This paper explores the optimization macrostructure to reach a stable low coefficient of thermal expansion αx of a composite with carbon fibers. To limit the search area, a necessary condition for the existence of αx local minima is proposed, expressed in terms of the radii of hyperspheres in the design space of the angular orientation of the layers transformed by the PСA algorithm. The analysis of the structure variants characterized by low αx shows different sustainability to lamina properties variability. Multi-criteria optimization was carried out. The objective functions are expectation E(αx) and variance Var(αx). The analysis of Pareto fronts and probability density functions make it possible to estimate the reachability of the calculated αx under given conditions of lamina properties variability. The reduction variance opportunity of αx distribution by modifying the polymer matrix with MWCNTs under conditions of reinforcing fibers disorientation and lamina properties variability is investigated. The microstructure modification of the polymer composite material allows to reduce the Var(αx) by 91.61 % with a volume ratio of MWCNTs up to 1 %. Requirement thermomechanical properties are reached by determining the orientation of anisotropic layers. Based on the obtained optimal structures, specimens of CFRP with 0, 1 and 2 vol.% MWCNTs were made. Scanning electron microscopy using FE–SEM Hitachi S–5500 was performed to check the uniformity of distribution and compatibility of the epoxy matrix and MWCNTs. The measurement of αx is determined using a TAInstrumentsQ400 thermomechanical analyzer. Measured αx of specimens is in the range from 6.2·10-8 to 1.98·10-7 1/K. The structure optimization approach proposed in this paper makes it possible to obtain a set of solutions with a consistently low αx in the range up to 1·10-7 1/K. The transformation of the design space of the layers’ orientation angles and the limitation of the search area allowed to reduce the range of solutions under consideration by 83.9 %.

In this study, the effect of carbon nanofibers (CNN), single-wall carbon nanotubes (SWCNTs) and multi-wall carbon nanotubes (MWCNTs) on the warpage expected value and warpage dispersion of a plate made of a fibrous composite material are investigated. Laminates with fiber disorientation were considered as asymmetric and the model proposed by Dano and Hyer was used to evaluate the warpage. The results obtained confirm that the addition of carbon nanoparticles as a modifier to the polymer matrix of a fibrous composite material can increase the dimensional stability (the mathematical expectation of the standard deviation) and the technological stability of the reinforcement scheme (the variance of the standard deviation of the composite plate). Modeling of the warpage of plate, taking into account the possible disorientation of the fiber, showed a decrease in the warpage dispersion by 12.6 and 26.6 % with the modification of the SWNTs and MWCNTs, respectively. The coefficient of thermal extension (CTE) of a nanostructured polymer matrix with various fillers were experimentally determined. It was found that carbon nanomodifiers are more effective as compensators for the thermal expansion of the polymer matrix in composite laminates reinforced with carbon fibers than the polymer matrix without macrofibers. The addition of 0.05 % SWCNTs, 1 % MWCNTs to the epoxy resin reduces the CTE by 9.7 and 15.4 %, respectively. At the same time, the addition of a similar amount of nanoparticles to the epoxy matrix of the fiber composite reduces the CTE in the transverse direction by 15.56 and 35.8 %, respectively. On the basis of the obtained results, the dependences of the transverse CTE of the polymer composite material, the mathematical expectation of the standard deviation, and the variance of the standard deviation of the composite plate form accuracy on the concentration of the modifier were constructed. According to the obtained data, it can be concluded that in order to reduce the mathematical expectation and the variance of the warping of the composite material, there is an effective concentration, the increase of which is impractical, despite the further decrease in the transversal CTE.

The effect of the carbon fibers coupling layer on the occurrence of the triple-shape memory effect of polyurethane reinforced is studied. Using thermomodulated differential scanning calorimetry, structural changes in a sample of Carbon fiber reinforced polyurethane with coupling layer were determined. The influence of the diffusion adhesion mechanism on the thermomechanical characteristics of the triple-shape memory effect of the polyurethane composite material is established.

The possibility of using a three-point bending clamp thermomechanical analyzer for study the shape memory effect of a constructional polyurethane composite is investigated. The viscoelastic properties of the sample in the region of the transition from the glassy to the highly elastic state are studied. The parameters affecting the recovery rate of the original form (Rr) and the fixation factor of the temporary form (Rf) are determined. The conditions for deforming and cooling the polyurethane composite are established, which allow to achieve the values of Rr = 99.98% and Rf = 99.70%.

The possible applicability of a three-point bending clamp of a thermomechanical analyzer to study the shape memory effect of a structural polyurethane composite is studied. The viscoelastic properties of the sample in the region of the transition from the glass to the highly elastic state are studied. The parameters affecting recovery rate Rr of the original shape and fixation rate Rf of the temporary shape are determined. Deformation and cooling conditions that allow one to achieve the values Rr = 99.98% and Rf = 99.70% are established for the polyurethane composite.

This article presents a research on Hexagonal Boron Nitride (h-BN) monolayer cell strain effect 2 % and 4 %. Structure of h-BN with nitrogen vacancy, with boron vacancy and with divacancy was considered for this. The calculations were carried out within framework of the density functional formalism with gradient corrections and using the VASP package. Vanderbilt Ultra-Soft Pseudopotential was used in the course of the calculations. It is possible to conclude that nitrogen vacancies are the most stable, regardless of monolayer deformation on the results obtained. Understanding of atomic scale stability and dynamics of defects in such systems is crucial for predicting their properties and applications in electronics.