Theoretical and experimental studies of tension of a rod of rectangular cross-section made of elastomeric material, accompanied by the formation of a homogeneous stress-strain state, were carried out. Assuming that the true axial strains in the transverse directions are proportional to the true axial strain in the longitudinal direction, based on the geometric pattern of deformation by introducing two Poisson’s ratios for a transversely isotropic material, exact analytical dependencies were obtained that relate the nominal normal stress recorded in experiments to the calculated true normal stress in the cross-section of the rod, the true axial strain measured in experiments to the calculated volumetric strain, and the true shear strain measures in axes rotated by 45 degrees. Experimental studies on tension of samples made of sheet technical rubber were conducted, and the experimental results were processed based on the obtained analytical dependencies valid for finite strains. It was established that even at considerable elongation ratios, the true normal stress in the cross-section of the sample can be acceptably related to the true axial strain by an elasticity relation obeying Hooke’s law, in which the Poisson’s ratios depend nonlinearly on the true axial strain. With the same degree of accuracy, similar linear relations exist between true shear stresses in rotated axes and the corresponding measures of true shear strains. The possibility of realizing the instability phenomenon of the tension process for samples made of the considered technical rubber was studied.

The development of technologies for producing compact layered composites by free compression based on self-propagating high-temperature synthesis (SHS) allows creating arbitrary proportions of both geometry and mechanical properties of material layers. This paper proposes the development of a two-layer SHS material model to the level of a multilayer two-component composite with symmetric and periodic (asymmetric) layer arrangement. The model is constructed within the framework of three parameters such as the ratio of the lower layer thickness to the total sample thickness, the ratio of flexural strengths of the lower layer material to the next layer, and the ratio of Young’s moduli. The maximum tensile stress criterion was used as the fracture criterion. Due to the high strength of the diffusion bond between layers achieved in SHS technology, delamination effects during loading were not considered, and the bending stiffness of materials such as titanium boride allowed limiting the problem kinematics to the framework of the Bernoulli-Euler beam model. The effect of changes in the ultimate load under three-point loading when changing the order of layers as a result of sample flipping is considered. Using the example of such layer materials as titanium and titanium boride, a comparison of the ultimate load predicted by the proposed model and experimental data on fracture under three-point loading is conducted. Good agreement between the model and experiment is obtained, and the effect of fracture initiation not from the outer layer of the sample but from the lower edge of the second layer is confirmed. Variants within the multilayer composite model are shown where fracture also begins not from the outer layer, which can complicate visual control of fracture initiation sites, for example, on the skin made of layered material.

Shape memory alloys are characterized by a cross-hardening effect, which essentially means that a sample made of this material can be hardened with respect to deformation in the martensitic inelasticity mode (a structural mechanism that does not change the type of crystal lattice but only increases the degree of orientation of low-symmetry martensitic crystal lattices contained in the representative volume of the material) by direct thermoelastic martensitic transformation under constant stress, in which the type of crystal lattice changes from high-symmetry austenitic to low-symmetry martensitic, and the degree of orientation of the resulting martensitic lattices of the representative volume is fixed. At the same time, according to experimental data, the stress for the onset of the structural mechanism at the deformation stage in the martensitic inelasticity mode can significantly exceed the stress under which the strain accumulation process occurred at the preliminary stage of complete direct transformation. The difference between these two stresses can be considered a quantitative characteristic of the cross-hardening effect. The work is devoted to elucidating the question of what properties of processes occurring at various structural levels in shape memory alloys provide the presence of the cross-hardening effect. To solve this problem, a structural-imitation model of shape memory alloy deformation is used, which directly appeals to the processes of nucleation and development of martensitic mesoelements during direct thermoelastic phase transformation, their degradation and disappearance during reverse transformation, and their reorientation during structural transition. Using this model, similar problems were previously solved for the effects of direct transformation strain accumulation, oriented transformation phenomenon, monotonic and reversible shape memory effects, and the martensitic inelasticity effect.

Polymer composite materials (PCMs) based on epoxy binders ED-20, EDT-10P, UP 2127A, ECT-1 of thermal curing are studied to determine their radiation resistance and to investigate the possibility of using radiation to control physical and mechanical properties. Irradiation was carried out on an ElT-1.5A electron accelerator with electron energies of 1.1 and 1.3 MeV at beam currents of 5 and 7 mA, which provided dose rates of 1.5 and 2.3 kGy/s, respectively. Irradiation was carried out by moving samples on a conveyor at a speed of 0.02 m/s under the accelerator window. The physical and mechanical properties of thermally cured PCMs after irradiation with doses up to 10 MGy are investigated. Thermal stability was assessed using thermographic analysis based on the decomposition onset temperature, the onset temperature of the thermal degradation reaction, and activation energy. Irradiation showed that two exothermic peaks appear. The first exothermic peak characterizes the intense interaction of epoxy groups with amines, and the second indicates the reaction between epoxy groups and secondary hydroxyl groups formed. This causes the formation of additional chemical bonds in the polymer and, as a consequence, an increase in mechanical strength. The degree of completion of processes occurring under the influence of ionizing radiation was assessed by the integral heat of thermal decomposition. It is shown that at low irradiation doses up to 1 MGy, it decreases, indicating an increase in the number of double bonds, i.e., additional curing under the influence of radiation. Tests of annular PCM samples using reinforcing materials VMN-4, VMS-8, RVMN, SVM showed that in the dose range of 1-2 MGy, additional structuring occurs (additional crosslinks are formed due to the appearance of reactive groups), the maximum value of which is shifted toward lower irradiation doses. As a result, the spatial network density increases, the level of internal stresses decreases, and the structural homogeneity of the binder increases, which leads to an increase in the thermal stability of the material.

To date, composite materials have gained great popularity in engineering and construction due to their unique properties, which can be optimized at the stages of development and design. Without their use, it is already impossible to create advanced aircraft, ships, automobiles, and various-purpose machines. The use of composites allows significantly reducing the weight of structures while maintaining and improving their strength and other operational characteristics compared to their analogs made of traditional materials: metals, plastics, polymers, glass, ceramics. Products made of composite materials can be adapted for operation in extreme ground and space conditions. Such products include the “space elevator” – a hypothetical astronomical-scale system for non-rocket launching of satellites into Earth orbit and outer space. Researchers’ interest in this idea does not wane, covering various engineering and economic aspects. The design is based on the use of a cable held by one end on the Earth’s surface and the other at a point stationary relative to the planet above geostationary orbit. The cable requires extremely high tensile strength combined with low density. This review will consider the main high-strength materials and draw conclusions about the possibility of using these materials to create high-strength cables for ground-space application systems.

Methods for experimental determination of static shear strength of polymer composite materials are considered. Their advantages and disadvantages are highlighted. The limits of their applicability are noted. The Iosipescu method (ASTM D5379/D5379M-12) is chosen as the method whose sample loading and fixation scheme can be adapted for shear fatigue testing at any cycle asymmetry coefficients, including symmetric loading cycle. The main criteria by which the choice was made are: creation of a pure and uniform working zone, the possibility of conducting fatigue tests for all three shear directions τxy, τxz, τyz, and the possibility of conducting fatigue tests at different asymmetry coefficients. Modern test fixtures made according to ASTM D5379/D5379M-12 do not allow fatigue testing under symmetric loading cycle. In this regard, requirements for the test fixture are formulated. The disadvantages of the sample geometry and loading scheme are shown, which are expected to be overcome through the design of the test fixture. It is noted that a uniform working zone in the sample is achieved when the distance between V-shaped notches is 60% of the total sample thickness. Among the disadvantages noted are: crushing of the sample at the ends, formation of cracks emanating from the V-shaped stress concentrator, the effect of bending and out-of-plane moment on the sample during testing. A separate advantage is the possibility of testing at elevated temperatures (up to 400°C). The overall stiffness of the fixture is assessed using finite element models. The conditionality of fatigue fracture of samples needs to be confirmed experimentally.

The study is aimed at solving the problem of ensuring long-term performance of products made of elastomer composites, which are used as part of vibration dampers in various structures. A distinctive feature of elastomer composites is their high reversible deformations under low loads and good dissipative properties, which make this class of materials susceptible to vibration effects. In this work, an experimental study of the mechanical properties of elastomer composites developed for use as structural elements of vibration dampers was carried out. The results of accelerated tests to study the effect of ultraviolet (UV) radiation on the micromechanical characteristics of elastomer composites based on a mixture of butyl rubber (BR) and ethylene-propylene rubber (EPDM) filled with carbon black P-324 with the addition of shungite rock particles of various dispersity are also presented. Unfilled compositions based on EPDM were also studied to evaluate creep during nanoindentation before and after UV irradiation. The samples were kept under a UV lamp for up to 12 weeks. The change in the surface structure of elastomer composite samples before and after UV irradiation was monitored using an optical microscope. Elastomer composites were developed for use in vibration damper structures of power transmission lines. It was found that the required set of mechanical characteristics of these materials is achieved by using a combination of BR and EPDM, as well as the addition of submicron shungite rock particles (5 vol.%). It was found that UV exposure affects the surface structure and micromechanical characteristics of the samples differently depending on the composition. When studying samples of elastomer composites based on EPDM, it was found that the addition of shungite rock microparticles increases the resistance of these composites to UV exposure. It is shown that the addition (5 vol.%) of submicron shungite rock particles in elastomer composites based on a combination of BR and EPDM makes it possible to increase the relative hysteresis of these materials while maintaining a set of elastic-strength properties. In nanoindentation experiments, it was found that the creep (creep effect) of elastomer composite samples changes under UV exposure. An increase in the rate and maximum indentation depth is noted when samples are exposed to UV. Coefficients are obtained for the function describing the change in indentation depth over time: before and after irradiation of elastomer composite samples.

The work investigated the necessity of accounting for irreversible deformation when modeling the operation of vibration protection devices with working elements made of shape memory alloys. A microstructural model capable of describing the main functional properties of these alloys was used to describe the mechanical behavior of these alloys. Its use allowed calculations to be performed both taking into account the irreversible microplastic deformation accompanying martensitic transformations and without considering it. A one-dimensional oscillatory system with two helical springs made of titanium nickelide, isolating the useful mass from external influences, was considered as a model device. Calculations showed that accounting for microplastic deformation leads to a decrease in the resonant frequency of vibrations, and this effect intensifies with increasing amplitude of external influence and does not depend on the phase composition of the material. In further studies, the behavior of the device was compared for cases with and without microplastic deformation accounting, at their respective resonance frequencies. It is shown that microplastic deformation leads to a qualitative change in the shape of deformation loops during oscillations, causing a decrease in maximum stresses and deformations, which positively affects the vibration protection properties of the device. A decrease in the effective stiffness of the device is also observed. With increasing amplitude of the disturbing influence, the difference between the deformation amplitudes in the considered cases increases. This is especially pronounced for the martensitic and two-phase states. Only at small amplitudes of influence is the difference between the studied cases insignificant because they correspond to elastic oscillations or oscillations with minor phase transformations that do not cause strong development of microplastic deformation. As a result, it was shown that the microplastic deformation mechanism qualitatively improves the operation of the vibration protection device and its accounting is necessary to obtain adequate results in calculations.