Bulk Modulus Research Articles

Machine learning-generated compression modulus database for 3D printing of gelatin methacryloyl

Machine learning-generated compression modulus database for 3D printing of gelatin methacryloyl

Slope Stability Analysis of Open-Pit Mine Considering Weathering Effects

Weathering processes gradually alter the physical and mechanical attributes of slope materials, weakening the structural integrity and stability of slopes. This paper presents an in-depth analysis of slope stability in an open-pit mine, emphasizing the pivotal role of weathering effects in determining slope stability. To accurately capture the impact of weathering on slope stability, a comprehensive analysis model was developed, incorporating field observations, laboratory testing, and numerical simulations. The effects of weathering on the mechanical properties of black shale were studied through extensive laboratory tests. The uniaxial compressive strength, shear strength, and modulus of elasticity significantly decreased with increasing weathering, indicating a heightened vulnerability to slope failure. The correlation function between mechanical parameters and weathering time was obtained, providing the basis for evaluating the stability of mine slopes. It was found that more severe weathering conditions were strongly correlated with elevated risks of slope failure, including landslides and collapses. Based on these findings, practical recommendations are provided for slope reinforcement and management strategies, aimed at mitigating slope failure risks and ensuring the safe and efficient operation of the mine. By incorporating weathering effects into slope stability analysis, mine operators can make informed decisions that account for the dynamic nature of slope materials and their susceptibility to weathering, thereby improving overall mine performance and safety.

Experiment and enhancement of compressive strength perpendicular to the grain of inorganic-bonded bamboo composite

ABSTRACT The inorganic-bonded bamboo composite (InorgBam) is a novel type of bamboo-based composite: a combination of magnesium oxysulfide inorganic adhesive and bamboo fiber strips, which exhibits significant material anisotropic characteristics with compressive strength perpendicular-to-grain typically lower than that of parallel-to-grain. The impact of loading form including full-area compression, middle and end local compression on strength perpendicular-to-grain was examined. The enhancement of compressive strength perpendicular to the grain using the glued-in rods (GiRs) method was tested. A prediction formula for ultimate load-carrying capacity perpendicular to the grain of enhanced InorgBam material was proposed considering the influence of load form and depths of GiRs. Results indicate that the full-area compression perpendicular to the grain exhibits a higher load-carrying capacity compared to the middle and end local compression. The GiRs method significantly enhances the compression strength and deformation behavior perpendicular to the grain of InorgBam material. The compressive load-carrying capacity and elastic modulus of the enhanced specimens can be increased by 83% and 157%, respectively. The prediction formula based on the replacement ratio of GiRs can well predict the strength of enhanced specimens.

A review of mixture design and preparation methods for high-performance recycled aggregate concrete

Recycled aggregate concrete (RAC) has been widely investigated for recent decades, during which there are a great deal of findings on the modification of RAC to overcome the drawbacks of RA, i.e. high absorption and low strength. In this paper, four methods for designing and preparing RAC are reviewed, including the particle packing method (PPM), equivalent mortar volume (EMV) method, two-stage mixing approach (TSMA) and distributing-filling coarse aggregate (DFCA) process, and their effects on the properties of RAC is compared to reveal the effective approaches to high-performance preparation of RAC. Among these methods, only TSMA presents a positive effect on the workability of RAC. In terms of the properties of hardened RAC, TSMA improves the compressive strength and penetration resistance by densifying the ITZs around RA, and the developed TSMAsc containing silica fume exhibits better efficiency in improving the properties of RAC. The EMV method and DFCA process are beneficial to the compressive strength, elastic modulus and volumetric stability of RAC, and the effectiveness of the DFCA process is superior to the EMV method, indicating that enhancing the coarse aggregate interlocking effect is an effective approach to obtain high-performance RAC. Furthermore, the combination of TSMA and EMV methods can synthesize the enhancements of ITZs and coarse aggregate interlocking effect, contributing to a further improvement in the properties of hardened RAC. It is conceived that the TSMA and DFCA process can be integrated as a promising combination to realize the high performance of RAC.

Mechanical Behavior Analysis of Lightweight Concrete Reinforced by Metalized Plastic Waste Fibers

This study evaluates the impact of adding metalized plastic waste (MPW) fibers to lightweight concrete that is used as a filler material in building slopes and bridge ramps. The goal is to open up new opportunities for recycling plastic waste and promote a more sustainable and productive construction industry. This study examined the mechanical behavior of lightweight concrete (LC) at 3, 28, and 90 days, both with and without MPW fiber (1%, 2%, and 3%). Compression tests, 3-point bending tests, and pull-out tests were used to measure the fibers' compressive strength, flexural strength, and maximum load-bearing capacity, respectively. According to the results, the compressive strength (CS) and elasticity modulus (MOE) decreased with increasing fiber content when MPW fiber was added. In the long term, the CS and MOE decrease for the LC containing 3% MPW fiber was 8% and 7%, respectively, lower than for the control concrete. At 90 days, the flexural strength of the LC with 1% MPW fiber was marginally higher than that of the control concrete, rising by 2.40%. After this initial rise, however, the flexural strength declined as the fiber concentration increased, eventually reaching an 8% reduction for LC with 3% MPW fiber.The optimum method for determining maximal load-bearing and comprehending the deformation mechanism is hence the fiber pull-out test. The microstructure study of the LC examined how the pull-out test affected the quality of bonding at fiber-matrix interfaces. The tensile and flexural strength of lightweight concrete are enhanced by MPW fiber's ability to bear significant pulling stress.

A robust low-friction triple network hydrogel based on multiple synergistic enhancement mechanisms

AbstractHydrogels exhibit promising applications, particularly due to their high water content and excellent biocompatibility. Despite notable progress in hydrogel technology, the concurrent enhancement of water content, mechanical strength, and low friction poses substantial challenges to practical utilization. In this study, employing molecular and network design guided based on multiple synergistic enhancement mechanisms, we have developed a robust polyvinyl alcohol (PVA)–polyacrylic acid (PAA)–polyacrylamide (PAAm) three-network (TN) hydrogel exhibiting high water content, enhanced strength, low friction, and fatigue resistance. The hydrogel manifests a water content of 63.7%, compression strength of 6.3 MPa, compression modulus of 2.68 MPa, tensile strength reaching 7.3 MPa, and a tensile modulus of 10.27 MPa. Remarkably, even after one million cycles of dynamic loading, the hydrogel exhibits no signs of fatigue failure, with a minimal strain difference of only 1.15%. Furthermore, it boasts a low sliding coefficient of friction (COF) of 0.043 and excellent biocompatibility. This advancement extends the applications of hydrogels in emerging fields within biomedicine and soft bio-devices, including load-bearing artificial tissues, artificial blood vessels, tissue scaffolds, robust hydrogel coatings for medical devices, and joint parts of soft robots.

Semiconductor-metal transition in TlPbF3 under isotropic pressure and its impact on optical, elastic and mechanical properties: A DFT computation with HSE06

Abstract This research aims to comprehensively evaluate the structure, elasticity, mechanics, anisotropy, electrical properties, and optical attributes of TlPbF3 at pressures from 0 to 60 GPa. A cubic structure of the material remains same without any phase changes, but there is a reduction in the lattice parameters. The material is determined to be mechanically secure by doing calculations on a variety of mechanical and elastic characteristics, including bulk, shear, and Young's modulus, stiff, and not particularly flexible. It also shows a significant resistance to shear force. The material's ability to withstand high pressures, its metallic bond nature, and ductility have been shown by the Kleinman's parameter, Poisson's ratio, Cauchy pressure, and Pugh ratio. Anisotropy can be confirmed by activating specific anisotropy factors. When we consider the electronic band structure, we observe a transition from a broad gap in the band (3.719 eV) comparable with a small band distance (0.65 eV), and converts to a metal (0 eV). To explore this, we have estimated the total, partial and elemental partial density of states. Additionally, we have computed the real and imaginary functions of dielectric, absorption factor, refractive index, extinction coefficient, loss function, reflectivity and real/imaginary conductivity to assess the material's applicability. As pressure is applied, the static values of ε1(⍵) and n(⍵) increase. This material is also well-suited for optoelectronic devices due to its high conductivity, reflectivity, absorption, and refractive index.

Preparation of magnetic scaffolds via supercritical carbon dioxide foaming process using iron oxide nanoparticles coated with CO2‐philic materials as nucleating agents

AbstractThe iron oxide nanoparticles (IONs), coated with different materials, are synthesized and utilized as nucleating agents to prepare magnetic multi‐modal porous scaffolds of poly (lactic‐co‐glycolic acid)/IONs using the supercritical carbon dioxide (ScCO2) foaming process. The effects of the modification materials, including citric acid, polycaprolactone, and polyvinyl acetate, on the foaming process and properties of the magnetic scaffolds are systematically investigated. The results indicate that the solubility and diffusion ability of CO2 in the foaming materials played a vital role in the foaming process. The use of CO2‐philic materials and high pressure proves beneficial in generating micropores. The scaffolds with multi‐modal porous structures can be obtained at relatively low pressure for the ScCO2 foaming systems evaluated in this study. Furthermore, the prepared scaffolds exhibit high porosity and a good compressive modulus (higher than 0.4 MPa), satisfying the requirements of tissue engineering for soft tissue scaffolds.

Higher Flower Hydraulic Safety, Drought Tolerance and Structural Resource Allocation Provide Drought Adaptation to Low Mean Annual Precipitation in Caragana Species.

Determining the differences in flower hydraulic traits and structural resource allocation among closely related species adapted to low mean annual precipitation (MAP) can provide insight into plant adaptation to arid environments. Here, we measured the maximum flower hydraulic conductance (Kmax-flower), water potential at induction 50% loss of Kmax-flower (P50-flower), flower pressure-volume parameters, dry mass of individual flowers and structural components (vexillum, wings, keels, stamens and sepals) of six Caragana species growing in regions ranging from 110 to 1400 mm MAP. Compared with species from high-MAP environments, those from low-MAP environments presented lower Kmax-flower, more negative P50-flower, osmotic potential at full turgor (πo) and turgor loss points (πtlp), and a greater bulk modulus of elasticity (ε). Consequently, a negative correlation between Kmax-flower (hydraulic efficiency) and P50-flower (hydraulic safety) was observed across Caragana species. Furthermore, the dry masses of individual flowers and structural components (vexillum, wings, keels, stamens and sepals) were greater in the species from the low-MAP environment than in those from the high-MAP environment. These findings suggest that greater flower hydraulic safety and drought tolerance combined with greater structural resource allocation promote drought adaptation in Caragana species to low-MAP environments.

The effect of nanocellulose and silica filler on the mechanical properties of natural fiber polymer matrix composites

Natural fiber-reinforced polymer matrix composites recently got great attention in biomedical applications due to their inherent characteristics such as biocompatibility, lightweight, and biodegradability. However, natural fiber composites suffer from poor mechanical properties and weak interfacial adhesion. It is well documented that the addition of nanofiller has improved the mechanical properties of different synthetic fibers such as glass and carbon composites. The main objective of this paper is to study nanofillers' effect on the mechanical properties of unidirectional false banana fibers reinforced polymer composites. The filler materials, crystalline nanocellulose fibrils, and crystalline nanosilica particles were extracted from sugarcane bagasse and its byproducts. The composite samples were fabricated by adding the nanofillers in unidirectional natural fibers arranged in four fiber orientations (0°, 0o/90o ±45o, and quasi-isotropic), and their tensile, flexural, compression strength, thermal stability, and void content were measured following ASTM standards. The results revealed that adding nanofillers increased the tensile, flexural, and compressive strengths by 16 % (98.83 Mpa), 11 % (161.60 Mpa), and 23 % (114.62 Mpa), respectively. Similarly, at 0° orientation, the addition of nanoparticles enhances the tensile, bending, and compressive modulus by 30 % (15.43 Gpa), 12 % (13.52 Gpa), and 60 % (42.6 Gpa), respectively. On the other hand, the void content was reduced with the addition of nanofillers. The results also revealed that composites with crystalline nanosilica particle fillers had superior thermal stability compared to crystalline nanocellulose fibril fillers. The overall results of this research give the confidence that nano particle-filled natural fiber composites can be used for bio-based engineering applications, such as prosthetic sockets.

Microstructural influence on compressive behavior and strain rate sensitivity of open-cell nickel foam

Open-cell nickel foam (OCNF) is a highly porous, three-dimensional material with potential applications in various fields, such as energy storage, catalysis, and thermal management. However, the microstructural effect of pores per inch (PPI), cell size and strain rate (SR) sensitivity on the mechanical properties of OCNF has not been fully explored. We characterized the samples of OCNFs using digital image correlation (DIC), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) mapping. Our results show that the OCNF exhibits a linear elastic response under quasi-static compression, with high compressive strength and a low compressive modulus. The dynamic compression test results demonstrate that the OCNF has a high energy absorption capacity and good structural stability. We designed and constructed a method to generate the 3D meshes based on the scans of the OCNFs obtained by X-ray micro-CT. The 3D meshes allow the finite element method to capture the key features of the mechanical behaviors with high fidelity. The simulated mechanical behavior of the OCNFs demonstrates strong concordance with the observed experimental findings.

Lattice dynamics and vibrational properties of scheelite-type alkali-metal perrhenates.

The present work provides insight into the structural, vibrational, and elastic properties of scheelite-type alkali-metal perrhenates AReO4 (A = Na, K, Rb, Cs) from first-principles calculations. Sodium, potassium, and rubidium perrhenates are isostructural and crystallize in a tetragonal structure whereas caesium perrhenate crystallizes in an orthorhombic structure. All phonon frequencies and their corresponding mode assignments were estimated, through the linear response method within density-functional-perturbation theory. The phonon density of states highlights the predominant participation of the oxygen anions and both the A-type and rhenium (Re) cations in the low-frequency range. In contrast, oxygen and Re atoms exhibit higher and moderate contributions to the remaining phonon frequency spectrum. Considerable splitting of the longitudinal and traverse optic modes was observed. Elastic constants and phonon dispersion calculations confirm the mechanical and dynamical stability of all the studied AReO4 compounds. A redshift was observed due in the frequency of the phonons following the sequence Na→Cs. The calculated low bulk modulus (ranging from 28.36 GPa to 14.15 GPa) and shear modulus values indicate a low resistance to deformation of the perrhenates. The values of these moduli decrease in the order of Na→Cs which is associated with the increase in the ionic radius of the anion. The response to pressure was found to be anisotropic. This characteristic and the ductile nature of the alkali-metal perrhenates, were confirmed through an elastic analysis.&#xD.

Structural and physical properties of the MAX phases RE2SX (RE = La ∼ Lu; X=B, C, N) via first-principles calculations

MAX phase layered compounds have high temperature stability, excellent mechanical properties, good thermal conductivity and electronic properties. In order to provide a certain theoretical basis for further experimental exploration of the MAX phase with rare-earth (RE) element, a detailed study of the RE2SX (RE = La∼Lu, X = B, C, N) MAX phase has been performed by using first-principles calculations. The study comprehensively examines the mechanical properties, elastic anisotropy, dynamical stability and thermal properties of the RE2SX phase, and the results demonstrate that 37 RE2SX phases satisfied the thermodynamical, mechanical and dynamical stabilities among the 45 compounds. The mechanical properties of the 37 stable phases were systematically analyzed, including bulk modulus, shear modulus, Young's modulus and hardness. Among these phases, La2SN, Ce2SB/N, Pr2SB/N, Nd2SB/N, Pm2SB, Sm2SB, Eu2SB, and Gd2SB were identified as exhibiting promising ductility potential. In the RE2SX carbides, the occupied states on the Fermi level of the RE2SC phase are very small, with the conduction band is mainly occupied by the valence electrons of the RE and S atoms, suggesting that these carbides exhibit notable electronic characteristics. These results can enhance our understanding of RE2SX phases and provide valuable guidance for future experimental research.

Explored the potential of Rb2SeX6 (X=Cl, Br) double perovskites for energy harvesting devices: A DFT study

In this study, we employed Density Functional Theory (DFT) to comprehensively analyze the structural, mechanical, electronic, optical, and transport characteristics of Rb2SeX6 (X=Cl, Br) double perovskite halides. Our investigation aimed to assess the stability and suitability of these materials for energy harvesting devices. To evaluate material stability, we performed optimization and mechanical calculations. The computed bulk modulus indicated that the Rb2SeX6 (X=Cl, Br) compounds possess mechanical stability. Nevertheless, both compounds satisfied stability requirements for cubic structures, ensuring their potential utility. Using the modified Beck-Johnson approximation, we determined the indirect electronic band gaps to be within the range of 2.15 eV to 2.61 eV. These values indicate that the indirect band gaps of Rb2SeX6 (X=Cl, Br) compounds fall within the visible region due to the strong orbital coupling of the cations. Notably, the conduction band minimum mainly consists of Se-4p elements, while the valence band maximum predominantly comprises X-3p elements. Furthermore, the replacement of halogen atoms significantly influences the optical characteristics of the double perovskites. We observed that the complex dielectric function advocates the maximum electron transition and absorption efficiency when photon energy (eV) subjected on the Rb2SeX6 (X=Cl, Br) compounds. Further, considered the transport properties against temperature, chemical potential, and carriers’ concentrations. These findings emphasize the potential of Rb2SeX6 (X=Cl, Br) compounds double perovskites for energy harvesting applications. In conclusion, our study highlights the favorable properties and stability of Rb2SeX6 (X=Cl, Br) double perovskites, as revealed through DFT analysis. These materials exhibit desirable electronic and optical characteristics, making them promising candidates for energy harvesting devices.

Dilatational rheological studies on the surface micelles of Poly(styrene)-[formula omitted]-Poly(4-vinyl pyridine) block copolymer at the air-water interface

A thin film of an amphiphilic block copolymer, poly(styrene)-b-poly(4-vinyl pyridine), is investigated at the air–water interface. The surface pressure - area per molecule isotherm and the static compressional modulus provide evidence of two phases, assigned as L1 and L2, respectively. The surface topography and the phase images of these phases obtained using atomic force microscope reveal the presence of surface micelles of different sizes and densities. The dilatational rheology of these phases was investigated using the oscillatory barrier method for different strain amplitudes (1−5%) and qualitatively assessed using Lissajous–Bowditch curves. It points out the emergence of nonlinearity (asymmetric shape and distorted ellipse) with an increase in strain amplitude. Using a fast Fourier transform, the amplitudes and the phases of different harmonics of the stress–strain curves were extracted, and the total harmonic distortion was determined. In contrast to L1 phase, the total harmonic distortion for the L2 phase increases monotonically with strain amplitude. Fixing the strain amplitude at 1% (small amplitude regime), the temperature as well as frequency dependence studies of the dilatational moduli were carried out. The dynamic storage moduli of the L1 phase is found to be insensitive to temperature while it decreases for the L2 phase suggesting softening. Further, evidence for solid-like viscoelastic response emerges (explained using the Kelvin–Voigt model) for the L1 phase, whereas the L2 phase show a cross-over behaviour.

Shock dynamics model based on the conductor hardening and thermal softening effects for single-turn coil

Single-turn coil (STC) is a destructive pulse magnet aiming at 100–300 T ultra-high magnetic field. In this study, a conductor shock dynamics model based on the hardening and thermal softening effects is proposed for STCs. Using this model, the changes in mechanical parameters of the conductor during discharge are investigated. The results show that the yield strength and bulk modulus of the conductors are significantly strengthened during discharge. Moreover, without considering hardening in the simulations, the deformation velocities and displacements of the conductors are higher than when hardening is considered, causing the magnetic fields obtained from the simulation to be smaller than the actual values. The model is validated by checking the consistency of the magnetic flux density at the central axis of the STCs, and the conductor deformation degrees of the simulation results, and the experimental data.

Simulation-Directed Construction of Bamboo-Forest-Like Heat Conduction Networks to Enhance Silicon Rubber Composites' Heat Conduction Properties.

Highly vertically thermally conductive silicon rubber (SiR) composites are widely used as thermal interface materials (TIMs) for chip cooling. Herein, inspired by water transport and transpiration of Moso bamboo-forests extensively existing in south China, and guided by filler self-assembly simulation, bamboo-forest-like heat conduction networks, with bamboo-stems-like vertically aligned polydopamine-coated carbon fibers (VA-PCFs), and bamboo-leaves-like horizontally layered Al2O3(HL-Al2O3), are rationally designed and constructed. VA-PCF/HL-Al2O3/SiR composites demonstrated enhanced heat conduction properties, and their through-plane thermal conductivity and thermal diffusivity reached 6.47W(mK)-1 and 3.98mm2s-1 at 12vol% PCF and 4vol% Al2O3 loadings, which are 32% and 38% higher than those of VA-PCF (12vol%) /SiR composites, respectively. The heat conduction enhancement mechanisms of VA-PCF/HL-Al2O3 networks on their SiR composites are revealed by multiscale simulation: HL-Al2O3 bridges the separate VA-PCF heat flow channels, and transfers more heat to the matrix, thereby increasing the vertical heat flux in composites. Along with high volume resistivity, low compression modulus, and coefficient of thermal expansion, VA-PCF/HL-Al2O3/SiR composites demonstrate great application potential as TIMs, which is proven using multiphysics simulation. This work not only makes a meaningful attempt at simulation-driven biomimetic material structure design but also provides inspiration for the preparation of TIMs.

A DFT investigation of Li substitution in CsCaY3 (Y[dbnd]F, Cl, Br) having admirable optoelectronic characteristics as a viable candidate for photocatalytic water splitting

In this study we investigated pristine and Li substituted Cs1-xLixCaY3 (YF, Cl, Br) lead free halide perovskite with different concentrations x = 0, 0.11, 0.33, 0.55, 0.77, and 1 using CASTEP under Density functional theory (DFT) has been employed under Perdew Burke Ernzerhof generalized gradient approximation (GGA-PBE) and Ultrasoft pseudo potential (USSP) approaches. Understudy pristine materials have a cubic phase Pm3 m space group. At the same time, doped compositions show a tetragonal phase structure except those in which Li completely swaps out Cs, so both end materials own a cubic nature. Li introduced at the Cs site is more effective than Ca because additional gamma points formed, influencing the electronic formation of pristine CsCaF3, CsCaCl3, and CsCaBr3 minimized band gap from 6.299 to 4.152 eV, 5.261–3.613 eV and 4.338–2.752 eV respectively. All compositions are thermodynamically stable, as suggested by the negative values of the formation energy. For all compositions, the Fermi level resides near the valence band which confirms the p-type behavior of the semiconductors. All of the materials retain the indirect bandgap. The total/partial/elemental density of states calculated has been approximated to provide a full picture of the band structure. Although elastic constants for all compounds, whether cubic or tetragonal, are used to predict mechanical parameters such as bulk modulus, shear modulus, young modulus, Poisson ratio, and Pugh's ratio, materials were first developed to support born stability criteria. From all of the compositions Cs1-xLixCaF3 for x = (0.11, 0.55, 0.77, and 1) and Cs0.23Li0.77CaCl3 are found to be mechanically unstable. All other combinations are stable, whether cubic or tetragonal. We evaluated and contrasted many optical properties like absorption spectra, refractive index, dielectric function, reflectivity, and energy loss function of pristine CsCaY3 (YF, Cl, Br) in comparison with Li substitution concentrations. For both pristine and Li substituted CsCaY3 (YF, Cl, Br) the overall water splitting was explored. All the compositions can be used for hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water splitting reactions but Cs0.23Li0.77CaBr3 is a good catalyst among all. It is proposed that the aforementioned materials have a bandgap range suitable for solar cell applications in addition to being lead-free for environmentally conscious applications in photocatalytic activity.

Support-Free Printing Origami Based 3D Negative Poisson Ratio Structured Piezoresistive Sensor for Motion Monitoring

A convenient strategy for preparing meta-structures with a negative Poisson's ratio (NPR), which enhance mechanoelectrical responsiveness and are typically based on inner concave hollow cells, is 3D printing without support structures. However, this process requires the material to have high melt strength, often linked to high viscosity and low printability. In this work, we introduced 0D carbon black (CB) into a thermoplastic polyurethane (TPU)/1D carbon nanotubes (CNT) composite to create a dimension-hybrid filler system, enhancing strength with minimal viscosity increase. The results show that the bending modulus and Young's modulus of CB/CNT(1:3)/TPU composites are increased by 1.6 times and 1.8 times that of TPU, while its viscosity (2697.98 Pa·s) is lower than the allowed value of printer. Then, the 3D-printed suspension bridge of TPU is 42.7% less saggy, significantly benefiting to preparing meta-structures. Based on a support-free 3D printable enclosed hollow structure, the TPU/CNT/CB composite material achieves an adjustable NPR between -0.59 and -0.20. Compared to unfolded structure, this NPR characteristic further improves the piezoelectric output voltage by 9.00 times, enhances the compressive modulus by 3.15 times, and improves the piezoresistive sensitivity by 122.0%. Sensors based on this 3D-printed material showcase high performance stability and reproducibility, demonstrating their potential in wearable equipment.

A FDEM study on the mechanical properties and failure behavior of soft-hard interbedded rocks considering the size effect

Soft–hard interbedded rocks are widely distributed at the Earth’s surface, and their mechanical properties and failure behavior directly affect the stability of local tunnel and slope engineering projects. Previous studies have rarely considered the influence of size effects on the mechanical properties and failure behavior of such rocks. Therefore, this paper used the combined finite–discrete element numerical method (FDEM) to study the mechanical properties and failure behavior of soft–hard interbedded rock samples considering the size effect. First, appropriate input parameters were calibrated and verified by using a new parameter calibration method. Second, the effects of the element size and loading rate were studied to obtain appropriate model parameters. Finally, the effects of the layer number, sample size, and height–diameter ratio of composite rock samples on their mechanical properties and failure behavior at different layer dip angles and layer thickness ratios were investigated. The results support the following findings: (1) For the composite rock samples with a layer thickness of 10 mm, reliable simulation results can be obtained by using a 2.2 mm element size, and the loading rate should not exceed 0.2 m/s in FDEM numerical modeling. (2) The number of layers in the sample should be at least 5, and when the height–diameter ratio is a constant 2.0, the height of the sample should not be less than 110 mm. (3) As the height–diameter ratio of the composite rock samples increases, both the compressive strength and elastic modulus decrease for all layer dip angles considered, but the rock failure mode changes for layer dip angles of 15–75°; in addition, the sample size effect is most significant for layer dip angles of 60° and 75°. (4) Taking horizontally layered composite rock samples as examples, both the compressive strength and elastic modulus of samples with different layer thickness ratios decrease with increasing height–diameter ratio and their failure modes also depend on the height–diameter ratio.