Interlocking Effect Research Articles

Surface modification of Cu electroplated layers for Cu–Sn transient liquid phase bonding

Transient liquid phase (TLP) bonding technology attracts great attention as it can produce a full intermetallic compound (IMC) bonding structure for high-temperature applications. In this study, the Cu–Sn TLP bonding is investigated based on the microstructural and mechanical analyses of a sandwiched structure of Cu/Sn-3.5 wt% Ag/Cu under thermal compression at 260 °C for 20 min. Electroplating is used to prepare the Cu base with various surface structures to investigate the topographical effect on the TLP bonding technology. The microstructural analysis indicates that two IMCs, Cu6Sn5 and Cu3Sn, are formed at the bonding interface. The shear strength test shows that the Cu base with a dome and step pyramid shaped surface structure benefits the TLP bonding and increases the shear strength as compared to common faceted Cu base. The improvement of shear strength is attributed to the riveting and interlocking effect of the Cu domes and pyramids which disadvantages the propagation of fracture.

Synergistic effect of polycarboxylate superplasticizer and silica fume on early properties of early high strength grouting material for semi-flexible pavement

Nowadays, the application of early high strength grouting material (EHSG) is in line with the development trend of semi-flexible pavement. In this paper, the synergistic effects of polycarboxylate superplasticizer (PCE) and silica fume (SF) on the properties of EHSG were studied. The results suggest that the flow time of slurry with high fluidity has a linear relationship with its dynamic yield stress. The mechanism of PCE and SF on rheological properties was analyzed via water film thickness (WFT), zeta potential, PCE adsorption, and SEM. It can be found that the crucial role of SF on slurry is to improve the adsorption of PCE on binders. The model describing the synergistic effect of SF and PCE on the particle aggregation of EHSG is proposed. SF addition weakens the interlocking effect and reduces the friction but may form the interparticle bridging effect between cement grains. PCE can not only inhibit the aggregation of cement grains but also mitigate the bridging effect of SF.

Superior Interaction of Electron Beam Irradiation with Carbon Nanotubes Added Polyvinyl Alcohol Composite System.

This work was conducted to investigate the effect of carbon nanotube (CNT) on the mechanical-physico properties of the electron beam irradiated polyvinyl alcohol (PVOH) blends. The increasing of CNT amount up to 1.5 part per hundred resin (phr) has gradually improved tensile strength and Young’s modulus of PVOH/CNT nanocomposites due to effective interlocking effect of CNT particles in PVOH matrix, as evident in SEM observation. However, further increments of CNT, amounting up to 2 phr, has significantly decreased the tensile strength and Young’s modulus of PVOH/CNT nanocomposits due to the CNT agglomeration at higher loading level. Irradiation was found to effectively improve the tensile strength of PVOH/CNT nanocomposites by inducing the interfacial adhesion effect between CNT particles and PVOH matrix. This was further verified by the decrement values of d-spacing of the deflection peak. The increasing of CNT amounts from 0.5 phr to 1 phr has marginally induced the wavenumber of O–H stretching, which indicates the weakening of hydrogen bonding in PVOH matrix. However, further increase in CNT amounts up to 2 phr was observed to reduce the wavenumber of O–H stretching due to poor interaction effect between CNT and PVOH matrix. Electron beam irradiation was found to induce the melting temperature of all PVOH/CNT nanocomposite by inducing the crosslinked networks.

Bondline Thickness Effects on Damage Tolerance of Adhesive Joints Subjected to Localized Impact Damages: Application to Leading Edge of Wind Turbine Blades.

The leading edges of wind turbine blades are adhesively bonded composite sections that are susceptible to impact loads during offshore installation. The impact loads can cause localized damages at the leading edges that necessitate damage tolerance assessment. However, owing to the complex material combinations together with varying bondline thicknesses along the leading edges, damage tolerance investigation of blades at full scale is challenging and costly. In the current paper, we design a coupon scale test procedure for investigating bondline thickness effects on damage tolerance of joints after being subjected to localized impact damages. Joints with bondline thicknesses (0.6 mm, 1.6 mm, and 2.6 mm) are subjected to varying level of impact energies (5 J, 10 J, and 15 J), and the dominant failure modes are identified together with analysis of impact kinematics. The damaged joints are further tested under tensile lap shear and their failure loads are compared to the intact values. The results show that for a given impact energy, the largest damage area was obtained for the thickest joint. In addition, the joints with the thinnest bondline thicknesses displayed the highest failure loads post impact, and therefore the greatest damage tolerance. For some of the thin joints, mechanical interlocking effects at the bondline interface increased the failure load of the joints by 20%. All in all, the coupon scale tests indicate no significant reduction in failure loads due to impact, hence contributing to the question of acceptable localized damage, i.e., damage tolerance with respect to static strength of the whole blade.

Analysis of Dowel Action in Reinforced Concrete Beams with Shear Reinforcement

Abstract The shear transfer mechanism was examined to view the contributions of different components of shear transfer such as aggregate interlocking, dowel force and uncracked compression zone. Understanding the role of various shear transfer components with transverse reinforcement provided was complex due to traditional difficulties involved in detail assessment of accompanying kinematics during the failure. In the present paper, the issue was addressed by employing sixteen specimens and grouped under two categories representing conventional beams and beams with preformed cracks and were tested under four - point bending load with a shear span to depth ratio of 1.26 by increasing the characteristic strength of concrete. From the results obtained, empirical formulas proposed were also evaluated and it was concluded that the results were consistent and contribution of shear transfer across uncracked compression zone was maximum in shear resistance with transverse reinforcement provided. Later structural behaviour was also assessed and it was concluded that beams with preformed cracks had exhibited greater stiffness thus nullifying the effect of aggregate interlocking in shear transfer.

Bonding Characteristics of Cold Sprayed Copper Coating on Alumina Coated Q235 Steel Substrate

Cold spraying metallic coatings on ceramics (Ceramics Metallizing) are widely concerned in electrical industry due to its high density, low oxidation and high electrical conductivity. However, the bonding reliability of cold spraying coating on ceramics is usually considered to be poor since the metal particles don’t experience melting. The present paper is to exam the bonding quality of a cold spraying copper coating on a thermal sprayed alumina layer influenced by ceramics roughness and copper particle hardness. Pure copper coatings were successfully deposited on Al2O3 coated Q235 steel substrate with different roughness by cold spraying at 260 ℃ and 1.6 MPa using different hardness pure copper powders. The bonding quality and characteristics were studied by analyzing the surface, the cross-sectional microstructure of the coating and its interface after pull-off test. The results indicate that the high bonding quality (ranging from 8.26 MPa to 11.35 MPa) between copper coating and Al2O3 layer attributes to both metallurgical and interlock effect, which is mainly influenced by the hardness of the copper powders instead of Al2O3 surface roughness. The soft character of the pure copper powder makes it ready for deformation, subsequently interlocks with Al2O3, fills into the pores more completely, which increases the bonding quality between the copper coating and the Al2O3 layer.

PRODUCTION OF INDIVIDUALISED MULTI-MATERIAL COMPONENTS USING A ROBOT-BASED PROCESS CHAIN

The production of individual work pieces in small to medium batch sizes requires an adaptation of the manufacturing strategy. Particularly, the manufacturing of multi-material components out of metal and plastic is characterized by high production costs as well as high production times. To resolve this challenge, a new, modular process chain for the production of these structures in a single manufacturing cell was developed. In this cell, a robot manufactures multi-material components with multiple end-effectors in several successive process steps. In the first step, interlocking structures are manufactured on a metal part by a surface structuring tool. Afterwards, an extruder is used to add a thermoplastic onto the structured metal part. Due to mechanical interlocking effects, the applied thermoplastic shows improved adhesion behavior. A study was conducted to analyze the achievable joint strength of the additive material application onto the structured metal samples. Investigations to determine the achievable manufacturing quality of a robot guided milling process for multi-material parts have been carried out. A recently developed suction hood is used to capture the metal and plastic chips. In this paper, the results regarding the efficiency of the individual end-effectors, including the extraction hood, are presented and it is demonstrated how they interact within the robot-based process chain.

Enhanced interfacial adhesion of carbon fiber/epoxy composites by synergistic reinforcement with multiscale “rigid-flexible” structure at interphase

Carbon fiber (CF) reinforced matrix composites have wide application prospect, however, the interfacial adhesion of composites is weak due to smooth and chemically inert of CF surface. To settle this problem, two kinds of synergistic hierarchical reinforcements with multiscale “rigid-flexible” structures [CF-graphene oxide (GO)-carbon nanotubes (CNTs)- polyamide (PA) and CF-CNTs-GO-PA] were fabricated through simple esterification and anionic polymerization reactions. The effects of the interface thickness and grafting sequence on the interfacial properties of the composites were explored. The interfacial shear strength (IFSS) of the CF-GO-CNTs-PA/resin composites was 88.3 MPa, which exceeded those of CF, CF-GO-CNTs, CF-GO-PA, and CF-CNTs-GO-PA by 80.9%, 11.5%, 2.3%, and 1.4%, respectively. This was mainly ascribed to the thicker gradient interface layer , the synergistic effects of GO and CNTs, the rigid and flexible structure, as well as the interfacial interactions and mechanical interlocking effect in the CF-GO-CNTs-PA/resin composite. This work provides a novel concept for the construction of interfaces suitable for advanced CF composites with different structures.

Using graphene oxide to improve physical property and control ASR expansion of cement mortar

Alkali-silica reaction (ASR) is a slowly occurring reaction in concrete between alkaline pore solution and reactive non-crystalline silica in aggregates, which is a challenge to physical property and durability of concrete. The oxygen-containing functional groups coupled with large surface area of graphene oxide (GO) nanomaterial renders highly reactive interaction with cement-based composite. Here, the physical properties and ASR expansion test of cement mortars modified with varied loadings of GO (wGO) or/and Pyrex glass (GOPM) were implemented after optimizing GO dispersion efficiency in water. The water absorption and microstructures of GOPM were observed to figure out the mechanism of GO’s effect on mechanical strength, permeability, and ASR expansion of GOPM. Results show, 15 kJ is the optimal sonication energy for the dispersion of 300 mL pristine GO-water suspension with 0.04% wGO; the effect of GO on improving the flexural and compressive strength of GOPM is remarkable, the maximal amplitude is up to 24.16%, 43.03% compared with the baseline, respectively; GO has great influence on long-term anti-permeability and controlling expansion, the nano-nucleation and interlocking effect of GO render the expansion rate of GOPM be well below 0.1% threshold.

Characterizing the fatigue cracking behaviors of OGFC pavements using the overlay tester

The objective of this study was to evaluate the fatigue performance of the composite specimens combined by OGFC and the underlying dense-graded layer (OGFC-AC) by conducting overlay tester (OT) tests. Other two types of specimens, including single layer OGFC13 and single layer AC20, were fabricated to make comparable analysis with OGFC-AC composites. For OGFC-AC specimens, the effects of tack coat application rate and contaminations (soil and oil) were quantificationally explored. Peak tensile stress, cracking rate index (CRI), and dissipated energy were obtained and analyzed. Meanwhile, the damage propagation during the fatigue tests were analyzed using a damage factor. Results indicated that the peak tensile stresses of OGFC-AC composites were somewhere between OGFC13 and AC20. Contaminations would attenuate the peak tensile stress. There existed a power exponential relation between dissipated energy and the load cycle. CRI and damage factor presented the same development law in demonstrating that the fatigue cracking resistance of OGFC13 was superior, followed by AC20, and the performance of OGFC-AC was inferior. The results of CRI and damage factor showed that an optimum tack coat application rate (0.4 kg/m2) existed at which the OGFC-AC composites presented the least cracking potential. The contamination of soil partially increased the cracking resistance, which was probably due to the fact that some sand particles in soil increased the friction and interlock effect between OGFC and the AC layer.

Study on surface texture patterns for improving tribological performance of bioimplants

A new surface texturing design was proposed for improving the tribological performance of bioimplants. Theoretical analysis was conducted to reveal the positive impact of round corner patterns. Experimental results indicated that round corner would significantly reduce the chance of interlocking phenomenon. Orthogonal experiments suggest that triangle pattern with 200 μm side length, 8–10 μm depth, 10% area density and square-distribution mode turns to be most effective in improving tribological performance of textured bioimplants, showing a 50% reduction in friction coefficient and 44.9% reduction in wear rate than that of polished samples. Working mechanisms of surface texturing in bioimplants were also comprehensively studied. It was confirmed that the extra lifting pressure provided by hydrodynamic effect was less than 1% of the ambient pressure. Further investigations proved that the negligible role of hydrodynamic pressure in the textured bioimplants was due to the low viscosity and slow sliding speed. On the other hand, the capacity to trap particles and second lubrication effect were found to be the main working mechanisms. • Interlocking effect could be the failure mechanism for some patten designs in bioimplants. • Only the patterns with round-corner should be adopted in the bioimplants. • Area density is the most influential pattern parameter while the distribution mode is the least one. • Capacity to trap particles and second lubrication effect are the main working mechanisms for textured bioimplants.

Role of dry ozonization of basalt fibers on interfacial properties and fracture toughness of epoxy matrix composites

Abstract The mechanical properties of basalt fiber-reinforced epoxy composites (BFRPs) are significantly dependent on the interfacial adhesion between basalt fibers (BFs) and the epoxy matrix. In this study, we proposed a simple and efficient method for deep and stable penetration of BFs into the epoxy matrix through dry-ozone treatments. To confirm the efficiency of the proposed method, BFRPs were fabricated using two types of composites: untreated BFs and dry-ozonized BFs in varying amounts, and the optimum amount of BFs for all the composites fabricated in this work was 60 wt%. With the addition of this amount of dry-ozonized BFs, the interlaminar shear strength and fracture toughness of the composites were enhanced by 21.2 and 23.2%, respectively, as compared with untreated BFs. The related reinforcing mechanisms were also analyzed, and the enhanced interfacial adhesion was mainly attributed to the mechanical interlocking effect. This approach shows that the dry-ozone treatment of BFs is a simple and efficient method for the preparation of BFRPs with excellent interfacial adhesion, which can be a potential application in the auto parts industry.

Fabrication, mechanical and thermal properties of copper coated graphite films reinforced copper matrix laminated composites via ultrasonic-assisted electroless plating and vacuum hot-pressing sintering

In the trend of integration of structure and function, novel thermal management materials are urgent to be developed owning good mechanical properties as well as excellent thermal properties. In this work, a complete and dense copper (Cu) coating with a thickness of 400 nm was deposited on the surfaces of graphite films (GFs) by ultrasonic-assisted electroless plating, which can improve the surface roughness of GFs and interfacial bonding between GFs and Cu foils. Cu-coated and uncoated GFs reinforced copper matrix laminated composites (noted as GFs(Cu)/Cu and GFs/Cu) were fabricated by optimized vacuum hot-pressing sintering. Based on the scratch test and microstructures of GFs(Cu) and GFs(Cu)/Cu composites, addition of Cu coating can improve the interfacial adhesion and element diffusion behavior, and intuitively explains the mechanical interlocking effect at the C–Cu interface. On basis of the nanoindentation mechanical properties across GFs(Cu)/Cu and GFs/Cu interfaces, the interfacial transition region with Cu coating of ~3 μm is three times of that without Cu coating. Flexural strength of 27.6 vol% GFs(Cu)/Cu laminated composite is 45.9 MPa, which is 56% higher than that of the corresponding GFs/Cu laminated composite. In-plane thermal conductivity (TC) and out-of-plane coefficient of thermal expansion (CTE) of 69.4 vol % GFs(Cu)/Cu laminated composite are 1177.8 W/m·K and −2.5 ppm/K respectively, which could be explained on the theoretical calculations and interfacial structures. In conclusion, the Cu coating on surfaces of GFs can generally improve the interfacial bonding, mechanical properties and thermal properties of GFs(Cu)/Cu laminated composites. It provides an effective way to develop novel structural and functional materials for thermal management.

Influence of calcined halloysite on technological & mechanical properties of wall tile body

ABSTRACT The effect of adding 0.1, 0.3, 0.6, 1.0 wt.% halloysite clay, which calcined at 600, 800, 1000 and 1200°C, to the standard wall tile slurry was studied. Wet milled halloysite was sieved with different sizes to examine the halloysite grain size effect. The granulated samples were pressed by applying a pressure of 30 MPa using a hydraulic press and made ready for sintering at 1150°C for 30 minutes. Detailed technological, mechanical and microstructural characterization studies were done on sintered samples. Compared to standard wall tile, almost all the halloysite added samples displayed similar technological properties but higher green and fired strength values. The produced sample with adding 0.6% halloysite (at 600°C calcined) by weight showed a higher firing strength with 28.75 MPa value than the minimum requirement (17.75 MPa). Observation of needlelike microstructure in the porcelain body led to establishing a simple relationship between the interlocking effects of thin needlelike mullite grains and increasing strength values. This study has shown that the addition of calcined halloysite may be an alternative to produce a thinner section wall tile product.

Stability prediction for asphalt mixture based on evolutional characterization of aggregate skeleton

AbstractThe aggregate skeleton significantly influences the deformation resistance of asphalt mixtures. A stable skeleton has good interlocking effects and load transfer ability to resist deformation of mixtures during loading. Therefore, the methodology to accurately evaluate the morphology of aggregate skeleton based on the mechanism of load transfer inside mixtures is of great value to predict the mixture stability. The objective of this study is to predict and validate mixture stability from the perspective of evolutional morphologies of the skeleton. The methodology has three main steps, which are as follows: (1) the initial morphology of the aggregate skeleton is characterized and evaluated; (2) the topological and non‐topological evolutions of the skeleton morphology during external loading are characterized; and (3) the strain energy of the mixture and the stress distribution on contact regions in the skeleton are used to analyze and validate the prediction of the mixture's stability. Simulations of uniaxial displacement‐controlled tests of three cylindrical specimens drilled in a field‐compacted test track were conducted, and 7.5, 15, 22.5, and 30 s were selected as time points in the simulation to analyze mixture stability. Results indicate that a mixture has a better load‐bearing capacity when its initial skeleton contains more chains with higher evaluation indices, which proves the reliability of the stability prediction using the proposed method.

Effect of IR‐laser treatment parameters on surface structure, roughness, wettability and bonding properties of fused deposition modeling‐printed PEEK/CF

AbstractIn this study, laser surface treatment was applied to alter the surface texturing and chemical compositions of fused deposition modeling (FDM)‐printed PEEK/CF samples to improve the deficiency of inert surface of PEEK as adherend substrate. The influence of IR‐laser parameters including treatment gaps, single pulse energy and pulse widths on surface properties and shear bond strength were discussed. The results indicated that surface roughness was enhanced with decreasing treatment gap or increasing pulse energy, which reached the highest value of Ra = 32.44 μm at 0.4*0.4 mm2 treatment gap and 300 mJ single pulse energy. By adjusting laser pulse width, surface wettability changed from hydrophobicity to hydrophilicity. After micro‐second laser ablation, the texturing structure was changed and acted as mechanical interlocking effect, and therefore make the shear bond strengths improve from 3.28 to 6.42 MPa compared with the untreated groups. On the other hand, functional groups on substrate surface were activated after nano‐second laser ablation, which contributes to an enhancement of shear bond strength through chemical interaction between adhesives and substrates. Therefore, our work highlights an efficient method of laser surface treatment on the adhesion property of FDM‐printed substrates.

Microscopic Mechanisms Behind the High Friction and Failure Initiation of Graphene Wrinkles.

Wrinkling occurs on the surfaces of large-area graphene ubiquitously. Despite that the wrinkled structures are found to degrade the lubricous property, the behind mechanisms remain less understood. Here, atomic force microscopy is adopted to characterize the friction and wear properties of graphene wrinkles (GWs) with different heights by nanoscratch tests. We verify the phenomena of high friction and reduced load-carrying capacity of wrinkles and report the observation of lubrication deterioration with increased heights. Using molecular dynamics simulations, we reveal that the contact quality at the interface is a dominant role in the friction evolution of wrinkles. The high friction of wrinkles is determined by the increased contact area and commensurability caused by the wrinkle deformation and topography changes. The wrinkle failure initiates near the root of the formed bilayer configuration due to the increased lateral stiffness and reduced atomic distance between the wrinkle layers. The increased interlocking effect results in a local shear stress of 91 GPa and induces the phase transitions of carbon atoms easily. As the wrinkle height decreases, the unstable local configuration weakens the interlocking effects and cannot fail even at a high load. This investigation sheds light on the microscopic frictional contact of GWs and provides guidance for tuning the tribological properties of graphene by controlling the wrinkle structures.

Use of digital image correlation to confirm the enhancement of concrete–epoxy resin mortar adhesion through surface precoating treatment

The method employed to bond concrete and epoxy mortar determines the strength of the interface in the resulting concrete composite structure. This paper presents a method for improving concrete–epoxy resin mortar adhesion through the precoating of concrete surfaces with resin. Resin concentrations of 10, 20, and 30 wt% were diluted in acetone. The failure process, interface strength, and crack propagation at the interface were investigated using a four-point bending test and digital image correlation technology. Increasing the amount of epoxy resin in the precoating solution improved the load-bearing capacity of the concrete–epoxy resin mortar interface by approximately 15% and changed the failure mode of the interface from near brittle to quasibrittle. Equivalent linear elastic fracture mechanics and double-K criteria analysis of the fracture toughness of the interface revealed that surface precoating considerably delayed initial cracking and improved surface toughness. Scanning electron microscopy of treated and nontreated specimens revealed that the toughness of the interface increased because the resin precoating on the concrete surface increased the area of contact between the epoxy resin mortar and concrete, which enhanced the interlocking effect and improved the strength of the interface.

Effects of steel fiber grout on the mechanical performance and failure characteristics of fully grouted bolts

In real engineering, with the gradual deterioration of mining geological conditions, the improvement of the bearing performance of fully grouted bolts is beneficial to better control of the roadway surrounding rock. For this purpose, based on the idea of steel fiber reinforced concrete, a systematic laboratory study was conducted to investigate the effect of steel fiber grout on the bearing performance of anchored specimens. Three steel fibers with different diameters (0.5, 1.0 and 1.5 mm) were selected. Fiber specimens and fiber-free specimens were prepared and a series of pull-out tests were conducted. The experimental results show that the steel fiber grout can effectively improve the bearing performance of the anchored specimens and enhance the anti-destructive ability of the anchored specimens. The steel fibers in the grout can enhance the mechanical interlocking effect, the dilatancy effect and the friction effect of the anchoring interface, thereby improving the ability of the anchored specimen to withstand additional loads. The reinforcement effect of steel fiber on the bearing performance of the anchored specimens presents an obvious diameter dependence. With the increase of the steel fiber diameter, the bearing properties of the anchored specimens tend to increase and the cumulative AE counts, cumulative AE hits, cumulative AE energy and AE events also increase. Moreover, the steel fiber grout can more fully mobilize the bearing performance of the anchoring interface, and the number of microcracks in the fiber specimens increases during the bearing process. This research results may provide a useful reference for the support design of fully grouted bolts.

Tribological and Thermo-Mechanical Properties of TiO2 Nanodot-Decorated Ti3C2/Epoxy Nanocomposites.

The micromorphology of fillers plays an important role in tribological and mechanical properties of polymer matrices. In this work, a TiO2-decorated Ti2C3 (TiO2/Ti3C2) composite particle with unique micro-nano morphology was engineered to improve the tribological and thermo-mechanical properties of epoxy resin. The TiO2/Ti3C2 were synthesized by hydrothermal growth of TiO2 nanodots onto the surface of accordion-like Ti3C2 microparticles, and three different decoration degrees (low, medium, high density) of TiO2/Ti3C2 were prepared by regulating the concentration of TiO2 precursor solution. Tribological test results indicated that the incorporation of TiO2/Ti3C2 can effectively improve the wear rate of epoxy resin. Among them, the medium density TiO2/Ti3C2/epoxy nanocomposites gained a minimum wear rate. This may be ascribed by the moderate TiO2 nanodot protuberances on the Ti3C2 surface induced a strong mechanical interlock effect between medium-density TiO2/Ti3C2 and the epoxy matrix, which can bear a higher normal shear stress during sliding friction. The morphologies of worn surfaces and wear debris revealed that the wear form was gradually transformed from fatigue wear in neat epoxy to abrasive wear in TiO2/Ti3C2/epoxy nanocomposites. Moreover, the results of thermo-mechanical property indicated that incorporation of TiO2/Ti3C2 also effectively improved the storage modulus and glass transition temperature of epoxy resin.