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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.

The article presents an analysis of the results obtained during the three-point bending test for seven variants of epoxy rubber–glass composites manufactured according to innovative technology. Different contents of rubber recyclate (3, 5, and 7%) and different methods of distribution of the recyclate in the composite structure (1, 2, and 3 layers with a constant share of 5% of the recyclate) were used in the tested materials. To determine the stress values at which critical failures of the tested materials are initiated in the bending test, an analysis was carried out using the Kolmogorov–Sinai (EK-S) metric entropy calculations. The analysis results showed that for each of the above-mentioned variants of the tested epoxy–glass composites, the onset of critical changes occurring in the material structure occurs below the recorded values of the flexural strength Rmg. The decrease in the RmgK-S value in relation to Rmg is different for different material variants and depends mainly on the % content of rubber recyclate and the amount and method of decomposition of rubber recyclate in the layers of the analyzed materials. The research showed that the introduction of rubber recyclate into the composition of composites has a positive effect on their strength properties. This process allows for the efficient use of hard to degrade waste and opens up the possibility of using the newly developed materials in many industrial sectors. [ABSTRACT FROM AUTHOR]

The study aims to analyze the strength properties obtained from three-point bending tests of epoxy-glass composite samples modified by adding rubber recyclate. A pure epoxy-glass composite is used as a comparative variant. The tested materials, which varies in the percentage of rubber recyclate and distribution, are cut through waterjet cutting to minimize the influence of temperature. The results undergo statistical analysis, and the microstructures are examined using scanning electron microscopy. The decreasing bending strength of the composites is observed, as the content of rubber recyclate in the material increased. However, adding rubber recyclate directly into the resin subtly decreases in bending strength compared to adding in the layers between the glass mat layers. Composites with rubber recyclate exhibits lower deflection under load compared to pure composites. The most favorable bending test parameters are obtained for the material containing 5% rubber recyclate distributed in three layers. [ABSTRACT FROM AUTHOR]

The paper presents acoustic studies of a multilayer composite made based on Synolite 1967-G-1 polyester resin and glass fabric with a three-way arrangement of +/-45° fibres, Triaxial type and a weight of 860 g/m2. As an addition, rubber recyclate created in the process of disposal of car tires was used. The material was made using the vacuum infusion method. By the vacuum lamination method, composite materials were produced in the form of plates with the addition of rubber recyclate in four variants of the amount of recyclate used in the produced composite - 20%, 30%, 40% and 50%. Each variant contained 6 layers of fabric and five layers of rubber recyclate. The samples were tested in the vibroacoustic laboratory on a dedicated measuring station of a set of reverberation chambers without flanking transmission, in which the specific acoustic insulation Rw was determined following PN-EN ISO 10140-2 and related standards, i.e. PN-EN ISO 10140-1, PN-EN ISO 10140-2, PN-EN ISO 10140-4, PN-EN ISO 10140-5 and PN EN ISO 717-1. All manufactured variants of the composite material with the addition of rubber recyclate were characterized by acoustic insulation in the range of Rw = (30.0 ÷ 35.7) dB. High sound insulation parameters for tested panels up to 12 mm thick act as a barrier to counteracting the spread of unwanted airborne noise. Combined with good mechanical properties such as tensile strength, toughness and hardness, they form the basis for the easy design of all shields in many industries. The use of rubber recyclate obtained in the process of disposal of car tires has a positive impact on improving environmental protection. [ABSTRACT FROM AUTHOR]

The article presents a method of modifying the strength properties of epoxy–glass composite by changing the percentage composition of the matrix by the addition of rubber recyclate. Taking into account environmental protection and economic conditions in the process of recycling and utilisation of waste, it is advisable to look for applications of non-degradable waste materials. Based on epoxy resin, a glass mat with a random direction of fibres and rubber recyclate, a test material with different percentage compositions was produced. Samples from the manufactured materials were subjected to a static tensile test on a ZwickRoell testing machine using the ARAMIS SRX measuring system. In addition, CT (computerized tomography) scans of the inside of the samples were made using a ZEISS METROTOM 6 Scout tomograph, and observations of the internal structures were made using a scanning electron microscope. The use of optical and microscopic techniques enabled the precise determination of strength parameters of the examined composites and the analysis of the behaviour of samples under load. The analysis of deformations over time in the examined samples showed a beneficial effect of the addition of rubber recyclate on the elastic properties of the examined composites. [ABSTRACT FROM AUTHOR]

The article attempts to assess the possibility of using rubber recyclate as a component of composite materials. Research is being carried out to develop a technology for the production of composite materials with the addition of rubber waste. These tests are aimed at increasing the reliability and safety of the operation of structures exposed to longterm impact of devices generating vibrations. At the same time, work is underway on the use of complex composite surfaces as sound-absorbing elements. The new direction of using recyclates will have a positive impact on the management of environmentally harmful waste, taking into account a favorable economic factor. [ABSTRACT FROM AUTHOR]