Composites For High-temperature Applications Research Articles

Bonding properties of C/C composites based on polyborosilazane ceramic precursor films

Liquid polyborosilazane, solid polyborosilazane, Si, and Sb2O3 were used as inorganic fillers to prepare low-temperature-cured and high-temperature-applicable polyborosilazane adhesive films. The mechanical properties of the bonded C/C composites were tested at 25 °C after treatment at different temperatures from room temperature to 1400 °C. The results showed that the addition of Sb2O3 significantly improved the mechanical properties of the adhesive, which was mainly due to the formation of borosilicate glass in the high-temperature melting decomposition system of Sb2O3, and the oxidation produced volume compensation. The shear strength of the bonded specimens gradually decreased from 12 MPa at curing to 4.18 MPa at 600 °C; then it increased up to 8.06 MPa at 1000 °C. When the temperature exceeds 1000 °C, the value decreases again. In general, the bonding strength of C/C composites at 1200 °C remains above 4 MPa. The adhesion strength of Si-modified polyborosilazane adhesive film was 4.88 MPa at 1000 °C, indicating that it should be suitable for joining C/C composites for high-temperature applications.

Low radiative heat transfer realized by 8YSZ/LaAl11O18 composites for high-temperature applications

Low radiative heat transfer realized by 8YSZ/LaAl11O18 composites for high-temperature applications

Manufacturing and mechanical properties of phenol Formaldehyde- Polyacrylonitrile based carbon composites for thermal protection system

The polymeric composite materials are a conventional solution to thermal protection that has been used to shield re-entry spacecraft. This paper presents the thermo- mechanical properties of polyacrylonitrile (PAN) based carbon fiber (Cf) reinforced with phenol formaldehyde resin (PR) composites for high temperature applications of thermal protection system (TPS). The Cf-PR composite laminates were made using the hand-layup method with a curing temperature of 150 °C and a weight of 100 kg/cm2 for 4 h in a hydraulic hot press machine. The composition and microstructure of Cf-PR composite laminates were determined using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The mechanical properties of bar coal hardness were determined, including interlaminar shear stress (ILSS). The density was one of the physical properties that was examined. The thermo-mechanical properties of TPS for re-entry space vehicles were proved to be responsible for their high strength and high temperature applications.

A comparative study on the effect of carbon-based and ceramic additives on the properties of fiber reinforced polymer matrix composites for high temperature applications

Ablative composites have been in use for thermal protection of space vehicles for decades. Carbon-phenolic composites have proven to perform exceptionally well in these applications. However with development in aerospace industry their performance needs improvement. In this field, different carbon-based and ceramic additives have been introduced into ablative composite systems. This review article gives a comparative analysis of researches done in this field in the recent past. Density, ablative, thermal and mechanical properties of ablative composites with different ultra-high temperature ceramic particles i.e. ZrSi 2 , Cenosphere, nano-SiO 2 , BN etc. and carbon-based nanoparticles i.e. CNTs, nano-Diamonds, Graphene oxide etc. used as additives, have been compared and discussed. Emphasis is put on carbon-phenolic composite systems although some epoxy matrix systems have also been discussed for comparison.

Online Cure Monitoring and Modelling of Cyanate Ester-Based Composites for High Temperature Applications.

A cure kinetics investigation of a high temperature-resistant phenol novolac cyanate ester toughened with polyether sulfone (CE-PES blend) was undertaken using non-isothermal differential scanning calorimetry. Thin ply carbon fiber prepreg, based on the CE-PES formulation, was fabricated, and plates for further in-situ cure monitoring were manufactured using automated fiber placement. Online monitoring of the curing behavior utilizing Optimold sensors and Online Resin State software from Synthesites was carried out. The estimation of the glass transition temperature and degree of cure allowed us to compare real time data with the calculated parameters of the CE-PES formulation. Alongside a good agreement between the observed online data and predicted model, the excellent performance of the developed sensors at temperatures above 260 °C was also demonstrated.

Highly Anti-Oxidized Ti-4Mo Alloy With Two-Scale Network Architectured Ti <sub>5</sub>Si <sub>3</sub> Reinforcement

Titanium alloys are desirable for applications in advanced hypersonic aircraft engines and gas turbines, but currently few materials can satisfy the associated high temperature oxidation requirements. Herein, we designed and fabricated a Ti5Si3 reinforced Ti-4Mo composite with a two-scale network architecture by low energy milling and spark plasma sintering. It displays superior oxidation resistance at 800°C owing to the in-situ formation of a multi-component surface layer. This oxide layer has been revealed to have a dense grain size gradient structure that consists of an outer TiO2 oxide layer and an inner TiO2 and SiO2 mixed oxide layer with a core-shell structure, which has remarkable oxidation resistance and thermal stability. Furthermore, it was revealed that the hitherto unknown interaction between Ti5Si3 reinforcements and nitrogen during oxidation would contribute to the formation of a TiN nano-twin interface layer, which accommodates the thermal mismatch strain between oxide layer and matrix. This along with high adhesion confers excellent thermal cycling life with no cracking or spallation during long term oxidation. In this regard, the secure operating temperature can be increased to 800°C, which can provide a design pathway for a new family of titanium matrix composites for high-temperature applications.

Enhancements of mechanical properties of materials through ECAP for high temperature applications

In the recent past aerospace industries are facing great challenges in enhancing the efficiency of jet engines in order to reduce the fuel consumption. This has led to a rigorous research in the field of advanced materials especially alloys and composites for jet engines. As evident, the melting point of aluminium is much lower than engine’s operating temperature which gives an edge over for the use of alloys and composites. In hotter parts of a turbine engine, temperature rises as high as to 1800 °C. Materials like intermetallic alloys, refractory materials e.g. ceramics and composites are now being used at a wide scale. In the current study mechanical properties after grain refinement of super alloys and composites being used in aircraft engine is carried out using Equal Channel Angular Pressing (ECAP). In the current study effect of ECAP on Al-SiC composite has been mainly studied. And Al-SiC composite has been majorly used by the aircraft manufacturers in the recent Boeing aircraft 787. It is expected that the present investigation will be useful for developing super alloys and composites for high temperature applications.

Tribological analysis of hybrid aluminum matrix composites for high temperature applications

This research investigation explores the tribological performance of LM16 aluminum alloy-based Hybrid Aluminum matrix composite (HAMC). In this work is aimed to find optimum proportionality of the reinforced with Nickel coated Graphite (Ni-Gr.) and Silicon Carbide (SiC) of the Hybrid Aluminum matrix composite (HAMC) for the high-temperature applications. The stir casting technique is used for preparing the HAMC with reinforcement of Nickel coated Graphite (Ni-Gr) in weight of 2% and Silicon Carbide (SiC) varies 5% & 10% of weight into the LM16 aluminum alloy. The wear properties have been evaluated with the aid of a pin on disc apparatus and the L9 orthogonal array has been chosen for experimentation to know the impacts of process parameters like load, sliding distance, the weight percentage of hybrid reinforcements, and temperature. ANOVA is used to determine the optimum coefficient of friction (COF) and the loss of wear conditions of the HAMCs. It was found that temperature and applied load are the primary influence paraments in the tribological properties of LM 16 based Hybrid Aluminum matrix composites, the wear and coefficient of friction characteristics were studied with the help of SEM images.

Experimental assessment of damage-thermal diffusivity relationship in unidirectional fibre-reinforced composite under axial tensile test

The influence of damage on thermal properties is an important issue for the design of reliable ceramic matrix composites for high temperature applications. This work is devoted to the experimental study of this influence on SiC/SiC minicomposite. This single tow reinforced composite is appropriate to investigating the damage mechanisms and thermal behavior. Relationships between the properties of constituents (fibre/matrix/interface) and behavior of the assembly can be established. Nevertheless, the literature review showed that no experimental study has focused on the thermal behavior during mechanical tests. Lock-in thermography was used to measure the thermal diffusivity during tensile tests on minicomposites while acoustic emission technique allowed monitoring damage. In this work, it is demonstrated that the evolution of the thermal diffusivity competes favorably with acoustic emission and Young's modulus as a reliable indicator of matrix damage.

Assessment of thermo-oxidative induced chemical strain by inverse analysis of shrinkage profiles in unidirectional composites

The present paper focuses on the assessment of thermo-oxidative induced chemical strain in HTS/TACTIX carbon/epoxy Organic Matrix Composites for High Temperature Applications, by inverse analysis of shrinkage profiles in unidirectional composites. First, measurement of matrix shrinkage in composites surface is carried out by Interferometric Microscopy for virgin samples (initial state) and for samples aged under oxygen pressure and air at atmospheric pressure: then, a model based on thermodynamics with Internal Variables and ABAQUS numerical simulations carried out on unidirectional composite realistic samples are employed for inverse identification of thermo-oxidative induced chemical strain and its evolution during conditioning. The identification is performed successfully and validated against chemical shrinkage profiles developing in pure resin systems. The model is then used for calculating thermo-oxidative induced stresses related to chemical shrinkage inelastic strains and for the prediction of the observed fibre/matrix debonding scenario. A Rayleigh-Ritz method is also developed for rapid prediction of matrix shrinkage in composite materials.

High velocity impact tests on high temperature carbon-carbon composites

Abstract This paper describes the effect of high velocity impact on the structural integrity of advanced carbon-carbon (C/C) composites for high temperature applications. Impact tests have been performed on heated C/C composite samples at high temperature to establish correlations between the mechanical performances of the composites and different impact factors. Two tensile tests were also performed to investigate the residual strength of the high temperature C/C structures with the impact damage. In this work we present two new equations to predict the dimensionless damage areas of the C/C impacted at elevated temperatures. The impact resistance of the C/C composites is affected by the diameter of the projectile, the temperature and thickness of the C/C laminates and - more importantly – by the impact velocity. The residual strength of the damaged C/C composites increased by 47% after heating the samples from 25 °C to 1206 °C.

Synthesis of Titanium Oxycarbide through Carbothermal Reduction of Titanium Dioxide Nanoparticles and Renewable Biopolymers

Metal carbides are highly useful engineering materials due to their high strength, resistance to wear, and their ability to withstand various extreme temperatures. Titanium carbide (TiC) is useful on an industrial scale due to its strength retention at high temperature with a melting point of 3065°C, relatively low density (4.93g/cm-3), and resistance to corrosion. TiC is also relatively inexpensive due to the natural abundance of its precursor, titanium. Consequently, it is commonly used in the manufacture of cutting blades, grinding wheels, and various other machining tools. The most common methods for the synthesis of titanium carbide are through powder, gas phase, and sol-gel reactions at high energy. While these three procedures are effective, most commercial manufacturers use the relatively inexpensive process of carbothermal reduction of powders. In this process, titanium oxide is reduced using a carbon source and a heated environment by the following reaction, where s stands for solid and g for gas: TiO2(s) + 3C(s) = TiC(s) + 2CO(g) [1] This carbon source is usually a derivative from petroleum, which is a nonrenewable and expensive source due to high demand from the energy market. Here we assess the feasibility of using pyrolysis of a renewable biopolymer to obtain this carbon. The biopolymer composite featured in this process consists of three components: carrier, filler, and titania nanoparticles. The carrier, iota-carrageenan (IC), is extracted from seaweed and is a common polymer used in the food industry as a thickener. Commercial chitin, obtained from shrimp shells, is used as the filler. Both IC and chitin are easily available and can provide sustainable, yet inexpensive precursors. For example, current prices for a gram of iota carrageenan, chitin and activated carbon are $0.62, $0.84, and $5.23 respectively. 2.09g of titanium oxide nanoparticles were initially mixed in 30ml of ultra-pure water using a Qsonica® CL-334 sonicator for 15 minutes until a homogeneous, colloidal dispersion was obtained. A gel-like composite was subsequently created upon addition of 1g of iota-carrageenan, 4g of chitin, and another 15ml of ultra-pure water. The composite was then mixed thoroughly using a small spatula and an Omni Macro® homogenizer. The resultant biopolymer composite was loaded into a syringe and shaped into different geometries, such as a three-dimensional cube, using manual extrusion. These shapes were then subjected to high temperature treatment in a tube furnace. Although the reaction temperatures for TiC synthesis from solid powder mixtures is usually above 1700°C, the colloidal nature of the TiO2 dispersion used here was expected to lower the required temperature for reaction. Consequently, the maximum temperature of the furnace was set to 1450°C for a period of 3 hours with a heating rate of 5°C/min and a vacuum environment. The resultant sample was analyzed using X-ray diffraction (XRD) As shown in Figure 1, the XRD results show a strong presence of TiC in the sample as well as Rutile and TiO2 in smaller, but significant quantities. It should be noted that amorphous carbon was not clearly discernible in this sample. Furthermore, it was observed that the original extruded shapes of biopolymer gel were still preserved, despite significant shrinkage. These shapes were highly porous and brittle. This initial result shows the feasibility of using a colloidal dispersion of titanium oxide nanoparticles in a biopolymer matrix to manufacture titanium carbide at reduced energy requirements. This is largely due to the use of non-petroleum based precursors and lower temperatures than those used in more conventional processes. The biopolymer composite can be easily shaped through extrusion and allows for titanium carbide to be produced in complex shapes not possible through traditional methods such as powder pressing. Although isometric shrinkage occurs, the original shape is maintained. Ongoing work is on analyzing the impact of the temperature, heating time, heating rate, and furnace atmosphere on the properties, porosity, and shrinkage of the resultant material. The TiC yield must be increased to make the process more efficient and eliminate Rutile and unreacted TiO2 from the product; creating a much stronger and more versatile carbide. Figure 1: X-ray diffraction of the biopolymer composite after heat treatment of 1450°C in a vacuum environment. References Koc, R. & Folmer, J. S. “Carbothermal synthesis of titanium carbide using ultrafine titania powders”. Journal of Materials Science, 32, 3101-3111 (1996).Bae, S., et al “Synthesis of titanium carbide nanoparticles with a high specific surface area from a TiO2 core-sucrose shell precursor”. Journal of American Ceramics, 92, 2512-2516 (2009).Durlu, N., “Titanium carbide based composites for high temperature applications”. Journal of the European Ceramic Society, 2415–2419 (1999). Figure 1

An empirical approach to evaluate creep responses in polymers and polymeric composites and determination of design stresses

This study presents determination of design stresses for high temperature polymer PMR-15 and carbon fiber/PMR-15 composites. The main purpose is to support design of structural components made of polymeric composites for high temperature applications. At elevated temperatures, polymers and polymeric composites show significant creep responses. Depending on the loading conditions (stress and temperature levels) and duration of loading, both transient and steady state creep responses are observed. An empirical model that is typically used for describing transient and steady state creep behaviors for metals and alloys at elevated temperatures is adopted to model creep responses of PMR-15. The rationale behind choosing the model is that the macroscopic creep responses of PMR-15 at elevated temperature are similar to the ones of metals and alloys tested at high temperatures. This creep model has been successfully used to determine design stresses for various metals and alloys operating at elevated temperatures. In order to determine creep responses of carbon fiber/PMR-15 composites a rule of mixture approach is adopted. A design criterion, which is to limit the permanent deformation to 0.2%, is considered for both polymer and composites. The design stresses and design spaces that satisfy the above design criterion are constructed for PMR-15 polymer, unidirectional carbon/polyimide lamina and [0/90]S symmetric laminate. As expected the mechanical performance of PMR-15 can be improved by adding carbon fiber. The proposed design spaces are useful in determining the maximum capacity of the materials under various loading conditions and duration, taking into account creep behaviors in materials, during the component design process.

Thermo-oxidative induced shrinkage in Organic Matrix Composites for High Temperature Applications: Effect of fibre arrangement and oxygen pressure

The present paper focuses on thermo-oxidative induced chemical shrinkage in HTS/TACTIX carbon/epoxy Organic Matrix Composites for High Temperature Applications, providing an insight on the effect of the fibre arrangement and of the oxygen pressure as an accelerating parameter. In particular, measurement of matrix shrinkage in composites surface is carried out by Interferometric Microscopy for virgin samples (initial state) and for samples aged under oxygen pressure and air at atmospheric pressure: some discussion about the “structural” effect (arrangement of fibres, fibre volume fraction) on matrix shrinkage development of unidirectional composites is provided; a link between the measured surface matrix shrinkage and the evolution of the surface elastic indentation modulus measured in pure resin samples can be clearly established: moreover, it is shown that matrix shrinkage development in composites can be conveniently accelerated by the employment of oxygen pressure, as in pure resin systems.

Cement Composites for High Temperature Applications

Fiber reinforced composites designed for better thermal resistance, which can be used in constructions with a higher fire hazard, are studied. The matrix of studied composite is based on aluminous cement, because of its proved higher thermal resistance than ordinary Portland cement. Basalt sand is used as alternative aggregate replacing silica sand, and basalt fibers are employed for an improvement of mechanical performance. The presented analysis of basic physical properties, mechanical, hygric and thermal properties shows that basalt is an appropriate material for cement based composites for high temperature applications.

Microstructure and Thermal Expansion of Hybrid - Copper Alloy Composites Reinforced with both Tungsten and Carbon Fibres

Tungsten as refractory material and high thermal conductive carbon fibres are promising candidates for production of copper matrix composites for high temperature applications. Three types of rod-like samples were prepared by gas pressure infiltration of different carbon/tungsten fibre preforms with copper and/or copper alloy (Cu-0.5Cr) respectively. The fibres are aligned parallel to rod axis and were combined with the tungsten wire cloth. The microstructure of prepared hybrid composites was examined. The samples were thermally cycled 3 times up to 550 °C at a relatively high heating/cooling rate (10 K/min) to touch real condition in applications where high heat is formed during short time. The thermal expansion behaviour in radial direction was also analysed. Results show that a combination of both types of reinforcements in rod-shapes samples insures good protection against composite disintegration during high temperature thermal loading.

Production of net-shaped dense metal-carbide-based composites through an infiltration process at intermediate temperature

Tungsten composites are interesting materials for high temperature applications. These composites are conventionally produced by solid state reaction, where elevated temperatures and long sintering processes are inevitable, and generally produce volatile components that increase defects and impair the properties of the composites for high temperature applications. In the present paper, synthesis of dense near net-shaped transition metal–metal carbide by reaction casting is studied, which creates a potential application for the composite at 2000°C. Since the pores of the ceramic preform are filled with reaction products, this technique is referred to as displacive compensation porosity (DCP). The effects of sintering and infiltration parameters on composition of ZrC/W composites produced by DCP were studied. For this purpose, porous WC preforms were first uniaxially pressed and then sintered at 1400°C for 2h leading to preforms with various porosities (54 to 57%). Unidirectional and spontaneous infiltration of the sintered preform by ZrCu liquid was performed at 1200°C for 1, 2 and 3h. The resulting specimens were then analyzed via X-ray diffraction. Scanning electron microscopy (SEM) was used to examine the microstructure and diffusion of molten phase into porous preforms. The microstructures show that grains of the WC are being surrounded with infiltrated eutectic melt, thereby promoting reaction between the melts and the preform components. Furthermore, the extent of incorporation of ZrCu melt into the preform was investigated as a function of time. It was concluded that infiltration time has a limited influence on residual unreacted reagent and the percentage of the resulting product. On the other hand, improvement in wettability/contact angle with reduction in either particle size or presence of additive can increase the efficiency of the infiltration process.

A novel polyborosilazane for high-temperature amorphous Si–B–N–C ceramic fibres

Polyborosilazane synthesised from BCl3, HMeSiCl2, and Me3SiNHSiMe3 is easy to cross-link for dehydrogenation of Si–H and N–H, which limits its practical applications for Si–B–N–C fibres on an industrial scale. Therefore, in this context, MeSiCl3 was used instead of HMeSiCl2 to synthesise a novel polyborosilazane with limited cross-linking density to fabricate Si–B–N–C fibres. The polyborosilazane synthesised from BCl3, MeSiCl3, and Me3SiNHSiMe3 exhibits good melt-processability and 1km long polyborosilazane fibre can be obtained by melt spinning. Prior to pyrolysis, chemical curing with vapour HSiCl3 at 80°C was utilised to make the λ green fibres infusible. The as-cured fibres were subsequently pyrolyzed at 1200°C in nitrogen atmospheres to provide Si–B–N–C ceramic fibres with ca. 1.5GPa in tensile strength, ca. 160GPa in Young's modulus, ca. 12μm in diameter and keeping amorphous up to 1700°C, which makes them to be promising reinforcements in ceramic matrix composites for high temperature applications.

Oxidation resistant Mo-Mo2B-silica and Mo-Mo2B-silicate composites for high temperature applications

Development of Mo composites based on the Mo-Si-B system has been demonstrated as a possible new route to achieving a high temperature Mobased material. In this new system, the silicide phases are replaced directly with silica or other silicate materials. These composites avoid the high ductile to brittle transition temperature observed for Mo-Si-B alloys by removing the Si that exists in solid solution in Mo at equilibrium with its silicides. A variety of compositions is tested for room temperature ductility and oxidation resistance. A system based upon Mo, Mo2B, and SrO·Al2O3·(SiO2)2 is shown to possess both ductility at 80 vol.% Mo and oxidation resistance at 60 vol.%. These composites can be produced using a powder processing approach and fired to greater than 95% theoretical density with a desirable microstructure of isolated boride and silicate phases within a ductile Mo matrix.

Synthesis of molybdenum silicide/mullite composites for high-temperature applications

Molybdenum silicide/mullite composite having about 31 wt. % MoSi2 has been SHS-produced from a reactive blend composed of MoO3, SiO2, and Al. Additional amounts of silica were added to undergo mulHte formation reaction. The overall reaction involves both exothermic and endothermic ones. The endothermic mullite formation reaction is loaded onto the exothermic reaction of the reactive mixture. The effects of Al grain size (from 45 to 20 μm) and pre-heating temperature (from room temperature to 500°C) on the synthesis of the target composite were studied. Al grain size and preheating temperature were found to have decisive influence on the mullitization reaction. The sample containing 36-μm Al and ignited at 400°C was found to undergo complete mullitization reaction. The mechanism of the overall combustion reaction was postulated. In addition, oxidation resistance of this composite at 1100–1300°C in open atmosphere was determined.