Interfacial Behavior Research Articles

Optimizing the rheological and mechanical properties of ultra-highly filled wood fiber/polyethylene composites through binary alloy matrix strategy

Enhancing the interfacial adhesion and rheological behavior of ultra-highly filled wood-plastic composites (UH–WPCs) presents a considerable challenge. We developed a bespoke binary alloy matrix of high-density polyethylene (HDPE) and maleated polyethylene (MAPE) to fabricate UH-WPCs with 70–90 wt% filler contents. Fourier-transform infrared spectroscopy and thermogravimetric analysis validated that about 22.3 % of MAPE engaged in esterification with wood fibers (WFs) in 80 wt% loading UH-WPCs, manifesting in noteworthy plasticization as evidenced by WFs' sheet-like structures. Rheological assessments illustrated that higher MAPE proportions reduced the viscosity of both the specialized alloy and UH-WPC melts significantly. By fine-tuning the MAPE to HDPE ratio to 16:2, we achieved marked enhancements in UH-WPCs' mechanical properties and dimensional stability: tensile strength and flexural strength increased by up to 141.7 % and 151.0 %, respectively, while creep strain and equilibrium water absorption decreased by as much as 27.3 % and 36.7 %. This research lays a robust scientific foundation for the efficient processing and enhancement of UH-WPCs, highlighting its potential for substantial improvements in mechanical performance, stability, and processability.

Using interfacial behavior and adsorption kinetics measurements as a predictor of bulk hydrophobic development of paper supercritically impregnated with food-grade waxes

Supercritical Impregnation methods are becoming popular in the development of food packaging materials. Bulk functional improvements of cellulose substrates using this method may be influenced by interfacial interactions between the impregnated solutes and cellulose. Hence, an interfacial adsorption kinetics study of solute molecules onto the substrate can provide insight on bulk property development, leading to an optimized packaging material with improved functionality. Paper substrates were impregnated with two food-grade waxes: Alkyl Ketene Dimer (AKD) and Carnauba Wax (CW). Hydrophobic development was monitored over a 3-week period. A quartz crystal microbalance (QCM-D) was used to determine interfacial characteristics and behavior of each wax with cellulose, and adsorption kinetics were quantified to compare the mass transfer processes of each wax at the interface. AKD significantly contributed to the substrate’s hydrophobic development over time. CW generated mildly hydrophobic substrates only when heated. AKD strongly adhered to the cellulose fibers at the interface, and demonstrated a 3-stage kinetic adsorption process, tentatively assigned (i) diffusion through the solvent; (ii) diffusion through the substrate; and (iii) attachment onto the fibers. CW readily washed off the cellulose surface, demonstrating only the first adsorption process. The different chemical structures also impacted these behaviors, as did concentration and temperature.Graphical

The effect of surface roughness, stiffness, and size on ice adhesion

The combined effect of parameters like surface stiffness, topography, and interface size on ice adhesion and its interfacial fracture behavior was studied. Ice adhesion on aluminum and polyurethane with three different surface roughness and two different surface sizes was evaluated experimentally through mode II interfacial fracture tests on a previously formed block of ice. Results showed that, for stiff surfaces the surface roughness increases the adhesion significantly, due to the transition from adhesive to cohesive fracture. Compliant surfaces do not show this transition, in the same roughness scale due to its susceptibility to deformation. The force required to fracture an ice block from stiff surfaces stabilize after a certain length, while compliant surfaces do not show this transition at the length scales studied. The article elucidates the relevance of different parameters and the consideration of size scales for designing low ice adhesion surfaces.

Effect of Temperature on the Corrosion Behavior of a Al2Cr5Cu5Fe53Ni35 Multi-Principal Element Alloy (MPEA) in Simulated Soil Environments

The effect of varying temperatures (15, 35, and 45 °C) on the corrosion behavior of a new single-phase distorted face-centered cubic (fcc) Al2Cr5Cu5Fe53Ni35 multi-principal element alloy (MPEA) was studied in simulated soil environments (NS4 solution). X-ray diffraction and electron backscattered diffraction were used to confirm the presence of a single phase throughout the microstructure. Electrochemical tests such as electrochemical impedance spectroscopy and linear polarization resistance were performed to evaluate the interfacial behavior and corrosion rate at various test conditions. Additionally, cyclic potentiodynamic polarization (CPP) tests were also carried out at the selected temperatures to study the pitting behavior of the MPEA. Surface characterization techniques such as X-ray photoelectron spectroscopy and scanning electron microscopy were used to identify the nature of the passive film formed in such complex materials as well as study the pitting characteristics after CPP testing. A stable passive film was found to be present all tested temperatures with the absence of preferential sites for pitting due to homogenous element distribution.

Microanalysis of behavior characteristics for asphalt binders on different mineral surfaces based on MD and SEM

To investigate the influence of different minerals on the behavior characteristics of asphalt binders at micro scale, molecular dynamics (MD) and scanning electron microscopy (SEM) were combined to study the interaction of asphalt binders and different mineral surfaces. Firstly, commonly used aggregates were analyzed by X-ray diffraction (XRD), and the main mineral categories were obtained, including quartz, albite, biotite and calcite. Secondly, the asphalt-mineral micro models were established by combining the reasonable asphalt micro model and mineral micro model, and the interface behavior characteristics were analyzed by MD simulation. Finally, the interface structure of asphalt and minerals was observed through SEM testing, which intuitively revealed the behavior characteristics of asphalt on different mineral surfaces. The results show that the relative concentration distribution of asphalt binders at the asphalt-mineral interface is relatively high, and it can be affected by mineral category, surface structure state and asphalt type. The transition zone of biotite, albite and asphalt interface is relatively wide, which means that the influence of biotite, albite and asphalt diffusion characteristics is relatively obvious, and the interface interaction ability is relatively strong. The study reveals the behavior characteristics of asphalt binders on different mineral surfaces, and provides a research basis for exploring the structural stability of asphalt-aggregate interface.

Contribution to the experimental and theoretical study of the behavior of soil-structure interfaces

Designing civil engineering works often requires taking into consideration the contact and interface conditions between the soil and structure. These may refer to the discontinuity surfaces between the soil and a structure such as foundations, geotechnical works, and others. Current research aims to improve the calculation methods for structures through a better understanding of the behavior of materials and interfaces. The present work falls into this context. It involves two parts. The main purpose of the first part is to present the results of the monotonic and cyclic soil-structure interface tests which were carried out using a modified direct shear box apparatus. The tests were conducted using a local material, namely the sand from the town of Messâad in the Wilaya of Djelfa (Algeria), in accordance with a constant normal stress path. In addition, a parametric study, dealing with the effect of density, interface roughness, and type of adhesive used on the behavior of the interfaces, was carried out as well. As for the second part, it primarily aims to validate the Modjoin interface model, which was developed at the Lille Mechanical Laboratory, based on the tests that were carried out in the first part. It is important to know that this model includes the main concepts used in soil modeling, such as isotropic hardening, characteristic state, critical state, softening, and others. Moreover, several validation tests are also presented in this work in order to describe the behavior of the soil-structure interface under monotonic loading to assess the performance of the model.

Failure Mechanisms in Stainless Steel/Carbon Steel Clad Plate Under Shear Tensile Loading: Experimental and Modeling Methods

The deformation behavior of a stainless steel/carbon steel (SS/CS) clad plate under interface shear loading is characterized in this work. A 2D digital image correlation method is applied to track the strain field variation near the interface during shear tensile tests. Then, a cohesive zone model (CZM) finite‐element method is developed to clarify the delamination behavior of the tested clad plate. Finally, the interfacial failure characteristics of the SS/CS clad plate are further presented through the comparison between the finite‐element method and fractography analysis at the interface. In the experimental and simulation results, it is shown that the mixed‐mode CZM, which couples the constitutive equations of three fracture modes, demonstrates excellent capabilities in capturing SS/CS interfacial deformation behavior. The main deformation mode in shear tensile tests is variable according to locations. The central region at the bonded surface is dominated by the shear delamination mode, and the region near the notches shows shifted crack propagation toward normal mode. These abrupt interfacial failures can be clarified via stress state and local damage analysis of the well‐reproduced finite‐element model of cladding material.

Probing the interfacial behaviors of interfacially active and non-active asphaltenes and their impact on emulsion stability

HypothesisAsphaltenes subfractions with distinct interfacial behaviors may play different roles in stabilizing oil–water emulsions. ExperimentsIn this work, whole asphaltenes were separated into interfacially active asphaltenes (IAA) and interfacially non-active asphaltenes (INAA). Employing advanced nanomechanical techniques, we have explored the compositions, morphologies, sizes, adsorption, and interfacial behaviors of IAA and INAA. FindingsIAA exhibits a high and unevenly distributed oxygen content, distinguishing it from INAA. In toluene, the diameters of IAA and INAA are about 60 nm and 6 nm, respectively. When adsorbed irreversibly on mica surfaces, the thickness of the IAA and INAA film was measured at ∼5.5 nm or 1 nm, respectively; while in a toluene solution, the film thickness reached ∼46 nm and 3.1 nm for IAA and INAA, respectively. IAA demonstrates superior interfacial activity, and elastic/viscous moduli compared to INAA at the water-toluene interface. Quantified surface force measurements reveal that IAA stabilizes water droplets in toluene at a concentration of only 10 mg/L, while INAA requires a higher concentration of 100 mg/L. This work provides the first comprehensive investigation into the adsorption and interfacial behaviors of asphaltene subfractions and provides useful insights into the asphaltenes-stabilization mechanism of emulsions.

Experimental and simulation study of the pulsation characteristics of underwater semiclosed initial intermittent bubbles

Bubbles at the cylinder outlet are a typical feature of the underwater ejection process. The interaction between gas and water is turbulent and results in an unstable bubble interface. In this work, experimental and numerical methods were used to determine the evolution of underwater semiclosed initial intermittent bubbles and their pressure propagation characteristics. Direct measurements of the interfacial migration behaviour of the bubbles were made using a high-speed video camera, and the variation in the pressure law in the flow field was obtained using a pressure sensor. The bubble pulsation characteristics were also analysed in conjunction with numerical simulations. The results show that the bubble at the mouth of the cylinder underwent the process of expansion, contraction, necking, and fracture under the coupled effect of the inertial motion of the liquid phase and the pressure inside the bubble and exhibited obvious periodic evolution characteristics. The flow instability driven by the velocity and density gradient gradually destabilised the bubble boundary, resulting in the phenomenon of necking of the gas cluster. Simulations were carried out for different diaphragm opening states to investigate the effects of the diaphragm cracking state on bubble evolution and pressure fluctuations.

Conjugation of coconut protein with ferulic acid promotes interfacial adsorption and mitigates lipid oxidation in O/W emulsion

The formation of small droplets in emulsion systems promotes lipid oxidation, affecting their shelf life. In this study, ferulic acid was covalently grafted onto coconut protein (CPI) through alkaline treatment method. The structural characteristics, interfacial properties, emulsifying properties, and oxidative stability of emulsions prepared by coconut protein-ferulic acid covalent complexes (CPF) were investigated. The results showed that covalent grafting of ferulic acid could change the physicochemical properties of coconut protein, including altering protein secondary and tertiary structures, enhancing the absolute value of zeta potential and antioxidant activity [2, 2-diphenyl-1-picrylhydrazyl (DPPH•) and 2, 2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS•+)]. Meanwhile, the interfacial behavior of CPI and CPF was characterized by dissipative quartz crystal microbalance and dilatational rheology analysis. Compared to CPI, CPF could diffuse to the oil-water interface quickly (from 0.084 ± 0.002 to 0.154 ± 0.003 mN/m/s1/2), and formed a thick interfacial layer dominated by elasticity, which enhanced the centrifugal stability of CPF-stabilized emulsions and effectively inhibited lipid oxidation within a 15-day storage period. Our results clearly demonstrated that coconut protein-ferulic acid conjugated complexes could improve emulsion stability and mitigate lipid oxidation, owing to the strong electrostatic repulsion interaction and high diffusion rate at interface. These findings may provide comprehensive insights for the further design and development of protein-polyphenol covalent complexes in the food industry.

Atomic-scale understanding on the influence of sliding angle on the interfacial structure and friction behavior of textured amorphous carbon films

Textured amorphous carbon (T:a-C) films have received great attention in the fields of hard drives, MEMS, and NEMS due to their excellent tribological properties. However, there is still a lack of research on the dependence of its friction behavior on different sliding angles. Especially, owing to the limitations of in-situ characterization in capturing the friction interface information, the potential friction mechanisms are still unclear. Hence, in this work T:a-C film with a rectangular shape was constructed and the impact of different sliding angles on friction behavior under dry friction condition was mainly explored through reactive molecular dynamics simulation. Results unveil that the friction properties of T:a-C films are closely dependent on the sliding angle. When the sliding angle increases from 0° to 45°, the decrease in the number of CC covalent bonds at the friction interface weakens the interfacial crosslinking effect, leading to a decrease in the friction coefficient by 20.11 %. However, as the sliding angle further increases from 45° to 90°, an increase in friction coefficient is observed, which is due to the increase of unsaturated bond content, weakening the interface passivation effect. These results reveal the friction mechanism of T:a-C films, induced by sliding angle, and effectively guide the design and technical application of textured a-C films.

Interfacial Behavior of Copper/Steel Bimetallic Composites Fabricated by CMT-WAMM

Interfacial Behavior of Copper/Steel Bimetallic Composites Fabricated by CMT-WAMM

Characterizing interfacial behavior of structurally cemented granular material using a large three-dimensional contact surface testing machine and a mesoscale bond model in DEM

Structuralized cementing technology takes full advantage of non-pressure controlled grouting technology to fill pores in coarse aggregates using self-compacting material with no need for vibration or mixing. By cementing the aggregates in a structured manner, structurally cemented material has properties between those of a discrete granular material and a continuous medium. The interface between different component structures exerts an important effect on the physical properties of the whole material. In this paper, the monotonic and cyclic mechanical properties of the contact interface properties of a structurally cemented material under different normal stresses are studied by performing experiments and numerical simulations. Through the study, the deformation displacement time history and volume change with the shear process are provided, the deformation process of the sample near the contact interface during the shear process is discussed, and the shear mechanics law with the strength mechanism under the simple shear condition is summarized.

An improved peridynamic model for mechanical behavior of steel-concrete interface

The steel–concrete interface is an important component of reinforced concrete (RC) materials, and accurately expressing the mechanical properties of the interface is crucial to the failure analysis of RC members. The unique superiorities of peridynamic (PD) theory in dealing with discontinuities make it extensively applied in the failure analysis of RC structures. This paper introduces a modified PD model for describing the mechanical behavior of the steel–concrete interface. The ideal microplastic PD model and bilinear PD model are applied to express the mechanical behavior of steel and concrete respectively. Furthermore, the strain rate effect of materials is also incorporated in the analysis of dynamic damage to RC members subjected to blast load. A parallel (OpenMP) program was developed using FORTRAN to implement the computation of the modified PD model. Finally, the modified PD model was utilized for the numerical simulation of the RC beam shear-flexural failure experiment and the RC slab explosion failure experiment. Research shows that the modified PD model can correctly describe the mechanical behavior of the steel–concrete interface.

Interfacial protein adsorption behavior can be connected across a wide range of timescales using the microfluidic EDGE (Edge-based droplet GEneration) tensiometer

HypothesisOur hypothesis is that dynamic interfacial tension values as measured by the partitioned-Edge-based Droplet GEneration (EDGE) tensiometry can be connected to those obtained with classical techniques, such as the automated drop tensiometer (ADT), expanding the range of timescales towards very short ones. ExperimentsOil-water and air–water interfaces are studied, with whey protein isolate solutions (WPI, 2.5 – 10 wt%) as the continuous phase. The dispersed phase consists of pure hexadecane or air. The EDGE tensiometer and ADT are used to measure the interfacial (surface) tension at various timescales. A comparative assessment is carried out to identify differences between protein concentrations as well as between oil–water and air–water interfaces. FindingsThe EDGE tensiometer can measure at timescales down to a few milliseconds and up to around 10 s, while the ADT provides dynamic interfacial tension values after at least one second from droplet injection and typically is used to also cover hours. The interfacial tension values measured with both techniques exhibit overlap, implying that the techniques provide consistent and complementary information. Unlike the ADT, the EDGE tensiometer distinguishes differences in protein adsorption dynamics at protein concentrations as high as 10 wt% (which is the highest concentration tested) at both oil–water and air–water interfaces.

Study on cohesion and adhesion behaviors of the zeolite foamed asphalt-warm mix mixture based on molecular dynamics simulation

Zeolite foamed asphalt - warm mix mixture (ZFA-WMM) has been applied in large quantities in asphalt pavement, however, a lower construction temperature, residual zeolite water and zeolite minerals have different effects on the cohesion and adhesion properties of zeolite foamed asphalt (ZFA), which indirectly affects the water stability of its mixture. This study analyzed the interface behavior in ZFA-WMM using molecular dynamics simulation. First, the molecular model of ZFA was constructed, and its thermodynamic properties were calculated and compared with experimental values and related simulated values to validated the reasonable of model. Then, the interface models of ZFA-aggregate (quartz and calcite) and ZFA-ZFA were established, simulating the effects of the zeolite mineral dosage, temperature, and interface moisture (residual zeolite water) content on the cohesion and adhesion of ZFA. Furthermore, the occurrence mode of cohesion or adhesion failures in ZFA-WMM were predicted by comparing the ZFA-aggregate adhesion work with ZFA cohesion work. The simulation results indicated that as the zeolite mineral dosage increased, the ZFA cohesion and ZFA-calcite adhesion increased, while ZFA-quartz adhesion first grew and then dropped, reaching its maximum at 9.4 % zeolite mineral dosage. Under the pavement operating temperature range (-15°C∼65°C), higher pavement temperatures are beneficial to ZFA-aggregate adhesion; the cohesion of ZFA first increases and then decrease as temperature rises, reaching its maximum at 25℃. The larger the interface moisture content, the higher the possibility of water separating ZFA from the aggregate surface and the water sensitivity of ZFA-WMM. The ZFA-WMM is prone to adhesion failure, especially at higher zeolite dosages.

Determination traction-separation parameters and its sensitivity analysis of bilinear cohesive zone model through experimental and numerical peeling analysis of electrodes

The optimization of traction-separation parameters within the cohesive zone model (CZM) is crucial for accurately simulating electrode peeling failure in lithium-ion batteries. This study performed 180° peeling tests on NCM electrodes and used Abaqus software alongside the sim-flow optimization tool for simulation analysis, aiming to accurately replicate the failure behavior at the lithium-ion battery electrode interface. Experimental results were used to determine the fracture energy of the electrode interface, while numerical simulations analyzed the peeling performance of the electrode. By fitting the force-displacement curves from both simulation and experiment, the traction-separation parameters within the bilinear CZM were optimized. Additionally, the study analyzed the effects of traction-separation parameters, as well as the modulus and thickness of the current collector, on peeling behavior. The results showed that a significant increase in the interface stiffness and strength increased the steady-state peeling force. Among these, the fracture energy had the most significant influence on the steady-state peeling force. Furthermore, while the modulus and thickness of the current collector affected the maximum peeling force, their effect on the steady-state peeling force was negligible. These findings enhance the accuracy of simulating the failure behavior of the electrode interface.

Study of Phase Transformations and Interface Evolution in Carbon Steel under Temperatures and Loads Using Molecular Dynamics Simulation

Carbon steel materials are widely used in mechanical transmission. Under different temperature and pressure service conditions, the microscopic changes of stress and strain that are difficult to detect and analyze by experimental means will lead to failure deformation, thus affecting their operational stability and life. In this study, the molecular dynamics method is used to simulate the heating–cooling phase transition process of common carbon steel materials. Austenite transformation temperatures of 980 K (0.2 wt.%) and 1095 K (0.5 wt.%) are acquired which is determined by the volume hysteresis before and after transformation, which is consistent with the results of JMatPro phase diagram analysis. The internal stress state of the material varies between compressive stress and tensile stress due to the change of phase structure, and the dislocation characteristics during the phase transition period are observed to change significantly. Then, an α/γ two-phase interface model is constructed to study the migration of the phase interface and the change of the phase structure by applying a continuously changing external load. At the same time, the transition pressure of α→ϵ is obtained with a value of 37 GPa under three different initial loads showing the independence of the initial load and the historical path. Based on the molecular dynamics simulation and the phase diagram calculation of the carbon steel, the analysis method for the microstructure transformation and the stress–strain behavior of the phase interface under the external load can provide a reference for the design of microstructure and mechanical properties of alloy steel in the future.

Optically Active Defect Engineering via Plasma Treatment in a MIS‐Type 2D Heterostructure

AbstractAt the interface of 2D heterostructures, the presence of defects and their manipulation play a crucial role in the interfacial charge transfer behavior, further influencing the device functionality and performance. In this study, the impact of deliberately introduced photo‐active defects in the h‐BN layer on the interfacial charge transfer and photoresponse performance of a metal‐insulator‐semiconductor type heterostructure device is explored. The formation and concentration of defects are qualitatively controlled using an inductive coupled plasma treatment method, as evidenced by enhanced h‐BN defect emission and more efficient optically induced doping of graphene at the graphene/h‐BN interface. Besides, the use of the h‐BN layer between graphene and WS2 not only suppresses charge carriers in the dark state, but also promotes the separation of photo‐generated electron‐hole pairs and interfacial charge transfer due to the existence of defect levels, leading to orders of magnitude improvement in the light on/off ratio and self‐driving performance of the heterostructure photodetector. This strategy of controlling defect states in the insulating layer provides a new approach to optimize the charge transfer processes at the 2D interfaces, so as to expand its potential applications in the fields of electronic and optoelectronic devices.

Quantitative assessment of impact damage in stitched foam‐filled Aluminium honeycomb Sandwich panels by experimental and machine learning methods

AbstractNovel Stitched Foam‐filled Honeycomb Sandwich (SFHS) panels have been fabricated using vacuum‐assisted resin transfer molding to address the weak interfaces between the face sheets and the core in the Foam‐filled Honeycomb Sandwich (FHS) panel. The SFHS panels have shown better load‐bearing capacity and performance characteristics compared to FHS panel after Low‐Velocity Impact (LVI) tests. After the LVI test, MATLAB image processing was used to analyze the impact damage areas and failure mechanisms. In addition, Machine Learning regression algorithms were employed to predict the optimal amount of energy absorbed during low‐velocity impact testing of fabricated panels with a maximum impactor drop height of 700 mm. The results indicated that nylon yarn stitching significantly improved energy absorption and interfacial behavior compared to unstitched honeycomb panels. This research also revealed that SFHS1 panels with adjacent honeycomb cell stitching are more impact resistant, provide increased load carrying capacity, and are cost‐effective. These panels can be utilized by modern engineers to increase economy, durability, and functionality in industrial, automotive, and construction applications.Highlights Stitched Foam Filled Honeycomb Sandwich (SFHS) panels, manufactured via resin transfer molding, and eliminates weak interfaces between the face sheets and core. SFHS panels outperformed unstitched panels in load‐bearing and energy absorption during low‐velocity impact, as confirmed by MATLAB image analysis showing reduced damage and failure. Machine learning algorithms particularly polynomial regression model predicted maximum absorption energy precisely with 99.9% accuracy, close to experimental results. SFHS panels can be used in automotive and industrial applications due to their through‐thickness stitching.