High-temperature Composites Research Articles

Modeling of thermal stresses in thin-walled composite structures with phase transformation

An asymptotic theory modified version for calculating thin elastic multilayer plates made of high-temperature composites with multistage phase transformations, considering the composites shear characteristics finite values has been developed. Proposed in this work method version does not contain any assumptions about the kind of the unknown functions and allows ones to find all 6 stress tensor components while ensuring the high mathematical accuracy that symbolic for asymptotic method. Using the developed model, it became possible to calculate temperature non-stationary field and thermal stresses in thin multilayer plates of fabric composite materials on an inorganic binder. For material properties calculation were used multiscale averaging method and finite element modeling for periodical cells. Some change stresses numerical simulation results for composite plate during heating and loading are given.

Glass Cullet as Additive to New Sustainable Composites Based on Alumina Binder

The article investigated the possibility of reusing heat resistant glass cullet to improve the mechanical properties of high-temperature composites. This is an excellent recycled aggregate that may be used as a substitute for alumina cement, and for fine natural aggregate in the production of concrete based on hydraulic binder. The experimental programme comprised of strength testing conducted on 40 × 40 × 160 mm cuboidal samples. The model mixture was modified by filler that comprised glass recyclate, amounting to 5%, 10%, and 15% of the mass of gravel and cement. Given the degree of glass grounding, use was made of two fractions, 0/4 and 0/0.125 mm. Six modified mixtures were produced. Tests were then carried out on their selected physical and mechanical properties as well as the impact of temperature, topography, and chemical composition exerted on the composite. Next, the progress and development of compressive strength and flexural strength after 14 and 28 days of curing were studied. Results showed that concrete with a 5% content of glass dust had a maximum compressive strength at the level of 85.1 MPa. Results also showed that concrete (Zk.I.5) heated at a temperature of 500 °C had a 46% higher compressive strength when compared to basic concrete (Z.I.0). The results show that it is possible to use the described components to obtain a composite that meets requirements imposed on structural materials used in construction engineering.

Influence of stitching on the out-of-plane behavior of composite materials – A mechanistic review

Fiber-reinforced polymer composites are widely used in the aerospace industry due to their high stiffness and strength-to-weight ratios. However, their applicability can be limited by their relatively low interlaminar properties when compared to metallic alternatives. Through-thickness reinforcement approaches, such as stitching, z-pinning, needling, tufting, and three-dimensional weaving, have been developed in recent decades to enhance the interlaminar properties of composites. Stitching is considered to be an efficient and cost-effective method to reinforce composites in the through-thickness direction. Additionally, stitch parameters (stitch density, linear thread density, thread material, pretension, etc.) highly influence the in-plane and out-of-plane properties. This paper summarizes results from over one hundred papers on the influence of stitch parameters on fracture energy, interlaminar strength, and impact characteristics of stitched composite laminates, sandwich composites, and high-temperature composites. Much of the research on the influence of stitch parameters has focused on thermoset polymer matrix composites (PMCs), while fewer studies have investigated the impact of stitch parameters on high temperature or sandwich composites. Modification of existing and new test methods have been developed to adequately measure the effectiveness of stitching on the out-of-plane behavior of PMC panels. Results demonstrate that out-of-plane properties of PMCs are highly dependent on stitch parameters and can be enhanced by through-thickness stitching.

Bio‐resourced eugenol derived phthalonitrile resin for high temperature composite

AbstractEugenol (EG) is an abundant renewable compound that has been widely used in the synthesis of bio‐based thermosetting resin, but there are few reports on the phthalonitrile (PN) resin derived from EG. In this study, a new kind of bio‐based PN resin (MEG‐PN) derived from EG derivative was successfully synthesized. PN is a traditional class of high‐performance thermosets with poor processability for its ultra‐high melting point and curing temperature. The MEG‐PN resin possesses excellent processability: its melting temperature is much lower (77°C), and it can be cured at a moderate temperature (281°C) in the absence of curing agents. The cured MEG‐PN resin exhibited great heat resistance according to its 5% weight loss temperature at 448°C and its char yield percentage as high as 75.6% at 800°C under nitrogen. The properties of the carbon‐fiber reinforced MEG‐PN composite were comparable to those of petroleum‐based PN resins: the glass transition temperature was around 397°C; the flexural strength and modulus were as high as 756 MPa and 119 GPa, respectively. Overall, a bio‐based PN thermoset with great comprehensive performance was synthesized possessing the potential in the application of advanced composite.

Study of the acoustic emission response to a core-shell rubber-toughened, high-temperature composite

This work explores the effect of core-shell rubber (CSR) addition on the cure reaction and resulting mechanical and thermal properties of a highly cross-linked network made from 4,4′- tetraglycidyl diamino diphenyl methane and 3,3′-diamino diphenyl sulphone. Up to 20 wt% of a CSR rubber, composed of a soft polybutadiene core and a hard poly methyl methacrylate (PMMA) shell was dispersed in the epoxy/amine and after cure was found to increase the glass transition temperature and thermal degradation temperatures modestly, while reducing the char yield. Flexural properties also reduced with CSR addition, although fracture toughness (KIC) was increased by 45% at 20 wt% of CSR. Furthermore, the fracture strain energy release rate (GIC) of the corresponding carbon fibre composite at the same CSR concentration, increased by almost 115%. Acoustic emission spectroscopy is introduced as a tool for investigating crack propagation during mode I loading and identifying any differences in the failure mechanism between the unmodified and the 20 wt% CSR-modified carbon fibre composites.

НИОБИЙ, АРМИРОВАННЫЙ ВОЛОКНАМИ α-Al2O3 Часть 1. Двухкомпонентные композиции

The paper reviews the results of development of a new class of high-temperature composites based on niobium and various types of reinforcers continuous monocrystalline fibers (MCF) α-Al2O3, with TiN, Mo, W barrier coatings, and with controlled (Si, Ti) and uncontrolled (O, C) impurities. The analysis of Nb–Si, Nb–C, Nb–O binary diagrams and Nb–Si–Ti, Nb–Fe–Ti ternary diagrams was performed, on the basis of which the matrix compositions were selected. The basis for the preparation of composites was the powder method of mechanical alloying of the mixture preparing, followed by its pressing together with α-Al2O3 MCF by spark plasma sintering (SPS) and further preparation of experimental samples. An analysis of the interaction of fibers with a matrix was carried out, where the matrix was Nb or system on the basis of the above mentioned binary or ternary diagrams.

Analysis of 3D-reinforced composite annular plate subjected to concentrated forces

This paper is dedicated to the solution of the problem about 3D-reinforced composite annular plate compressed by concentrated forces. 3D-reinforced composite materials, including high-temperature composites, are widely used in modern space industry, while their properties are insufficiently studied. Analytical solution of considered problem about annular plate compression will be a foundation for a method of determination of anisotropic composite materials stress-strain properties needed when conducting structural analysis: elastic and shear moduli, and Poisson’s ratio. Transverse shear deformations and changes in annular plate metrics during deformation are taken into account in the process of finding analytical solution of the problem. The analytical solution of the problem about annular plate compression was obtained by the authors. This solution is used to find relations between required properties of annular plate and radial displacements of annular plate characteristic points.

Утилизация отходов волокнистой теплоизоляции в составе слоистых высокотемпературных композитов на фосфатных связующих

Описан способ утилизации отходов волокнистых огнеупорных материалов типа муллитокремнеземистых волокон (МКВ), традиционно применяемых для теплоизоляции высокотемпературных печей и другого оборудования. Предложено использовать отработанную теплоизоляцию для изготовления композиционного материала типа сэндвич, в котором между двумя слоями заводского рулонного материала находится промежуточный слой, состоящий из переработанных волокон и фосфатного связующего. Утилизированная волокнистая теплоизоляция, содержащая связующее, предварительно была дезагломерирована. Установлен оптимальный состав промежуточного слоя, содержащего слоистый волокнистый материал типа МКВ (МКРР-130 или МКРРХ-150) и алюмоборфосфатной/алюмохромфосфатное связующее; определены свойства этих материалов. A recycling procedure is described for utilization of waste derived from spent fibrous refractory materials such as mullite-siliceous fibers, traditionally used for thermal insulation of high-temperature furnaces and other equipment. It is proposed to use the spent thermal insulation for manufacturing a composite material of the sandwich type, in which an intermediate layer consisting of the recycled fibers and a phosphate binder is located between two outer layers of an industrial roll material. In the case of using spent fibrous thermal insulation containing a binder the waste has been previously deagglomerated. The optimal composition of the intermediate layer containing a layered fibrous material of the mullite-siliceous fiber type (MKRP-130 or MKRKH-150) and an alumina-boron-phosphate/alumina-chromium-phosphate binder has been established, and the characteristics of the obtained composite materials have been determined.

Особенности учета и выбора технологических решений при изготовлении высокотемпературных композитов на основе углеродных волокон

Проведен анализ особенностей выбора проектных решений для технологических методов изготовления волокнистых высокотемпературных композитов на основе углеродных волокон. Показано, что изготовление таких композитов основано на принципиально иных технологических методах, в сравнении с общепринятыми в общем машиностроении. Выявлено, что указанные технологические методы изготовления не учтены в нормативной документации и вызывают различные сложности в поиске, учете и выборе проектных технологических решениях при производстве новой продукции по изделиям-аналогам и использования систем кодирования обозначений в ЕСКД и ЕСТД. Показана необходимость актуализации нормативной документации с учетом новых технологических методов изготовления данных композитов, разработки систем кодирования и формирования их архивов. The analysis of the features of the choice of design solutions for technological methods for the manufacture of fibrous high-temperature composites based on carbon fibers is carried out. It is shown that the manufacture of such composites is based on fundamentally different technological methods, in comparison with those generally accepted in general engineering. It was revealed that the indicated technological methods of manufacturing are not taken into account in the regulatory documentation and cause various difficulties in the search, accounting and selection of design technological solutions in the production of new products for similar products and the use of coding systems for signs in ESKD and UTDD. The necessity of updating the regulatory documentation taking into account new technological methods for manufacturing these composites, the development of coding systems and the formation of their archives is shown.

Yttrium-aluminium-perovskite-fibre/molybdenum-matrix composites: Strength, fracture toughness and oxidation resistance

Thermal efficiency of a gas turbine depends on the highest temperature of the thermal cycle in a machine. Nickel supperalloys used in modern gas turbines have approached their physical limit. Hence, transportation and energy technologies call for new generations of heat resistant materials. Among four families of future heat resistant materials, metal matrix composites (MMCs), ceramic matrix composites, alloys based on refractory metals, and high entropy alloys, materials of the first family, MMCs, are characterized by an attractive balance between strength and fracture toughness. The only choice of the matrix for really high temperature composites is a refractory metal, for example, molybdenum. Since composites are to be exploited in extremely hard environments and the requirements to various important properties of future materials of practical importance often contradict each other, the choice of a particular fibre/matrix combination is to be based on the results of studies of a large number of variants. In the present work, molybdenum matrix composites reinforced with fibres based on yttrium-aluminium perovskite (YAP) have been obtained for the first time using the internal crystallization method. The fabrication technology and fibres microstructures are briefly discussed. Strength, fracture toughness and oxidation resistance are discussed in details. The composites proved to be sufficiently strong at temperatures up to 1400 °C and of are characterized by low notch sensitivity at room temperature. Oxidation resistance of the molybdenum matrix of the composites at temperatures 1000 and 1100 °C is much better than that of pure molybdenum.

Constitutive relations of the endochronic theory of thermoplasticity for high-temperature composites under plane stress state

A variant of the constitutive relations of the endochronic theory of thermoplasticity for high-temperature composites is proposed. The relations for the plane stress state are considered. Examples of the use of the proposed relations in which the material behavior under complex loading is analyzed are given. The dependence of the elastic modulus of the material on the temperature of pre-heating is shown.

Исследование структуры и свойств многослойного композиционного материала на основе системы “высокотемпературная керамика – тугоплавкий металл”

Исследование структуры и свойств многослойного композиционного материала на основе системы “высокотемпературная керамика – тугоплавкий металл”

High temperature solid-lubricating materials: A review

Abstract This paper provides a review on the current research developments in high temperature solid-lubricating materials. We first briefly discuss fundamental of high temperature solid-lubricating materials, including design strategies of a low friction coefficient, a high wear resistance, a wide environment range, and how to construct high temperature solid-lubricating materials. And then the review highlights progress in the design and exploration of high temperature solid-lubricating coatings (monolithic coatings, multiphase coatings and self-adaptive coatings) and composites (metal, intermetallic and ceramic matrices high temperature solid-lubricating composites). Finally, we shortly introduce practical applications and trends of high temperature solid-lubricating materials in the future. These developments offer new avenues to both intensify the understanding of high temperature tribology and expand the diversity of practical applications.

The adjustment of CA<sub>6</sub> morphology and its effect on the thermo-mechanical properties of high temperature composites

In this paper, the morphology of CA6 was adjusted by changing the particle sizes of alumina powders (D50 = 7.26, 5.33 and 2.37 µm), and the effect of this on the thermo-mechanical properties of corundum based high temperature composites was investigated. The results indicated that when the alumina particle size was decreased from 7.26 to 2.37 µm, the morphology of calcium hexaluminate (CA6) transformed from equiaxial to platy shape. The microstructure changes of CA6 may be due to differences in CA6 nuclei numbers and the contact area between alumina and calcium dialuminate. This transformation process can proceed without liquid. Because of the transformation of the CA6 morphology, the hot modulus of rupture and residual cold modulus of rupture of corundum composites fired at 1600°C increased by 143 and 192%, respectively. The loop areas of in-situ elastic modulus also increased by 20%. The fracture ways of composites were transformed from intergranular to transgranular. Therefore, corundum-based composites with excellent properties including room temperature and high temperature properties can be obtained by adjusting the microstructure of CA6.

Tertiary-amine-free, non-planar, fluorine-containing tetrafunctional epoxy and its application as high performance matrix

N,N,N′,N′-tetraglycidyl-4,4′-diamino-diphenylmethane (TGDDM) is the most widely used epoxy matrix in aerospace/aircraft industries, however its cured product suffers from cyclization side reactions, inadequate toughness and water resistance, and relatively high dielectric constant, which are rooted in its amine-derived nature. In order to address those issues, a tertiary-amine-free, non-planar, fluorine-containing tetrafunctional epoxy (FCTE) was synthesized with high yield. When FCTE is mixed with DGEBA and cured with 4,4′-diaminodiphenylsulfone (DDS), the cured epoxy shows excellent balanced properties. At 20 wt% FCTE loading, the cured mixed epoxy shows a tensile strength and impact strength of 82.5 MPa and 30.5 kJ/m2, respectively, which are higher than those of TGDDM (76.5 MPa and 11.6 kJ/m2). Molecular simulation, PALS measurement, and TMA characterization suggest that the improved mechanical properties could be related to the marginal side reactions and larger free volume. The introduced fluorine-containing units also lead to better water resistance and lower dielectric constant compared with TGDDM. Despite a marginal drop in Tg, thermal degradation temperature is greatly improved. In addition, when FCTE is used as the matrix for a polyimide fiber reinforced composite, the interlaminar shear strength is also higher, making it a better candidate for preparing high temperature, light weight, and low-k composites.

Studying the Possibility of Obtaining High-Temperature Composites via Mechanochemical and Electron-Beam Treatment

Mechanochemical and electron-beam treatment allow new high-temperature composites to be obtained faster and with less consumption of energy. Model experiments on obtaining the high-temperature composite materials are performed using a combination of tungsten and titanium diboride powders.

Investigation of the Microstructure and Mechanical Properties of Copper-Graphite Composites Reinforced with Single-Crystal α-Al₂O₃ Fibres by Hot Isostatic Pressing.

Single-crystal α-Al2O3 fibres can be utilized as a novel reinforcement in high-temperature composites owing to their high elastic modulus, chemical and thermal stability. Unlike non-oxide fibres and polycrystalline alumina fibres, high-temperature oxidation and polycrystalline particles boundary growth will not occur for single-crystal α-Al2O3 fibres. In this work, single-crystal α-Al2O3 whiskers and Al2O3 particles synergistic reinforced copper-graphite composites were fabricated by mechanical alloying and hot isostatic pressing techniques. The phase compositions, microstructures, and fracture morphologies of the composites were investigated using X-ray diffraction, a scanning electron microscope equipped with an X-ray energy-dispersive spectrometer (EDS), an electron probe microscopic analysis equipped with wavelength-dispersive spectrometer, and a transmission electron microscope equipped with EDS. The mechanical properties have been measured by a micro-hardness tester and electronic universal testing machine. The results show that the reinforcements were unevenly distributed in the matrix with the increase of their content and there were some micro-cracks located at the interface between the reinforcement and the matrix. With the increase of the Al2O3 whisker content, the compressive strength of the composites first increased and then decreased, while the hardness decreased. The fracture and strengthening mechanisms of the composite materials were explored on the basis of the structure and composition of the composites through the formation and function of the interface. The main strengthening mechanism in the composites was fine grain strengthening and solid solution strengthening. The fracture type of the composites was brittle fracture.

Multi-scale modeling of thermo-oxidation effects on the flexural behavior of cross-ply bismaleimide composites

Mechanical properties of high-temperature polymer matrix composites deteriorate during their service. Oxidation plays a significant role in determining the residual elastic and strength properties of the composite. The present work investigates the oxidative aging damage of cross-ply bismaleimide composites, both experimentally and numerically. Also, this work introduces a better understanding of the significant damage mechanisms, and their respective time ranges. Micro/macro-scale thermo-oxidation behavior and flexural failure were simulated for 1,700 hours of aging. Thermo-oxidation behavior of the cross-ply laminates was simulated using a multi-fiber multi-layer representative volume element. Thermo-oxidation is a diffusion–reaction phenomenon that depends on temperature and oxidation state in time and space domains. In this work, the proportionality between oxidation state evolution and reaction rate was modeled using a new form of time-dependent parameter. Owing to aging damage, the required properties for the flexural test simulation were reduced in the meso-scale. The current study presents a damage state assuming proportionality between the average crack length and oxidized layer thickness based on a continuum damage mechanics approach. Scanning electron micrographs showed that the onset of the “blunt” transverse (through-thickness) micro-cracking/debonding in the superficial layers was at 500 hours under $176.7~{}^{\circ}\mbox{C}$ ( $350~^{\circ}\mbox{F}$ ), where oxidative cracking dominates aging mechanisms. The “blunt” micro-cracks propagated in the transverse direction near 1000 hours rendering the crack faces in contact with the oxidative air. After about 1,700 hours of aging, the weight loss ratio was 0.5%, and the flexural modulus and strength reduced by 19% and 10%, respectively. Prior to 500 hours, where cracking was not noticeable in the “crack-free region”, the strengths reduction was not significant based on the numerical simulations. In the crack-free and oxidative damage dominated regions, the elastic property numerical reduction was significant.

On the Oxidative Ablation and Mechanical Properties of T300 Carbon Fibers at Elevated Temperatures

Abstract Carbon fibers are the main component and load carrier within many high-temperature composites. Oxidative ablation of carbon fibers is the main failure mechanism of high-temperature composites and significantly affects the mechanical properties of the composites. The effects of the ablation of carbon fiber at high temperatures on carbon fiber mechanical properties, nevertheless, have not been systematically studied in the available literature. In the present investigation, the oxidative ablation behavior of carbon fibers from room temperature to 900°C has been systematically investigated by employing a thermogravimetric analyzer and in situ video detection. Detectable carbon fiber weight loss was initiated when the temperature was elevated to 600°C within the air environment. The video images showed that the color of the carbon fiber surfaces changed dramatically and then the fibers disappeared gradually, indicating that the carbon fibers underwent a chemical reaction, i.e., oxidative ablation. The static mechanical strength of carbon fiber at various temperatures was investigated and was found to start decreasing significantly at temperatures above 500°C, even though no obvious oxidative ablation occurred. X-ray photoelectron spectroscopy (XPS) and Raman spectrum reveal that the microstructure transition from graphite to nongraphite carbon is the main reason for strength reduction.

ICP-AES DETERMINATION OF ALLOYING ELEMENTS IN Nb – Si BASED COMPOSITES

At present, high-temperature composites of the Nb-Si-system are the most promising for use as High-temperature composites of Nb – Si-system are among the most promising materials to be used as heat-resistant structural materials and as an alternative to high- temperature nickel-based alloys that have largely exhausted their ability to increase the operating temperature. The next generation of high-temperature materials for casting blades of gas turbine engines should provide a temperature of about 1350°C or higher which can significantly improve the efficiency of engines and contribute to their environmental performance. Nb – Si composites are obtained by traditional methods of ingot production and powder metallurgy. Statutory regulations impose heavy demands on the chemical composition of aviation materials used for manufacturing heavy-duty parts of gas turbine engines. We present a technique for determination of the alloying elements Si, Ti, W, Mo, Hf, Cr, and Al in advanced high-temperature Nb – Si based composite materials (CM) using inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and microwave sample preparation. Conditions of sample dissolution, method of calibration line construction, and analytical lines free of significant spectral overlapping are specified to determine all the alloying elements of Nb – Si-based composites. To assess the metrological characteristics of the developed technique we used model solutions of Nb – Si composites prepared from state standard reference sample of solutions of ions of the elements. The repeatability of the technique does not exceed 1% rel., the intermediate precision does not exceed 3% rel.