Thermal Mechanical Behavior Research Articles

Effect of sintering temperature and aluminium addition on thermal stability, micrographic features, and mechanical properties of Fe-Ni based ODS alloys

In the present study, effects of titanium (Ti) and Ti+aluminium (Al) addition have been investigated on thermal stability and mechanical behaviour of Fe-42 wt% Ni-2 wt% Y2O3-X (X = Ti, Ti+Al) alloys. Accordingly, Fe-42 wt% Ni-2 wt% Y2O3-2 wt% Ti (2Ti), and Fe-42 wt% Ni-2 wt% Y2O3-2 wt% Ti-2 wt% Al (2AlTi) compositions were prepared through mechanical alloying followed by spark plasma sintering (SPS) at 1050 & 1100 °C. The sintered 2Ti alloy resulted in a huge grain coarsening (1815 nm) in contrast to the 2AlTi alloy sample (av. grain size 441 nm) sintered under same condition (1100 °C). Correspondingly, mechanical properties of the 2AlTi alloy found to be much superior (hardness-5.1 GPa, compressive yield strength-1075 MPa) to that of the 2Ti sample (hardness-3.6 GPa, compressive yield strength-580 MPa). Strengthening mechanisms analysis confirmed that the superior mechanical properties are attributed mainly to the grain boundary hardening (because of ultrafine matrix grains) and dispersion strengthening (due to the evolution of greater amount of nanosize complex dispersoids in the 2AlTi alloy). The experimental compressive strength properties were validated with simulated compression test data generated through the FE method. Barrelling effect due to the compression loading is compared and correlated with the FE-simulated data.

The effects of atomic percentage and size of Zinc nanoparticles, and atomic porosity on thermal and mechanical properties of reinforced calcium phosphate cement by molecular dynamics simulation

This study used the molecular dynamics (MD) simulation method to assess the effects of different percentages of NPs, sizes, and percentages of porosity on reinforced cement thermal behavior (TB) and mechanical behavior (MB) of samples. The temperature and kinetic energy (KE) converged to 300 K and 35.42 eV after 10 ns, which indicated the thermodynamic equilibrium and the atomic stability in the structures. Increasing the NPs percentage from 1% to 3% increased the maximum temperature from 1364 to 1405 K. By further increasing it to 5%, it was reduced to 1361 K. As the radius of Zn NPs increased to 16 Å, the ultimate strength (US) and Young's Modulus (YM) increased from 1.07 to 0.19 MPa to 1.2 and 0.22 MPa. The increase in the NPs' radius to 16 Å caused an increase in the maximum temperature from 1405 to 1455 K, maintaining atomic stability. As the porosity increased from 1% to 5%, the US and YM reduced from 0.91 to 0.17 MPa to 0.81 and 0.15 MPa. As the porosity increased from 1% to 5%, the maximum temperature was reduced from 1400 K to 1384 K. According to the results, Zn NPs' percentage and size effectively improved the MB of the final cement.

Effect of incorporating Expanded polystyrene beads on Thermophysical, mechanical properties and life cycle analysis of lightweight earth blocks

The excessive consumption of energy used for ensuring the indoor thermal comfort of buildings has led to a rise in the economic and environmental impacts of the construction sector. On the other hand, one of the most important challenges for future constructions is reducing energy consumption, which is why the scientific community is working on developing lightweight, insulating, environmentally friendly building materials.The main purpose of this investigation is to study lightweight blocks (LWB) made from raw earth, stabilized with lime, and mixed with Expanded Polystyrene (ESP). In this context, the study evaluates the effects of the incorporation of different contents of EPS beads (0, 40, 45, 50, 55, 60, 65% by volume) on the thermal properties, mechanical behavior and life cycle assessment of lightweight earth blocks. The results show that incorporating EPS beads improves the thermal insulation performance by an estimated 47.19% and 57.36% at a content of 40% and 65% of EPS beads, respectively, compared with control samples (without EPS beads). On the other hand, the results indicate a decrease in flexural and compressive strengths by an estimated 90.50% and 96.59%, respectively, for the sample containing 65% of EPS beads compared with reference samples. However, when compared to the reference samples, the findings of the curves of stress–strain revealed that the incorporation of the EPS beads improved the ductility of the lightweight blocks. Moreover, the life-cycle analysis of walls made of lightweight 65% EPS beads showed a decrease in the energy required and the effect of greenhouse CO2 with an estimated value of 19.82% and 15.86%, respectively, compared to conventional air blade walls.

Static and dynamic mechanical analyses of E-glass–polyester composite used in mass transit system

Composite materials have distinct properties such as a high strength-to-weight ratio, high corrosion resistance, a high modulus-to-weight ratio and wear resistance. The potential, strong mechanical properties and lower cost of E-glass fiber motivated the authors to carry out this work. Tensile, flexural and Izod impact tests were used in the current study to conduct a static analysis of an E-glass-reinforced isophthalic polyester composite and an E-glass-reinforced general-purpose (GP) or orthophthalic polyester composite. The thermal–mechanical behavior was investigated using thermogravimetric analysis and dynamic mechanical analysis tests. Furthermore, the surface morphology of the tested composites was examined using scanning electron microscopy (SEM). When compared with the E-glass-reinforced GP polyester composite, the E-glass–isophthalic polyester composite demonstrated superior flexural properties and thermal stability. However, the tensile and impact properties of the E-glass–GP polyester composite were found to be higher than those of the E-glass–isophthalic polyester composite. SEM images show fiber pullout, matrix cracking and fiber breakage, among other things. The loss modulus and damping values of the E-glass-reinforced GP polyester composite were found to be greater than those of the E-glass-reinforced isophthalic polyester composite. The current composite can be used in marine applications, particularly the hull frame or body of the boat.

Effects of the mesostructures and irradiation conditions on the thermo-mechanical coupling behaviors in LWR-used fully ceramic-microencapsulated fuel pellets

Fully ceramic microencapsulated (FCMTM) fuels, proposed as an accident tolerant fuel in light water reactors (LWRs), consists of tri-structural isotropic (TRISO) fuel particles and silicon-carbide ceramic matrix. To ensure the in-pile service safety with improving the fuel economy simultaneously, FCM fuels should be optimally designed. The effects of TRISO particle volume fraction, particle distribution pattern and irradiation conditions on the thermal-mechanical behavior in FCM fuel pellets are investigated via the self-developed code TMAIMF(Thermo-mechanical Analysis of Inert Matrix Fuels). The evolution results of temperature, deformation and stress fields with the increase of burnup indicates that (1) when the particle volume fraction increases from ∼15% to ∼43%, the central temperature gives a rise of ∼10% at 19% FIMA (fissions per initial heavy metal atoms); the radial size increment will be shortened; while, the maximum tensile stresses of each coating layer of the TRISO particles are slightly varied; (2) the results of temperature, deformation and maximum tensile stress have weak correlations with the fuel particle distribution pattern; (3) the integrity of FCM pellets can be maintained at high fission rate conditions and extended burnup levels; (4) the finite element models with the axial displacement constrained are representative, which can obtain more conservative analysis results than the free-end models. The numerical simulation results demonstrate that the TRISO-particle-based fuel pellets could be flexibly optimized to satisfy the demands of economy and safety.

Synthesis of a Multielement Flame Retardant and Its Application in Epoxy Resin

For the purpose of obtaining flame-retardant epoxy resin (FREP) with exceptional comprehensive properties, a multielement flame retardant SVPM was synthesized by sulfathiazole, 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), methylvinyldichlorosilane and vanillin. The effects of SVPM on the thermal stability, heat resistance, mechanical behavior and flame retardancy of epoxy resin (EP) were systematically revealed, and the flame-retardant mechanism of SVPM was deeply explored. In the presence of only 0.12 wt% phosphorus content in the system, FREP achieved V-0 rating of vertical combustion (UL-94) and the limiting oxygen index (LOI) value reached 31.1%. Additionally, SVPM reduced the smoke and heat release of EP. The mechanical properties of EP were enhanced by SVPM; specifically, the maximum increment of tensile strength and flexural strength of FREP were 26.23% and 16.67% respectively. The investigation of flame-retardant mechanism showed that the phosphorus-containing free radicals and SO2 decomposed by SVPM can quench the active free radicals in the combustion process, thus interrupting the chain reaction of combustion, and the noncombustible gas generated by SVPM during combustion can reduce the concentration of combustible volatiles. In the condensation phase, phosphoric acid and silicon dioxide produced by SVPM degradation can promote the stability and densification of the char layer, eventually effectively reducing the combustion intensity.

Nonlinear dynamic thermal-mechanical behaviors of framed structures under temperature variations

An abnormal change in dynamic characteristics is considered an indicator of structural damage and can help the optimal design of structures suffering from dynamic loads, but these characteristics are also affected by ambient temperature. Therefore, a novel advanced computational method based on the fiber-based approach is proposed for the first time to predict the nonlinear dynamic behaviors of frames under environmental temperature changes with linear and nonlinear profiles by using Fortran programming language. The cross-section will be divided into a matrix of fibers, and by assigning the different temperatures to each fiber, all linear and nonlinear temperature gradients in both vertical and horizontal directions will be operated. The material nonlinearity is traced by the distributed plasticity model using the same mesh as the fiber-based approach whereas the effects of geometric nonlinearity due to member curvature and member chord rotation are considered by using the stability functions and a geometric matrix, respectively. A sequential nonlinear thermal incremental-iterative solution scheme based on the Newton-Raphson algorithm and Newmark-β method is also developed to address the nonlinear dynamic problems due to temperature variations. The accuracy and computational performance of the proposed method are validated by comparing the obtained results with those from experiments and the Abaqus. Results obtained show that the proposed method is exact for the nonlinear inelastic dynamic thermo-mechanical analysis of framed structures. It would offer a tool for thermal-structural design practice instead of using time and cost-consuming commercial software.

Thermal Stability and Mechanical Behavior of Ultrafine-Grained Titanium with Different Impurity Content

Ultrafine-grained (UFG) commercially pure (Ti Grade 2) and high-purity (Ti 99.99%) titanium can be a good alternative to less biocompatible Ti alloys in many biomedical applications. Their severe plastic deformation may lead to a substantial increase of strength, but their highly refined microstructure show a lower thermal stability which may limit their range of applications. The purpose of this study was to investigate the effect of interstitial elements on the thermal stability of UFG Ti Grade 2 and high-purity Ti 99.99% processed by a multi-pass cold rolling to the total thickness reduction of 90%. The severely cold rolled Ti sheets were annealed at temperature in the range of 100-600 °C for 1 h and, subsequently, they were evaluated in terms of microstructure stability, mechanical performance as well as heat effects measured by differential scanning calorimetry (DSC). It was found that the microstructure and mechanical properties were relatively stable up to 200 and 400 °C in the case of UFG Ti 99.99% and Ti Grade 2, respectively. DSC measurements confirmed the aforementioned results about lower temperature of recovery and recrystallization processes in the high-purity titanium. Surprisingly, the discontinuous yielding phenomenon occurred in both investigated materials after annealing above their thermal stability range, which was further discussed based on their microstructural characteristics. Additionally, the so-called hardening by annealing effect was observed within their thermal stability range (i.e., at 100-400 °C for UFG Ti Grade 2 and 100 °C for UFG Ti 99.99%).

CALPHAD-aided design for superior thermal stability and mechanical behavior in a TiZrHfNb refractory high-entropy alloy

TiZrHfNbTa refractory high-entropy alloys (RHEAs) are now at the research frontier of advanced metallic materials due to their exceptional mechanical performance, particularly at high temperatures. However, the TiZrHfNbTa RHEAs exhibit poor phase stability at intermediate temperatures (600 – 1,000 °C). The present study aimed to tailor their phase stability and mechanical properties via the calculation of phase diagrams (CALPHAD) approach. We found that Ta and Hf were detrimental to the phase stability of the TiZrHfNbTa RHEAs. Accordingly, a Ta-free and Hf-depleted Ti30Zr30Hf16Nb24 RHEA with outstanding phase stability was designed, which could remain a single-phase body-centered cubic (BCC) structure after annealing at 600 °C for 200 h. Furthermore, numerous (Ti, Zr)-rich nano-precipitates were dispersedly formed in the cold-rolled plus recrystallization-annealed (CR+A) Ti30Zr30Hf16Nb24 RHEA. The nano-precipitates controlled by the spinodal decomposition mechanism had an identical BCC lattice. The lattice fringes with (11¯0) Miller indices bent from the matrix phase to the nano-precipitates, causing a strong local strain field near the phase boundaries. The CR+A alloy possessed a yield strength of ∼ 800 MPa and tensile fracture elongation of ∼ 34.0%, showing a superior strength-ductility combination. The strain measurement by a digital image correlation indicated that the CR+A alloy exhibited a more substantial plastic stability than the as-cast alloy. Detailed observations of deformation microstructures through a transmission electron microscope and electron back-scattered diffraction revealed the origin of strength and ductility. Dislocation cross-slip and kink bands tended to form in the CR+A alloy during deformation and were capable of accommodating dislocation slip against stress concentration. Labusch's model uncovered that solid-solution strengthening contributed the most to yield strength. The present study provides a paradigm for the superior thermostability and controllable nanophase-precipitation behavior in RHEAs.

Computational Modeling and Parametric Analysis of SMA Hybrid Composite Plates under Thermal Environment.

This paper presents a coupled thermoelastic finite element formulation for static and dynamic analysis of composite laminated plates with embedded active shape memory alloy (SMA) wires, which accounts for both the phase transformation and the nonlinearity effects of SMA wires. The equations of motion are obtained by using Hamilton's principle and first-order shear deformation theory (FSDT). Furthermore, based on Brinson's one-dimensional phase transformation constitutive law, a novel coupled thermoelastic finite element model that enables analysis of the SMA hybrid composite (SMAHC) plate is developed. The accuracy and efficiency of the developed computational model for analysis of SMAHC plates are reinforced by comparing theoretical predictions with data available from the literature. The results of the numerical examples also show the ability of the proposed model to predict the thermal-mechanical behavior of SMAHC plates in accordance with SMA's hysteresis behavior. In addition, based on the proposed model, the influence of temperature as well as SMA volume fraction, pre-strain value, boundary condition and layup sequence on the static bending and free vibration behavior of the SMAHC plates is investigated in detail. The results of parametric analysis show that the variations of both static deflection and natural frequency of the SMAHC plate over temperature exhibit a nonmonotonic behavior.

Thermal Adsorption and Mechanical Behaviour of Polypropylene Hybrid Composite Synthesized by Glass/Hemp Fibre via an Injection Moulding Process

Thermoplastic-based polymers are gathering importance in several engineering fields like electrical, electronic, automotive, aerospace, and structural. The additions of secondary phase reinforcements such as natural and synthetic fibre improve thermoplastic-based polymer’s properties. The thermoplastic and natural fibre combinations are found to have low mechanical strength and incompatibility and need special treatment for synthesizing the natural fibre. The present experimental investigation deals with the enhancement of polypropylene hybrid composite by using the combinations of glass (synthetic)/hemp (natural) fibre for the ratio of 0 : 35, 5 : 30, 10 : 25, and 15 : 20 reinforced with 5 wt% compatibilizer through injection moulding. The revealed test results of polypropylene hybrid composite showed improved mechanical impact and flexural and tensile strength of 37.5%, 14.2%, and 21.1%, respectively. The thermal adsorption characteristics were evaluated by thermogravimetric analysis apparatus. It showed the decomposition of composite limited by hemp fibre at 27°C to 700°C.

On the thermal hydro mechanical chemical behavior of bentonite sand mixture

The concept to high-level radioactive waste (HLW) repository generally involves anengineering-artificial barrier system, in which hardly compacted bentonite sand mixture blocks are placed carefully around the waste canister, and the canister is of stiffness in the design. Placed the bentonite sandmixture blocks, gradually receive hydration due to groundwater. Thermal-hydraulic-mechanical-chemical phenomena of compacted bentonite sand mixture after wetting, suction change and thermal effort are a critical parameter for buffered system This study proposes the influence of suction, relative humidity and thermal effort in thermal-hydraulic on deformation properties and mechanical properties for bentonite-sand mixture. A series of testing programs are prepared such as calibration test for changing of relative humiditywith temperatures, measurement of volume change involving heating and changing of suction, determination of unconfined compressive strength, for thermal performance triaxial compression tests for both unsaturated bentonite sand mixture and saturated bentonite sand mixture. The obtained results are further interesting, and summary provide as following. To suction increment incorporation with thermal heating produce induces obviously shrinkage of the bentonite sand mixture, and lead the decrement of strength. Elevated temperature confirm further reduction for maximum deviator stress using a developed triaxial compression apparatus that is regardless of unsaturated condition and saturated condition.

Evaluation of Thermal Adsorption and Mechanical Behaviour of Intralaminar Jute/Sisal/E-Glass Fibre-Bonded Epoxy Hybrid Composite as an Insulator

A thermal gravimetric analyzer analyzed the thermal adsorption properties of developed composites with the temperature range of 28°C–650°C at a 20°C/min constant heat flow rate. The epoxy hybrid composites were synthesized using natural jute/sisal fibre hybridized with the addition of synthetic E-glass fibres at 0-degree, 0/90-degree, and intralaminar orientations through the wet filament-winding process. The effects of orientations on tensile, flexural, and impact strengths of epoxy hybrid composites were studied using ASTM D3039, D790, and D6110. The evaluated results were compared, and the epoxy hybrid composite containing intralaminar orientations found better thermal stability with reduced weight loss at 650°C. Similarly, the test result for mechanical studies of the hybrid composite showed superior tensile, flexural, and impact strengths. The epoxy hybrid composite with intralaminar orientation was found to have a maximum tensile, impact, and flexural strength of 61.91 MPa, 770.61 J/m, and 83.90 MPa, respectively.

Development of PWR lower head failure model for severe accident analysis

Under the in-vessel retention (IVR) scenario, the lower head is loaded by the deadweight of melt and the vessel, the internal pressure, and the temperature field. This thermo-mechanical load will destroy the integrity of the reactor pressure vessel (RPV). The failure of the lower head indicates that the in-vessel accident progression has entered the final stage. If the failure occurs, its location and time have to be evaluated. However, most severe accident analysis codes judge RPV failures based on simple parametric models, which cannot accurately predict the failure time, modes, and locations. In this paper, the LHTMB (Lower Head Thermal-Mechanical Behavior) analysis module is developed to analyze the thermal–mechanical behavior of lower head by referring to the generalized Hooke’s Law, and combined with various failure criteria to judge RPV rupture. The module consists of three parts: thermal–mechanical behavior, failure judgment, and format output. The LHTMB module was verified by the OLHF-1 experiment data and numerical simulation results. The mechanical results show that creep rate is usually highest at the location where the lower head is most prone to failure. Comparison of various failure criteria shows that RPV failure can be determined with high confidence when Larson-Miller life fraction and Hedl-Dorn parameter criteria are satisfied.

Structure and properties of new biodegradable elastomers composed of poly(ethylene succinate)‐based poly(ether ester)s and poly(lactic acid)

AbstractThe green sustainability of the plastic industry always gives impetus to develop the biobased and biodegradable polymers for substituting chemical products. In this study, aliphatic poly(ethylene succinate)‐based poly(ether ester)s (PES‐based PEE) were firstly explored via one pot/two‐component industrial melt polycondensation of succinic acid (SA) and ethylene glycol (EG) in the catalytic combination of titanium tetraisopropoxide (TTP) and methylsulfonic acid (MSA). Their thermal properties and mechanical behavior were analyzed in detail. Based on complementary properties of PES‐based PEEs and poly(lactic acid) (PLA) in the aspect of the flexibility and ductility, the copolymerization of poly(ethylene succinate)‐poly(diethylene glycol succinate) (PES‐PDES) with PLA with low molecular weight was further systematically elaborated and characterized. The results from differential scanning calorimeter showed all the copolymers with different LA contents were amorphous without the melting temperatures. Only oneαrelaxation revealed by DMA indicated PES‐PDES and PLA segments were random distribution and compatible. The monotonical decrease in glass transition temperatures (Tgs) hinted the mobility enhancement of the copolymers with increasing PES‐PDES contents. All the copolymers PES‐PDES‐PLAs exhibited relatively high thermal degradation temperature withT5%above 280°C. The mechanical properties and degradable behavior of the copolymers were significantly ameliorated by changing the composition fractions of PES‐PDES and PLA in the architecture.

Improved Thermal and Mechanical Properties of [Ca24Al28O64]4+(4e−) Electride Ceramic by Adding Mo Metal

The low‐work function material [Ca24Al28O64]4+(4e−)—named as C12A7:e‐ or electride—is a promising candidate to replace established materials such as BaO–W or LaB6 electron emitters because of its good reported electron emission in plasma environments and decent chemical inertness. However, it has poor thermal conductivity and low mechanical behavior. Therefore, cracks due to thermal shock occur in applications under thermal load, when used as a thermionic emitter. The addition of a metal with high thermal conductivity to create a ceramic–metal composite (CerMet) is evident. Molybdenum has a very high thermal conductivity and a coefficient of thermal expansion comparable to C12A7:e‐. This allows the crack‐free sintering of a composite ceramic made of C12A7:e‐ and Mo with improved thermal and mechanical properties as well as still low work function of the C12A7:e‐. Herein, the C12A7:e‐/Mo CerMets are characterized in terms of their thermal conductivity, thermal expansion coefficient (CTE), hardness, toughness K1C, and strength as a function of Mo content. The CerMets have been tested in a plasma‐based cathode with disk‐shaped emitters for electron emission characteristics. An optimal range of the Mo content for the stability of the plasma discharge and the required discharge potential has been evaluated.

Reinforced Calcium phosphate cements with zinc by changes in initial properties: A molecular dynamics simulation

Calcium phosphate cement (CPC) has wide applications in medicine and dentistry, such as dental pulp coating, tooth root canal sealant, bone tissue engineering scaffolds, drug release systems, bone defect restoration, etc. Zinc nanoparticles, on the other hand, have special qualities that cause to provide the initial strength in CPC. The influence of starting temperature and beginning pressure on the thermal behavior (TB) and mechanical behavior (MB) of reinforced CPC was examined in this work using a molecular dynamics (MD) simulation. So, it was investigated how properties like temperature stability, Young's modulus, and ultimate strength changed. The mechanical stability of the simulated structure decreases from 300 K to 400 K at the starting temperature. In actuality, the force of absorption between the simulated structures has reduced as the temperature of the samples has risen. Additionally, the findings demonstrated that the US and YM underwent a downward trend and declined from 1.07 to 0.19 MPa to 0.89 and 0.16 MPa, respectively, when the starting temperature increased from 300 to 400 K. As a result, increasing the initial pressure reduces the inter-atomic distance in the reinforced matrix, and finally, cement particles absorb each other with a greater force.

Thermal mechanical behavior of energy piles with cap under embedded depth

Using energy piles with cap foundations under 3.0 m of backfill, four tests with different heat exchanger tube types (U&W) and operation modes (continuous and intermittent heating) were carried out. The temperature and stress changes of the energy pile and its adjacent structures were measured, and the experimental results were compared with those without buried depth conditions. The heat exchange rate per pile length with W-type heat exchanger tubes was approximately 1.39 times that with U-type tubes. The heat exchange rate per pile length during intermittent heating operation was approximately 1.30 times that during continuous heating operation. The overlying backfill showed a certain insulation effect, and the heat exchange rate per pile length was approximately 1.13 times that without burial. The soil above the pile was less susceptible to seasonal variations, and after 192 h of heating, the temperature rise at the pile top under the 3.0 m of backfill was 5.10 °C less than that without burial. The overlying 3 m of backfill also exhibited some restraining effects: this inhibited the thermal relative displacement of the pile top, with thermal expansion coefficients of 0.027 mm/°C and 0.037 mm/°C with and without burial, respectively. The corresponding thermal dissipation coefficients were 2.55 °C/m and 3.43 °C/m. The null point appeared at 0.78 times the pile length, and there were slight differential deformations in the cap with/without burial.

A DFT Characterization of Structural, Mechanical, and Thermodynamic Properties of Ag9In4 Binary Intermetallic Compound

The intermetallic compounds (IMCs) at the interface between the solder joint and metal bond pad/under bump metallization (UBM) exert a significant impact on the thermal–mechanical behavior of microelectronic packages because of their unique physical properties. In this study, a theoretical investigation of the physical properties, namely structural, mechanical, and thermodynamic properties, of the Ag9In4 IMC was conducted using ab initio density functional theory (DFT) calculations. The calculated equilibrium lattice constants were in good agreement with the literature experimental data. Furthermore, with the calculated elastic constants, we can derive the ductility and brittleness nature, elastic anisotropy, and direction-dependent elastic properties of Ag9In4 through several elastic indices, three-dimensional surface representation, and two-dimensional projections of elastic properties. The calculations inferred that the cubic Ag9In4 IMC confers structural and mechanical stability, ductility, relative low stiffness and hardness, and elastic anisotropy. Finally, the thermodynamic properties, i.e., Debye temperature, heat capacity, and minimum thermal conductivity, were also investigated. Evidently, the low-temperature heat capacity conforms to the Debye heat capacity theory and the high-temperature one complies with the classical Dulong–Petit law.

Interfacial heat transfer characteristics and thermal expansion behavior of heterostructure materials in arc-heated wind tunnel

Structural ceramics such as carbon fiber reinforced silicon carbide (C/SiC) are of great importance for supersonic aircraft, where thermal-mechanical coupling behavior of materials affects the service performance of structural ceramics. In order to advance the understanding of the high temperature thermal-mechanical coupling behavior of heterostructure materials (one typical type of structural ceramics), we adopted here an optical observation system to visualize the variation of the gap width between heterostructure materials in arc-heated wind tunnel test. The variation of the gap width (decreasing and then volatility increasing) was observed during the test. Numerical simulation shows that thermal conduction and thermal expansion between the substrate and specimens play a critical role in the evolution of the gap width, as evidenced by the experiments. Additionally, the variation of the gap width under various conditions was given and a one-dimensional unsteady thermodynamic model of double-layer plate was established to reveal the gap evolution mechanism of heterostructure materials. The results of theoretical model agree well with numerical simulation.