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Grafting nanomaterials on the carbon fiber (CF) surface is considered an effective strategy for enhancing the interfacial properties of CF-reinforced polymer composites (CFRPs). However, the mechanical properties of the CFs are often compromised during treatment. A new method for in situ growing silver nanoparticles (AgNPs) on the CF surface is proposed in this study. The CFs are first immersed in a low-viscosity silver nitrate solution to form a thin liquid film on the surface. Subsequently, using the abundant active particles in the plasma, the silver ions are reduced to silver atoms and grown into AgNPs on the CF surface. The tensile strength of CF@Ag was 38.74% greater than that of untreated CF, potentially due to the reparative action of AgNPs on defects in CF. The CF showed an evident improvement in surface wettability because of the AgNPs. Furthermore, the interfacial properties were noticeably improved, with the interfacial shear strength of CF@Ag increasing to 91.59 MPa, which was about twice that of pristine CF. Thus, the mechanical properties of composites are significantly improved (flexural strength increased by 190.74%). This study presents a non-destructive and convenient method for growing nanoparticles onto CF to establish a robust interface in CFRPs. [ABSTRACT FROM AUTHOR]

We report results on the mechanical and structural response to shear deformation of nanodiamond superstructures in interlayer-bonded twisted bilayer graphene (IB-TBG) and interlayer-bonded graphene bilayers with randomly distributed individual interlayer C–C bonds (RD-IBGs) based on molecular-dynamics simulations. We find that IB-TBG nanodiamond superstructures subjected to shear deformation undergo a brittle-to-ductile transition (BDT) with increasing interlayer bond density (nanodiamond fraction). However, RD-IBG bilayer sheets upon shear deformation consistently undergo brittle failure without exhibiting a BDT. We identify, explain, and characterize in atomic-level detail the different failure mechanisms of the above bilayer structures. We also report the dependence of the mechanical properties, such as shear strength, crack initiation strain, toughness, and shear modulus, of these graphene bilayer sheets on their interlayer bond density and find that these properties differ significantly between IB-TBG nanodiamond superstructures and RD-IBG sheets. Our findings show that the mechanical properties of interlayer-bonded bilayer graphene sheets, including their ductility and the type of failure they undergo under shear deformation, can be systematically tailored by controlling interlayer bond density and distribution. These findings contribute significantly to our understanding of these 2D graphene-based materials as mechanical metamaterials. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the effects of different bonding agents and application of glaze on the shear bond strength (SBS) between monolithic zirconia (MZ) and indirect composite (IC). Materials and Methods: Five different bonding agents (G-Premio Bond [GP]; Tokuyama Universal Bond [TU]; Signum Zirconia bond [SZ]; Clearfil Ceramic Primer Plus [CCP]; Z-Prime Plus [ZP]) were applied to a total of 200 MZ disk-shaped specimens (n = 100 glazed and 100 nonglazed). Half of the specimens then underwent thermocycling and the other half no thermocycling (n = 10 specimens each subgroup). The experimental setup was prepared as two pieces according to the ISO TR 11405 standards. Specimens embedded in acrylic resin were placed into the experimental setup and a universal testing machine at a crosshead speed of 0.5 mm/minute. Mann-Whitney U test and Kruskal-Wallis test were used for statistical analyses. Bonferroni correction was then performed, and test results with P < .05 were accepted as statistically significant. Results: The application of glaze significantly enhanced SBS when ZP or CCP was used; however, it did not have any significant effect when GP, TU, or SZ were used. Thermocycling significantly decreased the SBS in all bonding agent groups except GP specimens with glaze (P = .16). The highest SBS in all conditions was noted when GP and TU were used. Conclusions: These findings suggest that the bonding agents GP and TU may be recommended for better bonding between MZ and IC. [ABSTRACT FROM AUTHOR]

Earth pressure for saturated cohesive soils is closely related to the effective stress expression. For cohesionless soils, previous research indicated that the fraction of pore pressure (factor η) in the effective stress expression is below unity at high pressures. However, for cohesive soils, reliable η‐value has not been reported. In this study, experimental data from direct shear and triaxial tests were analyzed in order to derive the η‐values of two cohesive soils. It was shown that η‐value of cohesive soils decreases significantly with increasing effective stress, and the values of η derived from different experiments were consistent with each other. The obtained values of η were applied to the calculations of lateral earth pressure. The lateral earth pressure based on real η was compared with the results of traditional methods, i.e., effective stress analysis (ESA) and total stress analysis (TSA). The traditional ESA was conservative because of the overestimation of active earth pressure. Such conservatism was more significant for high plasticity clay. Contrastingly, TSA results were risky for both of the two cohesive soils. [ABSTRACT FROM AUTHOR]

Highlights Novel water‐soluble polymer‐based sizing agents for carbon fiber/poly(aryl ether ketone) composites (CF/PAEK) have gained attention. However, a challenge remains: the sized CF bundles lack flexibility, and the effect of this on the properties of the composite has not been discussed. Herein, a water‐soluble polyimide oligomer (OL) sizing agent was developed, and the sizing effect was comprehensively evaluated. The conventional molecular weight polyimide (HP) sizing agent was also assessed for comparison. Although the interfacial shear strength of the sized CF monofilaments is enhanced due to improved surface roughness and wettability, the effect of the OL sizing agent on the composite's interlaminar shear strength (ILSS) and tow's flexibility differed from that of the HP sizing agent. Compared with HP‐CF, the yarn spreading rate of OL‐CF tow is increased by about eight times, and the ILSS of OL‐CF/PAEK composites with 2 and 5 MPa molding pressure is increased by 69% and 222%, respectively. The HP sizing agent weakens the tow's flexibility and yarn spreading ability, which is not conducive to the resin penetration in the tow, resulting in lower ILSS. In contrast, the OL sizing agent considers the tow's flexibility and composite's interlaminar property, showing great application potential. Two PI‐based sizing agents with diverse film‐forming capacities were prepared. The ILSS of CF/PAEK with OL sizing agent was significantly improved. HP sizing agent weakened the tow flexibility and interlaminar property. The interaction of sizing layer—resin penetration—ILSS was proposed. [ABSTRACT FROM AUTHOR]

For improving the mechanical properties of MgAl 2 O 4 ceramic and maintaining its wide band transparency, the sapphire/MgAl 2 O 4 /sapphire laminated transparent composites with thin sapphire layers were fabricated by brazing with BaO–B 2 O 3 –SiO 2 (BBS) glass filler. The BBS glass filler had an appropriate CTE (coefficient of thermal expansion) value and good wettability on the surface of sapphire and MgAl 2 O 4 ceramics. Joining experiments were first carried out to optimize the preparation process parameters of laminated composites. The results indicated that high bonding temperature promoted mutual dissolution and diffusion of BBS glass and MgAl 2 O 4 ceramic, but led to the intergranular infiltration of glass filler and the formation of pores due to volatilization of B 2 O 3. When the bonding temperature was 1000 °C, the sapphire/MgAl 2 O 4 joints with the best transparency and acceptable shear strength could be obtained. On this basis, the laminated composites with 0.15 mm thick sapphire layers were fabricated by brazing using BBS glass at 1000 °C. The flexural strength of the laminated composite reached 320 ± 10 MPa, which was higher than that of MgAl 2 O 4 (195 ± 15 MPa). The in-line transmittance of laminated composite was 80.9 % at 1000 nm, which was slightly lower than that of MgAl 2 O 4 (82.2 %). [ABSTRACT FROM AUTHOR]

The implementation of hot melt adhesives reaching structural adhesion with both impact resistance and detachability is of prospective industry value but still remains challenging. In this work, 2‐amino‐4‐hydroxy‐6‐methylpyrimidine serving as both chain extender and end‐capping reagent due to its isomerism, was developed to construct a supramolecular polyurethane‐derived hot melt structural adhesive. The as‐synthesized PUM elastomers occurs obvious decrease of molecular weight at 80°C compared to room temperature, revealing the existence of self‐complementary 2‐ureido‐4[1H]‐pyrimidinone (UPy) motifs at chain ends. This unique structure allows to chemically incorporate abundant hierarchical and quadruple hydrogen bonding moieties, which results in remarkable enhancement of shear strength, ranging from 6.4 to 16.6 MPa. More importantly, it also exhibits unique impact‐strengthening and reproducible adhering ability. The Hopkinson‐press‐bar and cyclic tensile tests manifest that quadruple hydrogen bonds play a pivotal role in buffering external forces and increasing energy dissipation when exposed to high velocity impacts. The true stress and strain synchronously increase as the strain rate augments while the shear strength can even roar up to ~18 MPa at high tensile speed. With regard to mild synthetic conditions, atomic economic use of reactants, it is promising that this material has industrial potential to be utilized in applications referred to energy‐absorption and reproducible structural adhesion. [ABSTRACT FROM AUTHOR]

Hamstring strain injuries (HSIs) remain a burden with high prevalence rates. The Nordic Hamstring exercise (NHE) has been found to be effective in preventing HSIs. However, the preventive mechanisms are not fully understood. Changes in stiffness are postulated as a possible protective mechanism. Surprisingly, the effect of the NHE on the stiffness of different hamstring muscles has never been investigated before. Therefore, the aim of this Randomised controlled trial was to investigate the impact of a 10-week NHE programme on the eccentric strength and the shear wave velocity (proxy of stiffness) of the hamstrings. Thirty-six soccer players were randomly assigned to either the control or the experimental group. The experimental protocol consisted of the incorporation of a 10-week NHE programme within the normal training routine. The hamstring stiffness and eccentric strength were assessed before and after. Within-group analyses showed a significant increase in strength, only for the experimental group. However, no significant effect of the NHE was found on the stiffness of each hamstring muscle. A 10-week NHE programme does not affect hamstring stiffness, despite an increase in eccentric strength, indicating that the preventive mechanism of the NHE is probably not (co-)explained by alterations in hamstring muscle stiffness. [ABSTRACT FROM AUTHOR]

Objective: To explore the mechanical properties of weak expansive soil under different moisture contents and confining pressures. Methods: The triaxial remolded soil samples with different moisture contents (14%, 16%, 18%, and 20%) were prepared for the obtained Nanyang weak expansive soil. Four groups of 16 consolidated drained triaxial shear tests with a confining pressure of 50, 100, 200, and 300 kPa were carried out to study the effects of confining pressure and water content on the deviatoric stress and pore pressure of weak expansive soil with strain. Results: The study showed that the shear strength of weak expansive soil samples gradually increased with the increase of the water content, but its increase nonlinearly decreased as the confining pressure increased. When the axial strain was small, the pore pressure significantly increased, and the pore pressure increased tended to be stable slowly and gradually as the axial strain gradually increased. Therefore, the research results could be used to avoid the diseases caused by the characteristics of weak expansive soil in engineering construction and provide theoretical references for improving engineering foundations in weak expansive soil areas. [ABSTRACT FROM AUTHOR]

Chemical grafting is commonly employed to functionalize carbon fiber (CF) surface to enhance the interfacial properties of CF reinforced polymer composites (CFRP) by forming a robust interface. However, an overly rigid interface layer can result in relatively poor interface toughness. To balance interfacial strength and toughness, this paper proposes an effective method to simultaneously strengthen and toughen the interface of CF/epoxy composites by grafting branched polyethyleneimine (PEI) on CF surface using hexachlorophosphazene (HCCP) as active intermediate, which features a rigid ring structure and six active P‐Cl groups. The introduction of PEI provided a large number of amine and imine groups on CF surfaces, which were contributive to improving surface wettability and reactivity of CF, thus resulting in strong chemical bonding between CF and epoxy matrix. Additionally, the long and flexible molecular skeleton of PEI constructed a rigid‐flexible composite interface, which could effectively reduce stress concentration and absorb impact energy. After surface modification with PEI, the interfacial shear strength and fracture toughness of CF/epoxy composite were increased to 89.9 MPa and 200.3 J m−2, by 64.3% and 149.7%, respectively, in compared with desized CF reinforced epoxy composites. Highlights: A rigid‐flexible interface was constructed between CF and epoxy resin.The interfacial strength and toughness of CFRP were synergistically improved.IFSS and interfacial toughness increased by 64.3% and 149.7%, respectively. [ABSTRACT FROM AUTHOR]

Poor interfacial adhesion between carbon fibers (CF) and the resin matrix has been a limiting factor in advancing the properties of composites. To address this challenge, this study employs the sizing method to coat carbon nanotubes (CNTs) and hexagonal boron nitride nanosheets (h‐BN) onto the CF surface. The 3D structures formed by strategic of combination 1D and 2D nanomaterials, markedly enhances the mechanical, thermal and frictional properties of CF composites. The results reveal a significant boost in the flexural strength, flexural modulus, interlaminar shear strength and interfacial shear strength of the prepared CF composites, registering increases of 53.96%, 60.41%, 55.58% and 55.35%, respectively. These advancements stem from the heightened surface reactivity and roughness of the fibers, facilitated by the synergistic interactions between CNTs and BN. Furthermore, the thermal conductivity of the composites exhibits a remarkable increase of 63.56%, attributed to the synergistic coupling between CF and BN, establishing an efficient thermal conductivity pathway within the composites. This research provides a highly effective approach for crafting high‐performance CF composites. Highlights: Construction of 3D network structures on CF surfaces by the sizing method.Synergistic coupling between BN and CNT enhances composite properties.Synergistic enhancement of friction and thermal properties of CF composites. [ABSTRACT FROM AUTHOR]

Debris flow hazards are often interpreted through back-calculated simulation analysis or empirical methods. The mobility of a debris flow is greatly influenced by mechanical and hydrological parameters. The strength parameters play important roles in the debris flow initiation and flow stages. In particular, the rheological parameters of yield strength and plastic viscosity directly affect the debris flow runout distance and velocity. One of the most important parameters to consider when evaluating debris flow hazards is the shear strength. This strength is called the residual shear strength in the failure stage and the yield strength in the post-failure stage. The residual shear strength obtained from ring shear tests can be related to the initiation of mass movements; the yield strength obtained from rheological tests can be related to the mobilization of debris flows. The residual shear stresses obtained from ring shear tests of weathered soils typically range between 10 and 100 kPa and strongly depend on the normal stress and shear velocity. When progressive slope failure (i.e., strain-softening behavior) occurs at a relatively shallow slope depth (e.g., < 1 m), the soil strength ranges from approximately 5–10 kPa. If the liquid limit state (i.e., solid‒liquid transition) is reached, the shear strength of the soil is approximately 2 kPa. Once the soil fails and mixes with ambient water along the slip surface, the yield strength decreases dramatically, resulting in high mobilization. A suggestion on how strength parameters can be applied to estimate debris flow mobility is presented by considering the 2011 Miryang debris flow, which occurred in weathered soil deposits in Miryang city, Republic of Korea. The best approach for debris flow yield strength estimation would be to consider the residual shear strength in the initiation stage, the yield strength in the flow stage, and the reduction in yield strength with the entrainment effect of the flow in the rapid fluidization stage. [ABSTRACT FROM AUTHOR]

The textile industry uses a lot of adhesives to join materials together, and many of these adhesives use petroleum-based ingredients that are harmful to the environment. To replace petroleum-based adhesives with a more environmentally friendly option for the textile industry, this study set out to create and evaluate a hot-melt adhesive derived from cassava starch. By adding kaolin clay as a filler and tannin as a tackifier in different ratios of starch, the created adhesive was enhanced. Tannic acid to starch ratios of 2:1, 6:1, and 10:1 w/w and kaolin to starch ratios of 3:1, 5:1, and 7:1 w/w were used to investigate the effects of clay and tackifier, respectively. The adhesives's viscosity, moisture content, tensile strength, and shear strength were then measured. The presence of kaolin and tannic acid in starch-based adhesives favored a good interaction between the adhesive's ingredients. The adhesive's maximum shear strength was measured at 4.93 ± 0.11 Mpa when dry and 0.263 ± 0.21 Mpa when wet. The current data indicate that the optimal tensile strength was determined to be 3.45 ± 0.22 MPa. This result showed that hot melt adhesives based on cassava starch would be a good environmentally friendly substitute for petroleum-based adhesives, and more study in this field is necessary. [ABSTRACT FROM AUTHOR]

Shear strength (SS) parameters are essential for understanding the mechanical behavior of materials, particularly in geotechnical engineering and rock mechanics. This study proposes a novel hierarchical ensemble model (HEM) to predict SS parameters: cohesion (C ) and angle of internal friction (φ ). The HEM addresses the limitations of traditional machine learning models. Its performance was validated using leave-one-out cross-validation (LOOCV) and out-of-bag (OOB) evaluation methods. The model's accuracy was assessed with R-squared correlation (R2), absolute average relative error percentage (AAREP), Taylor diagrams, and quantile–quantile plots. The computational results demonstrated that the proposed HEM outperforms previous studies using the same database. The model predicted φ and C with R2 values of 0.93 and 0.979, respectively. The AAREP values were 1.96% for φ and 4.7% for C . These results indicate that the HEM significantly improves the prediction quality of φ and C , and exhibits strong generalization capability. Sensitivity analysis revealed that σ_3maxσ3max (maximum principal stress) had the greatest impact on modeling both φ and C . According to uncertainty analysis, the LOOCV and OOB had the widest uncertainty bands for the φ and C parameters, respectively. [ABSTRACT FROM AUTHOR]

This study investigates the shear strength prediction of Fibre-Reinforced Concrete (FRC) beams reinforced with Fibre-Reinforced Polymer (FRP) bars and without stirrups through the application of Machine Learning (ML) techniques. The utilisation of FRP bars, particularly Glass Fibre-Reinforced Polymer (GFRP) and Basalt Fibre-Reinforced Polymer (BFRP) bars, has emerged as a promising alternative to traditional steel reinforcement due to their superior mechanical properties and corrosion resistance. Moreover, the incorporation of macro- and micro-discrete fibres into concrete compositions enhances both shear and flexural behaviour while reducing crack propagation induced by tensile stresses. The primary objective of this research is to develop accurate predictive models for the shear capacity of FRP-reinforced concrete beams, considering various influential parameters. Six different ML techniques, namely Multiple Linear Regression (MLR), Gaussian Process Regression (GPR), k-Nearest Neighbors (KNN), Support Vector Machines (SVMs), Artificial Neural Networks (ANNs) and Random Forest Regression (RFR), are employed to analyse the complex interactions between input variables, such as fibre type, bar diameter, concrete compressive strength, beam dimensions and the resulting shear strength. By leveraging these computational approaches, we aim to overcome the limitations of conventional analytical methods and provide robust predictions for structural design and optimisation. [ABSTRACT FROM AUTHOR]

In deep tunneling and mining, high-level radioactive waste repositories, and geothermal reservoirs, the rock fractures are typically in the thermal–mechanical coupled condition. It is crucial to precisely replicate the geoenvironment in the lab, including stress, temperature, boundary conditions, and other factors, to derive trustworthy strength estimates for rock fractures. Utilizing the recently developed shear apparatus, we performed direct shear tests on rough granite fractures under thermal–mechanical coupled loading (room temperature to 400 °C, 1–30 MPa) to address the effects of normal stress and high in-situ temperature on the shear behavior of rough granite fractures, and the sequence of heating and normal loading on the strength parameters is also examined. Results show that the acoustic emission is more active if the fracture is heated under a large normal stress, while the expansion in the normal direction is more restricted. Besides, the shear strength tends to increase with increasing temperature, particularly if the fracture is heated under a large normal stress; at the greatest temperature, the shear strength is deteriorated. The strengthening of rock fracture upon heating is associated with the time- and temperature-dependent asperity contact creep which increases the real contact area of the macroscopically mated fracture surfaces. The sequence of heating and normal loading prominently affects the shear properties of granite fractures; the shear strength, post-peak stress drop and stick–slip amplitude are greater for granite fractures which were normal loaded first than heated first. The post-peak stress drop and stick–slip stress drop, which are vital parameters to estimate the seismic event intensity, are related to the corresponding dynamic slip and loading system stiffness. Highlights: Direct shear tests were conducted on granite fractures with a newly developed apparatus equipped with real-time heating capability. The thermal expansion is smaller while the AEs are more active when the fractures were heated under a larger normal stress. The shear strength of granite fractures first increases and then decreases with increasing temperature when heated under a large normal stress. The shear strength, post-peak stress drop and stick–slip are greater for granite fractures which were normal loaded first than heated first. The strengthening of fractures heated under a large pre-set normal stress is related to increase in fracture contact area due to asperities creep. [ABSTRACT FROM AUTHOR]

To characterize the performance of icephobic coatings for aerospace applications, various shear-based techniques have been used. Generally, these techniques are conducted in conjunction with comparison tests on metals. In this study, a review of the various approaches for measuring adhesion for static and impact ice for metal and icephobic surfaces was done. This review indicated that many details of the test conditions either varied significantly among studies or were omitted. To address this uncertainty, new measurements were taken to examine in-situ ice-shear-adhesion strength for impact and static ice with various surfaces, using a consistent icing-research-tunnel facility with well-characterized and detailed test conditions. The results for the two different metals tested revealed a significantly higher ice adhesion for static ice compared to that for impact ice. However, the tested self-lubricated icephobic coating significantly reduced ice adhesion strength for both impact and static ice and this performance was retained after multiple icing tests. Based on the methodology review and the current experimental study results, it is recommended that future ice adhesion studies fully characterize the following: the apparatuses for shear measurement, which include protocols and procedures used; the surface chemistry and roughness; the thermal conditions of the air, water, and surface; and for impact ice, the droplet conditions such as velocity and size in order to ensure repeatability within a study and comparison across studies. [ABSTRACT FROM AUTHOR]

The strength of rockfills and waste materials is significantly influenced by their particle size distribution (PSD). For large waste rockfills, PSD is fundamental to determine the shear behavior. Traditionally, PSD for rockfill, used in materials like coarse-grained aggregates, has been obtained through physical sieving. However, the particle sizes in hard rockfills can vary significantly from small particles (< 20 cm diameter) to large blocks or boulders over 100 cm, with the maximum size limited by the in situ ground conditions and blasting performance. Essentially, the sieving process is impractical, considering the scale of the mine waste dumps and the time required. Therefore, in this study, a workflow using digital detection to estimate the PSD is presented, aiming to quantify the waste dump shear strength using Barton–Kjaernsli empirical criterion. PSD from UAV is validated using manual field measurements of individual boulders. The error for coarse characteristic size prediction ranges within ± 4 mm, and the increase in the data collection frequency, area covered, and resolution of fragmentation measurement for rockfills and waste dumps using UAV allows to improve the statistical reliability of the PSD and fragmentation measurement. [ABSTRACT FROM AUTHOR]

Unsaturated soil is widely distributed around the world but less considered in design due to the absence of a convenient analysis method in practice. The Morgenstern–Price (MP) method incorporating the extended Mohr–Coulomb shear strength equation provides a reliable approach to evaluate slope stability in such conditions. However, this method is time-consuming due to the need for a tedious trial-and-error process in determining the scaling factor, which involves complex iterations during each trial. Furthermore, since the relatively complicated nature of unsaturated soil, a dense slice division is necessary to obtain reliable results, making the analysis even more cumbersome. In this paper, an improved MP method for unsaturated soil slope stability analysis is presented, which eliminates the need for a dense slice mesh by employing only a few strategically placed Gauss points along the slip surface. Moreover, the trial-and-error process for determining the scaling factor with the corresponding complex iterations is replaced by an efficient search algorithm with a more concise iteration process, resulting in a more convenient implementation of the proposed method. Extensive examples are provided to validate the effectiveness of the proposed improved MP method, indicating its potential as an accurate and efficient analysis method for unsaturated soil slopes in practical application and relative study involving repetitive analyses. [ABSTRACT FROM AUTHOR]

Transient liquid phase (TLP) bonding was used to bond an IN939 superalloy utilizing a traditional, two-step heating process. The bonding process was carried out using BNi-2 foil with a 70-µm thickness as the interlayer in the first step at 1160 °C for 1 min and then at 1120 °C for different isothermal solidification times (50, 65, 80, and 95 min) in the second, also at 1120 °C for 80 min in conventional TLP bonding under vacuum furnace at a pressure of 10-5 torr. All the bonded specimens are then subjected to heat treatment and examined before and after heat treatment. A single-phase (isothermal solidification) was generated at the centerline after 80 minutes using a two-step technique. Due to insufficient bonding times, eutectic-products consisting of (gamma solid-solution), (Cr rich-boride), and (Ni rich-boride phases) formed in the centerline. The diffusion-affected zone also contained blocky- and needle-shaped boride precipitates in addition to the eutectic phases. The Vickers micro-hardness, and shear tests were done on the joints to evaluate their mechanical quality. The duration of isothermal solidification was shortened by using two-step TLP bonding. The hardness profile across the bond area was better than the conventional method and became more uniform after the heat treatment, and the shear strength was 631 MPa, and became 885 MPa after heat treatment, while about 479 MPa with the conventional TLP after heat treatment for the specimen with the isothermal solidification time of 80 min. After being subjected to a two-stage post-bond heat treatment, the microstructure becomes close to the base metals, as a result, a homogenizing microstructure forms across the joint. With increased bonding times, all of the bonds' shear strengths increased, and the hardness distribution across the bond area was better than the conventional technique and following the heat treatment, became more uniform. The bond shear strength was enhanced after the heat treatment because a significant γ-'phase developed in the bond area. [ABSTRACT FROM AUTHOR]

(111)-oriented nanotwinned Cu ((111)nt-Cu) has shown its high surface diffusion rate and better oxidation resistance over common polycrystalline Cu (C-Cu). The application of (111)nt-Cu as an interface metallization layer in Ag-sintered technology under the role of oxygen was investigated in this work, and its connecting behavior was further clarified by comparing it with C-Cu. As the sintering temperature decreasing from 300 to 200 °C, the shear strength on the (111)nt-Cu substrate was still greater than 55 MPa after sintering for 10 min. The fracture surface correspondingly changed from the interface of Ag/die to mixed fracture mode, involving the interface of the Ag/Cu substrate and Ag/die. The existence of copper oxide provided a tight connection between Ag and the (111)nt-Cu substrate at all of the studied temperatures. Although lots of small dispersed voids were seen at the interface between copper oxide and (111)nt-Cu at 300 °C, these impurity-induced voids would not necessarily be a failure position and could be improved by adjusting the sintering temperature and time; for example, 200 °C/10 min or heating to 300 °C, and then start cooling at the same time. The microstructure of Ag-Cu joint on (111)nt-Cu behaved better than that on C-Cu. The thinner copper oxide layer and the higher connection ratio of the interface between copper oxide and Ag were still found on the (111)nt-Cu connection's structure. The poor connection between copper oxide and Ag on C-Cu easily became the failure interface. By controlling the thickness of copper oxide and the content of impurity-induced voids, the use of (111)nt-Cu in advanced-packaging could be improved to a new level. [ABSTRACT FROM AUTHOR]

Sn-10Bi low-bismuth-content solder alloy provides a potential alternative to the currently used Sn-Ag-Cu series due to its lower cost, excellent ductility, and strengthening resulting from the Bi solid solution and precipitation. This study primarily investigates the interfacial evolution and shear strength characteristics of Sn-10Bi joints on a Ni/Au surface finish during the as-soldered and subsequent isothermal aging processes. To improve the joint performance, a 0.2 or 0.5 wt.% dopant of Zn was incorporated into Sn-10Bi solder. The findings demonstrated that a 0.2 or 0.5 wt.% Zn dopant altered the composition of the intermetallic compound (IMC) formed at the interface between the solder and Ni/Au surface finish from Ni3Sn4 to Ni3(Sn, Zn)4. The occurrence of this transformation is attributed to the diffusion of Zn atoms into the Ni3Sn4 lattice, resulting in the substitution of a portion of the Sn atoms by Zn atoms, thereby forming the Ni3(Sn, Zn)4 IMC during the soldering process, which was also verified by calculations based on first principles. Furthermore, a 0.2 or 0.5 wt.% Zn dopant in Sn-10Bi significantly inhibited the Ni3(Sn, Zn)4 growth after both the soldering and thermal aging processes. Zn addition can enhance the shear strength of solder joints irrespective of the as-soldered or aging condition. The fracture mode was determined by the aging durations—with the brittle mode occurring for as-soldered joints, the ductile mode occurring for aged joints after 10 days, and again the brittle mode for joints after 40 days of aging. [ABSTRACT FROM AUTHOR]

In this study, an experiment was conducted to investigate the shear performance of reinforced concrete (RC) beams strengthened using fabric-reinforced cementitious matrices (FRCM). Four reinforced concrete beams, including a control specimen, were fabricated, and the shear strengthening effect of the FRCM was investigated on eight shear specimens, with the strengthening type and shear reinforcement as key variables. In particular, the digital image correlation (DIC) technique was applied to closely analyze the deformation of reinforced concrete beams subjected to shear forces. The average shear strain–shear stress curve of each specimen was derived, and the contributions of shear and bending to the vertical deflection and the change in the principal strain angle with increasing shear force were analyzed. The experiment results showed that all specimens failed with diagonal cracks within the shear span. In the specimens without shear reinforcement, the shear strength increased by up to 65% according to the FRCM strengthening, while in the specimens with shear reinforcement, only the sided bond strengthened specimen showed a strength increase of 16% compared to the control specimen. Based on displacement data of the DIC, it was confirmed that FRCM strengthening can control the deformation of the RC beam. To evaluate the shear strength of the FRCM-strengthened RC beams, a shear strength model was proposed by considering the contributions of the concrete section, shear reinforcement, and FRCM. The proposed model was capable of reasonably evaluating the shear strength of RC beams strengthened with FRCM, considering the shear contribution of FRCM and bond capacity between FRCM and concrete substrate, in which the shear strength of specimens was underestimated by 28% to 35%. [ABSTRACT FROM AUTHOR]

Fluorosilicone was combined with aluminum trihydrate (ATH) to induce synergistic flame-retardant and thermal-resistant properties. The surface of ATH was modified with four different silane coupling agents. The flammability and mechanical properties of the fluorosilicone/ATH composites were assessed using an UL94 vertical test and a die shear strength test. The change in shear strength was investigated under aging for 1000 h at −55 °C and 150 °C. Pure fluorosilicone had inherent fire resistance and thus achieved a V-0 rating even at 20 wt.% ATH loading. Upon addition of ATH treated with 3-glycidoxypropyl trimethoxysilane, the composites exhibited the highest shear strength of 3.9 MPa at 23 °C because of the additional crosslinking reaction of fluorosilicone resin with the epoxide functional group of the coupling agent. Regardless of the types of coupling agents, the composites exhibited similar flame retardancy at the same ATH content, with a slight reduction in shear strength at 180 °C and 250 °C. The shear strength of the adhesives gradually decreased with aging time at −55 °C, but increased noticeably from 3.9 MPa to 11.5 MPa when aged at 150 °C due to the occurrence of the additional crosslinking reaction of fluorosilicone. [ABSTRACT FROM AUTHOR]

The vibration pretreatment–microwave curing process can achieve high-quality molding under low-pressure conditions and is widely used in the curing of resin-based composites. This study investigated the effects of the vibration pretreatment process parameters on the void content and the fiber weight fraction of T700/TRE231; specifically, their influence on the interlaminar shear strength and impact strength of the composite. Initially, an orthogonal experimental design was employed with interlaminar shear strength as the optimization target, where vibration acceleration was determined as the primary factor and dwell time as the secondary factor. Concurrently, thermogravimetric analysis (TGA) was performed based on process parameters that corresponded to the extremum of interlaminar shear strength, revealing a 2.17% difference in fiber weight fraction among specimens with varying parameters, indicating a minimal effect of fiber weight fraction on mechanical properties. Optical digital microscope (ODM) analysis identified interlaminar large-size voids in specimens treated with vibration energy of 5 g and 15 g, while specimens subjected to a vibration energy of 10 g exhibited numerous small-sized voids within layers, suggesting that vibration acceleration influences void escape pathways. Finally, impact testing revealed the effect of the vibration pretreatment process parameters on the impact strength, implying a positive correlation between interlaminar shear strength and impact strength. [ABSTRACT FROM AUTHOR]

The shear strength of rooted soils depends on the principal stress direction owing to the anisotropy in the soil structure and root system. Existing failure criteria cannot describe the strength anisotropy of rooted soils under general loading conditions because they are mainly based on the test results of direct shear. This study presents a new generalised three-dimensional anisotropic failure criterion for rooted soils. The model employs the projection of two independent microstructure fabric tensors (soil fabric and root network) on the stress tensor. Twenty-four drained triaxial compression and extension tests were carried out to measure the strength anisotropy of silty sand vegetated with vetiver grass (Chrysopogon zizanioides L.) at different overconsolidation ratios and calibrate the material parameters for the proposed criterion. Anisotropies of both cohesion and friction angle exist in rooted soil. Roots contribute mainly to the increase in cohesion (hence root cohesion) from most of the direct shear test data. Roots with predominant orientation aligning in the tensile strain direction contribute the most to soil strength. In the case of vetiver grass, which has a taproot system, their roots show the strongest reinforcement effect in the conventional triaxial extension path, in which the maximum portion of the roots is subjected to tension. [ABSTRACT FROM AUTHOR]

In construction projects in Khuzestan province in Iran, electric-arc steel slag (EASS) materials are used as fill materials. In this research study, bio-cementation practice on EASS materials is examined and compared with that on natural sand. For this purpose, direct shear, unconfined compressive strength (UCS) and constant head permeability tests, together with scanning electron microscopy images obtained using an instrument equipped with an energy-dispersive X-ray spectroscope, were used to analyse and compare untreated and treated materials. The results showed that despite higher urease activity and higher calcite production of EASS materials compared with natural sand, the latter showed slightly higher UCS, higher cohesion intercept enhancement and higher permeability decrease after bio-cementation treatment. [ABSTRACT FROM AUTHOR]

Vertical drains installed in soft clay deposits enhance the rate of consolidation in preloading projects. Using a mandrel to install the prefabricated vertical drains, its insertion and withdrawal will result in the remoulding of the soil zone surrounding it, called the smear zone. The extent of the smear zone is an important parameter that characterises the smearing effect. This paper describes this effect in terms of smear ratio (i.e. the ratio of the diameter of smear zone ds to the diameter of drain, dw) on the consolidation characteristics of soil with radial drainage. A series of radial consolidation tests with a predetermined smear zone in a model unit cell was conducted by varying the diameter of the smear zone. The experimental results show that beyond a smear ratio of 4, the soil behaves as if it is in a fully remoulded condition. The results were compared with some of the theoretical approaches reported in the literature. The analytical solution that predicts the time–settlement curve in a better way is identified. Also, it is observed that the gain in undrained shear strength due to the consolidation of soft clay decreases with the increase in the diameter of the smear. [ABSTRACT FROM AUTHOR]

A set of direct shear tests was conducted to investigate the effects of sand mean grain size and geomembrane surface roughness on the shear behaviour of the sand–geomembrane interface. Four types of sands with different mean grain sizes were used and the interfaces included a smooth geomembrane (SGM) and four textured ones with different asperity characteristics. The samples were prepared in a direct shear box at five sedimentation angles. The experimental results showed that the peak friction angle of the soil–textured geomembrane interface was dependent on the mean grain size, inherent anisotropy and surface roughness of the geomembrane. The shear strength of sand–textured geomembranes was two to three times larger than that of the sand–SGM interface. The peak and residual friction angles of sand-SGM interface occurred at sedimentation angle of 72° while it was 108° for sand-TGM interfaces. An increase in mean grain size increased the shear strength of the sand–textured geomembrane interface; while a reverse condition occurred for the sand–SGM interface. The shear strength occurred at larger horizontal displacement as mean particle size increased and the effect of relative roughness on peak friction angle increased with increase in mean grain size. [ABSTRACT FROM AUTHOR]

In the Kashmir region of Pakistan, the presence of Siwalik clays engenders serviceability issues to the infrastructure causing substantial loss of property. In this study, an attempt has been made to address these issues using polypropylene fibres (PPFs) as a sustainable modifier. These fibres were used in five different proportions, namely 0.25, 0.5, 0.75, 1 and 1.25% as partial replacement of base soil to analyse their impact on the engineering behaviour of matrices. Classification, compaction, indirect tensile, unconfined and triaxial compression, swell potential, consolidation and California bearing ratio (CBR) tests were conducted on controlled as well as reinforced-clay samples for comparative analyses. The maximum improvements were observed in unconfined compressive strength (109%), tensile strength (300%), cohesion (13%), friction angle (110%), soaked CBR (800%) and un-soaked CBR (550%). Besides, the reduction in swelling strain by 92% was also recorded corresponding to 1 kPa effective vertical stress. The capital cost analyses showed that PPFs reduced the costs of backfill behind the retaining wall and foundation soil beneath isolated footing by 21 and 44.5%, respectively. Moreover, the modifier had no adverse effect on the aqueous media. Conclusively, PPFs can be used as sustainable modifiers leading to a potential solution for serviceability issues. [ABSTRACT FROM AUTHOR]

This research comprehensively explored the function of preheating temperature and quantified the contribution of degree of blending (DoB) to performance of recycled hot-mix asphalt (HMAs). Five groups were designed, including no blending group, full blending group, and three experimental groups at preheating temperatures of 60, 110, and 160 °C. It can be found that the preheating temperature played a positive impact on DoB and performance of recycled HMAs. As the preheating temperature increased by 50 °C, about 0.13%–0.2% of reclaimed asphalt binder can be additionally activated, and the tensile strength ratio, shear strength, and fracture energy of recycled HMAs can improve by around 6%–8%, 0.07–0.15 MPa, and 304.2–335.4 J·m2, respectively. Moreover, the results showed that the performance of recycled mixes designed at preheating temperature of 60 °C was close to that of no blending group, while the mixes designed at a preheating temperature of 160 °C can reach to those of full blending group. [ABSTRACT FROM AUTHOR]

AlCoCrFeNi2.1 eutectic high‐entropy alloy was introduced to join Cf/SiC composite by spark plasma sintering technique. The influence of holding times on microstructure, shear strength and fracture behavior of the joints was studied. When held for 7 min, the typical microstructure of the Cf/SiC‐AlCoCrFeNi2.1‐Cf/SiC joint was Cf/SiC composite → CrSi2 + FCC + Al8Cr5 + graphite → CrSi2 + FCC + Al8Cr5 → CrSi2 + FCC + Al8Cr5 + graphite → Cf/SiC composite. As the holding time extended, the Ni–Si and Fe–Si brittle phases in the joint gradually reduced, and the diffusion transition layer continued to thicken. The maximum joint strength was 23.9 MPa, which was obtained at 1450°C for 7 min. Analyzed by scanning electron microscopy and energy dispersive spectroscopy, the fracture modes of the joints joined at different holding times were all brittle fracture. [ABSTRACT FROM AUTHOR]

The undrained shear strength of marine sediment is of vital importance because of its critical role in seafloor slope stability, seafloor infrastructure, and influencing sediment dynamics that can lead to underwater landslides. Therefore, understanding the undrained shear strength of marine sediments and its influencing factors is a fundamental requirement for both offshore engineering and geoscience studies. Core data obtained from 198 sites across 46 legs of the Ocean Drilling Program/International Ocean Discovery Program (ODP/IODP) were used to analyze the undrained shear strength of marine sediments and their influencing factors. The undrained shear strength of marine sediments is significantly influenced by the depositional environment. Sediments deposited in active continental margins exhibit a higher undrained shear strength than those deposited in deep-sea and carbonate platform environments due to seismic strengthening and over-consolidation. It was found that fine-grained siliciclastic lithofacies with less than 50% carbonate content exhibited high variability and a rapid increase in the undrained shear strength with depth. In contrast, fine-grained carbonate lithofacies with more than 50% carbonate, as well as reef-facies carbonates, showed low variability and only a gradual increase in undrained shear strength with depth. Additionally, we showed a positive association between the undrained shear strength and physical characteristics including bulk density and P-wave velocity, as well as an inverse correlation with porosity. An exponential relationship was found between these physical properties and the undrained shear strength, with coefficients of determination (R²) values of 0.71, 0.74, and 0.69, respectively. [ABSTRACT FROM AUTHOR]

In the present investigation, diverse functionalized states of multi-walled carbon nanotubes (MWCNT) were employed in fabricating glass/epoxy composites, with the MWCNT consistently incorporated at a 0.5 wt.% concentration. These functionalization states included pristine, hydroxyl, amine, and carboxylic conditions, systematically compared against neat glass/epoxy composites. The findings elucidated that all three functionalizations positively influenced the enhancement of interlaminar shear strength, mode-I interlaminar fracture toughness, and mode-II interlaminar fracture toughness properties. Notably, the amine-functionalized MWCNT exhibited superior performance relative to other formulations. The composite reinforced with amine MWCNT demonstrated significant improvements in ILSS, mode-I ILFT, and mode-II ILFT by 41.82%, 37.75%, and 40.93%, respectively. These enhancements are attributed to factors such as the presence of a more functional group, the quantity of individual MWCNT, and the introduction of additional damage mechanisms, including MWCNT pullout and bridging. Highlights: Improvement in ILSS of glass/epoxy composite by functionalized MWCNT by 20.11-41.82% range. Improvement in mode-I ILFT of glass/epoxy composite by functionalized MWCNT by 5.54-30.81%. Improvement in mode-II ILFT of glass/epoxy composite by functionalized MWCNT by 8.46-40.93%. Microscopic characterization using field-emission scanning electron microscopy revealed existence of MWCNT pullout and bridging. [ABSTRACT FROM AUTHOR]

Molecular dynamic simulation along with experiments was used to study polycarbonate (PC) molecular conformation on composite interfacial properties. The interlaminar shear strength (ILSS) variations of composites with carbon fiber roughness were quite different between sized and unsized carbon fibers, which seem to conflict with the theory that rougher surface is harder to wet. By the results of molecular dynamic simulation, it was found that the conformation of PC molecules through solvent intervention could be higher, which is conducive to the formation of π–π stacking conformation between PC and carbon fibers and benefits the interface interaction, resultantly affecting the ILSS more when the carbon fiber surface area was low. When the specific surface area was high enough, the ILSS gets to a saturation value, because the fracture area changes from the interface to the matrix. It is concluded that the effects of sizing on ILSS varied with carbon fiber surface roughness, and the molecular conformation of the matrix affected by sizing or processing must be considered. Therefore, it is important to enhance the physical interactions with carbon fiber for thermoplastic resin matrixes. [ABSTRACT FROM AUTHOR]

The fracture resistance of adhesive joints depends on the bondline thickness, especially in the toughest systems. While increasing the adhesive thickness to operate at peak fracture toughness is anticipated to be attractive, it leads to a mass increase and to a decrease of the effective shear stiffness and strength, calling for a trade-off. Here, we follow a rational materials selection approach for mechanical design to address different sets of objectives and constraints representative of different classes of applications. The approach is applied to select the best conventional adhesive based on a novel database. Mechanical analysis with two different degrees of complexity is considered. The elementary level only accounts for the influence of thickness on toughness, while more advanced models introduce the dependence of shear strength on thickness as well as the stiffness mismatch with the adherends. The best adhesive choice strongly depends on the objectives, constraints, and loading configuration. However, the ranking is not drastically affected by the adherends' stiffness. Gaps found for stiff/strong and tough adhesives motivate the development of architected joints. Inserting stop holes improves damage tolerance and density but reduces the shear strength and stiffness, requiring an optimum design. [ABSTRACT FROM AUTHOR]

The mechanical properties and structure of polybutylene terephthalate (PBT)/aluminum (Al) composite prepared by ultrasonic-assisted hot-pressing were analyzed, and the influence of ultrasonic-assisted on the bonding properties of PBT/Al composite was studied. The experimental results showed that under the optimal ultrasonic-assisted conditions, the tensile shear strength of the PBT/Al composite reached 26.55 MPa, which was 22.18% higher than that of the PBT/Al composite without ultrasonic-assisted (21.73 MPa). Scanning electron microscopy (SEM) showed that during the hot-pressing process, ultrasonic-assisted promoted the embedding of PBT in the anodic oxide pores on the surface of Al, forming a stronger mechanical interlocking structure. X-ray diffraction (XRD) showed that ultrasonic-assisted did not change the crystal type of PBT, but the shear effect of ultrasound affected the arrangement and orientation of molecular chains in the PBT melt, resulting in changes in crystallinity. X-ray photoelectron spectroscopy (XPS) showed that ultrasonic-assisted did not generate new chemical bonds during the hot-pressing process. Therefore, during the hot-pressing process, ultrasonic-assisted promoted the embedding of PBT in the anodic oxide pores on the surface of Al, enhanced the mechanical interlocking effect between PBT and Al, and improved the tensile shear strength of the PBT/Al composite. [ABSTRACT FROM AUTHOR]

Reutilisation of waste tire chips to improve red clay is of great significance to environmental protection. The mechanical properties of tire chip and cement stabilised red clay (TCCSRC) at different proportions were investigated through compaction, compression, unconfined compression strength (UCS), and direct shear tests. The UCS and shear strength of TCCSRCs with different proportions were tested and analysed at their optimal moisture content (OMC). The results indicated that the porosity ratio, UCS, shear strength, and cohesion of TCCSRC decreased with increasing tire chip content. The addition of cement increased the sample UCS and shear strength. When the content of tire crumb is 20% and the cement content is 5%, the specimens show good performance in all basic properties, including UCS can reach 1034.3 kPa; the shear strength can reach 46.7 kPa when the axial pressure is 150 kPa. [ABSTRACT FROM AUTHOR]

Civil engineering projects are always at high risk of failure when constructed on weak or soft soils due to their lower shear strength and settlement issues. This study summarises the influence of various Nano additives such as Nano aluminium oxide, Nano magnesium oxide, Nano copper, Nano clay, Nano carbons and Nano calcium carbonateon the strength, mineralogical and morphological properties of problematic soils as reported by the researchers. The strength properties such as unconfined compressive strength, direct and triaxial shear strength, and California bearing strength were enhanced with the incorporation of Nano additives up to the optimum amount of dosage in the soil. The very low amount of dosage of Nano additives provided a dramatic change in the strength due to their higher specific surface area as compared to the traditional additives such as cement and lime. The mineralogical and morphological studies showed denser and stiffer soil matrices and depict the formation of new cementitious compounds. From the detailed review of past literature, it can be concluded that the inclusion of a small amount of Nano additives in soil is capable of some shadowing the negative effect of problematic soil for construction purposes. [ABSTRACT FROM AUTHOR]

This study utilised the principles of soil mechanics and the physiograph concept to establish pedo-geotechnical patterns of natural soils for the design of pavement structure. A total of 60 disturbed and undisturbed subgrades were sampled from 10 locations at the SB segment, 10 locations through the TZ and 10 locations at the BC end. A series of specific gravity, grain-size distribution, consistency limits, compaction characteristics (unsoaked and soaked CBR) and shear strength parameters were performed. Field observation and test results revealed that the studied area consists of extensive sand, interposed with clayey sand bodies along the SB segment. Also, particles of various sizes at the TZ and heterogeneous sandy clay in the BC segment were noted. Soils from the TZ under soaked conditions have the highest CBR (80.0–88.1%), MDD (19.0–19.1 kN/m3) and the lowest OMC (10.2–10.5%) values. They also have the highest cohesive strength (72.0–80.0 kN/m2) and angle of internal friction (14°−16°). Comparison among properties revealed that soils from the SB area especially, the TZ have much higher subgrade ratings compared to the soils from the BC terrain. The result revealed that the physiography factors affect the performance of the entire pavement structure. [ABSTRACT FROM AUTHOR]

Due to the wide particle size distribution of coral sand, There are significant differences in mechanical behaviour of coral sand with different particle size distribution. It is of great significance to propose a quantitative analysis method for mechanical properties considering the effect of gradation. In this study, 27 groups of coral sand specimens with particle size ranging from 5 mm to 0.125 mm were prepared. The consolidated undrained (CU) triaxial shear tests were carried out and the influence of gradation and relative density on the shear characteristic were discussed. The grading and relative density of coral sand are controlled by the median particle size (d50) and relative density (Dr), The results show that the peak deviator stress decreased, and the effective internal friction angle first increased and then decreased with the increase of d50. Both the peak deviator stress and effective internal friction angle of coral sand increase with the relative density. A parabolic relationship was founded between the effect internal friction and d50 as Dr was constant. The effective friction angle peaked when d50 was 2 mm. Finally, a calculation method of shear strength parameter considering the gradation and relative density of coral sand was proposed. [ABSTRACT FROM AUTHOR]

In this research, rock mass deformation modulus (Emass), classification of rock mass, cohesion (c) and internal friction angle (Φ), and intact rock properties of the Khersan 2 dam site were investigated. Factors affecting mechanical properties were investigated and compared with the results of previous studies. To assess the shear strength and the Hoek and Brown failure criteria parameters, the triaxial test was performed on samples under saturated conditions. The Q-system and rock mass rating (RMR) were calculated for five-metre sections of boreholes. Results of the Mohr–Coulomb failure criterion showed that the limestones have a mean Φ of 40 degrees and a mean cohesion of 1 MPa, marl limestones have an average of 30 degrees and cohesion of 0.50 MPa, and anhydrite and gypsum showed an average of 26 degrees and 0.10 MPa. The results showed that c and Φ increase with the increase in the shear box size. Based on the RMR and Q-system the site was classified in good class. The mean of Emass showed that the dilatometry test gives the lowest value. Linear and logarithmic relationships were established between RMR89 with compressional wave velocity (Vp) (R2 = 0.95 and RMSE = 1.63) and Q-system (R2 = 0.95 and RMSE = 2.05), respectively. [ABSTRACT FROM AUTHOR]

Large residual stress induced by significant difference in the coefficient of thermal expansion compromises the mechanical performance of a brazed joint between the WC–Co cemented carbide (YG20) and 3Cr13 stainless steel in a cutting tool of shield machine. In this study, a melamine formaldehyde foam precursor was utilized to produce a 3D hollow carbon foam (HCF) used as interlayer through a high‐temperature carbonization process to aid in the brazing process of YG20 and 3Cr13. First, the morphology and microstructure of the HCF interlayer were revealed as a defect‐rich carbon shell with a hollow structure. Afterward, the effects of introducing the as‐prepared HCF interlayer on the joint microstructure and shear performance were investigated. Results indicate that the HCF interlayer contributed to phase homogenization and, moreover, the residual stress relieving through in situ forming a core (metallic matrix)–sheath (ceramic shell) structure. This method outperformed the direct brazing approach without using an interlayer, with a 41% increase in the joint shear strength due to the synergistic strengthening mechanism of the HCF through residual stress reliving and joint seam toughening. Based on the results, in spite of the residual stress, the fast load transfer and the compensation from the matrix core to the ceramic sheath are responsible for the improved mechanical performance of the joint. [ABSTRACT FROM AUTHOR]

ZrSi2–SiC powder was employed as the joining material to join SiC ceramics in this study. The effects of SiC particle (SiCp) content and joining temperature on the phase composition, microstructure, and shear strength of SiC joints were studied and reported for the first time. Research results showed that introduction of SiCp into the interlayer improved the mechanical performance of the joint. When 10 wt.% SiCp was introduced into the interlayer, the optimal shear strength measured of the joint was 116.7 ± 6.7 MPa under the joining condition of 1500°C for 10 min. With the joining temperature increased, the shear strength of the joint gradually increases. When the joint was performed at 1600°C for 10 min, an ultra‐high temperature phase of ZrC was detected in the interlayer, and the shear strength of the joint was 168.1 ± 12.6 MPa. The SiC joint with high mechanical strength might have the potential for application in the field of nuclear industry. [ABSTRACT FROM AUTHOR]

Lack of investigation into the tensile strength characteristics of unsaturated tailings hinders their recycling as construction materials in bulk earthworks. Here, the strength characteristics and strength-dilatancy relation in the tensile stress regime of unsaturated tailings were investigated via flattened Brazilian and direct shear tests. A nonlinear variation of tensile strength with water contents was observed. The unsaturated tailings with water contents below the plastic limit were strain softening and dilative under low normal stress. Furthermore, an analytical equation was proposed to predict the tensile strength of compacted tailings via the soil water characteristics curve (SWCC) and corroborated via experiments. [ABSTRACT FROM AUTHOR]

Earthquake reconnaissance after the recent Kahramanmaras, Turkey, earthquake sequence in February 6, 2023 has shown that the majority of the reinforced concrete (RC) structural elements do not comply with the Turkish Building Earthquake Code (TBEC 2018) requirements. Accurate estimation of the actual strength of existing non-compliant RC structural members is critical to accomplish reliable earthquake performance assessments. This study aims to propose a machine learning-based framework to establish a realistic failure forecast as well as an accurate shear strength estimation depending on the expected failure modes of such walls. To achieve this, shear wall design properties are assigned as inputs whereas failure mode and shear strength were designated as outputs for the corresponding classification and regression problems, respectively. Widely used machine learning methods, namely: Ridge Linear Regression, Logistic Regression, Multi-layer Perceptron, Support Vector Machine, Random Forest, XGBoost, LightGBM, and CatBoost are employed using a database consisting of 432 non-conforming shear walls. The data is randomly split to train and test sets (80% and 20%, respectively) to develop the predictive models and to evaluate model performances, respectively. Performance metrics (e.g. ${R^2}$ R 2 , RMSE) are evaluated over a hundred random splits to ensure robustness. The proposed CatBoost-based models achieve overall accuracies above 90% for both failure prediction and shear strength estimation. The proposed framework is believed to be a promising tool for earthquake engineers for practical and accurate failure mode forecast and shear strength estimation of non-compliant RC shear walls. [ABSTRACT FROM AUTHOR]