In this paper, we present the experimental results obtained and corresponding inverse analysis employed to determine the amplitude-dependent damping properties of laminates made of glass fiber reinforced plastic (GFRP). Free damped vibration tests of cantilever beams with different symmetric stacking sequences were performed. Logarithmic decrement analysis was used to evaluate the effective amplitude-dependent loss factor of the samples. Inverse analysis was used to find the single-ply dynamic properties based on the laminated beam theory and the complex moduli approach. It was found that the loss factors of GFRP laminates almost linearly depend on the maximum strain amplitude. The maximum value of the loss factor of unidirectional ply was realized in the transverse direction to the fibers and reached similar to 0.023 for strain amplitudes up to 0.1% in the frequency range of 20-60 Hz.

Studies of changes in the limiting stresses of interlayer shear during loading of cured carbon-filled plastic after exposure to a microwave electromagnetic field with a frequency of 2450 MHz and with different energy flux densities, taking into account the thermal factor and time, have been performed. It is shown that with a rational combination of energy flux density and time, (17—18) · 104 mcW / cm2 and 2 min, respectively, the values of the limiting voltages increase by an average of 17% as compared with the reference specimens.

It is shown that distributed registry (blockchain) systems may be used in the supply chain for components, spare parts, tools, and accessories to manufacturers of civil aircraft and after-sales services; that would minimize the use of counterfeit products. A criterion is proposed for assessing the consequences of introducing blockchain systems.

Currently, there are great perspectives for the technology of manufacturing products and aggregates from PCM based on prepregs. Thus, the use of prepregs makes it possible to manufacture complex configuration parts in one technological operation. High competition and the increasing necessity of mass production of large-sized parts from PCM determines the emerging need for the use of automated layout equipment. The replacement of traditional, manual methods of layout by automated methods provides significant advantages, such as an increase in the quality of the resulting parts, a significant reduction in labor intensity of their production, an increase in accuracy and repeatability of the technological process of layout (reduction of defects) and, consequently, reduction of the cost of the finished product.

Work on the current topic of hybrid titanium-polymer composite materials (TPCM) is continuing. After checking the technological feasibility of two-stage processes for manufacturing parts of flat shapes and with a single curvature, identifying opportunities for improving the adhesive interaction, work is carried out to assess the possibility of varying design parameters, such as reinforcement schemes, combinations of components, etc.in order to obtain optimal properties of manufactured parts.

Остаточные напряжения могут появиться из-за технологических особенностей процесса изготовления, из-за конструктивных особенностей (несимметричности укладки), вследствие длительных силовых или температурных воздействий, и т.п. В работе исследуется применение корреляции цифровых изображений в методе зондирующих отверстий для определения остаточных напряжений в композиционных материалах. Исследовались образцы, вырезанные из панели полимерного композиционного материала с несимметричной укладкой, в которых определялись деформации, появившиеся после просверливания отверстия в образце. Фиксация деформаций проводилась бесконтактно, с использованием метода корреляции изображений. Для повышения точности фиксации деформации на образцы наносился паттерн. В рамках данной работы рассматривались два варианта паттерна: крупный (размер маркера 0,05-0,8 мм) и мелкий (размер маркера 0,02-0,2 мм). Так как остаточные деформации был небольшими, то крупный паттерн не дал показательных результатов. Полученные экспериментальные деформации сравнивались с численным расчетом методом конечных элементов. Решение обратной задачи теории упругости для идентификации остаточных напряжений проводилось в системе Comsol с использованием численного конечно-элементного моделирования, метода Монте-Карло и Нельдера-Мида. Метод Монте-Карло применялся для поиска глобального минимума функции невязок, а метод Нелдера-Мида для уточнения локального минимума. Функция невязок расчетных и экспериментальных данных вычислялась в среднеквадратичном приближении. Для уточнения среднего поля деформаций в эксперименте и игнорирования неустранимых погрешностей, связанные с неточностью экспериментальных данных, вводились малые значения поправки. В результате исследования было получено достаточное совпадение численных и экспериментальных результатов. Отличием реализованного метода от других методов измерения деформаций вокруг зондирующих отверстий является получение полной картины для всех компонент деформаций.

Methods for assessing the effect of the thickness of the adhesive layer in the adhesive joint of thin-walled composite structural elements on the strength of the entire joint are considered; a critical analysis of existing theoretical methods for predicting the strength of adhesive joints is given. The contradiction between the theoretical estimates of the effect of the adhesive thickness on the strength and the results of experiments and practical experience in the use of adhesive joints of composite panels is established. It is revealed that the most effective methods for predicting the load-bearing capacity of adhesive joints are energy models of fracture mechanics based on the intensity of the release of fracture energy and the formation of a pre-fracture zone in the adhesive layer. Assuming the determining role of changes in the size and shape of the initial fracture zone depending on the thickness of the adhesive layer, the results of the prediction of the strength of the adhesive joint are compared with experimental data.

This work advances solutions to the problem of insufficient electrical conductivity of adhesive material, the adhesive layer, and, ultimately, the entire adhesive connection. Sufficient electrical conductivity is necessary to ensure the survivability of composite structures under lightning strike conditions. Along the way, solutions to the problem of unhindered flow of static electricity charges which can occur when aircraft not in flight and has catastrophic consequences when interaction occurs in the presence of aviation fuel is proffered.

Work on the current topic of hybrid titanium-polymer composite materials (Ti-PCM) is continuing. After checking the technological feasibility of the two-stage process of manufacturing flat and single curvature of parts, work is carried out to optimize the composition, including through the introduction of elastic intermediate layers, the selection of the optimal parameters of the process.

The method of increasing of load-carrying ability of point joints of composite structures of holes for mechanical fasteners by installing fiberglass liners by thermal expansion resin transfer molding is proposed. The efficiency of the proposed solution in the aspect of restoring the strength and reliability of the compound is estimated.

The bearing capacity of a parts or units with a holes for fasteners and mechanical fasteners depends on the stress-strain state and its accompanying stress concentration in the local area of fasteners. In General, it is influenced by a set of operational and structural and technological factors. To replace the use of metal embedded elements, the technology of unloading the zone of point fastening of joints of composite structures is proposed by creating a combined connection with an intermediate element - a composite liner installed by a thermal compression method along the contour of the hole.

To study the distribution of temperature fields into a large-sized combined parts, it is necessary to devote a great attention for all the design features. A specimen for investigation the “behavior” of the material in different zones of a typical PCM panel must simultaneously contain both a monolithic and sandwich part of the structure.

The influence of the special modification of epoxy resins and polymer composites based on them on the basic technological properties of the composition is investigated. Modification is performed in order to reduce the opening damage. The most important technological properties of the initial epoxy composition and modified technological additives are studied and compared by standard methods (viscosimetry, thermoanalytical methods). A kinetic model of the curing process was created, the experimental production of samples from plastics filled with carbon long filler (impregnation under pressure, autoclave molding) and its non-destructive testing were carried out.

Developed and experimentally justified constructive and technological method of increasing strength and reliability of point mechanical connection of composite panels by thermocompression installation along the contour of the hole of the intermediate element-less rigid composite liner. The effectiveness of the method is provided by reducing the stress concentration in the hole area and confirmed finite element analysis and results of mechanical tests of samples of connection.

The influence of the special modification of epoxy resins and polymer composites based on them on the basic properties of the composition is investigated. Modification is perform in order to reduce the damage during machining holes. The dependence of thermal effects of processes depending on the degree of modification is revealed.

PURPOSE. The paper studies the effect of the special modification of epoxy matrices and epoxy matrix-based polymer composites on thermophysical parameters of machining processes under hole formation. A goal is set to produce experimental samples from matrices and experimental panels from carbon fiber plastics based on modified matrices. It is necessary to reveal whether there is any dependence of machining process thermal effects on the modification degree of matrices and carbon fiber plastics. METHODS. Experimental methods are used to achieve the purposes of this work. The experiment includes: production of experimental panels (binder preparation, liquid-phase combination with a dry filler, impregnation and vacuum-pressure oxidation molding); checking of their quality and mechanical properties (non-destructive testing of experimental panels by acoustic methods and standard mechanical tests); measurement of the cutting temperature under hole drilling in the sample made of experimental panels (infrared thermography of the hole formation zone). RESULTS AND THEIR DISCUSSION. It has been determined that the matrix samples feature the lowest heat release in the intervals from 0.1 to 0.3% wt depending on the type of the tool used. The peaks of the lowest heat release of the matrix-based carbon plastic samples are shifted to the range from 0.2 to 0.5%. The decrease in the maximum temperature in these ranges is due to the antifriction properties of the zinc stearate modifier: the coefficient and friction forces are reduced. Further increase in the modifier concentration leads to the recovery or even excess of the thermal effects relative to the initial unmodified matrices and carbon fiber plastics (0 % zinc stearate). This fact can presumably be explained by the decrease in cutting efficiency at reduced friction coefficients. The shifts of the peaks to the right and their “widening” for carbon fiber plastic samples is probably related to the thermophysical properties of the filler, which change the conditions of heat removal from the contact zone of friction bodies (a part and a processing tool). It is the carbon fiber plastic that is of some practical interest being a composite combination of a matrix and a carbon filler, which demonstrates more advantageous values of the thermal parameters of machining processes according to the study results. CONCLUSIONS. It has been shown that modification does not have any negative effect on the mechanical properties of modified composition-based carbon plastic. The dependences of the thermal effects of the machining processes under the hole formation in the samples on zinc stearate modifier concentration have been revealed. This fact proves the effectiveness of modification.