Interfacial Bond Strength Research Articles

Selective laser melting of metal structures onto graphite substrates via a low melting point interlayer alloy

We demonstrate a process to selective laser melt a metal alloy directly onto graphite. The heat transfer applications of metal features printed onto annealed pyrolytic graphite are compelling, as pyrolytic graphite has the second highest in-plane thermal conductivity (>1500 W/m-K at room temperature) of any bulk material. While the bonding of metal alloys commonly used in selective laser melting (SLM) with graphite is relatively weak, the proper interlayer material drastically improves the wetting and bonding. The challenge is the alloys that typically bond to graphite require extended bonding times at elevated temperatures (minutes to hours), while the SLM process delivers only brief exposures to high temperatures (∼100 µs). In this paper, we employ a Sn3Ag4Ti alloy that rapidly forms a nanometer-thin layer of TiC, as verified by transmission electron microscopy. The influence of graphite thermal properties on interfacial bond strength is shown by mechanical testing and simulations of selective laser melting.

Prediction of FRCM–Concrete Bond Strength with Machine Learning Approach

Fibre-reinforced cement mortar (FRCM) has been widely utilised for the repair and restoration of building structures. The bond strength between FRCM and concrete typically takes precedence over the mechanical parameters. However, the bond behaviour of the FRCM–concrete interface is complex. Due to several failure modes, the prediction of bond strength is difficult to forecast. In this paper, effective machine learning models were employed in order to accurately predict the FRCM–concrete bond strength. This article employed a database of 382 test results available in the literature on single-lap and double-lap shear experiments on FRCM–concrete interfacial bonding. The compressive strength of concrete, width of concrete block, FRCM elastic modulus, thickness of textile layer, textile width, textile bond length, and bond strength of FRCM–concrete interface have been taken into consideration with popular machine learning models. The paper estimates the predictive accuracy of different machine learning models for estimating the FRCM–concrete bond strength and found that the GPR model has the highest accuracy with an R-value of 0.9336 for interfacial bond strength prediction. This study can be utilising in the estimation of bond strength to minimise the experimentation cost in minimum time.

Ensemble Machine Learning-Based Approach for Predicting of FRP–Concrete Interfacial Bonding

Developments in fiber-reinforced polymer (FRP) composite materials have created a huge impact on civil engineering techniques. Bonding properties of FRP led to its wide usage with concrete structures for interfacial bonding. FRP materials show great promise for rehabilitation of existing infrastructure by strengthening concrete structures. Existing machine learning-based models for predicting the FRP–concrete bond strength have not attained maximum performance in evaluating the bond strength. This paper presents an ensemble machine learning approach capable of predicting the FRP–concrete interfacial bond strength. In this work, a dataset holding details of 855 single-lap shear tests on FRP–concrete interfacial bonds extracted from the literature is used to build a bond strength prediction model. Test results hold data of different material properties and geometrical parameters influencing the FRP–concrete interfacial bond. This study employs CatBoost algorithm, an improved ensemble machine learning approach used to accurately predict bond strength of FRP–concrete interface. The algorithm performance is compared with those of other ensemble methods (i.e., histogram gradient boosting algorithm, extreme gradient boosting algorithm, and random forest). The CatBoost algorithm outperforms other ensemble methods with various performance metrics (i.e., lower root mean square error (2.310), lower covariance (21.8%), lower integral absolute error (8.8%), and higher R-square (96.1%)). A comparative study is performed between the proposed model and best performing bond strength prediction models in the literature. The results show that FRP–concrete interfacial bonding can be effectively predicted using proposed ensemble method.

Experimental study and mechanics model of ECC-to-concrete bond interface under tensile loading

This work aims to investigate the effects of construction method and compressive strength of engineered cementitious composite (ECC), PVA fiber type, and interface roughness on the tensile performance of ECC-to-concrete interface with both experimental study and mechanical model. Two failure modes (i.e., interface debonding and concrete fracture) were observed in the experiment. The failure modes were significantly affected by interface roughness and ECC compressive strength, but the failure modes were slightly affected by PVA fiber types and construction methods. All load–displacement curves were similar, which means the change of curves were almost unaffected by the four studied parameters. The interface roughness value was defined and utilized to quantify interface roughness. With the increase of interface roughness value and ECC compressive strengths, interface bond strength increased significantly. While the types of PVA fiber had no effect on interfacial tensile strengths. An interface mechanical model was proposed to predict interface tensile strength, and a failure criteria of the interface was established to determine the failure modes based on the interface roughness value. The experimental results were in good agreement with the analysis results, indicating that the proposed model can be used to predict the interface bond strength and determine the failure modes.

Multi-objective optimisation design for GFRP tendon reinforced cemented soil

Rebar reinforced cemented soil is employed widely to solve the weak foundation problem led by sludge particularly. Nowadays, the glass fiber-reinforced polymer (GFRP) becomes a new tendon material instead of steel to avoid the performance degradation resulting from steel corrosion. The interface bond strength of GFRP tendon-reinforced cemented soils (GTRCS) displays its excellent mechanical capacity. Nevertheless, its application is obstructed by the deficient studies between the bond strength and influence factors. Therefore, this study investigates the effects of varying water contents (Cw: 50%-90%), cement proportions (Cc: 6%-30%), and curing periods (Tc: 28 days, 90 days) on both pullout strength (Tp) and unconfined compression strength (UCS) of GTRCS. The results showed that the pullout strength and compressive strength were positively related to Tc and Cc and negatively related to Cw. Besides, these experimental results were also utilised to develop support vector regression (SVR) models. The beetle antennae search (BAS) algorithm was used to adjust the SVR’s hyperparameters. The high correlation coefficients (0.988 for UCS and 0.972 for Tp) proved the reliability of the established BAS-SVR models. In addition, the multi-objective beetle antennae search algorithm (MOBAS-SVR) was developed for bi-objective optimisation designs (UCS-cost and Tp-cost). Finally, sensitivity analysis was conducted to range the significance of variables for Tp and UCS.

Preparation of Structural Color on Cotton Fabric with High Color Fastness through Multiple Hydrogen Bonds between Polyphenol Hydroxyl and Lactam.

Structural coloration is an important way to realize eco-friendly dyeing of textiles. Structural colored cotton fabric was obtained by fabricating a polydopamine (PDA) film on the white cotton fabric at different polymerization reaction times. PDA is prone to generate capillary tension during film formation, which damages the uniformity and interfacial bonding force of the film. Multiple hydrogen bonds will form between the lactam group of polyvinylpyrrolidone (PVP) and the phenolic hydroxyl group of PDA. The introduced hydrogen bonds will effectively enhance the interfacial bond strength and lead to structural color with high color fastness. The surface morphology of double-layer aggregates of the PDA film on structural colored cotton fabric was revealed by scanning electron microscopy. The chemical constitution of the PDA film and PVP was investigated by Fourier transform infrared spectroscopy and X-ray diffraction. The color characteristics of structural colored cotton fabrics were analyzed by UV-vis reflectance spectroscopy and spectrophotometry.

Study on the Applicability of Elastic Recovery (Resilience) Experiment for Asphalt-Rubber

In this paper, the applicability of the elastic recovery (resilience) experiment for asphalt-rubber (AR) binders has been quantitatively assessed. The mechanical model, based on the viscoelastic constitutive relation and particle inclusion theory, was developed. The interfacial detachment between crumb rubber (CR) particles and asphalt caused by stress concentration was analyzed with Weibull statistical equations. Based on the road roughness excitation, the vehicle-road coupling vibration model was established to analyze the impact of vehicle loading on road surface deformation. AR binders with different CR particle sizes were assessed using scanning electron microscope (SEM) imaging and prepared for testing the elastic recovery (resilience). The results showed that the greater internal stress caused by the longer stretch length of AR binders in the elastic recovery experiment was ten times higher than that obtained from the resilience experiment, leading to the interfacial detachment between asphalt and the CR particles. Hence, the elastic property of some of the CR particles with high modulus was not reflected, resulting in the test values being lower than actual values. With the reduction of CR particle size, the interfacial detachment was improved in the elastic recovery experiment due to intense material interchange and the enhancement of interfacial bond strength. The millimeter-scale compression deformation of the AR binder in the resilience experiment was closer to the actual deformation of the road surface. The experimental time of resilience (120 min) has been reported less than that for elastic recovery (200 min–230 min). This study shows that the resilience experiment has a significant advantage in assessing the elastic property of the AR binder.

Interfacial Bonding Strength in Cement Mortar Beams Reinforced with Metamaterial Bars

Reinforced concrete beam (RCB) elements show low mechanical performance when interfacial bonding strength (IBS) is not well controlled. New tailorable material-structure arrangements - Metamaterials - offer solutions to the IBS problem. This paper analyzes the mechanical characteristics of IBS on RCBs for reinforced cement mortar containing Metamaterial bars (MMB) that were machined from SAE 1020 Carbon steel. Each MMB has a stepped geometrical shape, with a cylindrical bar divided into equal-length segments, along with a ’rise height’ (p) change. Four geometries were defined, i.e., R0− Smooth bar, R1− p = 0.1mm, R2− p =0.3mm and R3− p=0.5mm. Three-point flexural strength tests were performed on the RCBs to determine the maximum bond strength (ML) between the MMB and cement mortar. Images of interfacial regions were obtained using SEM and 3D Roughness Reconstruction software to calculate the average roughness (Ra) and the roughness height (Rz). The reinforcement MMB geometry had a significant impact on the ML results, particularly on the first crack strength and the failure mode. The R3 geometry ML values were higher than the other tested geometries (44.5%). The results of the scale models are encouraging and offer a novel and prospective direction for further experimental and even numerical Metamaterial research to improve interfacial bond strength.

Interface performance of Bi<sub>2</sub>Te<sub>3</sub>-based micro thermoelectric devices optimized synergistically by surface modification engineering

The miniaturization of thermoelectric devices raises a strong requirement for the excellent interfacial properties of thermoelectric elements. Thus, achieving a heterogeneous interface with low interfacial contact resistivity and high interfacial bonding strength is a prerequisite for the successful fabrication of high-performance and high-reliability Bi<sub>2</sub>Te<sub>3</sub>-based micro thermoelectric devices. In this work, we adopt the acid pickling method to modify the surface structure of Bi<sub>0.4</sub>Sb<sub>1.6</sub>Te<sub>3</sub> material to synergistically optimize the interfacial properties of Bi<sub>0.4</sub>Sb<sub>1.6</sub>Te<sub>3</sub>/Ni thermoelectric elements. The acid pickling process effectively modulates the work function of Bi<sub>0.4</sub>Sb<sub>1.6</sub>Te<sub>3</sub> material, which dramatically reduces the contact barrier height of Ni/Bi<sub>0.4</sub>Sb<sub>1.6</sub>Te<sub>3</sub> heterojunction from 0.22 to 0.02 eV. As a consequence, the corresponding interfacial contact resistivity of the element is greatly reduced from 14.2 to 0.22 μΩ·cm<sup>2</sup>. Moreover, the acid pickling process effectively adjusts the surface roughness of the matrix, forming a V-shaped pit of 2–5 μm in depth on the substrate surface and leading to a pinning effect. This significantly enhances the physical bonding between the material surface and the Ni layer, which, together with the metallurgical bond formed by the interfacial diffusion reaction zone of about 50-nm-thick Ni/Bi<sub>0.4</sub>Sb<sub>1.6</sub>Te<sub>3</sub>, greatly enhances the interfacial bond strength from 7.14 to 22.34 MPa. The excellent interfacial properties are further validated by the micro-thermoelectric devices. The maximum cooling temperature difference of 4.7 mm× 4.9 mm micro thermoelectric device fabricated by this process achieves 56.5 K, with hot side temperature setting at 300 K, and the maximum output power reaches 882 μW under the temperature gradient of 10 K. This work provides a new strategy for realizing the synergetic optimization of interfacial properties and opens up a new avenue for improving the performance of micro thermoelectric devices.

Effect of silane coupling agent molecules on metal adhesive strength: a first-principles study

In recent years, the use of multi-materials for weight reduction and performance improvement has become popular in a wide range of fields, from the automotives to the medical devices. In this study, we focused on silane coupling agents, which enable strong adhesion between organic and inorganic materials, and investigated the adhesion mechanism to metals by first-principles calculations. In particular, we compared the molecular structures of silane coupling agents and analyzed their effects on interfacial bond strength. As a result, it was found that the adhesion strength of GPS to aluminum was high, followed by MPS and APS, which was the lowest. The difference in stiffness and adhesive strength was due to deformation of the molecular structure, i.e., it was dominated in the balance between stretching and rotation of molecular structures.

Use of fly ash cenosphere in the construction Industry: A review

The coal is the most widely used material in the power plant so that the electricity can be generated. The fly ash is the material as a waste product obtained from the power plant. There are many used of the fly ash and the utilization is important to dispose off the fly ash. The coal fly ash gives the material called cenosphere and this considered to be the good utilization in many sectors all across the globe. The properties of the cenosphere make it a good material with properties like good strength and workability, lesser density and thermal resistivity. From the different research observations it is seen that the peak strength was increased up to 43%, plateau strength increased up to 38%, energy absorption capacity increased up to 30% and density reduced up to 40% Therefore it can be observed that the light weight composite material can be produced effectively when the fly ash cenosphere is added to the concrete. The binder strength as well as the interfacial bond strength is the main parameters for the improvement in the mechanical properties of the material.

An Experimental Study on Interfacial Bond Strength between Hybrid Engineered Cementitious Composite and Concrete

An Experimental Study on Interfacial Bond Strength between Hybrid Engineered Cementitious Composite and Concrete

Study on Interfacial Bonding Strength of C/SiC after Rotary Ultrasonic Milling

Study on Interfacial Bonding Strength of C/SiC after Rotary Ultrasonic Milling

Interfacial bond behavior between ultra high performance concrete and normal concrete substrates

Ultra-high performance concrete (UHPC), possessing excellent mechanical properties, can be used as an excellent material to repair or strengthen the reinforced concrete structural elements. However, the effectiveness of repairing and strengthening by applying the layers of UHPC on the surface of substrate concrete depends on whether the interface between overlay and substrate ensures adequate bonding performance over the entire life span under different loading and exposure conditions. This paper presents an experimental investigation on the effects of key factors on the interfacial bond strength between UHPC overlay and normal concrete substrate (NC). The different surface roughness of the NC substrate, curing conditions, exposure conditions, and test methods (slant shear, bi-surface shear, splitting tension, and third-point flexure), were considered as variable parameters affecting the bond behavior. The results showed that while the curing conditions have an insignificant effect on the bond behavior, the surface roughness of the NC substrate affected the bond strength significantly. The preparation of the substrate’s surface using the sandblasting technique achieved the highest bond strength determined using different bond tests, except the bi-surface shear test, which gave the highest bond strength for the surface prepared using drill holes, owing to the interlocking action of the UHPC that filled the holes drilled in the NC substrate. Furthermore, it was found that the highest reduction of the bond strength under the cyclic exposure conditions with the drill holes' specimens. Even though the bond strength of the UHPC-NC composites subjected to the cyclic exposure conditions got significantly deteriorated, all bond strength results met the acceptable limits for applications as a repairing/strengthening, as specified by different design codes. Finally, the comparison between experimental results and predictions using different existing code models (i.e., CEB-FIP 1990, Eurocode 2 2004, CAN CSA A23.3 2014, AASHTO LRFD 2014 and AFGC 2013) revealed that the AASHTO LRFD and AFGC predictions were substantially conservative.

Evaluation of interfacial Adhesion between concrete substrate and self-compacting concrete as a repair material

This paper focuses on using self-compacting concrete (SCC) as a material in the repair technique given the advantages it presents in the fresh state, namely: stability, homogeneity, and deformability, because it perfectly matches the shapes of the surfaces to be repaired. The interest is mainly focused on the evaluation of bond strength at the interface: Repair/Substrate. The assessment is made via a repair applied to a half-cylinder of the ordinary concrete substrate (OC), by using as a repair material two classes of self-compacting concrete (SCC) of different strength (30 and 40 MPa), the interface bond strength obtained in this case is compared to that of a half-cylinder (BO) repaired with vibrated concrete (OVC) used as a reference control concrete. The rheological properties of the (SCC) used were determined with the aid of the Slump-flow, L-Box, V funnel, and stability under sieve tests. Mechanical properties include compressive strength, and tensile strength. The test to assess the interface bond strength of the specimens is based on a splitting tensile test (indirect tensile). Finally, to determine the type of failure produced after the test. The results obtained showed that self-compacting concrete appears to be a very promising material in the repair and rehabilitation of concrete structures. SCC offers good interfacial bonding and therefore gives satisfactory interface bond strengths.

Effects of steel surface treatment with silanized carbon nanotubes on the bonding properties between steel and epoxy adhesive

ABSTRACT The interfacial bonding properties of steel and adhesives are the key factors affecting the application of external bonded fiber reinforced polymer composites to strengthen steel structures. The present study proposed a new method to treat steel surface with carbon nanotubes (CNTs) for modification of the interfacial bond strength between steel and an epoxy adhesive. CNTs were modified in ethanol-water mixture by silane and PVP (Polyvinyl Pyrrolidone) to improve the dispersity of CNTs. Steel plates treated through dip-coating or spray-coating with the modified CNTs suspensions were used for single lap joint tests. Compared to the control samples, the treated steel surfaces resulted in a significant increase in the interface shear strength (i.e., by 52.8%). The desirable enhancement is attributed to the existence of CNT between the steel and adhesives, which is connected to the steel surface through Si-O-Fe covalent.

Experimental investigation on sing fiber pullout behaviour on steel fiber-matrix of reactive powder concrete (RPC)

A new single fiber pullout testing method was applied to characterize the interfacial bond performance, which includes the pullout load-slip relationship, pullout energy, bond strength, and fiber utilization ratio, of the steel fiber-matrix in reactive powder concrete (RPC). The bond properties and bond strengthening mechanism were investigated from the perspective of certain parameters, including the fiber type, fiber embedment angle, silica fume content, magnetic nanoparticles content, and curing time. The microstructure of the steel fiber and longitudinal morphology of the tunnel after the pullout test were determined by scanning electron microscope (SEM). In terms of the results, the bond strength of the end-hooked steel fiber is much stronger than that of the straight steel fiber. With the increasing of embedment angle, the ultimate pullout load and pullout energy of straight steel fibers increase, and the interfacial bond strength increases. It is found that the incorporation of silica fume can effectively enhance the matrix strength. In addition, RPC containing 20%∼30% silica fume shows significant improvement in pullout behavior. The appropriate curing age contributes greatly to the hydration reaction and the matrix strength of RPC. Steaming curing for 2 d can effectively improve the interfacial bond performance. A content of 1% magnetic nanoparticles enhances the pullout behavior of straight steel fibers with no brass coating, because the maximum pullout load and pullout energy increase by 33.6% and 79.0%, respectively. The microstructural observations confirm the conclusions regarding the bond mechanism drawn from the pullout tests. In conclusion, the performance of the matrix, the characteristics of the fiber-matrix interface area and the friction of the steel fiber in the tunnel can influence the bond performance of the fiber-matrix interface of RPC.

Mechanical, morphological, and fracture-deformation behavior of MWCNTs-reinforced (Al–Cu–Mg–T351) alloy cast nanocomposites fabricated by optimized mechanical milling and powder metallurgy techniques

AbstractThe carbon nanotube (CNT) is becoming more popular due to their low-density, high-strengthetc.Among CNTs, multi-walled carbon nanotubes (MWCNTs) are gaining more importance due to their enhanced thermal and electrical conductivity. The present research is exploring the applicability of MWCNTs reinforced with AA2024-T351 alloys for electromechanical applications. This study is currently undertaken for using MWCNTs as a reinforcing particulate for the purpose to enhance the characteristics including low density, high strength, and hardness together with excellent thermal and electrical conductivity of the aluminum alloy matrices. Therefore, this article provides a state-of-the-art experimental approach to fabricate and furthermore, to evaluate the mechanical characteristics, microstructural analysis, and fatigue behavior of Al–Cu–Mg–T351/MWCNT composites under both the mechanical and thermal loading by utilizing powder technology processing route. The uniform dispersion of CNTs has been exposed using ball milling process. Results revealed that the MWCNTs provide extraordinary synergistic strength, enhances fatigue resistance, creep resistance, ductility, and other mechanical characteristics of the aluminum-based composites. The mechanical loading of the composite exhibited increased properties as compared to thermal-loaded aluminum-MWCNT composites. Findings conclude that the maximum hardness of 35Hv obtained for sintered AA2024-T351 and 45Hv for 0.5% MWCNT heat-treated samples indicate that the addition of MWCNT enhances the hardness which may be because CNT is evenly dispersed at the interfacial space. Maximum UTS of 105.21 MPa was obtained with 0.5% MWCNT for sintered composites. Microstructural analysis of the Al–Cu–Mg–T351/MWCNTs composite exhibits reasonably uniform distribution, void formation, and good interfacial bonding. X-ray Diffraction method patterns of fabricated composite shows that the CNT is present at 2β= 23.6 and 44.6°, whereas high peaks of aluminum are present at uniform dispersed positions. Transmission electron magnifying instrument study further substantiates the above research. Fracture micrographs of the Al–Cu–Mg–T351/MWCNTs composite portray the resistant nature of the nanotubes due to the presence of CNTs, Al–Cu, and aluminum carbide elements in the alloy and the reactions that happened during heat treatment. This significant improvement was attributed to the shear interactions among the constituents and high load carrying capacity of the CNT, uniform dispersion, and interface bond strength among the matrix and constituents. The findings in the study will undoubtedly be beneficial for the development of high-strength, MWCNTs/Al–Cu–Mg–T351, matrix composites in future for multifunctional applications on broader spectrum.

Effects of Coupling Agent and Thermoplastic on the Interfacial Bond Strength and the Mechanical Properties of Oriented Wood Strand-Thermoplastic Composites.

Wood–plastic composites (WPC) with good mechanical and physical properties are desirable products for manufacturers and customers, and interfacial bond strength is one of the most critical factors affecting WPC performance. To verify that a higher interfacial bond strength between wood and thermoplastics improves WPC performance, wood veneer–thermoplastic composites (VPC) and oriented strand–thermoplastic composites (OSPC) were fabricated using hot pressing. The effects of the coupling agent (KH550 or MDI) and the thermoplastic (LDPE, HDPE, PP, or PVC) on the interfacial bond strength of VPC, and the mechanical and physical properties of OSPC, were investigated. The results showed that coupling agents KH550 and MDI improved the interfacial bond strength between wood and thermoplastics under dry conditions. MDI was better than KH550 at improving the interfacial bond strength and the mechanical properties of OSPC. Better interfacial bonding between plastic and wood improved the OSPC performance. The OSPC fabricated using PVC film as the thermoplastic and MDI as the coupling agent displayed the highest mechanical properties, with a modulus of rupture of 91.9 MPa, a modulus of elasticity of 10.9 GPa, and a thickness swelling of 2.4%. PVC and MDI are recommended to fabricate WPCs with desirable performance for general applications.

Experimental study on the effect of oil based filtercake on bonding strength at wellbore second interface

The integrity of the oil-gas wellbore is critically depending on the quality of the binding between cement and rock materials. Weak bond between cement and formation may lead to the potential leakage of high-pressure formation fluids through cracks and micro-annulus formed at the interface which results into blowout and groundwater contamination. Failure to properly displace mud prior to cementing can lead to poor bonding at the second interface (SI) of the wellbore. The main purpose of this study is to quantify the impact of oil based-filtercake on the bonding quality at the wellbore Second Interface during the drilling of sandstone reservoir well by using shear bond measurements and material characterization techniques. The results indicated that, the presence of oil based-filtercake at the SI has a detrimental effect on shear bond strength making it as weakest point of adhesion. The tested Blank samples had higher bond strength compared to treated (oil based filtercake) samples. The low bond strength for filtercake system was due to existence of oil based filtercake films which hindered the totally cement hydration process to form a strong bond as the oily film cannot allow the interact with aqueous cement slurry material to complete the hydration process. The FTIR analysis showed that, the lower transmittance (35%) at 1091 cm−1 band (Si–O) of mud treated samples revealed the low content of chemical binder material (Calcium Silicate Hydrate - CSH) at the interface while the blank samples gave 62% at 1088 cm−1 band (Si–O) showing the high content of CSH at the interface which led high bond strength. The results show that oil-based filtercake has a significant detrimental effect on shear bond strength of the second interface.