Search Results (132)

This study investigates the bond behavior of fabric-reinforced cementitious matrix (FRCM) composites with three common masonry substrates—solid clay bricks (SBs), perforated bricks (PBs), and concrete hollow blocks (HBs)—using knitted polyester grille (KPG) fabric. Through uniaxial tensile tests of the KPG fabric and FRCM system, along with single-lap and double-lap shear tests, the interfacial debonding modes, load-slip responses, and composite utilization ratio were evaluated. Key findings reveal that (i) SB and HB substrates predominantly exhibited fabric slippage (FS) or matrix–fabric (MF) debonding, while PB substrates consistently failed at the matrix–substrate (MS) interface, due to their smooth surface texture. (ii) Prism specimens with mortar joints showed enhanced interfacial friction, leading to higher load fluctuations compared to brick units. PB substrates demonstrated the lowest peak stress (69.64–74.33 MPa), while SB and HB achieved comparable peak stresses (133.91–155.95 MPa). (iii) The FRCM system only achieved a utilization rate of 12–30% in fabric and reinforcement systems. The debonding failure at the matrix–substrate interface is one of the reasons that cannot be ignored, and exploring methods to improve the bonding performance between the matrix–substrate interface is the next research direction. HB bricks have excellent bonding properties, and it is recommended to prioritize their use in retrofit applications, followed by SB bricks. These findings provide insights into optimizing the application of FRCM reinforcement systems in masonry structures. Full article

The salt flotation of graphite in the presence of lithium nickel manganese cobalt oxide (NMC) was assessed by performing colloidal probe atomic force microscopy (CP-AFM) on sessile gas bubbles and conducting batch flotation tests with model lithium-ion-battery black mass. The modeling of film drainage and detachment during particle–bubble interactions provides insight into the fundamental microprocesses during salt flotation, a special variant of froth flotation. The interfacial properties of particles and gas bubbles were tailored with salt solutions containing sodium chloride and sodium acetate buffer. Graphite particles can attach to gas bubbles under all tested conditions in the range pH 3 to pH 10. The attractive forces for spherical graphite are strongest at high salt concentrations and pH 3. The conditions for the attachment of NMC to gas bubbles were evaluated with simulations using the Stokes–Reynolds–Young–Laplace model for film drainage, under consideration of DLVO forces and a hydrodynamic slip to account for irregularities of the particle surface. CP-AFM measurements in the capillary force regime provide additional parameters for the modeling of salt flotation, such as the force and work of detachment. The contact angles of graphite and NMC particles during retraction and detachment from gas bubbles were obtained from a quasi-equilibrium model using CP-AFM data as input. All CP-AFM experiments and theoretical results suggest that pristine NMC particles do not attach to gas bubbles during flotation, which is confirmed by the low rate of NMC recovery in batch flotation tests. Full article

This study introduces a new method for modeling the nonlinear behavior of adhesively bonded composite steel–concrete T-beam systems. The model characterizes the interfacial behavior between the steel beam and the concrete slab using a strain compatibility approach within the framework of linear elasticity. It captures the nonlinear distribution of shear stresses over the entire depth of the composite section, making it applicable to various material combinations. The approach accounts for both continuous and discontinuous bonding conditions at the bonded steel–concrete interface. The analysis focuses on the top flange of the steel section, using a T-beam configuration commonly employed in bridge construction. This configuration stabilizes slab sliding, making the composite beam rigid, strong, and resistant to deformation. The numerical results demonstrate the advantages of the proposed solution over existing steel beam models and highlight key characteristics at the steel–concrete interface. The theoretical predictions are validated through comparison with existing analytical and experimental results, as well as finite element models, confirming the model’s accuracy and offering a deeper understanding of critical design parameters. The comparison shows excellent agreement between analytical predictions and finite element simulations, with discrepancies ranging from 1.7% to 4%. This research contributes to a better understanding of the mechanical behavior at the interface and supports the design of hybrid steel–concrete structures. Full article

As the core component for fracturing plug anchoring, dissolvable ball seat (DBS) slip performance directly determines the success of fracturing operations. However, frequent failures, such as tooth structural fractures, casing damage, and the slip breaking off entirely, compromise DBS reliability during high-pressure fracturing. This study investigates DBS slip anchoring performance through finite element analysis (FEA), anchoring performance tests, and structural optimization. We established a comprehensive safety and performance assessment framework incorporating strength criteria, peak contact pressure, and anchoring uniformity. Comparative stress analysis of nail-type versus block-type slip systems revealed superior performance in block-type configurations, demonstrating more uniform slip–casing interfacial stress distribution. To further enhance the anchoring performance of the block-type slip, a structural parameter analysis was conducted to identify critical factors influencing anchoring capability, with tooth apex angle and inclination angle determined as key parameters. The influence laws of these parameters on anchoring performance were systematically investigated. Subsequently, a multi-parameter optimization methodology was employed to optimize the structural configuration of the block-type slip. The optimization results revealed that an optimal slip tooth apex angle of 80° or 85° and an inclination angle of 70° enhance the safety and anchoring reliability of the dissolvable ball seat slip while providing a theoretical framework for future slip structure design improvements. At present, the new structure of the soluble ball seat structure proposed in this paper has been successfully applied in some oil fields. Field tests show that the anchoring efficiency has been significantly improved. This research not only provides a theoretical framework for the design of sliding structures, but also offers reliable technical support for the efficient development of deep oil and gas resources. Full article

Low-surface-energy and wettability-based antifouling coatings have garnered increasing attention in marine applications owing to their environmentally friendly characteristics. However, their limited functionality often results in suboptimal long-term antifouling performance, particularly under dynamic marine conditions. To address these limitations, a polydimethylsiloxane (PDMS)-based slippery (PSL) coating was fabricated on TC4 titanium alloy by integrating surface silanization via (3-Aminopropyl)triethoxysilane (APTES), antimicrobial Ag-TiO₂ nanoparticles, laser-induced hierarchical microtextures, and silicone oil infusion. The resulting PSL coating exhibited excellent oil retention and stable interfacial slipperiness even after thermal aging. Compared with bare TC4, low-surface-energy Ag-containing coatings, Ag-containing superhydrophobic coatings, and conventional slippery liquid-infused porous surfaces (SLIPS), the PSL coating demonstrated markedly superior resistance to protein adsorption, bacterial attachment, and diatom settlement, indicating an enhanced synergistic antifouling effect. Furthermore, it significantly reduced the diatom concentration in the surrounding medium without complete eradication, underscoring its eco-friendly and non-disruptive antifouling mechanism. This study offers a scalable, durable, and environmentally benign antifouling strategy for marine surface protection. Full article

In Gen-IV nuclear reactors, structural materials must endure unprecedented levels of neutron irradiation and hydrogen exposure, posing significant challenges for traditional Ni-based alloys. This study evaluates Ni–graphene nanocomposites (NGNCs) as a promising solution, leveraging their inherent radiation tolerance and hydrogen diffusion suppression. Using molecular dynamics simulations, we investigate how Ni/graphene interfaces influence mechanical properties under combined hydrogen permeation and displacement damage. Key parameters, such as hydrogen concentration, displacement damage level, strain rate, and temperature, are systematically varied to assess their impact on stress–strain behavior (including Young’s modulus and tensile strength), with comparisons to single-crystal nickel. Our findings reveal that NGNCs exhibit distinct mechanical responses characterized by serrated stress–strain curves due to interfacial slip. Hydrogen and irradiation effects are complex: low hydrogen levels can increase Young’s modulus, while higher concentrations and irradiation generally degrade strength, with NGNCs being more affected than single-crystal nickel. Additionally, NGNCs show enhanced thermal stability but increased strain rate sensitivity. These results provide critical insights for designing materials that balance reinforcement with environmental resilience in nuclear applications. Full article

With growing emphasis on sustainable construction, fiber-reinforced polymer (FRP) bars are increasingly being used as alternatives to steel rebars due to their high strength-to-weight ratio, corrosion resistance, and environmental benefits. This study has investigated the bond behavior between FRP bars and concrete of different strength grades under dynamic loading conditions. To analyze the microscopic properties of FRP bar surfaces, the study employs a variety of techniques, including scanning electron microscopy (SEM), atomic force microscopy (AFM), and non-contact surface profilometry. In addition, X-ray photoelectron spectroscopy (XPS), water contact angle (WCA) measurements, and energy dispersive spectrometry (EDS) are used to further investigate surface characteristics. The results reveal a direct correlation between the resin surface roughness of FRP bars and their wettability characteristics, which in turn influence the cement hydration process. Pull-out tests under different loading rates and concrete strength grades have been conducted to evaluate the bond–slip behavior and failure modes. The results indicate that bond strength increases with increasing concrete strength. Dynamic pull-out tests further reveal that higher loading rates generate heterogeneous stress fields, which limit the deformation of FRP bars and consequently diminish the contribution of mechanical interlock to interfacial bonding. Full article

This study investigates interface sliding behavior in composite I-steel–concrete beams reinforced with a composite material plate by analyzing various connection configurations combining shear stud connectors and adhesive bonding. The degree of composite action, governed by the shear stiffness at the steel–concrete interface, plays a critical role in structural performance. An analytical model was developed based on the elasticity theory and the strain compatibility approach, assuming constant shear and normal stress across the interface. Five connection modes were considered, ranging from fully mechanical (100% shear studs) to fully adhesive (100% bonding), as well as mixed configurations. The model was validated against finite element simulations, demonstrating strong agreement with relative differences between 0.3% and 10.7% across all cases. A parametric study explored the influence of key factors such as interface layer stiffness and composite plate reinforcement material on the overall interface behavior. The results showed that adhesive bonding significantly reduces slippage at the steel–concrete interface, enhancing bond integrity, while purely mechanical connections tend to increase interface slippage. The findings provide valuable guidance for designing hybrid connection systems in composite structures to optimize performance, durability, and construction efficiency. Full article

Hot press preforming of unidirectional prepreg composites plays a key role in the manufacturing of aerospace components. However, defect prevention remains challenging due to complex fiber reorientation and inter-ply friction phenomena that occur during the forming process. To address these challenges, this study proposes an integrated modeling approach comprising three key components: (1) a simplified linear friction model for characterization of inter-ply slip behavior, (2) a fiber-tracking algorithm that accounts for anisotropic deformation characteristics, and (3) a coupled linear shell–membrane formulation for simultaneous modeling of in-plane and out-of-plane deformation behaviors. The proposed approach is validated through comprehensive material characterization, finite element simulation, and experimental comparisons based on a 2 m Ω-stringer geometry. Simulation results align well with experiments, showing the model’s ability to predict defects. Parametric analysis also identifies temperature as a key factor in controlling interfacial friction and improving formability, with optimal results at 75 °C. This integrated modeling approach provides an effective approach for defect prediction and process optimization, contributing to reduced material waste and improved efficiency in aerospace composite manufacturing. Full article

In tunnel structures that traverse active fault zones, a vibration isolation layer is often installed between the primary support and the secondary lining. As a result, a three-layer flexible support structure composed of the initial support, damping layer, and secondary lining is formed. Currently, there is limited research on the mechanical behavior of interlayer interfaces. To address this, mechanical performance tests were conducted on composite specimens under compression-shear conditions, including foam concrete paired with C30 ordinary concrete (PC specimens) and foam concrete paired with Engineered Cementitious Composites (PE specimens). The interfacial shear mechanical properties under varying normal loads were analyzed. The results indicate that the shear mechanical properties of both PC and PE interfaces increase with rising normal stress. Under identical normal stress conditions, the PC interface exhibits higher shear strength, shear modulus, and shear-slip energy compared to the PE interface, but its failure displacement is smaller. When the normal stress increases from 0 MPa to 2 MPa, the interfacial shear strength of PC specimens increases by 1.6 times, while that of PE specimens increases by 2.7 times. The residual shear strength of the PC specimens and PE specimens increased by 6.1 times and 15.3 times, respectively. B Established the maximum shear strength formulas for PC specimens and PE specimens. These findings provide a scientific basis for the design of tunnel shock-absorbing layers and ductile linings. Full article

Polyurethane concrete (PUC) is a promising candidate for structural repair materials due to its excellent mechanical properties and durability. However, the bonding performance between PUC and concrete interfaces may limit its broader application. This study examined the factors affecting the shear strength at the PUC–NC interface. A total of 16 oblique shear tests, varying by interface treatment methods (smooth—GH, roughened—ZM, and grooved—KC), adhesive application rates—NJJ (0, 0.2, and 0.3 kg/m²), and steel fiber contents—GXW (0%, 0.5%, 1%, and 1.5%), to evaluate their impact on the mechanical properties of the PUC–NC interface. The results demonstrated that roughening the interface significantly improved the shear strength, resulting in a 32% increase compared to a smooth interface and 15% compared to a grooved interface. A moderate adhesive application rate (0.2 kg/m²) enhanced the interface strength, while excessive adhesive did not further increase the shear strength. The optimal steel fiber content (1%) resulted in the highest shear strength, improving it by 22%, whereas excess steel fibers (1.5%) reduced the interface strength. This is due to fiber agglomeration, which weakens mechanical interlocking and introduces defects that impair interfacial bonding. Load–slip curve analysis revealed that roughened interfaces combined with the appropriate amount of steel fibers improved the interface toughness, delaying the failure process. This study presents a model for calculating the shear strength of steel fiber-reinforced PUC–NC interfaces, incorporating shear slip. Compared to existing models, it more accurately reflects the experimental data. Full article

Secondary pre-tightening of clamping cable joints can effectively improve the load-bearing performance of U-shaped steel supports. However, the underlying mechanism of secondary pre-tightening has remained a critical knowledge gap in ground control engineering, and its design still relies on empirical approaches without theoretical guidance. To address these challenges, this study proposes a novel mechanistic framework integrating mathematical modelling, experimental validation, and parametric analysis. Specifically, a first-principle-based mathematical expression for the slip resistance of clamping cable joints under secondary pre-tightening was derived, explicitly incorporating the effects of bolt torque and interfacial friction; and a dual-phase experimental protocol combining axial compression tests and numerical simulations was developed to systematically quantify the impacts of initial pre-tightening torque, secondary pre-tightening torque (T₂), and the timing of secondary pre-tightening (u/u_max). Three groundbreaking thresholds were identified, as follows: critical initial pre-tightening torque (T₁ > 250 N·m) beyond which secondary pre-tightening becomes ineffective (<5% improvement); minimum effective secondary pre-tightening torque (T₂/T₁ > 1) for significant load-bearing enhancement; and the optimal activation window (u/u_max < 50%) balancing capacity gain (<10%) and deformation control. These findings establish the first quantitative design criteria for secondary pre-tightening applications, transitioning from empirical practice to mechanics-driven optimization. Full article

This study investigates the mesostructural damage evolution and creep deformation mechanisms in bedded rock salt through integrated scanning electron microscopy (SEM) and multistage creep experiments. Utilizing a self-developed in situ observation system coupled with digital image correlation (DIC) analysis, the microstructural heterogeneity, strain localization, and damage propagation patterns in the rock were systematically characterized. The results revealed distinct microstructural contrasts between rock salt and argillaceous interlayers, with interfacial regions exhibiting pore-rich, interconnected structures due to crystal gradation disparities. Creep damage initiation predominantly occurred in pure rock salt domains, manifesting as transgranular fractures and intercrystalline slip, followed by crack propagation into salt–mudstone interfaces governed by shear dilatancy. The integration of mesoscale structural characterization with macroscopic mechanical behavior establishes a framework for predicting the long-term stability of bedded salt formations under operational loads. Full article

To investigate the lubrication mechanism of phytic acid (PA) solution, a “copper–PA solution–copper” confined model with varying concentrations was established. Molecular dynamics (MD) simulations were employed to model the behavior of compression and the confined shear process. By examining the variations in key parameters such as dynamic viscosity, compressibility, radial distribution function, relative concentration distribution, and velocity distribution of PA solutions under different normal loads or shear rates, we elucidated the lubrication mechanism of PA solutions at the molecular level. The results demonstrate that under standard loading conditions, higher PA concentrations facilitate the formation of denser hydrated layers with decreased compressibility compared to free water, thereby significantly enhancing the load-bearing capacity. The shear stress at the solution–copper interface exhibits a substantial increase as the shear rate rises. This phenomenon originates from shear-driven migration of PA to the copper interface, disrupting the hydration layers and weakening hydrogen bonds. Consequently, this reduction in PA–water interactions amplifies slip velocity differences, ultimately elevating interfacial shear stress. The load-bearing capacity of the PA solution and the interfacial shear stress between the PA and copper are critical factors that influence the lubrication mechanism at the PA/Cu interface. This study establishes a theoretical foundation for the design and application of PA solution as a water-based lubricant, which holds significant importance for advancing the development of green lubrication technology. Full article

Lubrication is a well-established strategy for reducing interfacial frictional energy dissipation and preventing surface wear. Various lubricants have been developed, including mineral oil materials, vegetable oil materials, polymer-based materials, and solid lubrication materials. Among these, polymer-based lubrication materials have gained significant interest due to their versatility, leading to the development of tailored strategies to meet diverse application demands. In load-bearing scenarios, polymer-based materials enhance interfacial hydration, exhibiting exceptional frictional properties, including extremely low friction coefficients, high load-bearing capacity, and superior wear resistance. In contrast, in non-load-bearing scenarios, polymer-based coatings improve interfacial hydrophobicity, promoting boundary slip and reducing frictional resistance at the solid–liquid interface (SLI), making them an important strategy for drag reduction. Despite substantial advancements in polymer-based lubrication and drag reduction (PBLDR), the underlying microscopic mechanisms remain incompletely understood. Therefore, this review aims to provide a comprehensive analysis of the fundamental principles governing PBLDR. The main topics covered will include the following: (1) the fundamentals of the surface forces and hydrodynamic force, (2) the mechanisms underlying hydration lubrication, (3) joint lubrication and polymer brush lubrication, (4) the friction tuning and interfacial drag reduction via polymer coating design, and (5) the potential and limitations of polymer-based materials. By summarizing recent advancements in PBLDR, this work will provide valuable contributions to future research and applications in related fields. Full article