Linear Thermal Expansion Coefficient Research Articles

Thermal expansion and thermodynamic properties of Janus WSSe monolayer: A first-principles study

Materials with Janus structure play an important role in the emerging family of 2D materials. In this paper, based on a quasi-harmonic approach, the elastic, thermal expansion, and related thermodynamic properties of Janus WSSe monolayer are investigated by using first-principles calculations. For comparison, WS2 and WSe2 monolayers are studied as well. The linear thermal expansion coefficients of the three monolayers exhibit isotropy as their isotropic structures. All three monolayers show negative thermal expansion behavior at low temperatures (T < 30 K), with very small magnitudes. The value of the largest magnitude of negative thermal expansion is −0.376 × 10−6 K−1, contributed by the Janus WSSe monolayer. The linear thermal expansion coefficients also change from negative to positive as the temperature increases. This is consistent with macroscopic Grüneisen parameters. Remarkably negative values of the macroscopic Grüneisen parameter directly lead to negative thermal expansion at low temperatures. The linear thermal expansion coefficient of Janus WSSe is between those of WS2 and WSe2. The 2D bulk modulus has an important effect on the thermal expansion of three monolayers.

Tracking anharmonic oscillations in the structure of β-1,3-diacetylpyrene.

A recently discovered β polymorph of 1,3-diacetylpyrene has turned out to be a prominent negative thermal expansion material, with a linear thermal expansion coefficient of -199 (6) MK-1 at room temperature. Its unique properties can be linked to anharmonic oscillations in the crystal structure that can be attributed to several weak C-H...O interactions. The onset and development of anharmonic effects have been successfully tracked over a wide (90-390 K) temperature range using single-crystal X-ray diffraction. Experimental data of sufficient quality combined with Hirshfeld atom refinement of the crystal structures enabled a quantitative analysis of elusive anharmonic effects within the Gram-Charlier formalism. This example highlights that quantum crystallography tools can and should be applied in structural analysis even for data collected at high temperatures as well as of standard (∼0.8 Å) resolution.

Analysis of Material selection for automotive fender using the weighted sum method

Introduction: Material selection for automotive fenders involves the process of choosing the most suitable materials to be used in the construction of fenders based on various performance criteria, including mechanical properties, durability, weight, cost, safety, and environmental considerations. It involves assessing different materials and their characteristics to determine the optimal choice that meets the specific requirements of fenders. Research Significance: We will be able to choose a material with the right qualities thanks to research on the best materials for car fenders. Research on material choice for vehicle fenders was conducted for several reasons, including weight reduction and fuel efficiency, impact resistance including safety, resisting corrosion and durability, manufacturing procedure and cost optimisation, design flexibility and style, and environmental sustainability. It promotes innovation, aids in the creation of innovative materials, and aids automakers in meeting the changing demands of the market and customers. Method: This research employs the weighted sum approach to analyse the choice of material for an automobile fender. Alternate Parameters: High Strength Steels (Docol600DP and Docol1000DP), Aluminium alloys (AA2036T4 and AA6010T4), Thermoplastic polymers (PPE/PA/989Resin, PPO/PA66, NY66/40CF, PPS/40CF, AR/PC, PC/PBT resin) Evaluation Parameters: Ultimate Tensile Strength (UTS), Yield Strength (YS), Young's Modulus (YM), Linear Coefficient of Thermal Expansion (CTE), Material Cost (MC). Results: From the result it is seen that D1000DP is got the first rank where as is the PPE/PA/989 is having the lowest rank. Conclusion: the first ranking D1000DP is obtained with the lowest quality of PPE/PA/989.

Stress analysis of a hyperbolic elastic-plastic disk under thermomechanical loading

A general solution is constructed for the distribution of stresses within a thin, hyperbolic elastic-plastic disk subjected to external and internal pressures while in a steady-state temperature field and under plane stress conditions. The pressures applied to the disk are assumed not to induce any plastic flow at the initial, uniformly distributed temperature. The disk is loaded by increasing the temperature of its inner radius. The temperature of the outer radius is kept constant. Elastic and temperature strains are related to stresses by the Duhamel–Neumann law. In the plastic region, the von Mises yield criterion is valid. The tensile yield stress is taken as constant. The boundary value problem is statically determinate. Therefore, the plastic flow rule is not required to determine the stress field. The final part of the general solution depends on the parameters classifying the boundary value problem, including whether the plastic flow initiates at the inner or outer radius of the disk. The solution is presented in dimensionless form. The loading parameter comprises the inner surface temperature of the disk, the coefficient of linear thermal expansion, the initial temperature of the disk, the dimensionless inner radius of the disk, the yield stress under uniaxial tension, and Young’s modulus. The general solution is obtained for both cases (for a plastic region appearing at the inner or outer radius of the disk). A specific numerical solution is constructed for a disk subjected to external pressure and a steady-state temperature field. The temperature of the inner radius at which the plastic region first appears is calculated. As it increases, the plastic region extends. At a certain temperature value, another plastic region appears near the outer radius of the disk. This value is determined as part of solving the boundary value problem. The influence of the parameters classifying the boundary value problem on the development of the plastic region and the stress distribution along the radius of the disk is shown. The qualitative differences between the new and existing solutions for a disk of constant thickness under the action of a uniform temperature field are discussed.

Process for the Preparation of Artificial Analog of Sanbornite–Glass Composites

Barium silicates have been investigated as high-expansion components of solid oxide fuel cells (SOFCs) and, therefore, their synthesis and expansion have been the subject of intensive research in recent years. In this article, we briefly present a new process to make glass–crystalline composites, as well as two novel findings related to a synthesis route of sanbornite (BaSi2O5) and the fast in situ formation of a high-expansion sanbornite composite from a Pyrex-type glass powder. The low-temperature synthesis, composition, and expansion of one type of novel glass composite are described. The composites are made by the reaction of BaCO3 and Pyrex-type powders at 850–950 °C for a short time of one hour. The composites are well sintered and hard, and their linear coefficient of thermal expansion is about 12.3 × 10−6 C−1. The crystalline-phase formation, dilatometer measurements, SEM data, and possible applications of the composites are presented and discussed.

ABOUT ONE METHOD OF STUDYING THE COEFFICIENT OF THERMAL EXPANSION OF POLYMERS

The problem of studying the deformation response of film samples made of UV-curable polymers to temperature changes is considered. It is difficult to obtain massive samples of these polymers due to the peculiarities of their polymerization. This paper suggests a methodology for tests that allows us to determine the temperature dependence of the coefficient of linear thermal expansion (CTE) in a wide range, including the relaxation transition. As measuring equipment was used a dynamic mechanical analyzer TA Instruments Q800 DMA with liquid nitrogen cooling system GCA, which allows varying temperature and its rate of change in wide ranges, controlling and measuring forces and displacements with high accuracy. The proposed approaches are applicable to any film samples and provide an opportunity to establish functional dependences of CTE not only on temperature, but also on its rate of change. At the same time, in contrast to traditional methods, the described procedures allow obtaining correct data under the conditions of relaxation transitions taking into account the influence of the temperature change rate on these processes. Considerable attention is paid to calibrate the measuring equipment, in particular, the measurement and compensation of the temperature deformation of the tooling. The measurements results are compared with known literature sources, manufacturers data, the results of measurements of samples with known characteristics and with the results obtained on a horizontal dilatometer. It is shown that the proposed method of measurements is correct and has a number of advantages over traditional methods of research when working with film samples or in cases where it is necessary to take the effect of the rate of temperature change on CTE into account.

Temperature- and water-induced structural transformations in Ba(Ce0.7Zr0.1Y0.1Yb0.1)O3-δ proton conducting electrolyte

The crystal structure of Ba(Ce0.7Zr0.1Y0.1Yb0.1)O3–δ was studied depending on temperature in dry and wet atmosphere using in situ high temperature X-ray powder diffraction. Phase transition from tetragonal I4/mcm to cubic Pm-3m structure was shown to occur in Ba(Ce0.7Zr0.1Y0.1Yb0.1)O3–δ upon heating from 25 up to 1000 °C irrespective of air humidity. The cubic Pm m and tetragonal I4/mcm phases possess comparable coefficients of linear thermal expansion (CTEs), 10.6·10–6 K–1. Even in very dry atmosphere (10–4 atm H2O), chemical expansion caused by hydration contributes significantly to the observed structural transformations and the variation of the unit cell parameters of Ba(Ce0.7Zr0.1Y0.1Yb0.1)O3–δ.

Застосування фторидних вогнетривів для отримання функціо-наль¬них сплавів, що містять хімічно активні компоненти Ti, Zr, Hf, Nb, V

Refractory crucibles, cups and other products made of material based on alkaline earth metals fluorides, which are used for casting, isothermal melting, high-temperature homogenization of chemically aggressive alloys containing a large amount of Ti, Zr, Hf, V, Nb, have been developed and manufactured. However, due to the large difference in coefficients of thermal linear expansion (KTLE) of fluorides and metals, mechanical compression of the crystallizing alloy in the crucible occurs.Such a difference in KTLE leads to cracking and destruction of crucibles. Crucibles that can be disassembled into several parts have been developed. This makes it possible to use such crucibles a large number of times for high-temperature homogenization and melting of chemically active alloys containing Ti, Zr, V, Nb.The developed refractory and special cups made from it also provide new opportunities for scientific research: studying the capillary characteristics (surface tension) of metal melts with a high content of reactive metals, which was previously practically impossible, as well as determining thermodynamic properties (enthalpy of mixing and formation of alloys, activity of components) for these alloys. Keywords: functional metal materials, refractory materials, fluorides of alkaline earth metals, collapsible crucibles, chemically aggressive metals.

HTXRD based lattice thermal expansion and specific heat capacity modelling of C15-Fe2Zr Laves phase

Crystallographic phase pure C15-Fe2Zr was obtained through arc melting technique. X-ray Diffraction (XRD), scanning electron microscope (FESEM) along with energy-dispersive X-ray analysis (EDS) and differential scanning calorimetry (DSC)were employed to study the single phase in Fe-33.3at.% Zr alloy. Rietveld refinement of the high-temperature XRD patterns (from 298K-873 K) revealed the average linear and volumetric coefficients of thermal expansion of the alloys as αai= 0.3643 × 10−5 K−1 and αVi = 1.0916 × 10−5 K−1, respectively. The experimental heat capacity and enthalpy increment of the C15-Fe2Zr phase from 310K to 890K was modelled employing Quasi-harmonic Debye Grüneisen theoretical modelling by identifying the vibrational, electronic, anharmonic and magnetic contributions. Curie temperature(~625K) was determined from the magnetic contribution of the heat capacity.

Synthesis and Investigation of the Properties of a Branched Phthalonitrile Containing Cyclotriphosphazene.

To study the properties of cyclotriphosphazene (CTP)-containing phthalonitriles, a branched phthalonitrile containing CTP (CTP-PN) with self-catalytic behavior was designed and synthesized. The structure of CTP-PN was characterized by FT-IR (Fourier transform infrared spectroscopy), MS (mass spectroscopy), 1H-NMR (proton nuclear magnetic resonance spectroscopy), and 13C-NMR (carbon nuclear magnetic resonance spectroscopy). Then, the curing reaction of CTP-PN was studied using DSC (differential scanning calorimetry) and DRA (dynamic rheological analysis). The results show that the curing reaction of CTP-PN is initiated at 200 °C. Additionally, the change in the viscosity of CTP-PN as a function of the temperature was investigated. After curing at different temperatures, the generated structures were characterized by FT-IR. The fracture morphology and thermomechanical properties of cured CTP-PN were scanned and studied using SEM (scanning electron microscopy) and TMA (thermomechanical analysis), respectively. The results demonstrate that CTP-PN exhibits a smooth fracture surface and possesses a relatively low CTE (coefficient of linear thermal expansion) of approximately 25 ppm/°C at 285 °C. A Td5% (temperature at which 5% weight loss occurs) of as high as 405 °C can be obtained for cured CTP-PN, and its char yield at 800 °C exceeds 70% in N2. FT-IR and XPS (X-ray photoelectron spectroscopy) were used to study the thermal decomposition of cured CTP-PN, indicating that it remains stable below 350 °C. With an increasing temperature, there is decomposition first of CTP and P-NH-Ph and C-O-C bonds (>350 °C) and then nitrogen-containing aromatic heterocycles (>500 °C), ultimately resulting in the formation of P-containing residual char.

Designing the next generation of polymers with machine learning and physics-based models

Abstract The development of next-generation polymers necessitates optimizing several key properties simultaneously, a task that is expensive and infeasible using traditional trial-and-error experimental approaches. A promising alternative is employing a combination of machine learning and physics-based tools to rapidly screen the polymer design space and provide suggestions of new polymers that meet the critical properties required for industrial applications. In this study, we introduce a comprehensive workflow that utilizes machine learning and molecular modeling approaches to design new polymers with the focus on improving five polymer properties: (1) glass transition temperature, (2) dielectric constant, (3) refractive index, (4) stress optic coefficient, and (5) linear coefficient of thermal expansion. Using a small dataset ( < 200 unique polymers), we developed quantitative structure-property relationships (QSPRs) models to accurately predict the experimental polymer properties for both homo- and co-polymer systems. We tested several ML algorithms and identified the best models for predicting these polymer properties, achieving test set R 2 greater than 0.77 across all properties. We then explored new polymers by creating a library of over ∼10 000 homopolymers using R-group enumeration tools and applied the trained QSPR models to rapidly predict the five polymer properties. The predictions of QSPR models were used to create a multi-parameter optimization score, which helped downselect the large polymer space to ∼10 promising candidates. The properties of these selected polymer candidates were subsequently validated with classical molecular dynamics simulations and density functional theory, revealing a strong correlation with the QSPR model predictions. Finally, one of the top candidates was validated by experiments, which showed good agreement against QSPR and physics-based models. Our workflow underscores the power of combining data-driven and theoretical methods in the polymer design process given a small dataset size, offering a valuable resource for experimentalists looking to leverage computer-aided strategies in materials innovation.

Glass-ceramic binder of cordierite composition for low-temperature sintering of high-strength ceramic materials based on oxygen-free silicon compounds

The mechanical properties of composite ceramic materials obtained based on oxygen-free silicon compounds are largely determined by the properties of the glass binder. This paper presents the results of studies aimed at determining the most fusible glass in the pseudo-binary system 2MgO2Al2O35SiO2–2MnO2Al2O35SiO2 with a high tendency to crystallize as a glass-ceramic binder for low-temperature sintering of high-strength ceramic materials based on oxygen-free silicon compounds. The crystallization tendency of the experimental melts decreases with an increase in in the content of manganese cordierite, as confirmed by X-ray and infrared spectroscopic studies. Based on experimental studies, a melting diagram was constructed, which was used to determine the ratio between magnesium cordierite and manganese cordierite (50:50 wt.%), ensuring a minimum melt temperature of 12750C. The melting point of the glass of the specified composition is 14500C. The synthesized glass is characterized by a softening point of 8000C and crystallizes intensively at 10300C. The The thermal coefficient of linear expansion of the crystallized glass samples is 20.810–7 0C–1. X-ray diffraction and electron microscopic studies have shown that the developed glass is almost completely crystallized during heat treatment for 2 hours, forming a cordierite solid solution 2(Mg,Mn)O2Al2O35SiO2. The size of the cordierite phase crystals ranges from 0.5 to 3.0 m. Due to its fusibility and high crystallization tendency, the developed glass, can be proposed as a promising glass-ceramic binder for the production of high-strength ceramic materials (wear and impact resistant) based on SiC and Si3N4 with reduced sintering temperatures.

Radio-transparent celsian ceramics modified with glass in a pseudoternary system BaO–Al2O3–SiO2: synthesis, microstructure, thermal and physical properties

The article presents the results of the study of radio-transparent celsian ceramics, in which part of the components were introduced using eutectic glass of the pseudoternary BaO–Al2O3–SiO2 system. The bonding of the components of the experimental glass into the celsian phase was realized according to the principle of reactive structure formation by adding the missing components (crystalline fillers). In this case, the obtained dense sintered water-resistant ceramic, the only crystalline phase in the composition of which is the monoclinic form of celsian, which forms a microhomogeneous structural matrix of the material. Celsian is represented by distinct prismatic crystals of tetragonal and hexagonal shape. The size of celsian crystals increases from 3–5 m to 7–10 m with increasing the content of eutectic glass. The developed celsian ceramic has a set of enhanced physical and thermal properties: zero water absorption and open porosity, mechanical compressive strength (up to 157 MPa), refractory index is 1540–15800C. Celsian ceramic is characterized by a coefficient of linear thermal expansion of 3410–7 0C–1, which provides a sufficiently high thermal shock resistance of 7000C. In terms of the level of relative dielectric permittivity (5.5) and dielectric losses (0.0005) at a frequency of 1010 Hz, the developed ceramic meets the requirements for ultra-high-frequency radio-transparent materials for aviation and rocket technology, which operate under conditions of high-speed high-temperature heating.

Microstructure and Properties of Aluminum Alloy/Diamond Composite Materials Prepared by Laser Cladding.

In this article, AlSi10Mg aluminum alloy was used as the substrate to prepare aluminum alloy/diamond composite materials with laser cladding technology. The effects of the composition and laser power on the microstructure and thermal properties of the composite materials were studied. The results show that the prefabrication of tungsten carbide layer on the diamond surface enhances the wettability of diamond with aluminum alloy and reduces the laser reflection, which ensures the implementability of laser cladding technology for the preparation of aluminum alloy/diamond composites. The laser power and components determine the temperature of the molten pool and thus the state of the organization of the composite material to be formed by cladding. With the increase in the diamond content, the density, specific heat, mechanical properties, and average linear thermal expansion coefficient of the composite material gradually decrease, while the thermal conductivity first increases and then decreases. The thermal conductivity of the aluminum alloy/diamond composite material prepared by laser cladding is 200.68 W/mK, and the linear thermal expansion coefficient is 1.904 × 10-5/K, which are superior to those of the matrix AlSi10Mg aluminum alloy.

Study of Structural, Thermal and Electrical Properties of Sr-Doped CaMnO<sub>3</sub>

Sr-doped CaMnO3 materials have wide applications due to their thermal and electrical properties. The importance of the synthesis of Sr-doped CaMnO3 material for various applications encourages researchers to evaluate and refine the synthesis process. In this study, Ca1-xSrxMnO3 (x = 0; 0.05; 0.1; 0.15; 0.2) system has been prepared by sol-gel method followed by conventional sintering process at 850°C for 8 hr. A thorough discussion has been made on the outcomes derived from the investigation on the structural, electrical, and thermal properties of Sr-doped CaMnO3 system using powder x-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, DC fourprobe method, thermal expansion studies, and thermoelectric power analyses. The XRD patterns of all prepared samples exhibited single phase with orthorhombic crystal structure (space group Pnma). Rietveld refinements were performed for all the patterns by using Fullprof software to extract the structural properties. The values of unit cell volume of samples tend to increase with the increment of dopant concentration, whereas the crystallite size values were decreased with dopant concentration. The microstructures of all the samples were studied using SEM, and elemental compositions were confirmed from the EDS results. Linear thermal expansion coefficients of all the samples were found to have moderate values in the temperature range from 30°C to 800°C. The electrical properties of all the system of samples were studied in the temperature range from 30°C to 400°C using DC fourprobe conductivity setup. It was found that all the samples exhibited semiconductor nature. Sr-content on the A-site suppress the electrical resistivity up to 10% of concentration and 5% dopant content exhibited the lowest electrical resistivity. The values of Seebeck coefficient found to vary from -160 µV/K to -124 µV/K with the increase of dopant content in the parent compound.

Influence of highly dispersed phase of titanium carbide on physical and mechanical properties of alloys AM4.5Kd and AK10M2N

Dispersion-strengthened composite materials belong to the group of promising structural materials characterized by a diverse combination of properties. The work presents examples of the creation and heat treatment of composite materials based on aluminum alloys, strengthened by a dispersed phase of titanium carbide, and characterized by high hardness, elastic modulus and good wettability by the melt. The most accessible, inexpensive and effective way to obtain them is self-propagating high-temperature synthesis (SHS).The work shows the possibility of obtaining new aluminum matrix composite materials based on industrial aluminum alloys AM4.5Kd and AK10M2N by reinforcing them with 10 wt.% highly dispersed titanium carbide or AM4.5Kd–5.95 vol.% TiC and AK10M2N–5.78 vol.% TiC. The reinforcing phase is formed in alloy melts using the technology of SHS from the initial elemental components—titanium powder and carbon black. Using the obtained samples, an assessment was made of the uniformity of the ceramic phase distribution over the volume of the matrix alloys, which amounted to 0.15 and 0.12 for the samples AM4.5Kd–10%TiC and AK10M2N–10%TiC, respectively, which constitutes a high degree of uniformity.An assessment was made of physical properties such as porosity, density, electrical conductivity, as well as the coefficient of thermal linear expansion. Analysis of the data allows us to say that the final composite materials AM4.5Kd–10%TiC and AK10M2N–10%TiC have a slightly higher density (↑~4%) than the matrix alloys, due to the presence of a ceramic phase, low porosity values (~1%), lower TCLE (↓~6%) than matrix alloys and low electrical conductivity (~25% IACS). This article also presents data on the values of the mechanical properties of composite materials AM4.5Kd–10%TiC and AK10M2N–10%TiC. It has been shown that reinforcement with a ceramic phase contributes to a significant increase in hardness by 15 and 42 HB, as well as higher values of the compressive yield strength by 31 and 17 MPa, respectively, while maintaining a high level of relative deformation. The results obtained allow us to conclude that the developed composite materials can be recommended for products used under conditions of elevated temperatures and significant wear.

Effect of Plastic Deformation on Thermal Properties in Twinning-Induced Plasticity Steel.

The effect of plastic deformation induced by wire drawing on thermal properties in twinning-induced plasticity (TWIP) steel has been investigated. The investigation on the relationship between thermal conductivity (k) and the microstructure in the drawn TWIP steel wire was systematically performed to accurately understand the behavior of the k of a metal during wire drawing. The yield and tensile strengths linearly increased with drawing strain owing to the deformation twins and dislocations that were generated during wire drawing. However, the total elongation sharply decreased with drawing strain. The linear thermal expansion coefficient of the TWIP steel exhibited a similar value regardless of drawing strain. The density decreased linearly with temperature, and it was independent of the drawing strain. k increased initially and then decreased after reaching its maximum value with increasing drawing strains. At a nominal drawing strain of 0.26, k increased compared with the state of hot rolling because the increase in k due to grain elongation was greater than the decrease in k due to dislocations generated during wire drawing. However, as the amount of drawing step increased further, the influence of dislocations on k increased more than that of grain elongation, causing k to decrease.

Study on enhancing mechanical and thermal properties of carbon fiber reinforced epoxy composite through zinc oxide nanofiller

This study investigates the enhancement of mechanical and thermal properties of carbon fiber reinforced epoxy composites by incorporating zinc oxide (ZnO) nanofillers. The composites were developed by adding 3–15 g of ZnO nanoparticles into the epoxy matrix and were evaluated through experimental testing. The results showed significant improvements in mechanical performance, with the maximum tensile strength of 112.49 MPa and flexural strength of 114.82 MPa at the 15 g ZnO concentration. SEM analysis revealed a reduction in void content and improved fiber-matrix adhesion, enhancing load transfer. Thermal conductivity is 13.47 W/mK, while the coefficient of linear thermal expansion is 9.29 × 10−5/°C, indicating superior thermal stability. TGA analysis demonstrated a shift in decomposition temperature from 310 to 375 °C, confirming enhanced thermal stability. These results highlight the positive influence of ZnO nanofillers on both the mechanical and thermal properties of carbon fiber reinforced epoxy composites, making them more suitable for advanced structural applications.

Experimental Investigation on Thermal Behaviors of Benzoyl Treated Neem / Pineapple Fiber Reinforced Saw Dust Filled Epoxy Hybrid Green Composites

ABSTRACT Natural fibers have in recent times turned into reasonable to automotive production as a substitute corroboration for synthetic fiber reinforced thermoplastics. This research was motivated by evolving and assessing benzoyl-treated Neem and Pineapple fiber reinforced and particulated by sawdust in hybrid epoxy polymers for automotive. Seven types of composites were fabricated using hand layup technique. The prepared composites were cut according to their ASTM standard. The Hybrid Neem and Pineapple Fiber Reinforced with Saw dust Particulated Epoxy Composite (NPFRSPEC) was studied for thermal analysis like Thermal Conductivity (TC), Coefficient of Linear Thermal Expansion (CLTE), Heat Deflection Temperature (HDT) and Thermal Gravimetric Analysis (TGA). Morphological analysis was done through FESEM on failure surfaces. The results reveal that treatment fibers enhanced the thermal stability among the non-treated composite. The treated fibers exhibited 10% increase in heat deflection temperature and 28% increase in thermal conductivity. From the results, it’s also noticed that the treated hybrid composite delivers better thermal efficiency when compared with other natural fiber-reinforced polymers available in the sector which could potentially replace long fiber reinforced thermoplastic components in car doors and bumpers.

On the coefficient of linear thermal expansion of wet masonry at freezing temperatures

Introduction. Stone masonry is a structurally heterogeneous (composite) material; therefore, a number of its physical and mechanical characteristics are orthotropic, including the coefficient of linear thermal expansion. The article analyses the coefficient of linear thermal expansion of stone masonry under the conditions of its operation in different temperature and climatic conditions, including different humidity.Aim. To obtain the dependence of the coefficient of linear thermal expansion on masonry humidity at freezing temperatures by comparing the results of studies of wet masonry samples.Materials and methods. The study is based on the data of M.A. Mury published in his work "Temperature deformations of wet brickwork" and some of his previously unpublished data. Regression analysis was used to perform the research.Results. There were obtained graphical and mathematical dependences of the coefficient of thermal expansion of masonry in the form of piecewise linear functions at freezing temperatures, with account of material humidity.Conclusions. The presented dependences can be used in calculations of the stress-strain state of masonry structures with the use of modern program complexes. Published data on the coefficient of linear thermal expansion of masonry show a wide range of their values, which indicates fragmentary research based on the use of ceramic stones from a single manufacturer. Therefore, large-scale research with systematization of the results with a logically justified maximum number of varying parameters of masonry should be carried out, with subsequent amendments to the norms of design and construction of masonry structures based on the results of the research.