. During the test, the longitudinal and transverse elongations of the samples were measured using a strain gauge measuring system. On the basis of the measurements, the values of Poisson numbers were determined, which allowed for a preliminary assessment of the impact of the recyclate content in the composite on its deformability.