Interfacial Strength Research Articles

Wire arc additive manufacturing NiTi/Nb bionic laminated heterogeneous structure: Microsturcture evolution and mechanical properties

In the aerospace industry and the medical field, there is a demand for materials that combine the functional properties of NiTi with the excellent ductility of Nb. However, creating high-strength interfaces between these two materials has been difficult due to their inherent differences in physical and chemical properties. In this study, a laminated heterogeneous structure (LHS) combining NiTi and Nb was prepared using wire arc additive manufacturing (WAAM) with different layer thickness ratios. The resulting microstructure of the NiTi/Nb LHS components consisted of a large amount of NiTi and β-Nb eutectic structures. This was due to the metallurgical bonding between the NiTi and Nb layers. The NiTi/Nb LHS components exhibited excellent compressive strength, measuring at 2607.6 ± 31 MPa. Additionally, the interface strength of the NiTi/Nb LHS component was remarkable, showing an ultimate tensile strength of 789.3 ± 8 MPa. The enhanced strength of the NiTi/Nb LHS component can be attributed to the gradient microstructure of the NiTi layer, which promoted heterogeneous plastic deformation generation. Furthermore, this study unveiled the relationship between the formation mechanism of the heterogeneous eutectic microstructure and the strength-ductility synergistic mechanism. As a result, this study provides an innovative approach for additive manufacturing in the strengthening of laminated multi-material interfaces.

New insights of the microcrack initiation induced by Mo addition in Ni-based single crystal superalloys during creep at 900 °C

Mo has received much attention in Ni-based single crystal superalloys as a main strengthening element at elevated temperatures above 1000 °C. However, the effects of Mo addition in new generation single crystal superalloys at medium temperature conditions are still not clear. This paper investigated the creep property at 900 °C and 392 MPa in a 4th generation Ni-based single crystal superalloy with different Mo contents, indicating that Mo addition decreased the creep life and induced large amounts of microcracks. Higher Mo content could weaken the interface strength by inducing more stacking faults, causing crack initiation along the interface. The elemental segregation along the stacking faults triggered the nucleation of other precipitates, which could further lead to cracks. The precipitation of topologically close-packed (TCP) phases introduced by more Mo addition caused crack initiation along the interfaces between the TCP phases and γ′ phase. By investigating the microcrack formation induced by Mo during creep at 900 °C, we provided a new perspective for the alloy design.

Improving mechanical properties of PLA with pinus sylvestris char: exploring thermal stability, interfacial strengthening mechanisms, and applications in 3D printing

In the present study, submicron and micron-sized pinus sylvestris char (PS) was applied for the modification of polylactic acid (PLA) and the effect of the properties of PS on the mechanical, thermo-mechanical, and crystallization kinetics of PLA were investigated. As demonstrated, PS could enhance the toughness of the PS-PLA composites by forming interfacial "bridges" to facilitate stress transfer due to its stable lamellar structure and interaction with the PLA matrix. The tensile strength of PLA-PS composites increased by 98% and the bending strength increased by 25% compared to that of pure PLA. The addition of PS significantly increased the energy storage modulus (increased 22%) and loss modulus (increased 30%) of PLA, but led to a decrease in the crystallinity and thermal stability of the composite. In the practical utilization for 3D printing, PS-PLA composites possess good tensile strengths (41.5 MPa), allowing for smooth printing of complex products. This work provides an efficient strategy to modulate the thermodynamic and mechanical properties of PLA matrices by regulating the viscosity of the composites and modulating the interfacial strength with the addition of proper amounts of biochar.

Integrated test system for interfacial strength and morphology of multi-type hydrate-bearing sediments.

Predicting the strength parameters of multi-type sediments containing hydrates is the basis and precondition for the safe and efficient development of natural gas hydrates. However, studies on the shear mechanical behavior and morphology of multi-type hydrate-bearing sediments (HBS) are still insufficient. Herein, this study presents an integrated test system that can be used to measure the interfacial strength and morphology of multi-type sediments containing hydrates. This device integrates specimen preparation, shear test, morphology observation, and data analysis, which is helpful to comprehensively evaluate interfacial strength, roughness, and morphology. The propagation and development characteristics of microfractures of HBS during shearing can be obtained, which is favorable for identifying the damage and failure modes. Preliminary validation experiments have been conducted on massive pure hydrate, hydrate-sediment interface, and homogenous HBS to verify the applicability of the device for multi-type HBS. The device and corresponding analysis method are expected to support the evaluation of interfacial strength and morphology, thereby promoting a deeper understanding of hydrate-sediment interactions and failure mechanisms of hydrate reservoirs.

Effects of different corrugated rolls on the performance of BTW1/Q345R composite plate

Abstract BTW1/Q345R composite plate not only has the advantages of high strength and high wear resistance, but also helps to reduce energy consumption and production cost. This paper proposes a novel rolling process based on corrugated rolls for the preparation of wear-resistant steel BTW1/Q345R composite plates. In order to analyze and study the microstructure, and mechanical properties of BTW1/Q345R composite plates after rolling, techniques such as electron backscatter diffraction (EBSD) were used. The results indicate that the composite plate obtained through rolling with the corrugated roll of 72 cycles (3# corrugated roll) exhibits a yield strength of 550 MPa, tensile strength of 705 MPa, elongation at break of 17.57%, and shear strength of the composite interface at 242 MPa. Notably, the rolling process with a 3# corrugated roll yields the best combination of tensile mechanical performance and interface bonding performance for the composite plate.

Low Stress Level and Low Stress Amplitude Fatigue Loading Simulation of Concrete Components Containing Cold Joints under Fatigue Loading

Concrete linings containing cold joint defects may crack or detach under the aerodynamic fatigue loading generated by high-speed train operation, which posing a serious threat to the normal operation of high-speed trains. However, there is currently no simulation method specifically for fatigue damage of concrete linings containing cold joints. Based on the Roe-Siegmund cycle cohesive force model, a cohesive force fatigue damage elements were developed. A large dataset was constructed through numerical simulation software to build a BP neural network for back-calculated parameter of cohesive force fatigue damage elements. By combining experimental data, fatigue damage parameters corresponding to different pouring interval cold joints were back-calculated. These back-calculated parameters were then incorporated into the numerical model to compare simulation results with experimental results to validate the applicability of cohesive force fatigue damage elements and back propagation neural networks (BP neural network). The research results show that the difference between the fatigue life and fracture process calculated by numerical simulation and experimental data is small, verifying the applicability of the method proposed in this paper. The pouring interval directly affects the initial strength of the cold joint interface and the starting conditions of fatigue damage. The possibility of fatigue damage and fracture of concrete components containing cold joints increases with the increase of pouring interval, while the variability of fatigue life decreases with the increase of pouring interval. Interface strength and thickness are the main factors affecting the possibility of fatigue damage occurrence and the variability of fatigue life. The research results can be used to analyze the damage and cracking status of concrete linings containing cold joints under aerodynamic fatigue loading.

Experimental and numerical investigations on rate-dependent fracture behavior of concrete-rock interface

To ensure the safety and stability of the concrete gravity dams built in the seismic regions, this study investigated the rate-dependent fracture behavior of the concrete-rock interfaces with different roughness degrees. Firstly, direct tensile tests and three-point bending tests were conducted to measure the mechanical and fracture properties of the concrete-rock interface with three roughness degrees, i.e. the 4 × 4 interface, natural interface, and 7 × 7 interface, and under four strain rates, i.e. 10-5/s, 10-4/s, 10-3/s, and 10-2/s. By employing the fictitious crack model and initial fracture toughness-based crack propagation criterion, numerical simulations were conducted to analyze the crack propagation processes of the concrete-rock interfaces under different strain rates. The results indicated that the tensile strength and initial fracture toughness exhibited an obvious increasing tendency with the increase of the strain rates, and they showed a nearly linear relationship with the logarithms of the strain rates. Prediction models were proposed to calculate the tensile strength and initial fracture toughness of the concrete-rock interface under different strain rates. In addition, the initial fracture toughness-based crack propagation criterion was proved to be applicable to analyze the crack propagation processes of the concrete-rock interfaces under both quasi-static and seismic strain rates. It was found that the fully-formed fracture process zone lengths and the corresponding crack length decreased obviously with the increase of the strain rates, indicating that the boundary effect of the concrete became stronger under the higher strain rates, which approached to the fracture behaviors of the large-size specimens.

Joining and separating behavior of roughness interface in CF/PEEK nanocomposite

The rough contact plays an important role in the adhesion of carbon fiber/polymer matrix interface and interface modeling techniques are integral to quantify the effects of roughness factors on material properties. Taking the popular CF/PEEK materials as the object, an atomic method is proposed to construct CF/PEEK rough interfaces in this paper, which adopts a sinusoidal form to change the roughness regularly. Based on molecular dynamics (MD) simulations, CF/PEEK tensile separation experiment is processed and the response of the CF/PEEK interfaces with different roughness under mechanical loading are investigated. Based on the recorded CF/PEEK atomic force-displacement behavior, innovating roughness parameters, a traction separation law for the interface region is proposed. This study found the contact area between the two phases, which can be greatly improved through rough structures, determines the interfacial adhesion strength. In addition, this study observes interesting phenomena through the capturing atomic states, such as the polymer chains at the boundary between the two phases are greatly stretched.

Effect of Microstructural Changes by Friction Stir Processing on the Clad-to-Core Interfacial Strength of Thin Aluminum-Clad Aluminum Sheets

Effect of Microstructural Changes by Friction Stir Processing on the Clad-to-Core Interfacial Strength of Thin Aluminum-Clad Aluminum Sheets

The experimental and numerical simulation of interface shear behavior between ECC and coal gangue concrete

Composite concrete structures are designed to integrate various concrete types at different levels, thereby improving their shear properties. In this paper, the effects of the interfacial keyway, reinforcement ratio, and pouring sequence on the shear strength of concrete-coal gangue concrete interface are studied by experiments and analyses. A total of 10 specimens were made, and the push-off test was carried out. Nonlinear finite element simulation was carried out using ABAQUS, and the influence of keyway angle on crack development was studied based on the extended finite element method (XFEM). It is found that the remarkable tensile and crack stability of engineered cementitious composites (ECC) has a positive effect on the shear strength of the ECC-coal gangue concrete interface. The ultimate shear strength of the interface and the ductility of the interface under shear load are significantly improved by interfacial shear reinforcement. The introduction of an interfacial keyway improves the shear strength of the concrete interface, and the number of keyways has the most significant effect on the interfacial shear strength. The angle between the crack propagation direction and interface will increase with the increase of keyway angle, the simulation results are in good agreement with the experiments.

Thermodynamic properties, interfacial adhesion energy and tribological properties between MCN (M = Hf, Ta, Cr, Nb) coating and Ti alloy substrates investigated by experiment and first-principles calculations

A series of MCN (M = Hf, Ta, Cr, Nb) coatings were prepared by double glow plasma surface alloying (DGPSA) as protective hard coatings for Ti60 (Ti-5.5Al-4.0Zr-4.0Sn), aiming to solve the problems of low bonding strength between the ceramic coating and the substrate as well as the poor wear resistant of ceramic alloy coatings. First principles calculation was used to study the elastic constant of MC0.5N0.5 solids, thermomechanical parameters and the interfacial adhesive strength of Ti(101)/MCN(220). The calculated results indicated the HfCN solids show excellent mechanical properties, lower thermal expansion coefficient α, lower Gibbbs values and higher values of entropy (S), superior adhesion strength Wad ∼ 5.7 J/m2. The high-temperature tribological performance tests show that the HfCN and TaCN coatings exhibited better wear resistance compared with the CrCN and NbCN coatings at 500 °C -700 °C. The wear rate of HfCN coatings at 500 °C and 700 °C is about 2 times and 5 times lower than that of CrCN, which is in accordance with the HfCN coating’s excellent thermal stability and high interfacial bonding strength with the Ti substrate. The adhesion wear mechanism of all coatings gradually intensified with increasing temperature.

Comparison study of Izod impact properties on 3D printed thermoplastic and thermoset carbon fiber composite at different infill density

PurposeThis study aims to evaluate the low energy impact characteristics of 3D printed carbon fiber thermoplastic and thermoset polymer composite using the Izod impact test. The effects of infill density are examined on the Izod impact properties of 3D printed thermoset polymer and thermoplastic composite specimens. Furthermore, a thorough investigation is conducted into the effect of heat treatment using a hot-air oven on both types of 3D printed composite specimens. To characterize the impact characteristics of each specimen, the fracture surfaces caused by impact load are inspected, and the fracture mechanism is studied using scanning electron micrographs.Design/methodology/approachIzod Impact specimens of thermoset (epoxy resin) and thermoplastic carbon fiber of different infill density (70, 75, 80, 85, 90 and 100%) are fabricated using the different fiber impregnation 3D printing process. To carry out the heat treatment process, printing of composites is done for each infill design from both thermoset and thermoplastic composites and the impact characteristics of specimens are evaluated on a pendulum test-rig using the ASTM D-256 standard. Using a scanning electron microscope, each fracture zone underwent four separate scanning processes, ranging in size from 2 µm to 100 µm.FindingsThe impact resistance of the 3D printed thermoset and thermoplastic composite material is significantly influenced by the type of fiber placement and infill density in the matrix substrate. Because of the weak interfacial strength between the layers of fiber and polyamide 6, the specimen printed with continuous fiber implanted at the part exhibited reduced impact resistance. At 75% infill density, the impact specimen printed with coextruded fiber showed the highest impact resistance with a 367.02% greater magnitude than the continuous fiber specimen with the same infill density.Originality/valueThis work presents a novel approach to analyze the low energy impact characteristics and three-dimensional printing of carbon fiber reinforced thermoplastic and carbon fiber reinforced thermoset and thermoplastic composite material.

Effect of holding time on interfacial evolution and mechanical strength of wide-gap brazed K417G superalloy joints

Effect of holding time on interfacial evolution and mechanical strength of wide-gap brazed K417G superalloy joints

The interfacial behavior of a liquid crystal elastomer film bonded to an orthotropic substrate under light illumination

Bilayer soft actuators composed of a liquid crystal elastomer (LCE) film and a soft substrate have been widely used in soft robotics, bioengineering, and other fields. The existence of stress concentration at the interface edge easily leads to delamination damage of layered structures. Therefore, this article focuses on the distribution of interfacial stresses of the light-driven LCE film/orthotropic substrate system. The governing equations of the LCE film/substrate system are derived. The distributions of peeling and shear stresses on the interface are given and validated by using the finite element method (FEM). The effects of light illumination intensity, light attenuation distance and the director direction on the distribution of interfacial stresses are comprehensively analyzed. It is found that the signs of the shear stress and peeling stress depend on the director direction. This indicates that aligning the director in a certain direction may enhance the interface strength. The results may be useful for designing light-responsive LCE bilayer drivers.

Impact of groove-and-tongue parameters on the bonding behavior between 3d-printed UHP-SHCC and cast normal concrete

The utilization of 3D-printed formworks represents a significant advancement in traditional construction practices, offering the potential to enhance structural capacity and effectively address reinforcement challenges in 3D concrete printing. Ensuring strong bonding between formwork and cast concrete is critical for structural integrity. In this study, 11 composite specimens with varying groove-and-tongue parameters including the layer number, spacing, length, and thickness of tongues undergo splitting tests. Results reveal that increasing the tongue’s layer number enhances the interfacial splitting tensile strength, whereas tongue spacing has minimal impact on interfacial strength, and a thicker tongue negatively affects the interfacial splitting tensile strength. An optimized groove-and-tongue configuration can significantly increase the interfacial splitting tensile strength from 2.10 MPa to 3.66 MPa, with a maximum increase rate of 70.4% and achieving a higher value (20.8%) than that of fully cast normal concrete. A splitting tensile strength model is proposed, with predictions aligning well with experimental results.

Effective removal of aged protective coatings from natural heritage in yunyang using strong peelable hydrogels via enhanced interfacial interactions

Organic polymers such polyacrylates, silicones have been used to protect stone-based heritages. However, polymers degrade obviously with time which may lead to secondary damages to heritages. Removal of previously applied but now degraded polymers on stone surface becomes necessary for the long-term preservation of stone heritages. Current cleaning protocol is mainly based on dissolving or extraction of aged polymers by organic liquid, whose kinetics is dominated by the slow diffusion and dissolving processes at the interfaces. Such cleaning process is very time consuming and becomes almost not applicable in large area cleaning. In this work, peelable PVA-borate hydrogels are developed. Organic solvents are introduced to tune gel's mechanical strength and its interfacial adhesion strength. Aged polymer coating can be removed easily by mechanical peeling when appropriate adhesion forces between the gel and aged polymer coating are achieved. Such cleaning protocol has been successfully applied on a fossil wall around 1200 m2. Details, precautions and limitations of this protocol is discussed in this work.

Enhanced interface adhesion in shape memory alloy hybrid composites via an elastomeric interface: An experimental and numerical investigation

Shape Memory Alloy Hybrid Composites (SMAHCs) hold great promise for different applications. However, the interface between SMAs and the matrix presents challenges due to large strains associated with the martensitic transformations (MTs). Although different strategies have been proven effective in increasing interfacial strength, debonding and its prevention remain unresolved. Therefore, to enable MTs in SMAHCs, this paper proposes a novel solution using a rubber-like elastomeric interface. Pull-out SMAHC specimens were tested at different embedding lengths with and without the elastomeric interface. Specimens with the elastomeric interface showed better performance and stress-strain transfer during MT up to SMA wire breakage. The behaviour of the interface was studied using finite element analysis. A fine-tuning method was proposed for the cohesive zone model parameters. Simulated pull-out tests matched experimental data, revealing the debonding mechanisms. However, results with the elastomer underscored the need to fully represent the underlying physics of the highly deformable interface.

Experimental study on bond performance of recycled coarse aggregates concrete with circular steel tubes after freeze–thaw cycling

AbstractExtrusion tests were conducted on recycled coarse aggregate concrete with circular steel tubes (RCCST, 100% replacement of recycled coarse aggregate) to investigate the impact of freeze–thaw cycles on bond properties. RCCST samples were subjected to 0, 25, 50, 75, 100, 125 and 150 freeze–thaw cycles and their bond properties were then compared with those of natural coarse aggregate concrete with circular steel tubes (NCCST) after 0, 100 and 150 freeze–thaw cycles. The experimental results indicate that freeze–thaw cycling damages the internal structure of RCCST, causing a significant decrease in interfacial bond strength with an increase in the number of freeze–thaw cycles. Freeze–thaw RCCST exhibits lower peak load and higher peak slip compared to NCCST, with increases of 25.2%, 73.2%, and 70.3% after 0, 100, and 150 freeze–thaw cycles, respectively. Regression analysis was used to derive an exponential equation that describes the relationship between longitudinal strain and strain gauge position. Additionally, a segmented fitting method was employed to obtain an expression for the bond slip of the freeze–thaw RCCST with a circular steel pipe.

3D Printing MXene-Based Electrodes for Supercapacitors.

3D printing, as an advanced and promising strategy for processing electrode for energy storage devices, such as supercapacitors and batteries, has garnered considerable interest in recent decades. The interest in 3D printed electrodes stems from its exceptional performance and manufacturing features, including customized sizes and shapes and the layer-by-layer processing principle, etc., especially integrating with MXene which allows the manufacturing of electrodes from different raw materials and possessing desired electrochemical properties. Herculean challenges, such as material compatibility of the printing inks, nondurable interfacial or bulk mechanical strength of the printed electrodes, and sometimes the low capacitance, lead to inferior electrochemical performance and hinder the practical applications of this promising technology. In this review, we firstly summarize the representative 3D printing methods, then, review the MXene-based 3D printing electrodes made from different materials, and last, provide electrochemical performance of 3D printing MXene-based electrodes for supercapacitors. Furthermore, based on a summary on the recent progress, an outlook on these promising electrodes for sustainable energy devices is provided. We anticipate that this review could provide some insights into overcoming the challenges and achieving more remarkable electrochemical performance of 3D printing supercapacitor electrodes and offer perspectives in the future for emerging energy devices.

High‐strength, electrically insulated industrial meta‐aramid paper reinforced with polyethylene terephthalate microfibre pulp in a sandwich structure

AbstractThe weak interfacial strength and porous structure of the meso‐aramid paper cause mechanical and insulating deficiencies. Enhancing density, regulating pore structure, and improving interfacial interactions of meso‐aramid are crucial for promoting the performance of meso‐aramid papers. A PMIA/polyethylene terephthalate (PET) composite paper was prepared using the wet method with meso‐aramid short cut fibres (PMIA) and PET pulp as raw materials. The sandwich‐structured PMIA/PET paper was achieved by covering PET microfiber non‐wovens served as the surface layer while the PMIA/PET composite paper acted as the core layer. During the high‐temperature hot pressing process, the PET pulp transformed into a viscous melt that coated on aramid fibres in between layers, forming a typical ‘reinforced concrete’ interface structure within the core layer of the PMIA/PET composite paper. The PET non‐wovens on top and bottom surfaces were converted into a dense PET film that filled and covered the holes and defects in the PMIA/PET composite paper. This unique structure enabled the sandwich‐structured PMIA/PET composite paper to exhibit excellent tensile strength (80.41 N/cm) and breakdown strength (56.35 kV/mm), surpassing most reported performances of meso‐aramid papers in literature. This work not only provides novel insights for preparing high‐performance meso‐aramid papers, but also shows potential applications for other materials and structures.