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Interfaces of cementitious layers have widely existed in construction projects, and they are the weakest part of the whole building. In this article, laser scanning and ultrasonic pulse, splitting tensile, and semi-disc fracture tests were carried out to study the bonding performance of cementitious layers. Different performance metrics, such as splitting tensile bond strength, ultrasonic pulse velocity, and attenuation of first arrival, were used to evaluate the bonding characteristics of the concrete layers. The results revealed that the parameters of the interface curve decreased, and the mechanical properties of the interface became weaker with an increase of the interval time. The amplitude of the first wave was more sensitive to the presence of the interface than the ultrasonic pulse velocity. Finally, the relationships between the performance metrics were analyzed. The fracture toughness of model I and mode II was highly correlated with the parameters of the micromorphology of the layered concrete, and the correlation coefficient is not less than 0.9511. The fracture toughness of mode I was strongly related to the splitting tensile strength, with a correlation coefficient of not less than 0.9744. This study was useful for the future study of the mode I and I fracture performance, the morphology, and other physical properties of cementitious layers.

The performance of 3D printed materials differs from that of fully cured polymer materials because of the presence of interfacial areas between consecutively joined layers. These interfaces result in an inhomogeneous character of the printed objects and is frequently reported as their main cause of failures. We noted that the presence of nanosilica particles strengthens the 3D printed layers of the polymer matrix by inducing its additional crosslinking. A model resin composed of poly (ethylene glycol) diacrylate (PEGDA) and nanosilica (Aerosil R972) is used for vat photopolymer 3D printing. Evolution of the interface properties at different nanosilica loadings is tracked by mapping its surface stiffness (Young's modulus mapping) using quantitative Atomic Force Microscopy (AFM). Our research demonstrates that incorporating 6% w/v nanosilica in the polyPEGDA matrix unifies its mechanical properties within the layer, leading to a substantial reduction of microscopic inhomogeneity in the final 3D printed materials.

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Copyright of Tunnel Construction / Suidao Jianshe (Zhong-Yingwen Ban) is the property of Tunnel Construction Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An intuitive way to externalize spatial memory is to sketch it. Compared to traditional paper-based sketches, virtual reality (VR) creates new opportunities to investigate the 3D aspect of spatial memory as it empowers users to express 3D information on a 3D interface directly. The goal of this study is to design a 3D sketch mapping tool for researchers and non-expert users without sketching expertise that enables externalizing memories of spatial information after some 3D-critical tasks. There exist 3D sketching tools using VR, but there are two issues with the current mid-air 3D sketching approach: (1) distortion of sketches due to depth perception errors and (2) increased cognitive and sensorimotor demands due to an increased degree of freedom and absence of physical support. To address these problems, we implemented VResin, a novel sketching interface that synergizes 3D mid-air sketching with 2D surface sketching to scaffold 3D sketching into a layer-by-layer process. An experimental study with 48 participants on multi-layer building scenarios showed that VResin supports users in creating less distorted sketches while maintaining the level of completeness and generalization compared to mid-air sketching in VR. We also demonstrate the potential applications that can benefit from 3D sketch maps and the suitability of VResin for a variety of building shapes. [Display omitted] • We refined the concept of 3D sketch maps and provided design criteria for VR interfaces. • We implemented a layer-by-layer 3D sketching interface to create 3D sketch maps. • We conducted a user study with 48 participants on memorizing multi-layer buildings. • We presented application scenarios for 3D sketch maps. [ABSTRACT FROM AUTHOR]

When constructing concrete structures using 3D printing, it is important to consider the anisotropy due to the printing process. The print path influences the formation of layer interfaces and inter-filament voids, and the fracture propagation behavior of the printed specimen. In this paper, the fracture propagation behavior of printed mortar specimens under compressive, tensile, and bending stresses is evaluated for different print paths. X-ray computed tomography visualizes the interior of printed specimens and shows that the pressure during material extrusion elongates the intra-filament voids. The inter-filament void structure is influenced by the print path, forming an aligned structure in one direction or a complex lattice-like structure. Anisotropy in the deformation direction under compressive stress, which is influenced by the inter-filament void structure, is assessed by 3D scanning. Under tensile stress, Digital Image Correlation (DIC) visualizes that tensile stress is concentrated in the layer interface, causing cracks to propagate along the layer interface. Under bending stress, DIC evaluates the effect of the print path on fracture propagation behavior. The results show that the mechanical properties and fracture propagation behavior of printed specimens are affected by the arrangement of the layer interface and inter-filament void, which is governed by the print path. (200 words) • Layer interface arrangement and inter-filament void structure, influenced by print path, affect the mechanical properties of 3D printed concrete. • Anisotropic deformation of 3D printed specimens due to print paths can be evaluated by 3D scanning surfaces before and after loading. • DIC with a high-speed camera evaluates instantaneous bending fracture, strain distribution, and crack propagation behavior in printed specimens. [ABSTRACT FROM AUTHOR]

The increasingly complex layer structure of commercial Organic Light Emitting Devices (OLEDs) leads to higher manufacturing costs. In this paper, we demonstrate a simplified device structure with only two layers between the anode and the emissive layer, compared with the usual three or four layers in state‐of‐the‐art devices. The stack is designed so as to ensure efficient hole injection and transport. As a result, the devices achieve longer lifetime and higher efficiency, than the more complex structure, while maintaining equivalent chromaticity and a comparable operating voltage. Such a performance trend is observed in all three RGB colors, in both bottom and top emission devices, as well as in tandem devices. Fewer layers help cost‐effective mass production, and we demonstrate that such simplified device structure has a great potential in both OLED display and lighting applications. [ABSTRACT FROM AUTHOR]

This paper presents comprehensive research work on the crack initiation behavior of Semi Flexible Pavements (SFP) with the help of a one-way coupled multiscale modelling approach. The study focuses on elucidating the influence of layer interface conditions on potential cracking patterns under different temperature conditions. By integrating material properties at both local (mixture) and global (pavement) scales using a local de-homogenization approach, the interlocking effect was addressed within the asphalt binder's mesoscale properties. CT-image based mesostructure was employed to reconstruct the Representative Volume Element (RVE). Cohesive Zone Model (CZM) was utilized to simulate cracking initiation within the RVEs, with simulation results validated against practical engineering inspections. Additionally, a potential macroscopic failure index was introduced for SFP. It was found that the typical macroscopic failure indexes utilized for AC pavement may not be suitable for SFP due to the higher degree of heterogeneity. Analysis showed that SFP layer's coarse aggregate and cement grout at the bottom may experience compressive stress, while asphalt binder beneath the tire load may face high tensile stresses. Regardless of the interface conditions, top-down cracking was found to be the dominating failure mode in SFP. Besides, the vulnerable area in bonded interface SFP shifts from under tire load to the adjacent area with the rise in pavement temperature, while bottom-up cracking may appear only in unbonded interface SFP under low temperature conditions. Subsequent analysis demonstrated that top-down cracking is prominent in bonded interface SFP, especially at higher temperatures, compared to unbonded interface SFP. It is expected that critical observations for SFP highlighted above will certainly help in understanding critical failure modes and, hence, designing and constructing durable SFP structures. • A one-way coupled multiscale modelling approach considering interlocking effect was developed. • The interlocking effect was addressed using a local de-homogenization method. • The cracking initiation form of SFP was simulated and validated by pavement inspection. • A potential macro-mechanical failure index was proposed for SFP. [ABSTRACT FROM AUTHOR]

Abstract Through two lab-scale experiments, we investigated the hydraulic and mechanical characteristics of sediment layers during water film formation, induced by elevated pore pressure—considered one of the triggers of submarine landslides. These involved (1) sandbox experiments to prove the effect of water films on mass movement in low slope gradients and (2) experiments to observe the effect of the tensile strength of semi-consolidated sediment layers on water film formation. Portland cement was used to mimic the degree of sediment cementation. We observed a clear relationship between the amount of cement and pore pressure during water film formation; pressure evolution and sediment deformation demonstrated the hydraulic and mechanical characteristics. Based on the results of these experiments, conditions of the sediment layers during water film formation are discussed in terms of pore pressure, permeability, tensile strength, overburden pressure, and tectonic stresses. The results indicate that the tensile strength of the sediment interface provides critical information on the lower limit of the water film formation depth, which is related to the scale of potential submarine landslides.

The increasingly complex layer structure of commercial OLEDs leads to higher manufacturing costs. In this paper, we demonstrate a simplified device structure with only two layers between the anode and the emissive layer, compared to the usual three or four layers in state‐of‐the‐art devices. The stack is designed so as to ensure efficient hole injection and transport. As a result, the devices achieved longer lifetime than the more complex structure, while maintaining equivalent chromaticity, efficiency and operating voltage. Fewer layers help realize cost‐effective mass production. [ABSTRACT FROM AUTHOR]

PLA transcrystallinity (TC) is a novel type of crystal that is of significant importance.Owing to the low content, discontinuity, and random distribution of PLA TC prepared by traditional methods, its formation mechanism and growth rule remain unclear, and its impact on properties is still inclusive. In this work, the PLA and nucleating agent filled PLA (T-PLA) are coextruded to form the PLA/T-PLA alternating multilayers, in which the multilayered PLA/T-PLA interface induces the formation of the high content, continuous and ordered PLA TC. The SEM, 2D-WAXD and the polarized-FTIR results indicate that the PLA TC is consisted of highly stacked and oriented lamellae, where the b-axis lays perpendicular to, but the a-axis and c-axis PLA lamellae parallel to the multilayered interface. Compared with the spherulites, the compacted and oriented TC has a positive effect on the yielding strength, and this may result from the highly compacted and oriented lamellar arrangement. In brief, here we provide a facile route to construct high content, continuous and ordered PLA TC and thus provides an ideal prototype to further investigate the intrinsic properties of PLA TC.

Hydraulic fracturing is the common method for increasing the production rate in reservoirs with low permeability. It is also used to raise the extraction rate of wellbores with low production due to the long-term utilization. The interfaces aligned with direction of the hydraulic fracture propagation, and different physical and mechanical properties of the adjacent layers are the most important factors in the performance of hydraulic fracturing treatments in laminated reservoirs. In this paper, the effects of layer interfaces, inclinations, thicknesses, and physical and mechanical properties on hydro-fracturing breakdown pressure and fracture propagation path were investigated. To achieve this aim, the laboratory-scaled hydraulic fracturing test was performed on thick-walled cylinder samples with different layer thicknesses and inclinations. The effect of the material property contrasts between different layers on the complex behavior of hydraulic fracture propagation in laminated specimens is also studied. The obtained results have indicated that with varying the bedding plane inclination angle from 0 to 45°, the breakdown pressure would be decreased and then increase in breakdown pressure is observed from 45 to 90°. The minimum breakdown pressure would occur at an inclination angle of 45°. During the hydraulic fracture propagation from the hard layer to the soft layer, there is no deviation observed at the layer interface. However, the possible shear slippage along the layer interface and extending the fracture in the interface would occur, when the fracture propagates from the soft layer to the hard layer. The mechanism of fracture on the layer interface is assessed based on fracture energy in fracture tip. High fracture energy would significantly reduce the effect of the inclined interface on the hydraulic fracture propagation path. [ABSTRACT FROM AUTHOR]

• Multi-layer ceramics with precise layer thickness control were successfully prepared by electrophoretic deposition (EPD). • Spark plasma sintering (SPS) significantly improved the durability of piezoceramic laminates. • The significant suppression of crack formation and chemical reaction at the layer interfaces was achieved. • Combining EPD and SPS is a promising concept for preparing multi-layer ceramics for energy harvesting applications. In this paper, the concept of multi-layer ceramics based on a combination of piezoelectric layers BaTiO 3 (BT) or (Ba 0.85 Ca 0.15)(Zr 0.1 Ti 0.9)O 3 (BCZT) alternated with mechanically durable ZrO 2 (Z) layers is investigated. Both BT/Z and BCZT/Z laminates were successfully electrophoretically deposited (EPD) due to knowledge of the deposition kinetics of individual materials and their green densities allowing precise layer thickness control. The EPD was followed by conventional sintering (CS) or spark plasma sintering (SPS). The CS resulted in the development of cracks, pores, and significant chemical reactions at the layers interfaces in both types of laminates. Laminates sintered by SPS were crack free with suppressed or none chemical reactions at the interfaces. The mechanical properties development across layers was monitored using nanoindentation. This approach identified interlayer porosity evolution and estimated the significance of the reaction zone at the interface. [ABSTRACT FROM AUTHOR]

• Roadbed layers in mountainous area are characterized by DUCP, GPR, and LFWD. • Measured DCPI, shear wave velocity, shear modulus, and GPR image capture each layer. • Elastic modulus from DUCP is compare to LFWD modulus considering influence factor. • DUCP can be used to assess the interface, depth, and stiffness of roadbed layer. The characteristics and depths of the old roadbed layers must be assessed for the serviceability and rehabilitation of aging road pavements. This study's objective is to detect roadbed layers in mountainous areas using the obtained stiffness profile and ground penetrating radar (GPR) results. Down-up-crosshole penetrometer (DUCP), GPR, and light falling weight deflectometer (LFWD) tests were conducted to determine the overlay, surface, base, subbase, antifrost, and subgrade layers. The results show that the dynamic cone penetration index DCPI, shear modulus calculated by the shear wave velocity, and GPR image capture each layer. The elastic modulus estimated by the shear modulus is corrected by considering the strain influence factor and matches the LFWD modulus, despite the ranges of values differing owing to the disparate strain level. Therefore, the DUCP can be applied to roadbeds in mountainous areas to assess the stiffness at each layer as well as to detect the layer interface. [ABSTRACT FROM AUTHOR]

The performance of 3D printed materials differs from that of fully cured polymer materials because of the presence of interfacial areas between consecutively joined layers. These interfaces result in an inhomogeneous character of the printed objects and is frequently reported as their main cause of failures. We noted that the presence of nanosilica particles strengthens the 3D printed layers of the polymer matrix by inducing its additional crosslinking. A model resin composed of poly (ethylene glycol) diacrylate (PEGDA) and nanosilica (Aerosil R972) is used for vat photopolymer 3D printing. Evolution of the interface properties at different nanosilica loadings is tracked by mapping its surface stiffness (Young's modulus mapping) using quantitative Atomic Force Microscopy (AFM). Our research demonstrates that incorporating 6% w/v nanosilica in the polyPEGDA matrix unifies its mechanical properties within the layer, leading to a substantial reduction of microscopic inhomogeneity in the final 3D printed materials. [Display omitted] • Model photopolymer nanocomposite is 3D printed to study interfacial area between layers. • AFM shows variation of the Young's modulus across the layers. • Resin viscosity and light scattering by nanosilica lead to accelerated crosslinking and interface stiffening. • Adding nanofillers improves homogeneity of samples and reduces printing time. [ABSTRACT FROM AUTHOR]

Measurements of space charge density and trap levels are informative ways to predict failure conditions of insulation materials. The charges are injected from electrodes and penetrate from surface towards deep inside of the insulation material. In order to resist the charge injection, trapping, migration and increase charge recombination, detrapping and extraction rate, layer (nanocomposite-PI-nanocomposite) sandwich structure samples are used. Two techniques Pulse Electro Acoustic (PEA) and Thermal Stimulated Current (TSC) are combined to characterize space charge behavior and trap levels. Lab-view based program is used to detect the charge density distribution and total charge decay, different peaks of current using TSC technique are used to get activation energy and trap level density. The effects of structural interface (single, double, triple layers) and types of nano (Al2O3, SiO2) fillers are analyzed to influence charge accumulation polarity and trap levels. Trap levels are calculated using TSC data as well as total charge decay data. The trap values calculated from both data match each other. Al2O3-PI-Al2O3 sandwich structure showed remarkable improvements to resist accumulation of space charge for longer time. Mostly charges are shallow traps with 1.126 eV trap level and recombination rate is higher. In double layer structure in which interface is made up of SiO2 and Al2O3, deep trap level of 1.26 eV and higher trap density is observed. The charges decay is faster in three-layer structure than double and single layer structure. It is concluded that the interface formed with different type of nano and structure of insulation, both are an important parameter for manufacturing industry to suppress space charges accumulation and traps. [ABSTRACT FROM AUTHOR]

The integration and permeability of the interface between concrete layers of a dam considerably affect its structural functionality and safety. To understand the interface properties, several tests were conducted to examine the various characteristics of specimens with different layer interfaces. The mechanical property in terms of bond strength was assessed using the splitting tensile test, which was affected by interval time. On the other hand, the ultrasonic pulse test was used to confirm the influence of the interface on ultrasonic attenuation. The chloride and water permeability were also investigated by means of the rapid chloride permeability, alternating current resistance, and water permeability tests. The results of these tests proved that longer interval times lead to a weaker bond strength and higher permeability, which are harmful to layer structures. The change rules of mechanical and permeability properties were confirmed by the optical micrograph and hardness distribution of the overlay transition zone. Finally, the relationships among these tests were analyzed, and strong correlations demonstrated that the non-destructive ultrasonic pulse test and rapid electrical test could be employed to predict and evaluate the bond strength and permeability of a layered interface. [ABSTRACT FROM AUTHOR]

Measurements of space charge density and trap levels are informative ways to predict failure conditions of insulation materials. The charges are injected from electrodes and penetrate from surface towards deep inside of the insulation material. In order to resist the charge injection, trapping, migration and increase charge recombination, de-trapping and extraction rate, layer (nanocomposite-PI-nanocomposite) sandwich structure samples are used. Two techniques Pulse Electro Acoustic (PEA) and Thermal Stimulated Current (TSC) are combined to characterize space charge behavior and trap levels. Lab-view based program is used to detect the charges density distribution and total charge decay, different peaks of current using TSC technique are used to get activation energy and trap level density. The effects of structural interface (single, double, three layers) and types of nano (Al2O3, SiO2) fillers are analyzed to influence charge accumulation polarity and trap levels. Trap levels are calculated using TSC data as well as total charge decay data. The trap values calculated from both data match each other. Al2O3-PI-Al2O3 sandwich structure showed remarkable improvements to resist accumulation of space charge for longer time. Mostly charges are shallow traps with 1.126eV trap level and recombination rate is higher. In double layer structure in which interface is made up of SiO2 and Al2O3, deep trap level of 1.26 eV and higher trap density is observed. The charges decay is faster in three layer structure than double and single layer structure. It is concluded that the interface formed with different type of nano and structure of insulation, both are an important parameters for manufacturing industry to suppress space charges accumulation and traps. [ABSTRACT FROM AUTHOR]

The Mg 2 Sn/Mg multilayer films with different nano-sized modulation period were successfully prepared on single crystalline Si substrate with 500 ​nm thickness SiO 2 layer by alternately sputtering using high pure metal Mg target and Mg–Sn alloy target. The chemical composition, surface and cross-sectional morphology, phase composition, carrier transport process and thermoelectric properties of deposited films were deeply investigated. The results show that the deposited films possess obvious layered structure, which is composed of metal Mg layer and antifluorite cubic Mg 2 Sn layer. The atom ratio [Mg]/[Sn]<2.0 in Mg 2 Sn layer between metal Mg layers and deposited films are p-typed semiconductor due to the existence of Mg vacancy in Mg 2 Sn lattice. The carrier concentration, mobility and thermal conductivity at room temperature decrease with reducing the modulation period of the multilayer films due to scattering of layer interface, at which depletion layer and built-in electric field form, impeding motion of the carriers. The electrical conductivity slightly decrease, but the Seebeck coefficient, power factor and figure of merit (ZT) greatly increase with reducing modulation period due to the scattering of the carriers. The ZT value of the film with the smallest modulation period of 171 ​nm reaches 0.51. The introduction of the layer interface greatly strengthens the carrier scattering process and improves the thermoelectric properties of the deposited films. This work demonstrates that introduction of heterogeneous interfaces composed of the same elements into films can effectively improve its thermoelectric properties. [Display omitted] • The Mg 2 Sn/Mg multilayer films with nano-sized period were prepared by alternately sputtering. • The carrier concentration and mobility at room temperature reduce by layer interface scattering. • The Seebeck coefficient and figure of merit (ZT) greatly increase by more layer interface. • The introduction of the layer interface greatly improves the thermoelectric properties of films. [ABSTRACT FROM AUTHOR]

A mechanistic particle scale model is proposed for bilayer tablet compaction. Making bilayer tablets involves the application of first layer compaction pressure on the first layer powder and a second layer compaction pressure on entire powder bed. The bonding formed between the first layer and the second layer particles is crucial for the mechanical strength of the bilayer tablet. The bonding and the contact forces between particles of the first layer and second layer are affected by the deformation and rearrangement of particles due to the compaction pressures. Our model takes into consideration the elastic and plastic deformations of the first layer particles due to the first layer compaction pressure, in addition to the mechanical and physical properties of the particles. Using this model, bilayer tablets with layers of the same material and different materials, which are commonly used pharmaceutical powders, are tested. The simulations show that the strength of the layer interface becomes weaker than the strength of the two layers as the first layer compaction pressure is increased. The reduction of strength at the layer interface is related to reduction of the first layer surface roughness. The reduced roughness decreases the available bonding area and hence reduces the mechanical strength at the interface. In addition, the simulations show that at higher first layer compaction pressure the bonding area is significantly less than the total contact area at the layer interface. At the interface itself, there is a non-monotonic relationship between the bonding area and first layer force. The bonding area at the interface first increases and then decreases as the first layer pressure is increased. These results are in agreement with findings of previous experimental studies. [ABSTRACT FROM AUTHOR]

• Heat pulse data were analyzed in a double-layered soil. • Heat transfer pattern/models were studied with heating probe at layer interface. • Heat fluxes differed within the layers due to heterogeneous soil thermal properties. • Hetero-CPC model was proposed for heat pulse measurements in layered soil. In the case where a heat-pulse (HP) sensor installed in a layered soil with the heating and sensing probes positioned at different layers, the HP measurement violates the underlying assumption of soil homogeneity for the cylindrical perfect conductors (CPC) theory that is used to interpret the HP data. In this study, laboratory and numerical studies were performed to evaluate the heat transfer patterns and models to analyze HP measurement data when heating probe was positioned at the interface of a double-layered soil with different upper- and lower-layer properties. A parameterized hetero-CPC model was proposed to describe temperature-by-time curves at the sensing probes in the upper and lower soil layers. The hetero-CPC estimates matched well with the simulated values, and its accuracy relied on the thermal property differences between the soil layers. The heat distributions caused by heat pulse inputs in the layered soils showed semi-circular isotherms with different radii centered on the heating source, therefore showing discrepancies in heat fluxes for the upper and lower soil layers. The proposed hetero-CPC model was able to accurately describe the combined effects of finite probe properties and heterogeneous soil thermal property values on the HP data in a double-layered soil system with the heating probe positioned at the layer interface. [ABSTRACT FROM AUTHOR]