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In this research, 90% asymmetric unidirectional rolling and post‐annealing are applied to electrolytic tough‐pitch (ETP) copper. The effect of low‐temperature (200 °C) annealing on the microstructure and texture evolution, mechanical, and electrical properties are investigated. Static recovery (SRV) is the main softening mechanism at the annealing time range of 1–5 min. In contrast, complete static recrystallization (SRX) is observed after annealing for 10 min. Bimodal microstructure, consisting of coarse and fine grains, is evolved for annealing times more than 10 min. With increasing the post‐annealing duration, the intensity of deformation and shear textures is continuously decreased; however, the recrystallization (Cube) orientation becomes stronger up to 11.2 × R. After 1, 2, and 5 min of post‐annealing, the hardness, yield strength, tensile strength, ductility, and toughness of copper are higher than those of the 90% rolled sample due to annealing hardening. After 10 min of annealing, the hardness, yield strength, and tensile strength suddenly decrease and the ductility and toughness significantly enhance owing to the complete recrystallization. With increasing the post‐annealing time, the fraction of flat surfaces is decreased and the fraction of ductile dimples is increased. With the post‐annealing time increasing from 1 to 120 min, the electrical conductivity gradually increases from 84.9%IACS to 96.7%IACS. [ABSTRACT FROM AUTHOR]

Herein, two improved compression–torsion conversion (CTC) mechanical metamaterials are proposed with arrayed‐type and cylindrical shell‐type based on the optimization design of an inclined strut. Compared with the original design, improvements in CTC performance can be achieved by optimization of the strut shape in the feasible region. The CTC properties of the optimized metamaterials are studied by theoretical calculations, finite‐element simulations, and experiments. The effects of the shape coefficients of the S‐strut on the optimization efficiencies are discussed. The optimized structures significantly improve the mechanical properties of the CTC mechanical metamaterials. The optimized S‐strut metamaterials are increased by more than 25% higher CTC efficiencies than the original structures. The structures have improved CTC properties and are closer to the application. In addition, the proposed S‐strut mechanical metamaterials have a promising application in the aerospace field. [ABSTRACT FROM AUTHOR]

Exposure to mechanical stimuli such as pressure and stretching prompts the skin to undergo physiological adaptations to accommodate and distribute applied forces, a process known as mechanotransduction. Mechanotherapy, which leverages mechanotransduction, shows significant promise across various medical disciplines. Traditional methods, such as massage and compression therapy, effectively promote skin healing by utilizing this mechanism, although they require direct skin contact. This study introduces a novel contactless modality, Shear Wave Stimulation (SWS), and evaluates its efficacy compared to traditional massage in eliciting responses from human skin and fascia. Fifteen healthy volunteers received SWS, while another fifteen volunteers received massage. Tests of skin mechanical properties revealed significant enhancements in skin shear modulus for both methods, showing an increase of approximately 20%. Additionally, deformation analysis of ultrasound images showed distinct responses of the skin and fascia to the two stimuli. SWS induced extension in the dermis (∼18%), hypodermis (∼16%), and fascia (∼22%) along the X and Y axes. In contrast, massage compressed the skin layers, reducing the dermis by around 15% and the hypodermis by about 8%, while simultaneously stretching the superficial fascia by approximately 8%. The observed extension across the entire skin with SWS highlights its potential as a groundbreaking contactless approach for promoting skin healing. Furthermore, the differing responses in blood flow reaffirm the distinct stimulation modes of SWS and massage. These findings establish a foundation for future innovative skin therapy modalities. [ABSTRACT FROM AUTHOR]

In this study, two types of porous Cf/Cm composites were obtained by introducing pyrolytic carbon (PyC) and pyrolytic carbon/furan resin carbon (PyC/FRC). Subsequently, Cf/Cm-SiC-(ZrxHf1−x)C composites with different carbon matrices were prepared by introducing SiC and (ZrxHf1−x)C matrices into the porous Cf/Cm composites via the reactive melt infiltration method, specifically termed as Cf/PyC-SiC-(ZrxHf1−x)C and Cf/PyC/FRC-SiC-(ZrxHf1−x)C composites. The microstructures of the porous Cf/Cm and Cf/Cm-SiC-(ZrxHf1−x)C composites with different carbon matrices were examined, and a comprehensive analysis was conducted on microstructural evolution and mechanical behaviors of the Cf/Cm-SiC-(ZrxHf1−x)C composites. The results indicate that both Cf/Cm-SiC-(ZrxHf1−x)C composites underwent similar microstructural evolution processes, differing only in terms of evolution kinetics and final microstructure. Differences in the pore structures of porous Cf/Cm composites, as well as in the reactivities of carbon matrices, were identified as primary influencing factors. Additionally, both Cf/Cm-SiC-(ZrxHf1−x)C composites exhibited "pseudo-ductile" fracture characteristics, with flexural strengths of 214.1 ± 8.8 MPa and 149.6 ± 12.2 MPa, respectively. In the Cf/PyC-SiC-(ZrxHf1−x)C composite, crack initiation during loading primarily originated from the ceramic matrix, while in the Cf/PyC/FRC-SiC-(ZrxHf1−x)C composite, failure initially arose from the residual FRC matrix. Excessive fiber corrosion and the presence of residual low-modulus FRC matrix resulted in lower mechanical performance. [ABSTRACT FROM AUTHOR]

The steep Martian terrain features numerous notches and alcoves that could potentially be adapted as temporary shelters. By sealing their entrances and modifying the interior space, these alcoves can be transformed into habitable structures. Given their prolonged exposure to Martian temperature fluctuations, it is crucial to understand the mechanical properties of alcove rocks to design appropriate shelter parameters. This study investigates the mechanical behavior of basalt specimens subjected to Martian cryogenic freeze-thaw (F-T) cycles (−143∼35 °C) and subsequent uniaxial cyclic loading tests. The test results indicate that the longitudinal wave velocity, peak stress, and elastic modulus of basalt specimens degrade to varying degrees with an increasing number of F-T cycles. At higher stress levels, the ratio of dissipated energy density to elastic energy density in basalt specimens subjected to different F-T treatments converges to approximately 0.25. During the uniaxial cyclic loading tests, both cumulative acoustic emission (AE) counts and average maximum principal strains of the specimens increase stepwise. For specimens after F-T treatment, the spectral-domain characteristics can be classified into three frequency bands, with the middle and high frequencies predominating. The application of the Gaussian Mixture Model (GMM) clustering algorithm enhances the analysis of AE results, facilitating the identification of tensile and shear cracks. As the number of F-T cycles increases, the percentage of shear cracks in basalt specimens decreases from 76.5% (0 cycle) to 53.5% (7 cycles).

Seawater sea-sand concrete (SSC) structures reinforced with fiber reinforced polymer (FRP) bars were proposed to capture CO2 by means of carbonation curing in this study. FRP-SSC structures allowed sufficient carbonation to occur since the steel corrosion in traditional reinforced concrete structures would not exist. Herein, the pore structure of CO2-cured SSC with sufficient carbonation was examined, and the mechanical behaviors under uniaxial compression were also investigated. MIP testing was employed, and surface fractal dimension in various pore-size regions was calculated. The results indicate that CO2 curing leads to a more significant variation in smaller mesopores of SSC than CC. Regarding middle capillary pores, the surface fractal dimension in almost all CO2-cured specimens ranges from 2.6617 to 2.8124, which means that these pores show distinct fractal characteristics, but this phenomenon does not be observed in water-cured specimens. This indicates that CO2 curing can greatly reduce ink-bottle pores in concrete. Furthermore, the compressive strength gain of CO2-cured SSC with sufficient carbonation is above 30% at the 180-days age. The compressive strength gain can be attributed to the improvement in the surface fractal dimension. Moreover, CO2-cured specimens exhibit higher peak stress, smaller peak strain, and greater elastic module, resulting in lower plasticity. Consequently, CO2 curing renders SSC and CC more brittle. [ABSTRACT FROM AUTHOR]

In open-cut assembled subway tunnels, foundation pit enclosure piles are typically cast in place. However, this conventional approach limits the functionality of the piles to serving as retaining structures during excavation, resulting in resource inefficiency and the underutilization of prefabrication techniques. To address this issue, a fully prefabricated pile-wall composite scheme is proposed for cut-and-cover tunnels to optimize the retaining effect of the piles and leverage the benefits of prefabricated technology. In this scheme, the retaining pile and lining are both prefabricated. The pile is the temporary retaining structure during pit excavation and a part of the sidewall. This scheme was researched and applied in Jinan, China. Field monitoring and numerical simulation were used to investigate the load transfer within the fully prefabricated pile-wall composite structure (PPWS) and its mechanical response, respectively. The results show: (1) The development of lateral earth pressures on the PPWS experienced three stages. The lateral earth pressure distribution indicates that the PPWS can fully activate the retaining effect of precast piles. (2) Following the backfilling of the joints, the horizontal displacement at the bottom of the precast pile reduced by 0.39 mm. Numerical simulation results indicate the effectiveness of precast pile restraint in PPWS. (3) The PPWS exhibited uniform deformation transition at the joints. The joints play a crucial role in coordinating deformation between the precast piles and sidewalls, utilizing the restraining effect of the precast piles. [ABSTRACT FROM AUTHOR]

This study is intended towards enhancing the working life of the spur gear and improving its performance using the surface coating process. Mild steel C45 has been chosen as the base material for spur gear, and various specimens were synthesized by coating the base material with Al2O3-40%TiO2, Cr3C2-20%NiCr, and WC-10%Co-4%Cr using detonation thermal spray method. XRD pattern confirms the materials phase, and SEM analysis reveals the surface's topography and compositions. EDS spectra show the presence of elements. The analysis of properties such as contact stress, bending stress, and total deformation has been carried out, and the specimens have also been studied based on their hardness, tensile, and wear tests. The theoretical stress values of the spur gear have been obtained using the Hertz equation on ANSYS 2021 R2 simulator which is also employed to carry out finite element analysis. Simulations were carried out on single-gear and meshed-gear configurations. The microstructure and mechanical properties of coated materials were compared with uncoated Mild Steel C45. The investigation shows that all the coated materials exhibited better hardness, tensile strength, and wear resistance, and among these substrates coated with WC-Co-Cr possessed the highest abrasive resistance. [ABSTRACT FROM AUTHOR]

In this paper, the static and dynamic analysis of the higher-order shear deformation nanobeam is investigated within the framework of the two-phase local/nonlocal integral model, in which, the stress is described as the integral convolution form between the strain field and a decay kernel function to address the long-range force interactions in the domain. Based on the principle of minimum potential energy, the finite element formulation of the nonlocal higher-order shear deformation theory nanobeams is derived in a general sense through finite element method (FEM). The explicit expressions of the stiffness, geometric stiffness and mass stiffness matrix of the higher-order shear deformation theory nanobeams are derived directly. The efficiency and accuracy of the developed finite element model of higher-order shear deformation nanobeam are validated by conducting a comparation with the existing analysis results in the researches. Furthermore, under different loading and supported conditions, the effect of nonlocal parameter, nonlocal phase parameter and slenderness ratio on the bending, buckling and free vibration responses of higher-order shear deformation theory nanobeams is investigated in detail. [ABSTRACT FROM AUTHOR]

Combined dynamic and static loading tests with equal impact energy (about 150 J) were conducted on granite after high temperature by an improved split Hopkinson pressure bar (SHPB) test device. Effect of axial compression ratios (ACR) on the strength, dynamic elastic modulus (Ed), failure behavior, dissipated energy, and fractal dimension of heat-treated samples was investigated. Results indicated that post-peak strain of samples before 300 °C began to rebound with increasing ACR, belonging to type II. After 300 °C, the ACR would not change the curves’ type, belonging to type I. The sensitivity of dynamic uniaxial compression strength (DUCS) and combined strength to temperature was consistent, but their sensitivity to ACR was different. Empirical equations for variations of strength with ACR and temperature indicated that same strength corresponded to multiple combinations of ACR and temperature, but samples’ crushing degree existed differences. As the ACR or temperature increased, the Ed climbed up and then declined. As the temperature rose or the ACR declined, the percentage of dissipated energy during sample failure increased. When the ACR was 0.8 and temperature was within 300 °C, the dissipated energy was negative, i.e., the sample released elastic strain energy for debris ejection instead of absorbing energy. When the temperature or ACR increased, mass of small-sized sample debris increased, and the crushing degree enhanced. Fractal dimension D well characterized the crushing degree of samples. Scanning electron microscope (SEM) images explained the diminishing mechanical properties of samples with increasing temperature. Results provided a reference for the construction of deep high-stress and high-temperature rock engineering. [ABSTRACT FROM AUTHOR]

Mechanical metamaterials, whose unique mechanical properties stem from their structural design rather than material constituents, are gaining popularity in engineering applications. In particular, recent advances in self-assembly techniques offer the potential to fabricate load-bearing mechanical metamaterials with unparalleled feature size control and scalability compared to those produced by additive manufacturing (AM). Yet, the field is still in its early stages. In this perspective, we first provide an overview of the state-of-the-art self-assembly techniques, with a focus on the copolymer and colloid crystal self-assembly processes. We then discuss current challenges and future opportunities in this research area, focusing on novel fabrication approaches, the need for high-throughput characterization methods, and the integration of Machine Learning (ML) and lab automation for inverse design. Given recent progress in all these areas, we foresee mechanical metamaterials fabricated from self-assembly techniques impacting a variety of applications relying on lightweight, strong, and tough materials. [ABSTRACT FROM AUTHOR]

This study aims to address the complex stress state commonly observed in concrete structures in practical engineering, as well as the challenges posed by resource scarcity and environmental pollution. To achieve this, a total of 168 cylinder specimens of glass fiber recycled coarse aggregate concrete (GFRAC) were designed for conventional triaxial compression tests. The analysis of the test results reveals that the application of lateral restraint force induces a shift in the failure mode of GFRAC from longitudinal splitting failure to plastic deformation failure, occurring either in the middle or at the end of the specimen. The lateral constraint force can effectively improve the stress and strain at the peak point of GFRAC and the modulus of elasticity of the specimen. The glass fiber increases the peak stress of the specimen, and the maximum growth rate is 20%. On the contrary, the glass fiber reduces the peak strain, and the maximum reduction is 49.66%. Increasing the replacement rate of recycled coarse aggregate will lead to a decrease in peak stress, with a maximum decrease of 19.17%. Glass fiber (GF) limits the appearance and propagation of cracks by bridging, pulling out or breaking. Finally, three different failure criteria are used to analyze the triaxial compression state of GFRAC from a macro perspective. [ABSTRACT FROM AUTHOR]

Liquid nitrogen freeze–thaw (LNFT) cycles can realize the high-volume fracturing of coalbed methane (CBM) reservoirs, because they can effectively improve the distribution of pores and cracks inside coal. To quantitatively evaluate the mechanical behaviors and permeability evolution law of coal with LNFT cycles, the mechanical and permeability tests of the coal subjected to LNFT cycles under different geological conditions are performed. The structural damage of the coal under different LNFT cycles is analyzed from both macro- and micro-perspectives. The results indicate that under a low confining pressure, the LNFT cycle treatment can significantly aggravate the deterioration of mechanical properties of coal; whereas this deterioration effect will be weakened to some extent under a high confining pressure. The coal treated with LNFT cycles tends to shear failure under no confining pressure. However, under confining pressure, the coal treated with LNFT cycles is more prone to tensile failure, especially under relatively high confining pressure. The permeability of the coal presents a natural logarithm increase with LNFT cycles. The changes in the coal permeability are controlled by the internal structure of coal and the gas rarefaction effect. With the increase of LNFT cycles, the coal permeability change becomes more sensitive to confining pressure and gas pressure due to the gas rarefaction effect. During the LNFT of the coal, the temperature gradient mainly produces macro-main cracks, while the anisotropy of the thermal expansion coefficient of mineral grains, water–ice phase transition, and liquid nitrogen vaporization mainly induce internal micro-cracks including intergranular cracks and intragranular cracks inside the coal. The ideal number of LNFT cycles for CBM reservoirs is closely related to the geological condition including in situ stress and pore pressure. Highlights: The mechanical parameters and failure behavior of coal treated with liquid nitrogen freeze–thaw cycles have an obvious confining pressure effect. The gas rarefaction effect inside coal is significantly affected by liquid nitrogen freeze–thaw cycles and confining pressure. The ideal number of liquid nitrogen freeze–thaw cycles for CBM reservoirs is closely related to in-situ stress and pore pressure. The structural damage of coal under different liquid nitrogen freeze–thaw cycles is analyzed from both macro and micro scales. [ABSTRACT FROM AUTHOR]

Polyvinyl alcohol (PVA)-based scaffold fabricated by fused deposition modeling (FDM) shows great potential in cartilage repair field. However, the limited mechanical properties after being swollen by water molecules in the body fluid hinder their applications. Herein, the boric acid is introduced to improve the mechanical behaviors of FDM-printed PVA-based scaffold. The ICP, FTIR, SEM, and swelling behaviors are utilized to explore the influence of boric acid concentration on the materials. The results indicate that the boric acid would form boronic ester-crosslinked PVA (B-PVA) and the density of the crosslink will increase at first then decrease with the boric acid concentration increases. As the concentration of boric acid is 1 %, the densest crosslink point in materials can be obtained. Then the fatigue, relaxation, and creep behaviors tests are carried out, which indicates that the crosslinking will improve the mechanical behaviors of scaffold at a great level. At last, the scaffold shows a good mineralization ability and excellent biocompatibility. [ABSTRACT FROM AUTHOR]

In deep rock engineering, natural cracks in rock mass subjected to thermo-hydro-mechanical-chemical (THMC) loads have tendency to initiate and propagate, and result in potential safety hazards. Current literature on cracking behaviors and mechanism of pre-cracked rock under multi-field loads is focused on single (M), two (TM, HM) or three fields (THM, HMC), less on THMC fields. In this study, a series of self-designed triaxial compressive tests were performed to study different THMC fields influencing on mechanical behaviors and failure patterns of pre-cracked red sandstone specimens. A new THMC fracture criterion, recently proposed by our group team, is used to further analyze the crack initiation mechanism of red sandstone under THMC loads. Research results suggest that the stress-strain curve is greatly influenced by the temperature, confining pressure and acidity and alkalinity of chemical solution, but relatively less by the hydraulic pressure. As the temperature and hydraulic pressure increase, the confining pressure decreases, and the acidity or the alkalinity of chemical solutions becomes strong, both the elastic modulus, crack initiation stress and peak strength of specimen are decreased, and the failure pattern is changed from shear failure to tensile failure. The crack initiation stress and peak strength usually have the largest, middle, smallest values in the shear, tension-shear and tensile failures, respectively, while the peak strain has largest value in the mixed tensile-shear failure. The acid solution has greater weakening effect than the alkaline solution with the same concentration. Theoretical results indicate that the temperature and chemical fields influencing on crack initiation is mainly attributable to its weakening of rock fracture toughness, while seepage and stress fields on crack initiation to its change of the stress state at crack-tips. The THMC mechanism of crack initiation can be well revealed by the new THMC fracture criterion.

Underground hydrogen energy storage (UHES) in lined rock caverns (LRCs) presents a highly promising and innovative remedy to mitigate the inherent volatility of renewable energy sources. However, this approach necessitates a reliable sealing layer with enhanced mechanical properties to ensure stability and security. In this study, a novel composite sealing layer is fabricated by employing the epoxy (EP) as matrix and incorporating graphene oxide (GO) and aluminum oxide (AO) as nanofillers. The static behaviors of the sealing layers are evaluated combined with the digital image correlation (DIC) system and scanning electron microscope (SEM) under coupled temperature loading, while the fatigue behaviors are tested at various stress amplitudes and temperature environment. With the rise in temperature, the molecular thermal motion of EP becomes more pronounced, which reduce both the elastic modulus (E) and ultimate strength (σ ult) of the composite sealing layers. However, the ultimate displacement (s ult) increases with increasing temperature, which can be attributed to the softening of the EP matrix and the enhanced debonded and bridging effect of nanofillers. As the mass fraction (M f) of nanofillers increases, the magnitude of the increase in the maximum values of strain range (ε ran) diminishes, which can be attributed to the incorporation of nanofillers facilitate the absorption and dispersion of internal energy within the composite materials. The optimized composite sealing layer with 10% M f of binary nanofillers demonstrated s ult values of 28.54 mmm, 30.16 mm and 33.57 mm at room temperature, 50 °C and 100 °C, respectively, which represent a 32.77%, 38.03% and 46.21% increase compared to pure EP. Besides, the maximum value of ε ran when the upper fatigue stress is 0.7 σ ult is increased to 2.55 × 10−3. The findings presented in this study contribute to the improvement of safety and durability of UHES in LRCs. [Display omitted] • Sealing layers based on epoxy modified by nanofillers are fabricated for hydrogen storage in lined rock caverns. • Mechanical behaviors of the sealing layers coupled with temperature loading are tested. • The novel sealing layer exhibits excellent mechanical properties during hydrogen storage and release. [ABSTRACT FROM AUTHOR]

Dual-phase steels have received extensive attention in autobody frame manufacturing due to the resulting characteristics of an interesting combination of ductile ferrite and hard martensite. Moreover, the ductile ferrite and hard martensite lead to heterogeneous deformation in the boundary between the two phases. Then, geometrically necessary dislocations (GNDs) are created to accommodate a lattice mismatch due to the deformation incompatibility of the boundary in straining. In this study, a new empirical GND model is developed, in which the GND density is a function of local plastic deformation; the GND density is distributed in the phase boundary in accordance with an “S” model of material plastic strain. The boundary conditions are applied to define the parameters. The proposed model is verified with DP600 steel. The effects of the GNDs and the width between ferrite and martensite on the strain hardening of DP600 steel are evaluated.

Precursor-derived ceramic SiOC (PDC-SiOC) microlattices exhibit excellent oxidation resistance, high-temperature stability, and superior mechanical properties. However, the printing accuracy of the PDC-SiOC microlattices by 3D printing is still limited, and mechanical properties of the PDC-SiOC microlattices have not been studied systematically. Here, PDC-SiOC octet microlattices were fabricated by projection micro stereolithography (PμSL) 3D printing, and photoabsorber (Sudan III)’s effect on the accuracy was systematically analyzed. The results showed that the addition of Sudan III improved the printing accuracy significantly. Then, the ceramization process of the green body was analyzed in detail. The order of the green body decreased, and most of their chemical bonds were broken during pyrolysis. After that, the PDC-SiOC microlattices with different truss diameters in the range of 52–220 μm were fabricated, and their mechanical properties were investigated. The PDC-SiOC microlattices with a truss diameter of 52 μm exhibited higher compression strength (31 MPa) than those with bigger truss diameters. The size effect among the PDC-SiOC microlattices was analyzed. Our work provides a deeper insight into the manufacturing of PDC-SiOC micro-scaled architectures by 3D printing and paves a path to the research of the size effect in ceramic structures.

Exposure to mechanical stimuli such as pressure and stretching prompts the skin to undergo physiological adaptations to accommodate and distribute applied forces, a process known as mechanotransduction. Mechanotherapy, which leverages mechanotransduction, shows significant promise across various medical disciplines. Traditional methods, such as massage and compression therapy, effectively promote skin healing by utilizing this mechanism, although they require direct skin contact. This study introduces a novel contactless modality, Shear Wave Stimulation (SWS), and evaluates its efficacy compared to traditional massage in eliciting responses from human skin and fascia. Fifteen healthy volunteers received SWS, while another fifteen volunteers received massage. Tests of skin mechanical properties revealed significant enhancements in skin shear modulus for both methods, showing an increase of approximately 20%. Additionally, deformation analysis of ultrasound images showed distinct responses of the skin and fascia to the two stimuli. SWS induced extension in the dermis (∼18%), hypodermis (∼16%), and fascia (∼22%) along the X and Y axes. In contrast, massage compressed the skin layers, reducing the dermis by around 15% and the hypodermis by about 8%, while simultaneously stretching the superficial fascia by approximately 8%. The observed extension across the entire skin with SWS highlights its potential as a groundbreaking contactless approach for promoting skin healing. Furthermore, the differing responses in blood flow reaffirm the distinct stimulation modes of SWS and massage. These findings establish a foundation for future innovative skin therapy modalities.

In this study, two types of porous Cf/Cm composites were obtained by introducing pyrolytic carbon (PyC) and pyrolytic carbon/furan resin carbon (PyC/FRC). Subsequently, Cf/Cm-SiC-(ZrxHf1−x)C composites with different carbon matrices were prepared by introducing SiC and (ZrxHf1−x)C matrices into the porous Cf/Cm composites via the reactive melt infiltration method, specifically termed as Cf/PyC-SiC-(ZrxHf1−x)C and Cf/PyC/FRC-SiC-(ZrxHf1−x)C composites. The microstructures of the porous Cf/Cm and Cf/Cm-SiC-(ZrxHf1−x)C composites with different carbon matrices were examined, and a comprehensive analysis was conducted on microstructural evolution and mechanical behaviors of the Cf/Cm-SiC-(ZrxHf1−x)C composites. The results indicate that both Cf/Cm-SiC-(ZrxHf1−x)C composites underwent similar microstructural evolution processes, differing only in terms of evolution kinetics and final microstructure. Differences in the pore structures of porous Cf/Cm composites, as well as in the reactivities of carbon matrices, were identified as primary influencing factors. Additionally, both Cf/Cm-SiC-(ZrxHf1−x)C composites exhibited “pseudo-ductile” fracture characteristics, with flexural strengths of 214.1 ± 8.8 MPa and 149.6 ± 12.2 MPa, respectively. In the Cf/PyC-SiC-(ZrxHf1−x)C composite, crack initiation during loading primarily originated from the ceramic matrix, while in the Cf/PyC/FRC-SiC-(ZrxHf1−x)C composite, failure initially arose from the residual FRC matrix. Excessive fiber corrosion and the presence of residual low-modulus FRC matrix resulted in lower mechanical performance.

Herein, the mechanical properties and corrosion behavior in simulated body fluid of the β‐type Ti29Nb13Ta4.6Zr alloy (TNTZ) are investigated and compared to Ti6Al4V alloy. The samples are obtained from the solution‐treated (ST) and water‐quenched TNTZ bars. Following quenching, the bars are cold rolled aged (CRA) at 673 K for 20 min in order to reach a desired combination of high yield strength and low elastic modulus. The corrosion tests are conducted using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) during a long period of immersion in physiological Ringer's solution (up to 144 h), and the mechanical behaviors are assessed through uniaxial tensile tests. The results show that both TNTZ ST and CRA conditions have lower Young's moduli than Ti6Al4V. However, with CRA treatment, the alloy is significantly strengthened due to a homogeneous precipitation of nanometer‐sized α‐phase with lenticular morphology in the β‐matrix. Potentiodynamic polarization and EIS results reveal that both TNTZ CRA and Ti6Al4V passivate under testing conditions, and the passive current density is very low, providing corrosion resistance in the potential range studied. The EIS results also reveal that the passive film formed on the surface of both materials is highly corrosion resistant. [ABSTRACT FROM AUTHOR]

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In this work, microstructural evolution and mechanical behavior of Co-free (Fe40Ni30Cr20Al10)100-xTix (x = 0, 2, 4, 6, and 8 at%) high-entropy alloys (HEAs) are investigated. All as-cast HEAs consist of face-centered-cubic (FCC)- and bodycentered-cubic (BCC)-structured phases, wherein the BCC-structured phase is composed of disordered BCC (A2) and ordered BCC (B2) phases. The HEAs show FCC dendrite and BCC inter-dendrite microstructure when x = 4. As the Ti content increases to 6 and 8 at%, the microstructure evolves from dendrite structures to complex lamellar structures, leading to a significant loss in ductility. With the increase of Ti, the strength is enhanced with the sacrifice of ductility. The (Fe40Ni30Cr20Al10)96Ti4 alloy exhibits promising combinations of strength and ductility, displaying a yield strength of 680 MPa, an ultimate tensile strength of 1132 MPa, and a total elongation of 16.6%. The simple FCC þ BCC dendrite microstructure and optimal content of the BCC-structured region containing A2 þ B2 phases are responsible for the excellent tensile properties of the as-cast (Fe40Ni30Cr20Al10)96Ti4 HEA. In this work, it is suggested that good combinations of strength and ductility of low-cost Co-free FeNiCrAl-based HEAs can be achieved by tailoring Ti addition. [ABSTRACT FROM AUTHOR]

With the increasing interest in biopolymer nanofibers for diverse applications, the characterization of these materials in the physiological environment has become of equal interest and importance. This study performs first‐time simulated body fluid (SBF) degradation and tensile mechanical analyses of blended fish gelatin (FGEL) and polycaprolactone (PCL) nanofibrous meshes prepared by a high‐throughput free‐surface alternating field electrospinning. The thermally crosslinked FGEL/PCL nanofibrous materials with 84–96% porosity and up to 60 wt% PCL fraction demonstrate mass retention up to 88.4% after 14 days in SBF. The trends in the PCL crystallinity and FGEL secondary structure modification during the SBF degradation are analyzed by Fourier transform infrared spectroscopy. Tensile tests of such porous, 0.1–2.2 mm thick FGEL/PCL nanofibrous meshes in SBF reveal the ultimate tensile strength, Young's modulus, and elongation at break within the ranges of 60–105 kPa, 0.3–1.6 MPa, and 20–70%, respectively, depending on the FGEL/PCL mass ratio. The results demonstrate that FGEL/PCL nanofibrous materials prepared from poorly miscible FGEL and PCL can be suitable for selected biomedical applications such as scaffolds for skin, cranial cruciate ligament, articular cartilage, or vascular tissue repair. [ABSTRACT FROM AUTHOR]

Dual-phase steels have received extensive attention in autobody frame manufacturing due to the resulting characteristics of an interesting combination of ductile ferrite and hard martensite. Moreover, the ductile ferrite and hard martensite lead to heterogeneous deformation in the boundary between the two phases. Then, geometrically necessary dislocations (GNDs) are created to accommodate a lattice mismatch due to the deformation incompatibility of the boundary in straining. In this study, a new empirical GND model is developed, in which the GND density is a function of local plastic deformation; the GND density is distributed in the phase boundary in accordance with an “S” model of material plastic strain. The boundary conditions are applied to define the parameters. The proposed model is verified with DP600 steel. The effects of the GNDs and the width between ferrite and martensite on the strain hardening of DP600 steel are evaluated. [ABSTRACT FROM AUTHOR]

In open-cut assembled subway tunnels, foundation pit enclosure piles are typically cast in place. However, this conventional approach limits the functionality of the piles to serving as retaining structures during excavation, resulting in resource inefficiency and the underutilization of prefabrication techniques. To address this issue, a fully prefabricated pile-wall composite scheme is proposed for cut-and-cover tunnels to optimize the retaining effect of the piles and leverage the benefits of prefabricated technology. In this scheme, the retaining pile and lining are both prefabricated. The pile is the temporary retaining structure during pit excavation and a part of the sidewall. This scheme was researched and applied in Jinan, China. Field monitoring and numerical simulation were used to investigate the load transfer within the fully prefabricated pile-wall composite structure (PPWS) and its mechanical response, respectively. The results show: (1) The development of lateral earth pressures on the PPWS experienced three stages. The lateral earth pressure distribution indicates that the PPWS can fully activate the retaining effect of precast piles. (2) Following the backfilling of the joints, the horizontal displacement at the bottom of the precast pile reduced by 0.39 mm. Numerical simulation results indicate the effectiveness of precast pile restraint in PPWS. (3) The PPWS exhibited uniform deformation transition at the joints. The joints play a crucial role in coordinating deformation between the precast piles and sidewalls, utilizing the restraining effect of the precast piles.

Natural resources have been excessively consumed, and large amounts of construction wastes have been generated, owing to the fast development of civil industry, causing crucial environmental issues. Therefore, reusable construction waste fabricated into recycled concrete offers a good strategy to solve this issue. Thus, this article first develops thin-walled steel tubes stub columns filled with self-compacting concrete containing recycled coarse aggregate. Afterwards, the compressive behaviors of the columns when undergoing axial compression loading to failure are explored. Subsequently, the effect of types of self-compacting concrete and wall thickness on failure modes and the relationships between load and displacement/strain is discussed comprehensively. Moreover, models of load–displacement/strain behaviors are proposed. The results show that columns with identical wall thicknesses containing both natural and recycled coarse aggregate display similar failure modes, mainly presenting as local buckling and rupture. The shape of the load–displacement/strain curves for identical wall thicknesses are almost the same. Nevertheless, the maximum load and stiffness of columns containing recycled coarse aggregate are lower than those of columns containing natural coarse aggregate. Additionally, the maximum loads corresponding to wall thickness of 1.2 mm and 3.0 mm are decreased by 18.4% and 5.8%, respectively. Moreover, the proposed models can reasonably evaluate the relationships between load and displacement/strain. This paper demonstrates that thin-walled steel tubular columns containing recycled coarse aggregate present positive compressive behaviors and thus exhibit great potential for developing environmentally friendly and sustainable civil infrastructures. [ABSTRACT FROM AUTHOR]

This study aimed to use hydrogel to stabilize expansive clayey soil. The effect of sodium alginate content on mechanical behaviors, swelling, and durability of hydrogel-impregnated clayey soil were investigated through unconfined compression tests, consolidated and undrained triaxial tests, free swelling tests, and durability tests. The tests results indicated that the sodium alginate added in the clay soil had a positive effect on the residual strength of the soil samples. The Ca-alginate hydrogel produced in the soil samples improved their ductility significantly. The swelling deformation of clay soil decreased along with higher sodium alginate content. The results showed that the swelling deformation decreased from 0.8 mm to 0.5 mm when 0.4% sodium alginate was added in the clay soil which was nearly 37.5% reduction. The connection between clay soil particles was improved by the gelation connection provided by hydrogel the friction of soil was also enhanced a lot. For wet–dry and freeze–thaw cycles, 60% and 80% of the original unconfined compression strength of hydrogel-impregnated clay remained after 12 cycles. It can be concluded that the Ca-alginate hydrogel has a good durability performance against wet–dry and freeze–thaw cycles. [ABSTRACT FROM AUTHOR]

The effects of doping concentration and doping models of yttrium (Y) on mechanical behaviors are researched by using molecular dynamics and the second nearest-neighbor modified embedded-atom method (2NN-MEAM) formalism for nano Mg-Y alloy systems. The results confirm the effect of Y-doping on the mechanical properties and the polycrystalline structure of Mg-Y alloys. When the content of Y atoms is about 7-8%, the models of pristine doping and grain boundaries (GBs) doping have the highest Young's modulus, and the strength also increases obviously. Doping Y atoms at GBs can enhance the stability of GBs and significantly improve the elastic modulus and strength of nano Mg alloys. And the smaller the grain size is, the more obvious the strengthening effect is. As the grain size decreases to the critical value, Young's modulus of the nano Mg-Y alloys decreases, and the strengthening effect weakens. These results have important guiding significance for the design and improvement of mechanical properties of Mg-Y alloys and will provide references for preparing high strength nano Mg alloys materials by controlling impurity atoms doping. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract With the increasing interest in biopolymer nanofibers for diverse applications, the characterization of these materials in the physiological environment has become of equal interest and importance. This study performs first‐time simulated body fluid (SBF) degradation and tensile mechanical analyses of blended fish gelatin (FGEL) and polycaprolactone (PCL) nanofibrous meshes prepared by a high‐throughput free‐surface alternating field electrospinning. The thermally crosslinked FGEL/PCL nanofibrous materials with 84–96% porosity and up to 60 wt% PCL fraction demonstrate mass retention up to 88.4% after 14 days in SBF. The trends in the PCL crystallinity and FGEL secondary structure modification during the SBF degradation are analyzed by Fourier transform infrared spectroscopy. Tensile tests of such porous, 0.1–2.2 mm thick FGEL/PCL nanofibrous meshes in SBF reveal the ultimate tensile strength, Young's modulus, and elongation at break within the ranges of 60–105 kPa, 0.3–1.6 MPa, and 20–70%, respectively, depending on the FGEL/PCL mass ratio. The results demonstrate that FGEL/PCL nanofibrous materials prepared from poorly miscible FGEL and PCL can be suitable for selected biomedical applications such as scaffolds for skin, cranial cruciate ligament, articular cartilage, or vascular tissue repair.

This paper experimentally studied the influence of the notch shape and size on the damage evolution and failure strength (tension and torsion) of carbon fiber-reinforced epoxy matrix (CFRP) laminates. Hashin's damage criteria were utilized to monitor the evolution of multi-damage modes, and FEM simulations were also performed by using the ABAQUS code to clarify the specific damage modes in detail as an instructive complement. The failure characteristics of all the notched samples were analyzed and compared with those without notches. The measured results presented that the existence of a variety of notches significantly impaired the load carrying capacity of CFRP laminates. The tensile strengths of C-notch and U-notch increase with an increasing notch radius, while the ultimate torques of C-notch and V-notch decrease with an increasing notch size and angle. The variation in notched properties was explained by different notch shapes and sizes, and the failure characteristics were also presented and compared among notched CFRP laminates with varied notches. [ABSTRACT FROM AUTHOR]

Seasonal freeze–thaw (F–T) cycles in cold regions may affect the stability of the slope rock mass in open-pit coal mines and even induce engineering geological disasters, such as landslide. In this paper, the moisture-control and water-immersion F–T tests of lignite obtained from the slope in an open-pit mine were carried out, respectively, and the uniaxial compression tests of lignite subjected to the F–T effect were conducted with the acoustic emission monitoring in the whole test. The results showed that the quality, height and porosity of lignite samples increased with the F–T cycles, accompanied by increase in the development degree of macro- and micro-horizontal cracks, and the cracks appeared earlier and larger for the water-immersed rock samples. Mechanical parameters such as uniaxial compressive strength presented a decreasing trend with increase in F–T cycles, accompanied by decline of strain energy, which was significant for the water-immersed samples. In addition, the acoustic emission activity was gradually significant with increase in F–T cycles, which also caused the intensification of microstructure responses. The interior of lignite had significant horizontal bedding structure and banded areas of water, which contributed to the rapid development of horizontal cracks caused by the F–T effect, resulting in the gradual deterioration of lignite; meanwhile, the deterioration degree was more prominent for water-immersed lignite due to continuous water supply and response of free water. [ABSTRACT FROM AUTHOR]

High stress caused by excavation is an inevitable part of deep underground rock mass engineering or mining process, which is the key to induce disasters such as rockbursts. Drilling pressure relief (DPR) is a measure to eliminate deep excavation stress and prevent rockburst disasters, which is simple but effective. The experimental research results based on macroscopic (mechanical behavior characteristics, energy evolution) and microscopic (crack evolution) perspectives to study the mechanism of rockburst prevention by DPR were reviewed. According to the stress state of deep surrounding rock and current testing equipment conditions, six development directions for studing the mechanism of rockburst prevention by DPR were proposed: (1) developing drilling rig test equipment for real-time DPR simulation test under high stress; (2) considering real-time DPR simulation test with cyclic load disturbance factors; (3) exploring the relationship between drilling’s spatial size and surrounding rock stress field and strain energy evolution under two-dimensional high stress; (4) combining with true triaxial testing system to simulate the real-time DPR after rock excavation; (5) focusing energy perspective to study the mechanism of rockburst prevention by DPR; and (6) calculating and visualizing the energy evolution inside the rock mass based on ‘real-time DPR test + numerical simulation calculation’.

The fundamental aim of this study is to acquaint a novel sustainable cellulosic fiber obtained from beetroot plant for using in composite and textile industries. Natural cellulosic beetroot fibers were extracted from beetroot plant with biological degradation method. In order to determine the fiber properties, chemical, physical, and instrumental tests were carried out for fibers. The surface of samples was scanned using a scanning electron microscope (SEM). The elemental composition of fibers was analyzed with an energy dispersive X-ray analysis (EDX) device. Crystallographic properties of fibers were determined with X-ray diffraction (XRD) technique. Thermal degradation behavior of fibers was investigated with thermogravimetric analysis. SEM analyses show that the fibers have a cylindrical morphology and a 284.04-µm diameter. EDX analysis revealed that the fibers have 52.39% carbon and 47.46% oxygen. The XRD analysis indicates that beetroot fiber contains crystallinity index (Crl) of 87% and crystallite size (L) of 3.92 nm. According to the TGA analysis, the major degradation of fibers occurs at a temperature range of 288.09°C to 358.54°C. Mechanical characteristic of fibers was detected with tensile test, which provided information about strength, elongation, Young’s modules, and microfibril angle. The tensile strength, elongation, and Young’s modules of fibers are 50.68 MPa, 7.72%, and 6.56 GPa, respectively. The results show that mechanical behaviors and chemical characteristics of beetroot fibers are compatible with other cellulosic fibers.

M-X have emanated as a potential material for numerous mechanical uses ascribed to their exceptional physicochemical features, multilayered architectures, superior strength, and electrical conductivity along with their flexibility. The mechanical features of M-X polymeric nanoarchitectures are critical to their application in advanced engineering structures and include Young's modulus, bending rigidity, elasticity, sliding resistance, adhesion, ideal strengths, theoretical and experimental affiliations. Furthermore, the deformation along with failure mechanism of materials are essential in engineering applications. Engineering finite elemental models as well as prediction of M-X nanosheets mechanical behavior are imperative in understanding the mechanical behavior of M-X/polymeric nanoarchitectures. Therefore, this paper elucidates the mechanical, deformation, and failure mechanism of M-X and M-X polymeric nanoarchitectures with special emphasis on models utilized in predicting the mechanical behaviors of these materials. [ABSTRACT FROM AUTHOR]

Water is a crucial factor that influences the mechanical behavior of rock and can induce failure. The aim of this study was to investigate the effects of water content and water distribution on the mechanical behavior of sandstone subjected to triaxial compression. Sandstone samples under different water states, including dry, unsaturated, saturated, and long-term saturated, were prepared. Some saturated samples were dried in air for different periods to prepare samples that were dry on the outside but remained wet on the inside. The triaxial compression tests were performed on the samples under four confining pressures: 5, 10, 15 and 25 MPa. The results indicated that the water state of a sandstone sample can be characterized by its water content, soaking time, water distribution, and long-term saturation. The different water states can affect remarkably the strength, deformation, and failure pattern of the sandstone samples subjected to triaxial compression. Several empirical equations were established to describe the evolution of the mechanical behavior of sandstone with increasing water content and soaking duration. The nonuniform distribution of water promotes the generation of tensile cracks, while increasing confining pressure promotes the development of shear cracks. The strength of sandstone samples with dry outside and wet inside are lower than that of samples with wet outside and dry inside. What is more, a long-term saturated state increases the strain-softening of the sandstone samples, thereby increasing their deformation and lowering their strength. Highlights: Influence of water state including water content and water distribution on sandstone is comprehensively investigated by triaxial experiments. A series of predictive empirical equations are established to describe the evolutions of the mechanical properties of sandstone with water content/soaking duration. The strengths of the sandstone samples in the dry outside but wet inside state are smaller than those of samples in the wet outside but dry inside state. A long-term saturated state increases the softening of the rock, thereby increasing the deformation and lowering the strength. Water especially nonuniformly distributed water promotes the propagation of tensile cracks near the surface of the rock. [ABSTRACT FROM AUTHOR]

Thermoplastic polymer fiber–thermoplastic polymer matrix composites (PPCs or PRFPs), often recognized as self‐reinforced or single polymer composites, are potential candidates for future advanced polymer composites because of various advantages (e.g., recyclability, formability, low‐cost, ultra‐lightweight, environmental friendliness, etc.). The manufacturability and mechanical behavior of these composites compared to conventional carbon‐/glass‐/aramid‐fiber‐reinforced polymers is of great interest to the composites community, but there are a limited number of studies in this area. To this end, this paper reviewed fabrication methods with different processing parameters and mechanical behavior of uni‐/multi‐directional thermoplastic PPCs featuring continuous thermoplastic polymer fibers from limited data in the literature. It was shown that most specific behaviors (normalized by density) of these materials in various loading conditions (e.g., quasi‐static tension/shear/flexure, tension‐tension fatigue, and out‐of‐plane impacting, etc.) are comparable to or better than glass‐/aramid‐fiber‐reinforced polymers. Particularly, the specific ductility in the foregoing conditions outperforms all the carbon‐/glass‐/aramid‐fiber‐reinforced polymers. Thermoplastic PPCs with remarkable performance can be achieved through several uncomplicated methods (e.g., film stacking, hot compaction, powder and solution impregnations, matrix infusion and injection molding, additive manufacturing, etc.), which have some similarities to the methods used for carbon‐/glass‐/aramid‐fiber‐reinforced polymers. Moreover, several opportunities and challenging problems of thermoplastic PPCs were summarized at the end of this review paper. Efficient solutions may require countless efforts in the composites community to further strengthen the performance and understanding of thermoplastic PPCs for wide applications in various engineering fields in the future. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of High Pressure Physics is the property of Chinese Journal of High Pressure Physics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fluid saturation plays an important role in rock weakening. However, few researches reveal the controlling factor(s) behind the rock weakening particularly from geochemical perspective. We performed rock failure/fracture reactivation tests on dry and wet samples (saturated with high/low salinity brine). We examined the effect of fluid saturation and salinity on rock mechanical properties through a unique triaxial compression system with combination of micro-seismicity monitoring. Besides, the induced time-dependent micro-seismicity events were located to characterize the fracture orientation together with medical CT imaging. Moreover, we performed geochemical modelling to link the surface energy to rock mechanics from geochemical perspective. Our results show that the peak stress of saturated samples is 11.7% to 15.0% less than unsaturated samples, confirming that fluid saturation can weaken rock. Lowering salinity appears to play a negligible role in the reduction of elastic modulus and peak stress of intact sandstones. We also did not observe the expansion of micro-seismicity cloud along main fracture plane, suggesting that lowering salinity may not trigger micro-fracture generation under confining condition. However, sample saturated with low salinity brine shows a much slower increase rate of differential stress during the plastic deformation to reach yield point during fracture reactivation process compared to the sample saturated with high salinity brine. This work contributes to the existing knowledge of rock weakening by providing quantitative geochemical characterization with implications in water-assisted enhancing hydrocarbon recovery and CO2 geological storage. [ABSTRACT FROM AUTHOR]

A Kevlar tether usually exhibits strong nonlinearity in engineering applications, bringing new challenges to the modeling of tether dynamics. The nonlinear mechanical behaviors, including creep behavior, nonlinear stiffness, hysteresis effect, and dynamical property of a Kevlar tether, are investigated through a series of experiments. The longitudinal loading experiment setup is established, from which the relationships between tether deformation, tension, and time can be obtained. The creep process of Kevlar tethers is divided into three stages, namely, linear creep stage, deceleration creep stage, and long-term creep stage. This paper studied the longitudinal nonlinear stiffness of a Kevlar tether, whose nonlinearity is fitted by the cubic function model. The hysteresis effect under single loading and unloading is fitted well by the Kawabata stress-strain model, which verifies the correctness and validity of Kawabata model. The nonlinear dynamical model, which includes the elastic force, hysteresis force, and damping force, is established to describe the general dynamical property of the Kevlar tether. The experiment results verify the correctness of the dynamical model form. To simplify the analysis, a simplified model is proposed to describe the dynamical property of the Kevlar tether, and the parameters have a good consistency. The works in this paper contribute to the accurate modeling of flexible tether and lay the foundation for the further research of tether dynamics and control. [ABSTRACT FROM AUTHOR]

The connection of subway stations to surrounding underground spaces inevitably involves opening construction in the existing underground structure. The opening construction can strongly impact the existing underground structure when there is no reserved condition. In this study, three-dimensional numerical simulation, model test, and theoretical analysis are used to analyze the mechanical behaviors of side wall opening construction in a mined excavation subway station-Xuanwumen Station of Beijing Subway Line 4. Based on the deformation and stress characteristics of the existing side wall structure, two different reinforcement measures are compared. It is found that the vertical and horizontal deformations of the existing structure caused by opening construction is −1.58 and −1.79 mm, respectively, which are lower than the subway deformation control requirements (3 mm). However, the first and third principal stress increments are 2.14 and −4.62 MPa, respectively, which are markedly higher than the control requirement (10%). A “two-step opening” method is proposed for side wall opening construction in underground structures based on the solution of complex function to the orifice problem. This theoretical method is validated by numerical simulations and model tests, achieving highly consistent results. The allowable ultimate span of side wall opening is 5.75 m without reinforcement. Findings of the present study provide a reference for the design and construction of side wall openings in similar underground spaces.

The fundamental aim of this study is to acquaint a novel sustainable cellulosic fiber obtained from beetroot plant for using in composite and textile industries. Natural cellulosic beetroot fibers were extracted from beetroot plant with biological degradation method. In order to determine the fiber properties, chemical, physical, and instrumental tests were carried out for fibers. The surface of samples was scanned using a scanning electron microscope (SEM). The elemental composition of fibers was analyzed with an energy dispersive X-ray analysis (EDX) device. Crystallographic properties of fibers were determined with X-ray diffraction (XRD) technique. Thermal degradation behavior of fibers was investigated with thermogravimetric analysis. SEM analyses show that the fibers have a cylindrical morphology and a 284.04-μm diameter. EDX analysis revealed that the fibers have 52.39% carbon and 47.46% oxygen. The XRD analysis indicates that beetroot fiber contains crystallinity index (Crl) of 87% and crystallite size (L) of 3.92 nm. According to the TGA analysis, the major degradation of fibers occurs at a temperature range of 288.09°C to 358.54°C. Mechanical characteristic of fibers was detected with tensile test, which provided information about strength, elongation, Young's modules, and microfibril angle. The tensile strength, elongation, and Young's modules of fibers are 50.68 MPa, 7.72%, and 6.56 GPa, respectively. The results show that mechanical behaviors and chemical characteristics of beetroot fibers are compatible with other cellulosic fibers. [ABSTRACT FROM AUTHOR]

This study will investigate the effect of non-woven PET plastic tissue on the fresh, physical, mechanical, acoustic, thermal, and microstructural behaviors of concrete. Including reference specimens, non-woven fabrics were considered in two ways: (a) as a layer with four various configurations of 1-layer, 2-sides, 3-sides, and full wrapping (4-sides) to strengthen specimens, and (b) as (10 × 10) mm cut pieces with three different incorporated percentages of 0.25%, 0.50%, and 0.75%. Based on the experimental results, mechanical properties (compressive, split tensile, and flexural strengths) were remarkably improved by applying non-woven sheets as a layer. For instance, the cylindrical compressive and split tensile strengths were improved by 13.40% and 15.12% for the strengthened specimens compared to the reference specimens, respectively. Moreover, control specimens were damaged to many fragments after mechanical testing, but the samples strengthened by such fabrics or containing cut pieces were maintained and not separated into many small parts. The acoustic behavior and thermal conductivity declined by 9.83% and 19.67% with the attachment of tissue on one side and 2-sides, respectively. Acoustic behaviors decreased by 10.0%, 17.60%, and 26.30% and thermal conductivity decreased by 6.60%, 12.10%, and 15.50%, with the incorporation of 0.25%, 0.50%, and 0.75% of cut pieces, respectively. Finally, it was discovered that non-woven tissue is advised to enhance particular properties of concrete. [ABSTRACT FROM AUTHOR]

Air-hardening organic polymer (AHOP), a new soil stabilizer, can form a cross-link among soil particles with high strength and toughness. In this study, the effect of the polymer content and density on the mechanical behavior of stabilized silty sand was investigated. The results indicate that the unconfined compressive strength and tensile strength of stabilized silty sand keep a prominent linear relationship with AHOP content that increases with the increment in density; the increment in AHOP content also leads to a higher elastic modulus of stabilized silty sand. The cohesion was also significantly enhanced by the increase in AHOP content and density; the internal friction angle of loose specimens (ρ≤1.50 g/cm3) keeps increasing with AHOP content; however, for dense specimens (ρ≥1.55 g/cm3), 3% polymer content is a turning point, at which the internal friction angle changes nonmonotonically. AHOP film can connect loose silty sand particles and adhere to the surface of particles, leading to silty sand with good strength properties. Based on failure modes, the failure of polymer–particle interactions can be divided into four modes, including (1) tensile fracture at membrane, (2) tensile fracture at polymer–particle interface, (3) shear at membrane, and (4) shear at polymer–particle interface. [ABSTRACT FROM AUTHOR]

Traditional ceramic materials are suboptimal for use in complex environments because of their brittleness and sensitivity to flaws. As such, developing flexible and elastic ceramic materials is extremely urgent in frontier domains where high‐frequency vibration or high‐intensity bending environments are inevitable. Fibrillation of ceramic materials is an effective way for the transition of brittleness to flexibility and elasticity, due to its ability to absorb and dissipate stresses through large axial deformations. Here, a comprehensive review of the newly emerging flexible and elastic ceramic fiber materials is presented, starting from an introduction to the fundamental concept, followed by an in‐depth analysis of the relationship between their microstructures and mechanical behaviors, laying emphasis on the toughening mechanism of both individual fibers and fiber assemblies. Finally, current challenges and future development are demonstrated. It is expected that this review may provide meaningful guidance for the advancement of ceramic fiber materials toward better performance and brighter prospects. [ABSTRACT FROM AUTHOR]

Geomechanical behavior of methane hydrate-bearing sediment (MHBS) plays a major role in evaluation of the stability of a hydrate reservoir. A series of triaxial compression tests were conducted on MHBS to study the influence of temperature and pore pressure conditions on its mechanical behaviors. The experimental results show that temperature and pore pressure have a significant effect on the stress–strain curve, stiffness, and strength of MHBS. As temperature decreases and/or pore pressure increases, the stress–strain curve manifests an enhanced strain-softening characteristic, stiffness, and strength. Furthermore, MHBS cohesion also tends to exhibit a significant increase, but its internal friction angle almost remains constant with decreasing temperature and/or increasing pore pressure. These findings imply that the change in temperature and pore pressure affects the strength of MHBS, which occurs predominately due to change in its cohesiveness. To describe these impacts, a phase state parameter is introduced to characterize the temperature and pore pressure conditions. Meanwhile, three empirical formulas for relating the secant modulus, strength and cohesiveness to phase state parameter are presented. Good agreement between simulation and measured data indicates that the phase state parameter can effectively describe temperature and pore pressure conditions. The proposed empirical formulas are able to address the influences of temperature and pore pressure conditions on geomechanical characteristics of MHBS. [ABSTRACT FROM AUTHOR]