Interfacial Failure Mechanisms Research Articles

Interface Degradation of LaCl3-Based Solid Electrolytes Coupled with Ultrahigh-Nickel Cathodes.

Despite competitive compatibility with high-nickel cathodes, chloride solid electrolytes (SEs) still experience inevitable side reactions at the cathode/SE interface, causing capacity decay in all-solid-state lithium batteries (ASSLBs) during cycling. Herein, a three-electrode ASSLB testing device is developed to comprehensively reveal the interface failure mechanisms of the ultrahigh-nickel LiNi0.92Co0.05Mn0.03O2 (NCM92) cathode paired with LaCl3-based chloride SE Li0.447La0.475Zr0.059Ta0.179Cl3 (LLZTC). Distribution of relaxation time (DRT) analysis clearly shows the ASSLB degradation accompanied by a significant NCM92/LLZTC interface impedance increase, which becomes more pronounced at the higher cutoff charging voltage of 4.8 V vs Li+/Li. Furthermore, time-of-flight secondary ion mass spectrometry (ToF-SIMS) and focused ion beam scanning electron microscopy (FIB-SEM) analysis also confirm the deterioration arising from active lattice oxygen and loss of physical contact at the NCM92/LLZTC interface. These findings reveal both electrochemical degradation and physical contact failure at the cathode/SE interface as key causes of the ASSLBs' capacity decay.

Understanding interfacial failure mechanisms of advanced high strength automotive steels resistance spot welds under opening-mode loading

This paper addresses interfacial failure (IF) of automotive steel resistance spot welds under opening mode loading (i.e., Mode I), simulated through the cross-tension test. Two modeling approaches were developed to predict cross-tension strength (CTS) during IF: one based on structural stress and the other on fracture mechanics. The structural stress model correlates CTS with the hardness of the fusion zone, while the fracture mechanics model links CTS to the fusion zone’s toughness. Our evaluation of these models across various automotive steels reveals that the hardness-based model is suitable for steels with fusion zone hardness below 350 HV, where IF typically results in ductile fracture. In contrast, for higher-grade steels with fusion zone hardness exceeding 400 HV, the toughness-based model is more appropriate, as IF occurs through brittle crack propagation. The transition in the interfacial failure mechanism of spot welds under Mode I loading—from ductile tensile failure to brittle crack propagation—is governed by the ratio of toughness and hardness of the fusion zone. These insights not only refine the prediction of CTS but also inform the design of effective post-weld heat treatments aimed at enhancing CTS without sacrificing strength under shear loading mode particularly through martensite refining strategy.

Retention and interfacial failure mechanism of single diamond grains in resin-bonded grinding tools

Abrasive grains and the associated bonding agent are the two significant components in the manufacturing of fixed abrasive machining tools. The material properties and interfacial bonding behavior between the grains and the bonding matrix determine machining performance. In precision machining processes with diamond abrasives, the primary failure modes of fixed abrasive tools are grain dislodgement and premature loss, leading to abrupt change in machining load and ultimately causing inaccurate and inefficient machining performance. This study develops a comprehensive model for understanding abrasive grain retention and interfacial failure mechanisms in resin-bonded diamond tools. Finite element analysis of a single diamond grain embedded in a resin matrix was conducted to examine the influence of the grain shape, protruding height, and orientation angle on critical interfacial failure force. A series of single diamond scratching experiments validated the model, revealing that the maximum retention force reached 43.56 N for grains with a 0.9 mm protruding height and a 60° orientation angle. The results also show that, within a specific grain size range, grain shape—quantified by the sphere deviation coefficient proposed in this paper, has the greatest impact on retention and failure behavior. Protruding height plays a secondary role, while the contribution of orientation angle is minimal. These findings provide valuable insights for the design, manufacture, and optimization of precision abrasive machining tools, particularly for applications requiring high precision and reliability.

Multiscale study of interfacial properties of carbon fiber reinforced polyphthalazine ether sulfone ketone resin matrix composites

In view of the limitations of traditional research tools on interfacial failure mechanisms in fiber/PPESK composites, this work proposes a multiscale research tool to carry out an in-depth study of the interfacial behavior between fibers and matrix. Based on microdroplet debonding tests, at the mesoscopic scale, the influence of residual thermal stress on the interface damage mode is explored through finite element (FEM) simulations. The evolution mechanism of composite material interfaces in spatial and temporal dimensions is examined based on changes in interfacial stress distribution, energy dissipation, and damage morphology during the debonding process, which can be summarized as follows: accompanied by elastic-plastic deformation and friction effects, the progressive process from localized to complete failure presents a dominant Type II damage mode at the interface. To further explore the interface failure mechanism at the molecular level, an interface model of CF/PPESK composite materials was established using molecular dynamics (MD) method. By monitoring the atom movement trend, the “fiber-matrix displacement synergistic effect" in the interfacial shear damage process was revealed, thereby establishing a multiscale mapping relationship of composite material interface. Based on this, the combination of FEM and MD was utilized to investigate the interface damage process of composite materials under different service conditions and to reasonably predict the initiation and expansion of microcracks. This study provides a pioneering perspective on interface damage research in composite materials with a “top-down” multiscale approach.

Enhancing interfacial locking of the CF and PBPESK resin by in-situ electrochemical deposition of MOF nanoparticles

The interfacial bonding of carbon fiber reinforced polymer composites plays a critical role in the overall performance of the composites. Poor interfacial bonding leads to catastrophic damage of composites when subjected to external loads. In this study, three-dimensional (3D) NH2-UiO-66 nanoparticles in-situ synthesis on the carbon fiber (CF) surface using an electrochemical method was achieved facilely and efficiently to enhance the interfacial adhesion of CF/PBPESK composites. The influence of incorporating 3D NH2-UiO-66 nanoparticles into the interphase on the interfacial and mechanical properties of carbon fiber reinforced composites was systematically investigated. The NH2-UiO-66 nanoparticles significantly increased the carbon fibers surface energy. The flexural, interlaminar shear and interfacial shear strength of the N–CF–6min/PBPESK composite were improved by 19 %, 31 %, and 93 %, respectively, compared to the D-CF/PBPESK composite. Furthermore, the interfacial failure mechanism of the composites was investigated. This approach offered a simple and efficient strategy for the in-situ synthesis of interfacial phase characterized by robust mechanical locking effects.

Interfacial Stress Transfer and Fracture in van der Waals Heterostructures.

Artificially stacking 2D materials (2DMs) into vdW heterostructures creates materials with properties not present in nature that offer great potential for various applications such as flexible electronics. Properties of such stacked structures are controlled largely by the interfacial interactions and the structural integrity of the 2DMs. In spite of their crucial roles, interfacial stress transfer and the failure mechanisms of the vdW heterostructures, particularly during deformation, have not been well addressed so far. In this work, the interfacial stress transfer and failure mechanisms of a MoS2/graphene vdW heterostructure are studied, through the strain distributions both laterally in individual 2DMs and vertically across different 2DMs revealed in-situ. The fracture of the MoS2 and the associated states of stress and strain are monitored experimentally. This enables various interfacial properties, such as the interfacial shear strength and interfacial fracture energy, to be estimated. Based only on the measured strength and interfacial properties of a single vdW heterostructure, a failure criterion is proposed to predict the failure mechanisms of similar vdW heterostructures with any lateral dimensions. This work provides an insight to the deformation micromechanics of vdW heterostructures that are of great value for their miniaturization and applications, especially in flexible electronics.

Interfacial bond behavior of steel fibers embedded in manufactured sand-based ultra-high performance concrete

The interfacial bond region between matrix and fibers is a non-negligible weak link that can significantly affect the mechanical properties of manufactured sand-based ultra-high-performance concrete (UHPMC). This study investigates the interfacial bond characteristics between steel fiber-UHPMC matrix using single-fiber pullout tests. Four variable parameters were considered: manufactured sand (MS) replacement ratio, stone powder content, fiber embedment length, and steel fiber geometry. Additionally, the microstructure of the steel fiber-UHPMC matrix interface was evaluated using backscattered electron microscopy (BSEM) and scanning electron microscopy (SEM). The results indicate that two typical failure modes including fiber pullout slip failure (in straight and hooked-end fibers) and fiber rupture failure (in corrugated fibers) were observed. The analysis of interfacial evaluation indicators shows that increasing the MS replacement ratio from 25 % to 100 % results in a decreasing trend in peak load, peak tensile stress, and energy consumption. Peak bond strength decreases with increasing embedment length. With the increase in stone powder content, the peak load, peak bond stress, and energy consumption increase initially and then decrease. Additionally, the interfacial failure mechanisms between straight/hooked-end steel fibers and the UHPMC matrix were further elucidated through bond-slip behavior characterization and microstructure analysis. Finally, a design-oriented bond-slip model was developed to predict the interfacial pull-out behavior of steel fiber -UHPMC matrix, showing favorable agreement between predicted and test results. These findings contribute to understanding the interfacial pullout behavior of steel fibers-UHPMC matrix, providing data reference for the performance optimization of UHPMC.

A comprehensive evaluation of crumb rubber modified asphalt-aggregate interfacial behavior and the effect of water: Molecular dynamics simulation and experimental investigation

The incorporation of crumb rubber (CR) makes the asphalt-aggregate interfacial properties highly complex and uncertain, while water is a key environmental factor causing interfacial failure. This paper aims to evaluate the characteristics of crumb rubber modified asphalt (CRMA)-aggregate interaction and the interfacial failure mechanism under the influence of different material properties and water at ambient temperature. Firstly, the CRMA-aggregate interfacial behavior before and after water intrusion is investigated using molecular dynamics simulations at the molecular scale. Next, the failure process and characteristics of the CRMA-aggregate interface were analyzed using the disk-shaped compact tension (DCT) test at the macro scale. Finally, the effect of water intrusion on the interface failure mode was analyzed through image processing. The results show that CR enhances binder cohesion and significantly affects its adhesion to aggregates with high CaO and MgO contents regardless of the presence of water. The asphalt concentration distribution on the CaO and MgO surfaces is more concentrated with higher peak concentration, leading to superior interfacial adhesion and water damage resistance with binder, while Al2O3 and SiO2 were inferior. The use of asphalt with higher creep stiffness, high-strength alkaline aggregates, and smaller CR particle size is beneficial for enhancing the CRMA binder-aggregate interfacial fracture performance. Water intrusion severely affected the interfacial adhesion, resulting in a significant increase in the proportion of adhesion failure, which is the main cause of the deterioration of the interface properties. The findings of this study provide insights into the factors affecting the CRMA-aggregate interfacial behavior, which facilitate the accurate design and application of high-strength durable CRMA mixtures.

Joint load-bearing behaviors and interface failure mechanism of encased coal samples under uniaxial compression

Concrete-encased coal pillars that serve as an effective support structure in coal mines have attracted increasing attention. This paper aims to explore the coupling bearing behaviors and the properties of interface force transfer between the interior coal and the encasing concrete. Laboratory uniaxial compression experiments were conducted on encased coal samples. Additionally, an interface force formula was derived based on deformation coordination and equilibrium conditions, and a mathematical formula was developed to estimate the load-bearing capacities of both the interior coal and the encased concrete. The research indicates that the stress–strain curve of the concrete-encased coal samples exhibits a distinct “double-peaked” phenomenon, and the load is transferred from the interior coal to the external concrete during the failure process. In the early stages of failure, the interface force enhances the strength of the coal pillar, while the lateral strain of the interior coal column exacerbates the damage to the encasing concrete. Moreover, the force at the concrete-coal interface is proportional to the axial loads and the mechanical properties of both materials. The strength of the coal pillar is significantly enhanced by lateral confinement. This study provides an experimental basis and theoretical analysis support for reducing the disaster of coal pillar instability.

Interface Stress Analysis and Failure Mechanism of Rock–Concrete Composite Structures Under Multi-directional Stress Waves

Interface Stress Analysis and Failure Mechanism of Rock–Concrete Composite Structures Under Multi-directional Stress Waves

Interfacial microstructure characteristics and failure mechanism of the laser welding-brazing steel-Al joints with various welding parameters

The microstructure details of the interface, mechanical properties and failure mechanism of laser welding-brazing (LWB) steel-Al joints with various welding parameters were comparatively investigated. The emergence of ternary Fe–Al–Si intermetallic compounds (IMCs) was observed in the interfacial area of the joints prepared utilizing ER4047 filler. In contrast, only the binary Fe–Al IMCs were formed in the interfacial area of the joints prepared employing ER5356 filler. With the same laser tilt angle, the IMCs layer of the joints prepared with ER4047 was thinner than that of the joints prepared with ER5356, implying the rapid growth of the IMCs welded via the ER5356 filler. The tensile strength exhibited by the former surpassed that of the latter. Employing the same filler metal, the average thickness of the IMCs layer of the joints with laser tilt angle of 10° was smaller than that of the joints with laser tilt angle of 20°. The strength of the joints with smaller tilt angle was better than that of the ones with bigger tilt angle. The tensile test outcomes revealed that there existed failure competition among the Al alloy base metal (Al-BM), weld metal (WM) and interface structure. If the interface structure was Fe–Al IMC with high brittleness, the cracks propagated along the interface, and finally fractured at the interface. If the interface structure was Fe–Al–Si IMC with good toughness, the crack propagation in the interface region could be hampered. In this case, the joint was prone to occur via WM failure or even Al-BM failure modes.

Bamboo as a natural optimized fiber reinforced composite: interfacial mechanical properties and failure mechanisms

Bamboo is a typical natural fiber-reinforced composite with an optimized distribution of vascular bundles as reinforcement and parenchyma tissues as bio-matrix. The interfacial bonding performance between vascular bundles and parenchyma tissue is critical for the mechanical properties and failure mechanisms of bamboo. This study employed pull-out tests to determine the interfacial shear strength (IFSS) between bamboo vascular bundles and parenchyma tissue and evaluate the critical embedded lengths () of vascular bundles. The effects of embedded vascular bundle lengths on interfacial strength and failure behaviors were also investigated. The results revealed a value of 2.51 mm, lower than the majority of plant fiber-reinforced composite materials, with an IFSS of around 20 MPa, surpassing most artificial bamboo fiber composites. The pull-out process of the vascular bundles involved elasticity, debonding, and sliding friction stage, where debonding energy absorption (DEA) outweighed frictional energy absorption (FEA) and increasing with embedded length. The primary failure features include interfacial debonding, parenchyma tissue ripping, delamination of fiber thin layers, and fiber breakage. Moreover, the parenchyma cells between the two fiber sheaths and at the top of the bamboo block readily detached. The interfacial failure mechanisms of bamboo included debonding, reinforcement, and matrix failure, with the proportions varying as the embedded length increased. Quantitative analysis of the interfaces structure and mechanical properties between vascular bundles and parenchyma tissues could provide a reference for the biomimicry of bamboo structures and the manufacturing of natural fiber-reinforced composite materials.

Deciphering the Interface Failure Mechanism for Aqueous Na-Ion Batteries at Low Temperatures

Deciphering the Interface Failure Mechanism for Aqueous Na-Ion Batteries at Low Temperatures

Marginal integrity in minimally invasive molar resin composite restorations: Impact of polymerization shrinkage

ObjectivesThis study utilized non-linear finite element (FE) models to explore polymerization shrinkage and its impact on marginal integrity in molars following both selective caries removal (SCR) and conventional treatment. Specifically, we performed 2D in silico simulations to study residual stresses post-resin polymerization shrinkage and their influence on the marginal integrity of various restoration types. MethodsInitially, FE models were developed based on a cohesive zone framework to simulate crack propagation along the bonded interfaces between restoration and tooth structure in SCR-treated molars with class I and class II restorations. The modeled resin composite restorations first underwent polymerization shrinkage and were then subjected to various occlusal loading conditions. Stress magnitudes and distributions were identified to evaluate the margin integrity and predict the mechanism and location of interfacial failure. Results and discussionThe FE models computed polymerization shrinkage stresses of less than 1 MPa, exerting a minor influence on the composite/tooth interface. Occlusal loading, however, significantly impacted the load-bearing capacity of the composite/tooth (c/t) interface, potentially jeopardizing the restoration integrity. Especially under bi-axial occlusal loading, interfacial debonding occurred in the vertical cavity walls of the class I restorations, increasing the risk of failure. Notably, SCR-treated teeth exhibited better margin integrity than restored teeth after complete caries removal (NCR).These findings provide valuable insights into the mechanical behavior of SCR-treated teeth under different loading conditions and highlight the importance of considering the load scenarios that may lead to failure at the c/t interface. By investigating the factors influencing crack initiation and delamination, this novel research contributes to the optimization of restorative treatments and aids in the design of more resilient dental restorations.

Static and Dynamic Mechanical Behavior of Carbon Fiber Reinforced Plastic (CFRP) Single-Lap Shear Joints Joule-Bonded with Conductive Epoxy Nanocomposites

The potential of electrically conductive graphene nanoplatelets (GNPs)/epoxy, multi-walled carbon nanotubes (MWNCTs)/epoxy and hybrid GNPs-MWCNTs/epoxy nanocomposites as adhesives for out-of-autoclave (OoA) and in-the-field CFRP repair via Joule heat curing was investigated. Scanning electron microscopy revealed a good dispersion of the nanoparticles in the matrix in all the nanocomposite adhesives above their percolation thresholds, which led to a homogeneous distribution of the heat generated during Joule CFRP repair. The joints bonded with neat epoxy and the nanocomposites showed similar lap shear strengths, with the addition of nanoparticles enhancing the fatigue performance of the adhesively bonded joints relative to when neat epoxy was used as an adhesive and oven-cured. The interfacial and cohesive failure mechanisms were found to coexist in all the cases, with an increasing dominance of the cohesive when nanofillers were embedded into the adhesive. No effect of the specific type of nanofiller incorporated into the epoxy as the conductive component was observed on the mechanical performance of the bonded joints, with the adhesives containing MWCNTs showing similar results to those filled with GNPs at considerably lower loadings due to their lower percolation thresholds. The independence of the properties regardless of the curing method highlights the promise of these Joule-cured adhesives for industrial applications.

Effects of bonding temperature on mechanical properties and interfacial morphology of YG8/40Cr joints fabricated using SPS diffusion bonding

The diffusion bonding of YG8 cemented carbide and 40Cr steel was performed using spark plasma sintering with Ni powder as the interlayer. The influence of bonding temperatures ranging from 700 to 1100 °C on the bonding interface morphology, mechanical properties, and failure mechanism of the joints was studied. By calculating the diffusion coefficients of Ni and Fe and observing the changes in the interface morphology, the pores at the Ni/40Cr interfaces were identified as Kirkendall voids formed because of the unbalanced diffusion of Ni and Fe. The diffusion activation energy of Ni in Fe was 87.37 kJ/mol, and that of Fe in Ni was 58.08 kJ/mol. The use of a pulsed current significantly reduced the diffusion activation energy, making diffusion easier. The bending strength of the joints increased sharply in the range from 700 to 900 °C, subsequently increased slowly, and tended to stabilise in the range from 900 to 1100 °C. The highest bending strength of 1080 MPa was achieved for the joint bonded at 1100 °C, which was attributed to the improved bonding of the YG8/Ni and Ni/40Cr interfaces and the resulting effects of the interlayer plastic constraint. The thickness of the CoNi diffusion zone at the YG8/Ni interface appeared to form a decisive factor in determining the failure locations of the joints. As the bonding temperature increased, the improved diffusion of Co and Ni enhanced the metallurgical bonding of the YG8/Ni interface, and the fracture position shifted from the polished surface of the YG8 base material (700 °C) to the Ni interlayer (1100 °C).

Bearing failure and strengthening mechanism of countersunk thin-ply laminated joints using an interference-fit bolt

By experimentation, this study investigated interference-fit effects on the bearing failure of thin-ply composite countersunk single-lap joints. A comparative study of the mechanical behaviour and strengthening of the bolt-hole wall during the assembly of thin-ply and thick-ply specimens with varying interference sizes has been carried out. The effect of the interference-fit on the strength of countersunk composite bolted joints with thin-ply has been studied in detail under quasi-static tensile loading. The interface strengthening and failure mechanisms of thin-ply interference joints were characterized by means of SEM micrographs. Thin-ply laminates exhibited lower installation forces during assembly. The use of thin-ply in the interference joints' area could still demonstrate suppression of the damage's generation and propagation. More importantly, thin-ply laminates could accommodate larger interference sizes than thick-ply laminates and have higher load-bearing capacities, approximately 10%–20 % higher. Thin prepregs could be used to facilitate the design process and improve composites' structural properties, providing new perspectives for improvements and innovative applications of interference joining technology. The results of this study have some guidance for the aerospace application of thin prepregs in thin-walled structures.

Nanoscale Insights into the Mechanical Behavior of Interfacial Composite Structures between Calcium Silicate Hydrate/Calcium Hydroxide and Silica

The failure of the interfacial transition zone has been identified as the primary cause of damage and deterioration in cement-based materials. To further understand the interfacial failure mechanism, interfacial composite structures between the main hydration products of ordinary Portland cement (OPC), calcium silicate hydrate (CSH) and calcium hydroxide (Ca(OH)2), and silica (SiO2) were constructed while considering their anisotropy. Afterwards, uniaxial tensile tests were conducted using molecular dynamics (MD) simulations. Our results showed that the interfacial zones (IZs) of interfacial composite structures tended to have relatively lower densities than those of the bulk, and the anisotropy of the hydration products had almost no effect on the IZ being a low-density zone. Interfacial composite structures with different configurations exhibited diverse nanomechanical behaviors in terms of their ultimate strength, stress–strain relationship and fracture evaluation. A higher strain rate contributed to a higher ultimate strength and a more prolonged decline in the residual strength. In the interfacial composite structures, both CSH and Ca(OH)2 exhibited ruptures of the Ca-O bond as the primary atomic pair during the tensile process. The plastic damage characteristics of the interfacial composite structures during the tensile process were assessed by analyzing the normalized number of broken Ca-O bonds, which also aligned with the atomic chain break characteristics evident in the per-atom stress map.

Enhancing mechanical properties and thermal conductivity in polymer bonded explosives by multi-scale surface modification of carbon fibers

Poor interfacial interaction and strength largely restrict the overall performance and practical application of carbon fibers (CFs) reinforced composites. The favorable interfacial properties were the key to realize superior mechanical properties in composites. Herein, we reported a novel multi-scale surface modification strategy of CFs to strengthen interfacial properties. Based on chemical oxidation treatment, the surface of CFs was further in situ grafted by a crosslinked high-strength polymer network consisting of aromatic diisocyanate, graphene oxide (GO) and polyethylenen glycol (PEG), which significantly improved the interfacial bonding and mechanical strength of interface layer itself. Benefitting from this multi-scale surface treatment, a high-efficiency mechanical enhancement of polymer bonded explosives (PBX) was achieved. With only 0.3 wt% fiber content, the maximum tensile and compressive strength PBX composites were both significantly improved, which were 63 % and 39 % higher than those of pure PBX, respectively. Meanwhile, the thermal conductivity was also enhanced, yielding a significant synergistic enhancement effect. The interface failure mechanism of the composite under stress was clarified by the fracture morphology characterization. This study sheds a light for exploring novel surface modification and has the potential application in in high performance polymer composites.

The influence of geometric characteristic on the pullout behavior of basalt FRP minibar embedded in concrete

AbstractWith the increasing demand on structural toughness and energy absorption capacity, the addition of fiber to concrete has become an issue of significance. This paper studies the bond behavior of Basalt FRP (BFRP) minibar with straight, twisted and crimped geometric characteristics. The failure modes, pullout curves and bond strength were compared, and their interface degradation, damage evolution and failure mechanism between single fiber and concrete matrix were analyzed. Additionally, commercial steel fibers and polypropylene fibers were compared with the BFRP minibars to clarify the effect of fiber type on failure morphology, bond strength and interface properties. The results showed that the pulling out process for straight BFRP minibars, twisted BFRP minibars and crimped BFRP minibars was constituted by the elastic bonding stage, the partial de‐bonding stage, the complete de‐bonding stage and the pullout of fiber. The bond strength was composed of chemical adhesion and mechanical bond, where the mechanical bond play important role after the initial failure of chemical adhesion. The bond strength of crimped BFRP minibar, the hooked steel fiber, the indented polypropylene fibers and the twisted BFRP minibar were enhanced by 358%, 324%, 115%, and 54.5% compared to straight BFRP minibars. The interface bonding strengths improve with the increase of matrix strength. Dense microstructures of matrix improve the bond strength. The bond‐slip constitutive model was proposed for crimped, twisted and straight BFRP minibars with regression coefficient of 0.978, 0.891, and 0.992, respectively.Highlights Influence of fiber geometry and concrete strength on the pullout behavior Interface degradation, damage evolution and failure mechanism between minibar and concrete Bond‐slip constitutive model of straight, twisted and crimped BFRP minibars