Modulus Ratio Research Articles

Theoretical investigation of structural, mechanical, electronic, optical, and thermal properties of ternary compounds of heusler alloy ANiSn (A= TI, TH, U) using first principles calculations

In this study, we investigated the ANiSn (A = Ti, Th, U) half-Heusler materials for various properties, including structural, electronic, mechanical, elastic anisotropic, optical, and thermal properties, using Density Functional Theory (DFT) with the Cambridge Serial Total Energy Package (CASTEP) code. The elastic constants satisfied Born's criteria, confirming the thermodynamic and mechanical stability of the ANiSn compounds. Mechanical stability was further assessed through bulk modulus, shear modulus, and Poisson's ratio. Our analysis revealed that TiNiSn and ThNiSn exhibit ductile behaviour, whereas UNiSn is brittle. The calculated elastic modulus indicated that the compounds we studied are elastically anisotropic. The electronic and optical properties confirmed the semiconducting nature of these materials, with significant absorption and conductivity observed in the ultraviolet region. ANiSn is suitable for manufacturing various optoelectronic devices, such as laser diodes (LDs), photodetectors, LEDs, and UV sensors, due to its high absorption coefficient in the IR to UV regions. Additionally, measured Debye and melting temperatures confirmed that TiNiSn is more thermally conductive and can be used in high-temperature structural substances. The low minimum thermal conductivity suggests that UNiSn may be a more efficient material for thermal barrier coatings (TBC) compared to TiNiSn and ThNiSn.

Investigation of Gnetum Gnemon and Ramie Natural Fiber on the Mechanical Properties of Composites with the Combination of Aramid and Carbon Fiber as Reinforcement for Military Personnel Applications

Every equipment infrastructure in a TNI unit will be needed to support an operation in the defence system to maintain the integrity of the Unitary State of the Republic of Indonesia. Personal protective equipment is needed for a war operation’s safety or continuity. Protective components made from composite fibers have the advantage of being resistant to corrosion caused by the environment. The natural and carbon fibers will be mixed/reinforced with epoxy resin to become composite materials. This study aims to identify Gnetum Gnemon fiber composites with carbon fiber and aramid fiber to determine the mechanical properties of the composite material resulting from a collision. Natural fiber Gnetum gnemon has not been widely studied as a reinforcing material for polymer composites. Gnetum gnemon fiber chemical composition is hemicellulose approx. 25%, 40% alpha cellulose, 10% lignin and 3-5% benzene extractive. Its density is quite light, 1.2087 g/cm³ - 1.8069 g/cm³. Because this fiber has a continuous fiber structure and a strong natural weave, its use is still minimal. Special treatment such as alkali treatment on Gnetum gnemon, can increase the strength of natural fibers. Due to its exceptional mechanical properties, Kevlar or aramid fibre are extensively used in industrial and military applications. The aramid fiber exhibited a transversely anisotropic nature in a small strain range, with its stress-strain behavior as linear and elastic. The anisotropic nature of the aramid fiber was due to its high tensile-to-shear modulus ratio. The high strength and modulus were also found to be scattered due to the larger distribution of defects in the longer fiber. Epoxy resin is a type of polymer characterized often by one or more epoxide functional groups, with at least one of the epoxide functional groups acting as a monomer and terminal unit of the polymer within the structural chain.

Vibrational Analysis of Composite Conical-Cylindrical Shells with Functionally Graded Coatings in Thermal Environments.

This article studies the vibrational behavior of composite conical-cylindrical shells (CCSs) with functionally graded coatings (FGCs) in thermal environments using the first-order shear deformation theory. Firstly, the equivalent material parameters, fundamental frequency, and resonant displacement responses of the CCSs with FGCs are derived using the mixture principle, complex modulus method, and transfer function approach. Then, detailed thermal vibration tests are performed on CCS structures with and without coatings to assess the reliability of the proposed model, revealing that the current model accurately forecasts the thermal vibration behavior of the CCSs with FGCs. Finally, the effect of key parameters on the vibrational properties of the CCSs with FGCs is investigated. The results demonstrate that increasing the functionally graded index, coating thickness, and Young's modulus ratio can greatly enhance the vibration suppression capability of the structure.

DEVELOPMENT OF A CORRELATION MODEL FOR TORSIONAL SHEAR MODULUS PROPERTIES BETWEEN STRUCTURAL SIZE SPECIMENS BASED ON EN 384:2016 AND SMALL CLEAR SPECIMENS (MS544: PART 2)

In timber design, the shear modulus of beams is crucial for ensuring torsional stability and minimizing vibrational issues. Traditionally, the ratio of modulus of elasticity (E) to shear modulus (G) is assumed to be 16:1. However, bending tests often combine flexural and shear stresses, making it difficult to assess pure shear properties. The British Standard BS EN 408:2012 now recommends the torsion test as the preferred method for determining the shear modulus of structural-size timber and timber composites. This method has received limited attention in Malaysia. This study investigates the torsional shear modulus of Malaysian tropical timber species across different strength groups (SG), including Balau (SG1), Kempas (SG2), Kelat (SG3), Kapur (SG4), Resak (SG4), Keruing (SG5), Mengkulang (SG5), Light Red Meranti (SG6), and Geronggang (SG7). Torsion tests were conducted in line with BS EN 408, and the results were compared with modulus of elasticity values from MS554: Part 2. The findings showed that the E to G ratio for these species ranged from 17:1 to 29:1, with an average of 21:1—exceeding the conventional 16:1 ratio. This indicates that torsional shear modulus must be experimentally tested rather than inferred from the traditional ratio.

Tune Al/Ti to adjust FCC+L21 hetero-structured Ni-based high-entropy alloys for improved mechanical properties and wear resistance

Outstanding mechanical properties of Ni-based superalloy benefit from its coherent γ/γ’ structure via precipitation strengthening of γ matrix (FCC structure) by L12 Ni3Al-type γ’ phase. Back-stress strengthening is another effective strategy to further enhance the FCC+L12 structured Ni-based superalloy. In this work, we extend such approaches to high-entropy alloys (HEAs) by introducing different Al and Ti contents (5 at.% ∼18 at.%) into a Ni-based CrFe2Ni4 alloy to form FCC+L21 heterostructured AlxCrFe2Ni4Tiy HEAs. Detailed microstructural analysis indicates that L12 Ni3(Al,Ti)-type nanoparticles form in a (Ni,Fe,Cr)-rich FCC matrix. The volume fraction of L21 AlNi2Ti-type phase can be varied by adjusting the Al/Ti ratio and concentrations of Al and Ti. Higher Al and Ti contents promote L21 phase formation and higher Al/Ti ratio (>1) prohibits the high Ti-containing compounds such as D024η-Ni3Ti and C14 Laves Fe2Ti phases, which are hard but brittle. Corresponding Young's modulus, Poisson's ratio, hardness, and the bulk to shear modulus ratio (B/G) can be readily modified. Compressive tests demonstrate that Al1.5CrFe2Ni4Ti1.0 alloy with half FCC and half L21 phases possesses the optimal strength-ductility combination (with compressive yield strength of ∼1564 MPa and fracture strain of ∼28 %). DFT calculations were performed to elucidate relevant mechanisms. Sliding wear tests were also performed, which demonstrate superior wear resistance of the HEAs at both room and elevated temperatures, compared with a commercial Ni-based superalloy, UHT-Nickel.

Evaluating a Stochastic Singularity Level in a V-Notch Isotropic Domain Due to Randomness in Material Properties

Abstract The singular level of a v-notched isotropic domain is crucial as it relates to the domain’s stress intensity factor (SIF), which is essential for failure prediction. Typically, the singular level is calculated using deterministic material properties (like mean values), but this can misrepresent the severity of the singularity. The singular level’s accuracy is influenced by the stochastic nature of material properties, particularly Poisson’s ratio. This paper presents a stochastic approximation of eigenvalues for an isotropic v-notched domain with stochastic material properties. While both Young’s modulus and Poisson’s ratio are independent stochastic variables, only the stochasticity of Poisson’s ratio affects the eigenvalues. The generalized polynomial chaos method is applied to these stochastic eigenvalues, resulting in a polynomial approximation based on the domain’s stochastic Poisson ratio. The polynomial’s deterministic constants are derived from eigenvalues computed using chosen deterministic material properties according to the stochastic properties of Young’s modulus and Poisson’s ratio. A numerical example illustrates the stochastic approximation of the first two eigenvalues, showing fast convergence as the number of polynomials increases. Results are validated against the Monte Carlo method, highlighting the importance of stochastic approximation in accurately predicting the singular level, which may be more severe than expected when using deterministic approximations. These findings have significant practical implications, as they underscore the need to consider stochastic material properties in structural design and failure prediction.

Dynamic characteristics and microscopic mechanism of graphene oxide modified coastal soft soil under small strain

Graphene oxide (GO) has been shown to improve the static mechanical properties of cement soils. However, the dynamic mechanical properties of GO-modified cement soils are rarely investigated. Therefore, in this study, the effects of different confining pressures, GO contents, and curing ages on the small-strain dynamic shear modulus (G) and damping ratio (D) of GO-modified coastal cement soil (GOCS) are investigated via resonant column tests. The results show that the G of GOCS increases with the confining pressure, GO content, and curing age, whereas D decreases. Moreover, the GOCS indicate the highest stiffness improvement when 0.05 % GO is used as a modifier. The variation patterns of the maximum dynamic shear modulus and maximum damping ratio with the increase in the confining pressure, GO content, and curing age of the GOCS are consistent with the measured results. Microstructural analysis shows that the incorporation of GO can promote the early cement hydration of GOCS and increase its internal calcium-silicate-hydrate gel as well as its crystal types and numbers. The filling and bridging effects of GO not only enhance the stiffness of GOCS, thus increasing its G value, but also effectively reduce the energy consumption of the vibration wave in the sample, thus reducing its D value. The results of this study can provide important references and guidance for the design and construction of coastal soft-soil roadbed projects.

First-principles calculations to investigate phase stability, elastic and thermodynamic properties of TiMoNbX (X=Cr, Ta, Cr and Ta) refractory high entropy alloys

This work uses first-principles calculations to investigate the phase stability, thermophysical and mechanical properties of refractory high entropy alloys (RHEAs) at finite temperatures. On the basis of plane wave quasi-potential and density functional theory, construct the structure model of a solid solution. The TiMoNbX (X = Cr, Ta, Cr and Ta) RHEAs have been determined to preserve a single body-centered cubic solid solution structure by calculations and the equilibrium lattice parameters and elastic modulus are consistent with experimental data obtained by laser cladding, which is combined with TC4 (Ti-6Al-4V) substrate. Using the quasi-harmonic Debye-Grüneisen model, the thermophysical characteristics of three RHEAs are investigated. The Voigt-Reuss-Hill scheme is used for calculating the Young's modulus (E), bulk modulus (B), shear modulus (G), and Poisson's ratio (ν), which indicates that all three RHEAs are ductile materials. Additionally, the modulus and hardness of materials decrease as temperature rises, whereas the properties of TiMoNbX RHEAs are predicted, as the nanoindentation hardness values at room temperature are comparable to, and slightly higher than the calculated values.

Ab-Initio calculations on physical properties of Dirac semimetal AMgBi (A=K, Rb, Cs)

This study presents a comprehensive first-principles investigation of the structural, mechanical, vibrational, thermodynamic and electronic properties of AMgBi (A = K, Rb, Cs) compounds using Density Functional Theory. Also, the effect of substituting alkali atoms on the physical properties has been discussed. The tetragonal PbClF-type structure has been confirmed by the analysis and the results revealed good agreement between calculated and experimental lattice parameters for KMgBi. The mechanical properties have been investigated for the first time for RbMgBi and CsMgBi. The mechanical stability of the materials in the ground state has been confirmed through the use of obtained elastic constants. Furthermore, derived parameters from elastic constants such as bulk modulus, shear modulus, and Poisson's ratio indicated that the materials are brittle and exhibited anisotropic mechanical behavior due to their layered structure. This study conducts a detailed analysis of phonon modes, explores their connections to thermal and elastic properties, visualizes the movements of phonon modes at the gamma point, determines Born effective charges, and discusses LO/TO splitting, which is for the first time for RbMgBi and CsMgBi. Phonon dispersion calculations confirmed the dynamical stability of the compounds and revealed the presence of phonon band gaps, supporting their quasi-two-dimensional nature. Investigation of thermodynamic properties using the quasi-harmonic approximation has shown the temperature dependence of internal energy, Helmholtz free energy, specific heat, and entropy for the first time for all compounds. The materials exhibited relatively low thermal conductivity, following the order KMgBi > RbMgBi > CsMgBi. The calculated Grüneisen parameter values were found to be 1.42, 1.44, and 1.53 for KMgBi, RbMgBi, and CsMgBi, respectively, suggesting relatively weak anharmonicity within the materials.

Microstructure and dynamic behaviours of polyurethane-cured sea sand under traffic–load–induced stress path

Employing sea sand as fill material for roadbeds presents significant challenges due to its naturally high dispersibility and low bearing capacity, which contribute to substantial settlement deformations under traffic load impacts. In this investigation, a two-component polyurethane was applied to enhance mechanical properties of sea sand. Alterations in the microstructure and dynamic behaviours of the polyurethane-cured sea sand were observed via Scanning Electron Microscopy (SEM) and hollow cylindrical torsional shear testing. It was found that polyurethane is incorporated into the sea sand as adhesives between particles, attachments on the particles and floating adhesives. With an increase in polyurethane content, a transition from a granular to a solid state in the sand was noted, accompanied by a progressive improvement in structural integrity. This resulted in an enhanced bonding effect at interparticle contacts with diminishing relative particle movements during shearing, leading to an increase in the critical dynamic stress ratio and a decrease in the maximum damping ratio, with both ratios being higher in cured sea sand with lower polyurethane content compared to that with higher content. Additionally, high polyurethane content induced strain hardening in the cured sea sand, resulting in a higher maximum dynamic shear modulus in low-content cured sea sand compared to high-content. Furthermore, the dynamic shear modulus ratio in sea sand with high polyurethane content was found to increase with the number of vibrations.

Determination of elastic moduli of polymeric materials using microhardness indentation

Young's modulus of elasticity (or stiffness, E) is an important material property for many applications of polymers and polymer-matrix composites. The common methods of measuring E are by measuring the velocity of ultrasonic pulses through the material or by resistance to flexure, but it is difficult for ultrasound to penetrate polymers that contain filler particles, and flexural measurements require large specimens that may not mimic the clinical case. Thus, it may be difficult to determine E using conventional techniques. It would be useful to have a relatively rapid technique that could be applied to small specimens, highly filled materials, and even specimens cured in situ. We suggest using a microhardness indentation technique that was originally developed for ceramic materials. We tested two unfilled rigid polymers, four resin composites, and four unfilled polymers with lesser hardness for this study. The study found that greater Vickers hardness loads yielded more consistent results than lesser loads. We developed a modified equation for E based on Knoop microhardness indentations. We concluded that laboratories may use a microhardness indenter to estimate the elastic moduli of polymers and resin composites. The results support our initial hypotheses that the slope of the equation relating the indentation parameter and the hardness/elastic modulus ratio was different for polymers and resin composites than for ceramics; however, the intercept is the same irrespective of the material tested.

Triceps surae muscle-tendon length changes and shear modulus ratios across the ankle motion in adolescents with cerebral palsy

Triceps surae muscle-tendon length changes and shear modulus ratios across the ankle motion in adolescents with cerebral palsy

Parametric analysis of vibration characteristics of laminated composite plate structures

Abstract In order to conduct the vibration performance of laminated composite structures, the relationship between the vibration frequency and the parameters such as aspect ratio, width-thickness ratio, elastic modulus ratio and lay-up angle of the plate structure under different boundary conditions was investigated and the variation law of its vibration characteristics was obtained. The conclusions are as follows: 1. The vibration frequency tends to be smaller and smaller as the value of length increases. 2. The vibration frequency tends to be larger and larger as the value of thickness increases. 3. The vibration frequency increases with the increase of the value of elastic modulus.4. The symmetrical lay-up structure with the lay-up angle of the middle ply at 45 degrees has the lowest vibration frequency.

Mechanical Properties of Re-Entrant Hybrid Honeycomb Structures for Morphing Wings.

The exceptional energy absorption, deformability, and tuneable Poisson's ratio properties of negative Poisson's ratio (NPR) honeycomb biomimetic structures make them highly suitable for applications in aerospace, medical, and acoustic stealth industries. The present study proposes a re-entrant hybrid honeycomb (REHH) structure comprising a re-entrant octagonal unit cell and a re-entrant hexagonal unit cell. Theoretical models of the in-plane elastic modulus and Poisson's ratio are established based on beam theory, and these models are validated through finite element (FE) simulations and tensile experiments conducted on the REHH samples. The influence of the cell geometry parameters on the in-plane elastic behaviours is investigated. The results indicate that the NPR performance of the REHH structure exhibits superior deformation capability compared with the four-point star hybrid honeycomb (FSHH) structure. The experimental REHH structure samples exhibit significant tensile displacement capabilities in the x-direction.

Machine learning-based prediction method for drying shrinkage of recycled aggregate concrete

The objective of this study is to develop a broadly applicable, high-precision, and robust prediction model for the drying shrinkage of recycled aggregate concrete, a material that exhibits significantly greater shrinkage compared to natural aggregate concrete due to its complex characteristics. To achieve this, the study began by selecting relevant characteristic parameters based on international concrete codes, followed by the application of various machine learning algorithms including Backpropagation Neural Network, Support Vector Machine, Random Forest, eXtreme Gradient Boosting, Gaussian Process Regression, k-Nearest Neighbor, Linear Regression, and Long Short-Term Memory to model and forecast the drying shrinkage of recycled aggregate concrete. Subsequently, the SHapley Additive exPlanations (SHAP) method was employed to identify the crucial factors influencing RAC drying shrinkage, such as drying age, elastic modulus, and water-binder ratio, thereby optimizing the input parameters of the ML model. To further enhance the XGBoost algorithm, the sparrow search algorithm (SSA) and the whale optimization algorithm (WOA) were utilized. The optimized WOA-XGBoost model exhibits superior predictive performance, with a determination coefficient of 0.980 and a mean ratio of predicted to experimental values of 1.025, significantly outperforming traditional specification models. The model's applicability may be limited since the dataset is mainly derived from laboratory conditions, which may differ from actual engineering environments. Future research could consider different types of recycled aggregates and curing conditions and test the model on larger data sets to improve its robustness and applicability.

On the relationship between young's modulus, shear modulus and Poisson's ratio

On the relationship between young's modulus, shear modulus and Poisson's ratio

Static and Dynamic Characteristics of 3D-Printed Orthogonal Hybrid Honeycomb Panels with Tunable Poisson’s Ratio

By adjusting the two wall angles of the orthogonal hybrid honeycomb (OHH), the tunable Poisson’s ratio change from negative to positive values and the variation in stiffness can be achieved. To effectively analyze its static and dynamic characteristics, a two-dimensional equivalent Kirchhoff–Love model (2D-EKM) is established based on the variational asymptotic method (VAM).This model aids in effectively addressing the complexity arising from anisotropy. The obtained equivalent orthotropic properties are validated through unit-cell uniaxial compression tests and three-point bending experiments on 3D-printed specimens. The numerical simulation results suggest that the VAM-based 2D-EKM can predict the in-plane and out-of-plane static behaviors of OHH panels, with a maximum error below 10%. Particularly in the dynamic analysis of a four-sided fixed OHH panel, the analysis time required by 2D-EKM is only 0.37% of that needed for the 3D FE model. The OHH-ZPR panel exhibits exceptional resistance to deformation, with a maximum deformation under in-plane tension reaching only 27% of that in the OHH-PPR panel. Moreover, each 1% increase in the height–length ratio results in a respective increase of 275.62% and 281.93% in equivalent bending stiffness along both directions. This highlights that enhancing this ratio effectively boosts the fundamental frequency compared to the elastic modulus ratio, effectively prevents low-frequency resonance occurrences, and offers vital insights for the design and optimization of OHH panels.

Numerical Simulation Study on Vibration Characteristics and Influencing Factors of Coal Containing Geological Structure

Accurately determining the natural frequency of coal-containing geological structures is crucial for preventing mine dynamic disasters and utilizing vibration waves to break coal and enhance its permeability. Based on the modal theory of rock, vibration models of coal-containing geological structures, including layering and fractures are established. By analysis, the undamped vibration equation and its characteristic equation for both the layered coal system and the fractured coal system are derived. Subsequently, the Lanczos method is employed to solve the system’s vibration modes using ABAQUS. The effects of the layering position, layering thickness, layering physical properties, crack width, and crack length on the natural frequency and vibration response of coal-containing geological structures are investigated. The results indicate that when a single influencing factor is altered, the displacement response distribution of the coal body vibration system with geological structures remains essentially the same, and these single influencing factors have a minimal impact on the vibration displacement of the coal-containing geological structure. The natural frequency of the system decreases exponentially as the distance between the layering and the geometric center of the coal system with geological structures increases. The presence of layering in the coal system with geological structures significantly reduces the system’s natural frequency. The natural frequency of the coal system with geological structures increases in a power function manner as the layering elastic modulus increases. Conversely, the natural frequency decreases with an increase in crack length. When the change ranges of crack width and bedding thickness are the same, the natural frequency of the fractured coal body system exhibits more significant changes. The natural frequency of the coal system with geological structures initially decreases and then increases as bedding thickness and crack width increase. The trend in the natural frequency changes and the position of the extreme point are related to the ratio of the elastic modulus and density of the geological structure.

Fracture mechanics of bi-material lattice metamaterials

The advent of additive manufacturing technology empowers precise control of multi-material components or specific defects in lightweight lattice metamaterials, however, fracture mechanics and toughening design strategies in such metamaterials remain enigmatic. By incorporating theoretical analysis, numerical simulation, and experimental investigation, our study reveals that stretch-bend synergistic strut deformations caused by bi-material components or topology defects contribute notably tougher lattice structures surpassing its ideal single-material lattices. A peak fracture energy at a critical modulus ratio was found in a designed bi-material lattice composed of triangular soft struts and hexagonal stiff struts, which originates from the shift of fracture modes at crack tip from strut bending to stretching dominated failure modes as the modulus of soft struts increases, where the compromise in competition between bending-enhanced and stretching-weakened energy dissipations of struts deformations results in the maximized fracture energy. A parametric design protocol was proposed to optimize fracture energy of bi-material lattices through tuning the modulus ratio and relative density. Furthermore, the concept of stretch-bend synergistic toughening can also be applied to make tougher single-material lattices with specific topological defects. Our findings not only provide physical insights into directing crack propagation but also provide quantitative guidance to optimize fracture resistance within low-density tough lattice metamaterials.

Study of glutaraldehyde-treated crosslinking protocols for placental decellularized matrix sponges

Extracellular matrix sponge plays a positive role in the wound healing process, but requires proper structural strength and biological properties. In order to solve the problem of lyophilized dissolution of placenta-derived sponge, glutaraldehyde was selected for use in the lyophilized crosslinking process to improve the necessary mechanical properties of the placental decellularization matrix sponge. In this work, the effects of three cross-linking methods of glutaraldehyde (Fumigation/Slurry/Soak) on the physical and biological characteristics of lyophilised sponges derived from placental acellular matrix was investigated. The results revealed that the sponges prepared by all three cross-linking methods exhibited excellent blood coagulation ability and stability. The fumigation cross-linked sponges had good mechanical properties of soft and elastic, and safe cytotoxicity, which were more compatible with the requirements of wound dressing. The slurry cross-linking process was uneven due to the stacked matrix materials, resulting in obvious cracks and easy to break when stretching. The soak crosslinking can obtain a higher degree of crosslinking, which leads to the poor antibacterial performance and the harder sponge scaffold with larger elastic modulus and smaller tensile ratio. In general, fumigation cross-linking is more suitable for the preparation of acellular sponge derived from placenta materials which can maintain basic mechanical properties and biological validity.