Changes In Elastic Modulus Research Articles

Calculation of the elastic modulus of steel during tensile

The rational use of resources in the design of vessels and devices and ensuring their growing needs requires the performance of strength and stability calculations, which require the use of appropriate values of the modulus of elasticity during tension E. The purpose of the article is to improve the definition of the modulus of elasticity of steels during tension, the value of which is normalized by the current in Ukraine by regulatory documents. On the basis of standard tables, dot graphs of changes in modulus of elasticity of carbon, low-alloy, heat-resistant, corrosion-resistant chromium, heat-resistant and heat-resistant austenitic steels and iron-nickel-based alloys during tension E depending on temperature t were constructed and analyzed. It is proposed to approximate these dependencies with simple mathematical equations. As a result, it was determined that the dependence E = f (t) for carbon and low-alloy steels in the range of changing t from 20 oС to 300 oС is described by a simple linear equation E = – 100t + 2.01.105. When changing t from 300 oС to 450 oС inclusive, it is proposed to apply cubic regression E = – 5.33.10–3t3 + 5.2t2 – 1.827.103t + 3.95.105. In the above and further proposed formulas, the temperature t is substituted in °C, and the result is obtained in MPa. Heat-resistant and corrosion-resistant chromium steels in the temperature range t from 20 oС to 100 oС inclusive are characterized by the same modulus of elasticity during tension E = 2.15.105 MPa. The dependence of E = f (t) in the range of changing t from 100 oС to 250 oС inclusive can be described by the cubic regression E = 1.33.10–3t3 – 2.63.102t + 2.4.105, and when changing t from 250 oС to 600 oС inclusive – by cubic regression E = – 7.5.10–4t3 + 0.722t2 – 3.426.102t + 2.4748.105. The value of the modulus of elasticity during tension for heat-resistant and heat-resistant austenitic steels and iron-nickel-based alloys E = 2.15.105 MPa in the temperature range t from 20 oС to 100 oС. The dependence of E = f (t) in the range of changing t from 100 oС to 700 oС inclusive is described by the quadratic regression E = – 0.152t2 + 9.101t + 2.009.105. The obtained formulas make it possible to abandon the use of standard tables and additional interpolation of intermediate values of the modulus of elasticity of steels during tension when performing calculations, which in turn simplifies both the calculation itself and the development of appropriate computer programs. The average error value of the performed approximations is in the range from 0 % to 0.218 %, which indicates a high level of coincidence of the regression equations with the actual values. The use of the proposed formulas for calculating the modulus of elasticity of steels during tension makes it possible to simplify the calculation of vessels and devices for strength and stability.

Impact of internal pre-damage due to drying shrinkage under various humidity conditions on DEF expansion in cement paste and mortar

This study explores the impact of internal pre-damage from early drying shrinkage on the delayed ettringite formation (DEF) expansion behavior of cement-based materials subjected to high-temperature processes. Specimens of cement paste and mortar with water-cement (W/C) ratios of 0.4, 0.5, and 0.6 were characterized after curing under relative humidity (RH) conditions of 50, 70, and 100 for 56 days. The parameters assessed were drying shrinkage, dynamic elastic modulus, and free water content. Subsequent DEF expansion over time was quantified, and the underlying mechanism was analyzed using XRD and SEM techniques after 270 days of underwater curing. Results indicate that: (1) a lack of adequate early curing humidity significantly reduces the dynamic elastic modulus with more than a 10% drop in cement paste following 56 days at RH50; (2) a higher W/C ratio and lower early curing humidity lead to more internal damage due to shrinkage, thereby promoting DEF expansion; (3) drying intensifies internal pre-damage in the interfacial transition zone (ITZ), causing an earlier deterioration of DEF expansion in mortar compared to cement paste. However, the presence of aggregates constrains this, leading to lesser DEF expansion in mortar; (4) dynamic elastic modulus changes as measured by ultrasonic methods can quantitatively characterize the extent of deterioration caused by DEF expansion, thus offering a tool for non-destructive testing and DEF expansion deterioration analysis.

A molecular dynamics study on the size effects of Fe3O4 nanoparticles on the mechanical characteristics of polypyrrole/Fe3O4 nanocomposite

ABSTRACT Nanoparticle size effects on elastic properties of polymeric bio-nanocomposites were studied using atomistic molecular dynamics (MD) simulations. Spherical magnetite nanoparticles (MNPs) were placed at the centre of amorphous polypyrrole (PPy) polymer in three models with different sizes. Three models of nanocomposites with the same particle volume fractions with different sizes were considered. The Lennard-Jones 6-12 potential modelled the interface interaction between polymer and particles. Initially, the obtained mechanical properties for pristine PPy and magnetite in the bulk state showed an acceptable agreement with experimental data. Subsequently, simulation results illustrated that incorporating MNP into the PPy matrix improves the elastic modulus of the matrix by 28-58%, and more importantly, decreasing the size of the nanoparticle from 2.40 to 1.80 nm in the system leads to increasing Young's modulus of the nanocomposite from a 3.20 to 3.94 GPa. Furthermore, the atomic investigation demonstrated that this change in elastic modulus is due to the change in interatomic interaction between nanoparticle and polymer when the nanoparticle size changes. Finally, the comparison between the results of MD and micromechanical analysis shows that as the size of the nanoparticle in nanocomposites increases, the elastic properties of nanocomposites converge with the results obtained by the micromechanical approach.

Facile fabrication of high-strength biocomposite through Mg2+-enhanced bonding in bamboo fiber

The emerging interests in high-performance biocomposites grows significantly driven by their superior environmental sustainability. This study proposes a unique biocomposite strategy by implementing an acetic and ball-milled treatment to disrupt the bamboo cell wall structure, thereby facilitating further processing by effectively increasing the active sites and specific surface area in the bamboo fiber. The fibers are subsequently carboxymethylated to introduce carboxyl groups which facilitate physical bonding between the fibers and Mg2+ ions that are added to the system. These ions form metal-coordination bonds with the carboxyl groups, acting as ion bridges that significantly strengthen the inter-fiber bonding. The resulted biocomposite exhibits impressive mechanical properties, including a high tensile strength (94.24 MPa) and flexural strength (104.14 MPa), not only that, changes in elastic modulus also highlight changes in fiber bonding, the flexural modulus is 21.29 GPa and the tensile modulus is 7.01 GPa. Moreover, it maintains a low water uptake capacity of only 6.8 % despite being submerged for 12 h. The thermal conductivity and fire retardancy have also been improved. The synergic bonding ability between the cellulose and lignin in the fibers, coupled with the glue-free thermoforming process, enhances the material performance and renders it fully recyclable, thus reducing environmental pollution and providing cost-effective engineering materials to society.

Evaluation of drying shrinkage effects on the elastic properties of porous sandstones using a modified micromechanical model

SUMMARY The effects of pore fluids on the elastic properties of sedimentary rocks can be broadly categorized into two mechanisms: variations in pore compressibility due to the physical properties of the fluids and alterations in the stiffness of the rock frame resulting from rock–fluid interactions. Particularly, as rock–fluid interactions alter the stiffness of contacts between mineral grains, changes in the fluid properties around grain contacts can induce volumetric deformation of the rock as well as in variations of the associated elastic coefficients. Even though many previous studies have explored the influence of swelling of clay minerals, the relationships between changes in elastic moduli and deformation in rocks, which hardly contain swellable minerals, remain to date enigmatic. In this paper, to evaluate quantitatively these effects, drying rates, strains and ultrasonic velocities of small cylindrical Berea sandstone samples were measured as their water saturation was decreased by evaporative drying. The measurements clearly showed drying shrinkage and drastic increases in shear and compressional moduli for all the samples under an almost fully dried condition. Previous studies considered that the alteration in surface energy of grain minerals between wet and dry states affected the contact stiffness between them. Some of them used micromechanical model, uniting the Digby grain contact model with the effective medium theory, to interpret the changes in elastic moduli observed in the non-swellable sandstones during water adsorption on the grain surface. The conventional micromechanical model assumes that a mineral grain is a pure sphere and that the number of contacts between the grains is one. However, grains in a sedimentary rock are generally not purely spherical, and the contact surface is composed of several adhesive asperities. We therefore modified the conventional model by introducing the curvature radius and the number of asperities per contact surface. The modified model well reproduced the shear moduli under wet conditions using the strain and moduli measured under dry conditions. On the other hand, the predictions of the compressional moduli using the model were partially in agreement with the experimental results. Therefore, we attempted to qualitatively interpret the relationship by combining the model with the viscoelastic effect associated with wave-induced fluid flow. The deformation and changes in the elastic moduli of rocks resulting from multiple pore fluids within them can be better understood by the present combined model.

Enabling resonant ultrasound spectroscopy in extreme environments

Elastic moduli are fundamental thermodynamic susceptibilities that connect to thermodynamics, electronic structure, and mechanic properties. Thus, determining the changes of elastic moduli as a function of time or temperature is a powerful tool to study several thermodynamic and materials phenomena. Resonant Ultrasound Spectroscopy (RUS) determines elastic constants with high accuracy and precision from a single measurement of the mechanical resonances of a sample. Conventionally, the quantitative extraction of elastic moduli with RUS assumes free boundary conditions but lead to unstable positioning of the sample making it incompatible with extreme environments like high magnetic fields. In practice, even holding the sample produces contact forces that deviate from free-boundary conditions shifting resonant frequencies. In this talk, we show that, we can reduce the free-boundary conditions (by gluing/adhering the sample to the transducer), while still being able to obtain the full elastic tensor by a simple model of the sample-transducer interaction. This means elastic constants can be determined to within the uncertainty of conventional RUS, but with significant improvements in sample stability and control of sample orientation. We show the results of studying of several magnetic and structural phase-transitions using this new method.

Study on cross-section distortion behaviors for tube bending at varying geometry parameters

Tube bending is often plagued by the critical forming defect of cross-section distortion, which increases flow resistance, affects the strength and stiffness of bent-tube, and thus directly influences the usage performance of bent-tube components. To achieve accurate tube bending forming, the distortion behaviors for cross-section during tube bending should be clarified. A finite element (FE) model accounting for the change in elastic modulus was employed for addressing the distortion behaviors of the cross-section for high strength 0Cr21Ni6Mn9N (0Cr21Ni6Mn9N-HS) tube in NC rotary draw bending at varying geometry parameters. The findings indicate that accounting for the change in elastic modulus can aggrandize the distortion ratio of the cross-section, but has no significant impact on the distortion behaviors for the cross-section. The cross-section ovality behaviors of the 0Cr21Ni6Mn9N-HS tube at various geometry parameters for NC rotary draw bending have been clarified, and the ranges of sound parameters have been determined.

Tendon biomechanical properties are altered by storage duration but not freeze-thaw temperatures or cycles.

Tendon allograft and xenograft processing often involves one or more steps of freezing and thawing. As failure strength is an important graft consideration, this study aimed to evaluate effects on failure properties when varying freeze-thaw conditions. Kangaroo tendons, a potential xenograft source, were used to evaluate changes in ultimate tensile strength (UTS), failure strain and elastic modulus after exposure to different freezer-storage temperatures (-20°C vs.-80°C), storage durations (1, 3, 6, 9, or 12 months), number of freeze-thaw cycles (1, 2, 3, 4, 5, or 10), or freeze-thaw temperature ranges (including freezing in liquid nitrogen to thawing at 37°C). Tendons stored for 6 or more months had significantly increased UTS and elastic modulus compared with 1 or 3 months of storage. This increase occurred irrespective of the freezing temperature (-20°C vs.-80°C) or the number of freeze-thaw cycles (1 vs. 10). In contrast, UTS, failure strain and the elastic modulus were no different between storage temperatures, number of freeze-thaw cycles and multiple freeze-thaw cycles across a range of freeze and thaw temperatures. Common freeze-thaw protocols did not negatively affect failure properties, providing flexibility for graft testing, storage, transportation and decellularisation procedures. However, the change in properties with the overall storage duration has implications for assessing the consistent performance of grafts stored for short versus extended periods of time (<6 months vs. >6 months), and the interpretation of data obtained from tissues of varying or unknown storage durations.

Static elastic modulus prediction at early ages using a modified resonant test for concrete cylinders using mems microphones

Concrete Young’s modulus is seldom verified on-site due to the time-consuming and costly nature of current testing standards. This article proposes a new, quick and affordable testing methodology to estimate the ultimate static elastic modulus of normal strength concrete cylinders on-site at early ages using a smartphone. Impact-resonance tests were performed on several concrete cylinders from different mixtures at different ages, using an accelerometer and a smartphone microphone to measure the cylinders' flexural and longitudinal resonant frequencies. Measurements from both sensors were compared to show the validity of estimating the dynamic elastic modulus using acoustic signals from the cylinders recorded with a smartphone's built-in microphone. The cylinders' static and dynamic elastic moduli were determined, and the change in elastic modulus over time as the cylinders aged was also examined. This study shows the advantages of microphones over accelerometers, being less susceptible to measurement errors and proposes a filter algorithm to extract the resonant frequencies from environmental noise. A forecasting methodology to estimate static elastic modulus based on early dynamic impact-resonant tests can help engineers make early decisions on their supplied concrete on-site.

Study on micromolecular mechanical properties of C-atom reinforced SBR polymer composites

A three-layer microscopic model with Fe atoms as the top and bottom layer and SBR polymer composites as the middle layer and SBR polymer composite was established and studied. By adding C atoms as reinforcement, the stability and elastic modulus and frictional coefficient changes of SBR polymer composites before and after adding C atoms were studied. In this study, the molecular dynamics method was used to change of elastic modulus was observed by stretching, compression and shear of the SBR polymer composite; The simulation shows that after adding C atom the elastic modulus of SBR polymer composite increased, the friction coefficient of polymer composite upper and lower decreases and the relative atomsic concentration, temperature, velocity, overall temperature average, kinetic energy, total energy and MSD in the thickness direction are reduced after adding C atoms. The stability of SBR polymer composites is enhanced, and the deformation under shear is weakened. In addition, it is found that the binding energy between SBR polymer composites and Fe atoms is reduced after adding C atoms.The stability of SBR polymer composites is improved during use. This work provides a method for studying the properties of rubber composites by studying the enhancement of the stability of SBR polymer composites from the microscopic point of view.

STUDY OF THE RELATIONSHIP BETWEEN FATIGUE CHARACTERISTICS AND ELASTIC MODULUS OF METASTABLE AUSTENITIC STEELS

This work is devoted to studying the influence of cyclic deformation on the elastic moduli of metastable austenitic steel. The estimated calculation of the modules of the strain-induced martensite and the modules of the matrix of the material (austenite) in the Voigt approximation. The modulus calculations were made according to the ultrasonic wave velocity measurements taking into account changes in the density of the material due to the difference in the volumes of the unit cells of the matrix and the ??-martensite. The volume fraction of ??-martensite and its change during cyclic deformation were determined by the eddy-current method. The influence of the strain cycle amplitude on the increase in the volume fraction of martensite was studied. The dependences of the relative change in Young's modulus, shear modulus, volume compression modulus on the number of loading cycles for metastable steel 12Kh18N10T are given. Relationships between the moduli change and the characteristics of cyclic loading of steel are obtained: the hardening of the material and the energy density in the cycle, used to calculate the service life using the methods of deformable solid mechanics. Studies shown that the critical change in the modules corresponding to the appearance of a microcrack depends on the strain cycle amplitude.The maximum change in the modules of metastable steel 12Kh18N10T was 4.5%; that by an order more than in steels that don't undergo phase transformations. A high degree of correlation between the change in elastic moduli and the fatigue characteristics of metastable austenitic steel is revealed: the hardening of the material and the energy density in the cycle. Correlations between the fatigue life of 12Kh18N10T steel and the change in elastic modulus – shear modulus and Young's modulus are obtained, which makes it possible to assess the state of the studied steel based on acoustic measurements.

Characterization of drying-induced changes in moduli and internal stresses in a constrained gel using laser vibrometry.

Hydrogels, water-saturated polymer networks find widespread use in soft robotics, biomedical, pharmaceutical and food industries. Both solid and water constituents of hydrogels are sensitive to external stimuli such as temperature, humidity, osmolarity, and light. For instance, common hydrogels swell or shrink in the presence of chemical potential gradient between the sample and surrounding environment. Corresponding changes in internal water content lead to significant changes in mechanical properties of hydrogels. Besides, internal stresses build up if the gel samples are constrained during swelling or dehydration. In the present research, we utilize modal analyses technique on drying hydrogels to identify dehydration-induced changes in elastic moduli and internal stresses. In particular, natural frequencies and damping ratios of the first two axisymmetric transverse vibration modes are measured on clamped gelatin disks using non-contact laser vibrometry at various water loss states. Experimental modal frequencies are then compared to the predictions of a pre-stressed thick plate model. The evolutions of elastic moduli and internal stresses for water losses up to 80% are identified. The broadband loss capacity of gelatin is also determined from the measured modal damping ratios. Highly transient mechanical response observed on the gelatin disks further demonstrates the need for non-contact and rapid mechanical characterization of hydrogels. As illustrated in this work, vibration and wave-based techniques are promising candidates to fulfill that need.

Investigations on tensile mechanical properties of rigid insulation tile materials at elevated temperatures based on digital image correlation algorithm

This work investigates the tensile mechanical properties of rigid insulation tile (RIT) materials at room temperature (26 °C) and elevated temperatures (700–1000 °C) through experimental and digital image correlation (DIC) methods. Experimental results indicate that the tensile strength of RIT materials changes nonlinearly with increasing temperature and that the primary fracture mode under tension load is fiber root fracture. In terms of the DIC algorithm, this work builds an elevated-temperature DIC test system. A zero-mean Gaussian filtering algorithm and an image gradient difference square sum algorithm (SSDGI) are proposed to improve the precision of the DIC algorithm. The derived tensile stress-strain curve of RIT materials reveals that the elastic modulus changes nonlinearly with increasing temperature. The reliability and precision of the DIC algorithm are confirmed through the tensile test of silicon carbide particle-reinforced aluminum matrix composites. Hence, this work provides guidance for evaluating mechanical properties of RIT materials under elevated temperature environments.

Developing Porcine Acellular Dermal Matrix by Using Sodium Dodecyl Sulfate and Biomechanical Property Testing

ABSTRACT Introduction: An alternative for supporting wound closure is acellular dermal matrix (ADM), which serves as a scaffold. Humans and porcine possess a similar biochemical makeup. Using sodium dodecyl sulfate (SDS), a decellularization technique was developed and its biomechanical properties were assessed. Methods: This work uses a pig dermis layer for an in vitro experimental investigation with a posttest-only control group. Using SDS 0.5% for 14 days, the decellularization procedure compares the biomechanical properties and cellular components of the ADM with control. The Mann–Whitney U-test for data with a nonnormal distribution or the t-test for continuous variables with a normal distribution was used for the study. Results: Histological analysis revealed that none of the cells were detected in four fields of analysis in the treatment group; however, 48.00 ± 4.86 cells were observed in the control group (P &lt; 0.001); the collagen organization in the control group appeared to be identical. The variables elastic modulus (MPa) (136.78 vs. 129.19; P = 0.556), thickness (mm) (3.27 vs. 3.15; P = 0.397), and width (mm) (8.50 vs. 8.56; P = 0.40) did not differ statistically. The following data showed significant differences between the treatment group and the control group: break strain (%) (108.46 vs. 67.48; P &lt; 0.001) and tensile strength stress (MPa) (19.916 vs. 22.1; P = 0.030). Conclusions: SDS decellularization is an efficient method for creating an ADM. Although the break strain was considerably lower, the treatment group’s tensile strength was higher. Elastic modulus changes were not observed.

Impacts of E-Beam Irradiation on Polycrystalline Metals in Both Bulk and Thin Film Forms

This study aims to explore the impact of e-beam irradiation on the mechanical and structural characteristics of four different polycrystalline metals (Ni, Cr, V, and Ti), in both bulk and thin film forms. Thin metal films are fabricated using magnetron sputtering. The primary goal is to identify suitable metal candidates for growing thin films, which could serve as exit windows for e-beam accelerators. This selection is based on their properties, power dissipation capabilities, and the effects of irradiation on mechanical attributes such as hardness, ductility, defect density, and strength.For the bulk polycrystalline metal samples, a series of nanoindentation tests has been conducted before and after e-beam irradiation to investigate changes in hardness and elastic modulus. Additionally, to compare performance with the bulk samples, thin metal films are subjected to the same procedure before and after irradiation, allowing for the evaluation of film hardness, moduli, and creep properties. Results indicate that irradiated bulk samples of Ni, Cr, and V become harder, whereas Ti experiences softening. There is no significant irradiation effect on modulus for all for polycrystalline metal samples. To understand the underlying reasons behind these effects, both the fabricated metal films and bulk metal samples undergo comprehensive characterization tests for their microstructural properties, elastic behavior, and chemical composition. This involves the utilization of SEM with EDS, FESEM and AFM to analyze microstructure and surface attributes of the films, followed by X-ray diffraction to gain insight into film morphology and lattice orientation.

Comprehensive computational investigation of structural and mechanical characteristics of crystalline C3N4 under high pressure based on experimental data

This study presents a comprehensive investigation of the structural and mechanical characteristics of crystalline C3N4, encompassing seven distinct phases within the pressure range of 0–150 GPa, employing the GGA-PBE method. The analysis reveals significant insights, including the phase transitions of C3N4 from g-C3N4 of P-6m2 at 0 GPa to α-C3N4 of P31c at 9.1 GPa, culminating in c-C3N4 of I-43d at 95.3 GPa. Moreover, the minimal enthalpy difference observed between the gr-C3N4 and g-C3N4 at 0 GPa suggests the potential coexistence of these phases, indicating the likelihood of multiple graphitic carbon nitride structural coexistences at this pressure. The enthalpy difference between α-C3N4 and β-C3N4 structures also indicates the possibility of their coexistence. Furthermore, the study explores the pressure-dependent mechanical properties of C3N4, including changes in elastic constants and major elastic moduli with pressure, though it raises concerns regarding the potential instability of g-C3N4 under high-pressure indicated by calculated stability conditions.

Influence of Temperature and Atmospheric Pressure on Nonlinear Elasticity of Rock

We conducted a 28-day long period co-propagating longitudinal acoustic wave experiment to monitor the change of nonlinear elastic modulus of rock. During the monitoring period, we monitored the atmospheric pressure and temperature of the environment. We analyzed the relationship between the change of nonlinear elastic modulus of rock and atmospheric pressure and temperature. We found that the change of them appears high consistency. But the change of ΔM\\/E is not sensitive to small amplitude change of atmospheric pressure. And there is a certain delay with the influence of temperature to the ΔM\\/E.

Determinating optimum combination of ageing and manufacturing parameters for laminated composites using response surface methodology

This study mainly focuses on the effects of ageing and manufacturing parameters on the water absorption behaviour and mechanical characteristics of the glass-fibre reinforced polymer (GFRP) composites, and multiple optimizations of these parameters based on the quasi-static mechanical properties and low-velocity impact performances. Utilizing response surface methodology (RSM), an experimental design was executed varying curing temperature (20-100°C), ageing temperature (20-70°C) and salinity (3-35%). After 59-days ageing period, gravimetric, tensile and low-velocity impact tests were conducted to assess weight gain at saturation, changes in tensile strength, elasticity modulus, peak force and peak energy. Tensile fracture surfaces of aged and un-aged samples were examined using scanning electron microscopy. ANOVA results indicated the adequacy of RSM models, supported by high R2 (&gt;80%) and R2adj (&gt;65%) and proper residual distribution. Gravimetric tests revealed that higher curing and ageing temperatures resulted in greater water sorption-induced weight gain, while elevated salinity had the opposite effect. Ageing temperature and salinity are the most influential factors on tensile strength change. Optimal mechanical properties, minimizing differences between aged and un-aged samples, were achieved at 100°C curing temperature, 20°C ageing temperature and 19.8% salinity. Data from this study can be a valuable reference for designing GFRP composites, particularly in marine applications.

Hydrostatic piezoelectric properties of 1-3 type piezo-composite with a porous polymer matrix

ABSTRACT Piezoelectric sensors for underwater sonar require high hydrostatic piezoelectric properties (dh, gh and HFOM), and research is being conducted on various types of piezoelectric composites to improve them. In this study, research was conducted to improve the hydrostatic piezoelectric properties of 1–3 type piezoelectric composites using PZT piezoelectric ceramics and polymers. First, the appropriate material and volume fraction of the piezoelectric ceramic were selected through numerical analysis, and then experimental specimens were produced by applying various porosity of the polymer matrix. As a result of the experiment, it was confirmed that dh increased by 75% as the porosity of the polymer matrix increased. This phenomenon was analyzed to be caused by a change in elastic modulus. In addition, gh and HFOM also increased by 70% and 210% as the porosity of the polymer matrix increased. These results experimentally demonstrated that controlling the porosity of the polymer matrix is useful for improving the hydrostatic piezoelectric properties of type 1–3 piezoelectric composites.

A Thermodynamic Strength Theoretical Model to Explain and Predict Pseudo-Ductility Behavior of SiCf/SiC Composite Material

In order to explain and predict the pseudo-ductility behavior and mechanical properties of [Formula: see text] composite material, a thermodynamic strength theoretical model based on fracture mechanics and thermodynamic method has been established. Compared with other theoretical models, the model proposed in this investigation unifies different cracks and defects based on energy method. Meanwhile, the stress–strain behavior of materials can be obtained with as few parameters as possible. Compared with previous experimental data, the correctness of this theoretical model has been verified. Some key material properties, such as elastic modulus, proportional limit stress (PLS) and yield stress (YS), have been investigated by calculating based on the theoretical model. The effect of the initial matrix porosity and the material properties of the matrix and fiber have been investigated. Results show that PLS and YS are almost not influenced by initial matrix porosity and can be seen as intrinsic parameters. Elastic modulus of the SiC reinforced fiber and the matrix can also affect material properties. Compared with the SiC matrix, PLS of the [Formula: see text] composite material is more sensitive to changes in elastic modulus of the SiC reinforced fiber. However, the improvement of elastic modulus and shear modulus of the [Formula: see text] composite material is much more difficult. For this purpose, the elastic modulus of both the SiC reinforced fiber and the matrix need to be enhanced. Results and conclusions in this investigation can provide guidance for predicting material properties of [Formula: see text] composite material and preparation in industry.