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(111)-oriented nanotwinned Cu ((111)nt-Cu) has shown its high surface diffusion rate and better oxidation resistance over common polycrystalline Cu (C-Cu). The application of (111)nt-Cu as an interface metallization layer in Ag-sintered technology under the role of oxygen was investigated in this work, and its connecting behavior was further clarified by comparing it with C-Cu. As the sintering temperature decreasing from 300 to 200 °C, the shear strength on the (111)nt-Cu substrate was still greater than 55 MPa after sintering for 10 min. The fracture surface correspondingly changed from the interface of Ag/die to mixed fracture mode, involving the interface of the Ag/Cu substrate and Ag/die. The existence of copper oxide provided a tight connection between Ag and the (111)nt-Cu substrate at all of the studied temperatures. Although lots of small dispersed voids were seen at the interface between copper oxide and (111)nt-Cu at 300 °C, these impurity-induced voids would not necessarily be a failure position and could be improved by adjusting the sintering temperature and time; for example, 200 °C/10 min or heating to 300 °C, and then start cooling at the same time. The microstructure of Ag-Cu joint on (111)nt-Cu behaved better than that on C-Cu. The thinner copper oxide layer and the higher connection ratio of the interface between copper oxide and Ag were still found on the (111)nt-Cu connection's structure. The poor connection between copper oxide and Ag on C-Cu easily became the failure interface. By controlling the thickness of copper oxide and the content of impurity-induced voids, the use of (111)nt-Cu in advanced-packaging could be improved to a new level. [ABSTRACT FROM AUTHOR]

Purpose: The surface characteristics of thermally and chemically modified wood, such as surface roughness, surface free energy (SFE) and wettability, are important properties that influence further manufacturing processes such as gluing and coating. The aim of this paper was to determine the influence of the surface roughness of thermally and chemically modified teak wood on their SFE, wettability and bonding quality for water-based acrylic and solvent-based alkyd varnishes. In addition, durability against subterranean termites in the field of these modified teak woods was also investigated to give a valuable information for their further application. Design/methodology/approach: The woods tested in this study were fast-growing teak woods that were prepared in untreated and treated with furfuryl alcohol (FA), glycerol maleic anhydride (GMA) and thermal. SFE values were calculated using the Rabel method. The wettability values were measured based on the contact angle between varnish liquids and wood surfaces using the sessile drop method, and the Shi and Gardner model model was used to evaluate the wettability of the varnishes on the wood surface. The bonding quality of the varnishes was measured using a cross-cut test based on ASTM 3359-17 standard. In addition, durability against subterranean termites in the field of these modified teak woods was also investigated according to ASTM D 1758-06. Findings: The results showed that furfurylated and GMA-thermal 220°C improved the durability of teak wood against termites. The furfurylated teak wood had the roughest surface with an arithmetic average roughness (Ra) value of 15.65 µm before aging and 27.11 µm after aging. The GMA-thermal 220°C treated teak wood was the smoothest surface with Ra value of 6.44 µm before aging and 13.75 µm after aging. Untreated teak wood had the highest SFE value of 46.90 and 57.37 mJ/m2 before and after aging, respectively. The K values of untreated and treated teak wood increased owing to the aging treatment. The K values for the water-based acrylic varnish were lower than that of the solvent-based alkyd varnish. The untreated teak wood with the highest SFE produced the highest bonding quality (grades 4–5) for both acrylic and alkyd varnishes. The solvent-based alkyd varnish was more wettable and generated better bonding quality than the water-based acrylic varnish. Originality/value: The originality of this research work is that it provides evaluation values of the durability and SFE. The SFE value can be used to quantitatively determine the wettability of paint liquids on the surface of wood and its varnish bonding quality. [ABSTRACT FROM AUTHOR]

In practice, for the manufacture of plywood, the veneer is usually dried to a moisture level suitable for bonding. However, anatomical differences within and between veneer sheets are a significant factor and some of them may contribute to significant differences in moisture content (MC). The novelty of this work was to study the possibility of using wood veneers of different MC in adjacent layers in one structure of plywood panels and how this affects the physical and mechanical properties of the panels. The Norway spruce (Picea abies L. Karst) wood veneers with mean MC approximately of 2%, 5% and 7% and phenol-urea-formaldehyde (PUF) resin were used in the experiments. The five-layers plywood panels were manufactured at the two pressing pressures of 0.8 MPa and 1.2 MPa. There was no significant difference in the bending and bonding properties, but only wood failure as measured on bonding specimens which showed higher average values on specimens manufactured with high pressure during hot pressing. Higher differences in MC of each veneer with constant MC of the veneer stack didn't worse bending and bonding properties of plywood. [ABSTRACT FROM AUTHOR]

The experimental study of ultrasonic transmission coefficient measurement method was carried out for the problem of bonding quality inspection of bonded structures of composites with thick adhesive layer. For the uniaxial CFRP bonded specimens, the ultrasonic waves' phase velocity distribution and the ultrasonic transmission coefficient spectrums were measured by the water-immersion ultrasonic transmission method. Then their complex elastic constants were inversed by the particle swarm optimization algorithm based on simulated annealing. Based on this, CFRP bonded specimens in perfect bonding status and having single weak bonding interface, dual weak bonding interfaces were manufactured. Then the ultrasonic transmission coefficient spectrums were measured, and the distinction of bonding quality between different bonding specimens was predicted. At the same time, according to the shift characteristics of the measured ultrasonic transmission coefficient spectra, the influence of the symmetry of the CFRP bonded structures with thick adhesive layers on the ultrasonic transmission coefficient spectrums was investigated experimentally. In addition, by comparing the time-domain and coefficient spectra characteristics of transmitted waves, the advantage of using the coefficient spectrum measurement method in bonding quality detection was expounded. [ABSTRACT FROM AUTHOR]

The proper choice of raw materials and manufacturing parameters for Cross Laminated Timber is essential to promote the proper bonding of the lamellas, aiming at their application in construction. However, few Brazilian species are currently used in the production of Cross Laminated Timber. The aim of this work was to characterize the bonding quality of four Brazilian reforestation species (Pinus elliottii (pino ellioti), Eucalyptus grandis (eucalipto), Toona ciliata (toona) and Acrocarpus fraxinifolius (lazcar)) in the manufacture of Cross Laminated Timber with two-component polyurethane adhesive and five different pressure levels (from 0,1 MPa to 1,3 MPa). Bonding quality was evaluated through delamination and glue line shear tests based on the European standard. Delamination was affected by the wood species, and the best adhesion occurred for the Cross Laminated Timber manufactured with Pinus elliottii (pino ellioti) and Acrocarpus fraxinifolius (lazcar) at the bonding pressure of 0,7 MPa. Cross Laminated Timber bonding pressure did not affect the percentage of wood in the shear test fractured surface, whereas higher density Cross Laminated Timber showed higher percentages. [ABSTRACT FROM AUTHOR]

This study investigates the influence of different machining processes on the tensile shear strength of glued lumber, focusing on optimizing the tool geometry of face milling. The data obtained were analyzed using statistical methods. The roughness of the surface produced by the machining process and the damage to the microstructure under the cutting edge are identified as important factors influencing the quality of the bond. The results show that the optimized process (low roughness and microstructure damage) leads to more effective gluing. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the potential use of solid wood waste of the following species Cedrela odorata, Enterolobium schomburgkii, Erisma uncinatum, and Qualea paraensis for the manufacture of edge glued panels. The quality of the finger joint and edge bonding with PVA and EPI adhesives, respectively, with spreading rates of 180 g.m-2, was evaluated through static bending, parallel tensile, and shear tests, using ASTM D 5572, EN 13353, and EN 13354 standards. A total of 1,460 test specimens exposed to dry, high temperature, triple cycle, and wet pre-treatments were tested for glue line resistance. The results of all tests for all pre-treatments of finger joints and edge bonding demonstrated the potential of wood waste for the manufacture of edge glued panels for interior use in dry environments. There was a tendency for resistance values to be balanced in splices and joints combined with mixtures of species, possibly due to the densities of the wood pieces. Wet pre-treatment delivered excellent lower 5th percentile results, highlighting the potential of Amazonian tropical solid wood waste for the production of edge glued panels.

In this work, the effects of some geometric and mechanical parameters that characterize curved and relatively soft structures integrated with piezoelectric actuators are investigated. The effect of parameters such as the curvature, location, and extension of the piezo device, as well as the thickness of the bonding and its strength, are considered in view of a potentially lighter model that replaces the piezoelectric device via its actions, namely pin forces, whose layout and values are strongly dependent on the curvature. When comparing the results obtained by a finite element model of the structure with the piezo device and of the structure alone under the action of pin forces, dedicated indicators were found, which could be useful to support lighter modeling approaches and to predict the authority of the piezoelectric device. [ABSTRACT FROM AUTHOR]

In this study, three PLA-TPU compounds were prepared by the melt mixing method and after the process of compounding, filament preparation, and 3D printing with Fused Deposition Modeling (FDM). The mechanical properties under compression, tensile, bending, shear modes, and fracture toughness were comprehensively and experimentally assessed. Also, for thermal analysis and microstructural evaluation, Dynamic Mechanical Thermal Analysis (DMTA) and Scanning Electron Microscopy (SEM) were used. The thermal analysis of the PLA-TPU compounds showed an increase and decrease in the loss and storage modulus with increasing PLA value, while all compounds had almost the same glass transition temperature. The results of mechanical tests showed that by raising the amount of PLA, the strength and formability increased and decreased, respectively in all loading modes. The UTS values for PLA50, PLA70, and PLA90 were achieved 27.27 MPa, 40.91 MPa, and 54.18 MPa, respectively. Also, the fracture toughness results were consistent with the mechanical properties. The PLA90 had 1.69 and 2.36 times higher fracture toughness than the PLA70 and PLA50 compounds, respectively. SEM images showed that with the increase in the amount of TPU, the voids caused by the printing and neck growth due to the incomplete integration of the inter and intralayer rasters rises, which is the reason for the decrease in strength and printability. The shear test results also confirmed the SEM images quantitatively and showed that the connection between the layers and density improves with increasing the amount of PLA.

Wood surface roughness, surface free energy (SFE), wettability, and bonding quality for water-based acrylic coatings were investigated. The samples tested in this study included Pinus radiata, Pinus sylvestris, Larch, Hemp oak, Catalpa tree, and Camphor. Sandpaper with grits of 180, 240, 320, 400, and 500 was utilized to sand wood surfaces. The van OSS-Chaudhury-Good equation (vOCG) was used to calculate the SFE values. The modified model (M-D) was used to calculate the wettability based on the contact angle change rate (K value). The higher the K value, the faster the contact angle approaches equilibrium. A cross-cut test was used to evaluate the coating's bonding quality. The anatomical structure of wood has an impact on the roughness of hardwood. The equilibrium contact angle is influenced by the wood species and sandpaper grit size. Sanding can make the surface of wood more wettable. Radiata pine that had been sanded to 180 grit had the highest SFE value. After finishing with waterborne acrylic, hardwood had a slightly better coating adhesion than softwood. Hemp oak wood had the lowest coating adhesion (0.6) and the highest K value (0.82). The best bonding quality (0.4) was supplied by the camphor wood with the lowest K value (0.13). Wettability in terms of K values was a good indication of determining the bonding quality of the water-based acrylic coatings. [ABSTRACT FROM AUTHOR]

The reservoir formations in the Baran Hetao Basin have the characteristics of low maturity, high permeability, low strength and high shale content. The formations drilled have high water sensibility, instability and leaking potential. Deep well cementing is faced with many difficulties, such as long cementing section, low displacement efficiency, low bonding strengths of the two interfaces and high requirements on the mechanical performance of the cement sheath in late fracturing jobs, etc. To solve these problems, a batch-mixing batch-injecting DRJ-2S flushing spacer and a slight-expansion high strength rough cement slurry DRE have been developed with two key cementing materials, which are an interface strengthening agent DRJ-2S and an expanding toughening agent DRE-4S. Laboratory studies show that the DRJ-2S flushing space has a flushing efficiency of more than 96%, which is 30% higher than that of clean water, and a spacer of density 1.60 g/cm³ has 7 d compressive strength of 9.6 MPa. The DRE2S flushing spacer has the ability of remarkably enhancing the compressive strength of mixed fluids and the bonding strengths of the interfaces of a cement sheath. At 90 ℃ and 21 MPa, a high strength tough slight-expansion cement slurry treated with 4% – 6% DRE-4S has compressive strength of at least 24 MPa, elastic modulus of equal to or less than 7 GPa, and linear ratio of expansion of at least 0.02%, indicating that the cement slurry has good adaptability to mechanical alternation. The DRE cement slurry and the DRJ-2S spacer have been used on more than 40 wells in the Bayan Hetao basin, with average well cementing pass rate of 96.5% or higher, greatly improving the quality of well cementing job in the basin. The application of the DRE and the DRJ-2S has provided a powerful technical support for the safe and efficient development of the complex oil and gas wells, and is worth promoting. [ABSTRACT FROM AUTHOR]

The bonding quality is a key property for wood-based composites. Determination of the bonding quality of sandwich panels with veneer faces and <50 mm thick cork core is not covered either by the EN 314-1, which refers to plywood, nor by its Annex B, which refers to insulating cores with a thickness of at least 50 mm. This technical note assesses the possibility of using the prescriptions of Annex B of EN 314-1 to test the bonding quality (shear strength) of the concerned panels. For this purpose, sandwich panels were realized by bonding fromager (Ceiba pentandra) veneers to a 5 mm thick core, and their bonding quality was tested. Two types of panels were realized, based on the adhesive used (glue spread 340 g/m2 for double glue lines): urea–formaldehyde (UF) and urea–melamine–formaldehyde (UMF); the panels were pressed at 103 °C for 8 min at a nominal pressure of 0.4 MPa. Pre-treatments were dry-conditioned at 20 °C/65% relative humidity until attainment of the equilibrium moisture content, and immersed in water: cold water for UF panels (5.1.1 of EN 314-2) and boiling water for UMF panels (5.1.2 of EN 314-2). The effect of pre-treatment was statistically significant, with shear resistance reductions of 56% and 43% in UF and UMF panels, respectively. Based on this first investigation (2 panels × 10 specimens per panel = 40 specimens), the test method can be considered suitable for providing reliable results. This study constitutes a useful reference to test the bonding quality of sandwich panels with veneer faces and thin cork cores. [ABSTRACT FROM AUTHOR]

Plywood is a structural composite mainly applied in construction. For this purpose, some sort of preservative treatment is recommended to increase its durability. One option of the available treatments is heat treatment, which promotes the modification of the wood properties. This treatment is carried out on the final product (plywood), because it can reduce strength if applied to the veneers. However, no study has proven such a reduction. Therefore, the aim of this work was to evaluate three different temperatures (160 °C, 180 °C and 200 °C) of the heat treatment on the veneer surface and on the physical properties (specific gravity, moisture content and swelling in thickness) and mechanical properties (MOE and MOR in static bending) of Pinus taeda plywood. A reduction was observed in the roughness of the veneer's surfaces and the total extractives content changed, with a minimum value reached in the 160 °C treatment. The plywood specific gravity initially increased with the heat treatment and did not change at higher temperatures, moisture content reduced, and thickness swelling was not affected. There was no change in the mechanical properties of the plywood, evidencing that the veneer heat treatment does not prejudice mechanically the final product. [ABSTRACT FROM AUTHOR]

In this work, the effects of some geometric and mechanical parameters that characterize curved and relatively soft structures integrated with piezoelectric actuators are investigated. The effect of parameters such as the curvature, location, and extension of the piezo device, as well as the thickness of the bonding and its strength, are considered in view of a potentially lighter model that replaces the piezoelectric device via its actions, namely pin forces, whose layout and values are strongly dependent on the curvature. When comparing the results obtained by a finite element model of the structure with the piezo device and of the structure alone under the action of pin forces, dedicated indicators were found, which could be useful to support lighter modeling approaches and to predict the authority of the piezoelectric device.

The objective of this study was to analyze machining performance (characteristic and quality), as well as bonding quality of densified wood, and then compared to those of un-treated (control) wood and boron-treated wood. Characteristic and quality of machining properties were directly evaluated by qualified technician during processing, while bonding quality was evaluated through its shear strength. The results showed that densification employed was able to improve machining performance and bonding quality of the 5-year-old faster-grown teakwood. Compared to control wood and boron-treated wood, machining performances of densified teakwood are greater, while bonding quality increased by 18.79 and 26.86%, respectively. The surface became much fine and even, and has similar colour to older teakwood. Analysis hierarchy process (AHP) proves that densified teakwood is the best raw material for furniture manufacturing since its machining performances, appearance, colour, and bonding quality are better either than control wood or boron-treated wood.

Three-ply plywoods were produced using pine and Eucalyptus northeast Argentinian woods. A no-added formaldehyde biobased-adhesive was used for assembly, based on chemically modified soy protein concentrate. In this work we focused on the relationship between bonding quality parameters of the plywoods and the morphology of the glued line. Wood characteristics such as contact angle, roughness, density and moisture content were measured prior to plywood assembly. Bonding quality parameters (percentage of wood failure and shear strength) of the plywood were measured according to Argentinean standard IRAM 9562 (2006) and the results were evaluated with respect to microscopic observations of the glue joint. Eucalyptus wood was suitable for plywood interior condition applications, while pine barely exceeded the standards imposed by the norm. [ABSTRACT FROM AUTHOR]

This theoretical study focuses on the verification of the possibility of using ultrasonic waves to characterize the bonding quality in an Aluminium/Adhesive/Aluminium multilayer structure where the two aluminium layers have the same thickness. This special case poses a problem in quality control because the same thickness implies identical resonance modes from the ultrasonic point of view, which means that the first aluminium layer will hide the second one. However, there is a mode doubling relative to the two aluminium layers under certain bonding conditions. This work is based on the monitoring of the behavior of this mode doubling from the evolution of the ultrasonic response modeled by the calculation of the theoretical reflection coefficient corresponding to the multilayer. This study has showed that this mode splitting depends on both the thickness of the aluminium layer and the adhesive layer, and it depends strongly on the quality of the bonding at the interfaces between aluminium and adhesive. From these results, it has been possible to deduce which multilayer structure can be characterized and in which frequency range this characterization is possible. The evolution of the modulus of the reflection coefficient as a function of the percentage of normal stiffnesses at the interfaces has showed the existence of a promoter parameter, called the resonance depth, which allows following accurately the quality of the bonding at these interfaces. This very interesting result makes it possible to express the quality of the bonding in terms of percentage, since it reflects the percentage of adhesion at the interfaces. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the density, chemical properties and bonding quality of two lesser-used Mozambican wood species known as messassas (Brachystegia spiciformis and Julbernardia globiflora) aiming at edge-glued panel production. The bonding was performed using structural adhesive polyvinyl acetate D4, semi-structural adhesive emulsion polymer isocyanate and non-structural polyvinyl acetate D3 applied at 120·m-2 and 180·m-2 weights. Density, chemistry, edge shear bonding, wood failure percentage and the finger-joint tests were performed in accordance with ISO 13061-2:2014 (E), TAPPI, EN 13354:2008, ABNT-NBR ISO 12466-1:2006 and ASTM 5572:2005 standards, respectively. The results showed that both species have medium density, high extractives and lignin contents typical of tropical wood. The emulsion polymer isocyanate adhesive was approved with better performance compared to polyvinyl acetate D3 and D4 adhesives. It can also be affirmed that Brachystegia spiciformis and Julbernardia globiflora have similar bonding behaviour and the potential for producing edge glued panel panels, especially for indoor use.

For aluminum laminated composites (ALCs), interlayer bonding strength plays a crucial role in its performance. In this work, 7050/Al/7A52 and 7A62/Al/7A52 ALC were studied to explore the effects of recrystallization and element diffusion on interfacial bonding quality and mechanical properties. The results show that attributed to the deformation localization occurs at the 7A52/pure Al interface, continuous dynamic recrystallization (CDRX), discontinuous dynamic recrystallization (DDRX) and geometric dynamic recrystallization (GDRX) coexist, while only DDRX exists at the bonding interfaces of 7050/pure Al and 7A62/pure Al. Among them, 7A62/pure Al interface has the most obvious element diffusion behavior among the three kinds of interfaces. Notably, recrystallization would have a higher effect on improving bonding quality, which causes the 7A52/pure Al interface of the composites more difficult to delaminate during the tensile test. Besides, the enhancement of element diffusion depth at the 7A62/pure Al interface promotes the bonding strength of 7A62/Al/7A52 ALC to increase by 21.0% compared with that of 7050/Al/7A52 ALC. After the dynamic impact test, the peak flow stress and energy absorption value of 7A62/Al/7A52 ALC reached 567.1 MPa and 72.2 MJ/m3, and the interface remains intact. However, due to the existence of huge strength deviation in the 7A62/pure Al interface, it is more prone to fail during the tensile process, resulting in a decrease in the elongation of the composites. • Systematically investigates the effect of recrystallization and interfacial element diffusion on interface of 7xxx/pure Al. • Recrystallization would have a higher effect on improving bonding quality than element diffusion. • The huge strength deviation would accelerate the failure of bonding interface thus affect the elongation of composites. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of the addition of recycled concrete aggregate (RCA) on the properties of self-compacting cement-based materials at the mortar scale, at the incorporation ratios of 0, 25, 50, and 100 %. The results showed that the yield stress and the plastic viscosity of the mortar increased with the incorporation ratio of RCA. Slump flow and V-funnel time were used to assess these properties. The mechanical strength of the mix also increases with the RCA incorporation ratio. A quantitative analysis of the data demonstrated that the effect of the addition of RCA on the mortar's rheological properties can be attributed to a decrease of the aggregate's packing density (morphology effect), a decrease of the effective water-to-cement ratio of the mix (water-to-cement ratio effect), and an increase of the aggregate's effective volume fraction (volume fraction effect). The latter two effects are caused by the aggregate's high water absorption, whose impact on mechanical strength is stronger than that caused by the morphology effect. In addition, the increase of the mix's strength can also be attributed to the increase of the effective water-to-cement ratio of the mix and to the bonding quality between the aggregate and the cementitious matrix. The increment in the incorporation ratio of RCA causes a reduction of the effective water-cement ratio of the mix and an increase of the bonding quality. [ABSTRACT FROM AUTHOR]

By adding Na₂B₄O₇ into the Al-Fe₂O₃-Cr₂O₃ reaction system, the Al₂O₃ ceramic-lined steel pipe was prepared with the gravitational separation SHS method, and the influence of the Na₂B₄O₇ addition on the structure and properties of the produced composite steel pipe was investigated. The obtained results showed that the phase composition of the ceramic coating was Al₂O₃-FeCr Alloy-(Al0.9Cr0.1)₂O₃ composite, and with the increase of the amount of Na₂B₄O₇ addition, the Fe-Cr alloy particles left in the ceramic coating increased and distributed uniformly, and the denser ceramic coating was obtained. However, when the amount of Na₂B₄O₇ addition increased further to over 4%, the ceramic coating became fractures, the hardness of ceramic coating decreased. The transition structure of steel pipe-transition layer-ceramic coating was formed, the thickness of the transition layer decreased with the addition of Na₂B₄O₇, and the boundaries between the transition layer and the ceramic layer were less obvious, which would have a significant effect on the improvement of the bonding quality of the composite steel pipe.

Highlights • Increasing the bonding pressure enhances delamination and wood failure percentage. • Pre-treatment with primer enhanced results for all the bonding quality parameters. • Layer thickness and adhesive spread rate showed few influence on results. • Shear strength requirements of EN 16351 were always fulfilled. • Delamination requirements of EN 16351 were not always fulfilled. Abstract This paper presents an experimental study about the bonding quality of Maritime pine (Pinus pinaster Ait.) cross-layered wood elements glued with one-component polyurethane adhesive. The experiments comprised shear and delamination tests according to standard EN 16351 focusing on the influence of the following parameters: bonding pressure, adhesive spread rate, pre-treatment with primer and layer thickness. The results obtained show that increasing bonding pressure increases significantly the wood failure percentage after delamination or shear tests, while the delamination and the shear strength are not significantly affected. Moreover, it was found that the use of primer enhances significantly the bonding quality; nevertheless, EN 16351 requirements are fulfilled even for the lower bonding pressure and adhesive spread rate recommended by the manufacturer of the adhesive used in the experiments. The layer thickness, for the tested range, had no influence on the delamination and shear results and limited one on the wood failure percentage after shear or delamination tests. No relevant influence was found for the adhesive spread rate. In the experiments the combination of gluing Maritime pine with Australian blackwood (Acacia melanoxylon R.Br.) was also investigated and, for this combination, the standard requirements were successfully fulfilled. [ABSTRACT FROM AUTHOR]

In order to improve the energy utilization ratio of explosives and reduce the noise and dust for explosive welding, honeycomb structure explosives covered by colloid water were put forward as explosive materials. Using 304 stainless steel and Q235 steel as flyer plate and base plate respectively, explosive welding tests were carried out with different covering thicknesses. The dynamic parameters in the collision process were obtained by experimental measurement and theoretical calculation. The microstructure of the bonding interface was observed through optical microscopy and analyzed by welding window. The results showed that, compared to the explosive welding without covering, the impact velocity of flyer plates was increased by 38.9 %, 57.5 % and 71.9 % respectively when the covering thickness was 15 mm, 30 mm and 45 mm. The impact velocity predicted by Gurney formulas was significantly larger than the measured value, however, after considering acceleration history, the calculated value was in good agreement with the experimental result. Metallographic analysis showed that wave bonding interfaces without defects such as voids and cracks were obtained when the welding conditions were within the welding window. However, voids and cracks were found at the bonding interfaces when the welding conditions were close and above to the upper limit of the welding window. [ABSTRACT FROM AUTHOR]

The present paper investigates the physical and mechanical modifications of both poplar (I-214 clone) and ceiba veneers and plywood after heat treatments of different intensities (5 and 7 % of dry mass losses). Plywood panels were glued before and after heat treatment with urea-formaldehyde (UF) and melamine-urea-formaldehyde (MUF) resins. In order to assess the treatments’ effects on both the wood and the glues, the dry mass, the density, the bending strength, the Young’s modulus and the bonding quality were measured before and after heat treatment. The results of the different treatments were compared as well. Results showed that the loss in cell wall polymers due to the heat treatment caused a significant reduction of the equilibrium moisture content of the samples. From a mechanical point of view the treatment resulted in an important reduction of strength and in a small reduction of stiffness. Bonding quality as well as mechanical properties were widely affected by the heat treatment. The different intensities of the treatments (the treatment range was up to 5% and 7% of dry mass loss) did not show significant differences for most of the features assessed. The mechanical performance as well as the bonding quality of treated samples suggested that veneers should be glued after heat treatment. Apparent cohesive wood failure showed that different degradations affect wood and glues with a prominent effect on the glues for UF resins and a prominent effect on the wood for MUF resins.

A new approach to monitoring the quality of adhesive bonding in the carbon fiber—reinforced polymer (CFRP) is developed by using a local nonlinear response of the laminate. It is shown that a degraded (contaminated) boundary layer of the adhesive contributes to an overall nonlinear response of the laminate that enables to evaluate and quantify bonding quality caused by various types and levels of single contaminations. In the context of aviation applications, two typical stages during the life of a structural part for which the adhesive properties of a bonding joint could be degraded were considered: the production process and the maintenance/repair scenario. All kinds of single contaminations studied result in enhancement of the nonlinear response of the CFRP laminate, which is an indication of deterioration of the bonding quality. The effect of multiple contaminations confirms a cumulative decline of adhesion caused by increase of the contents of single contamination components. [ABSTRACT FROM AUTHOR]

Wettability and bonding quality of exterior coatings on fast-growing wood surfaces were studied. Samples of air-dried flat-grained (tangential surface) and edge-grained (radial surface) pattern of jabon ( Anthocephalus cadamba) and sengon ( Paraserianthes falcataria) woods were used. Before application of exterior coatings, the surfaces of the lumber samples were sanded. To provide wood surfaces with various degrees of roughness, abrasive papers of 120, 240, and 360 grits were used for the surface preparation. The wettability of two exterior coatings (water-based acrylic and oil-based alkyd varnishes) on the sanded wood surfaces was measured using a sessile drop contact angle method. The Shi and Gardner (S/G) model was used to evaluate and compare the wettability of the surface coatings on the wood. The sanded wood samples were coated with the two coatings (two layers each). Bonding quality of the coating layers was measured using a crosscut tape test method. Experimental results show that constant contact angle change rate ( K value) of the S/G model decreased as the grit number of abrasive paper increased. This indicates that the wettability decreased as the roughness of the surface decreased (surface becomes smoother). There was no evidence of differences in wettability between tangential and radial wood surfaces. The oil-based alkyd coating generated better wettability compared to the water-based acrylic. The crosscut tests showed that the bonding quality of the coating films on both jabon and sengon wood decreased as the surface became smoother. The sengon wood compared to jabon wood provided better coating wettability and bonding quality. Wettability in terms of the K values was a good indication for determining the bonding quality of the two varnish layers. [ABSTRACT FROM AUTHOR]

The steam-chest molding process can be used to prepare molded bead foams, including expandable polystyrene (EPS), expanded polyethylene (EPE), expanded polypropylene (EPP), and expanded polylactide (EPLA) with complex three-dimensional shapes. A new thermoplastic elastomer bead foam, which is described as expanded thermoplastic polyurethane (ETPU), now exists. Notably, it has an excellent soft touch quality and is ductile. It has also generated widespread interest in both the academic and industrial communities. In this study, three types of ETPU foams with various sample sizes were steam-chest molded. We concentrated on the preparation of the molded ETPU (METPU), which was followed by a mechanical test. Our morphological observations showed that the ETPU bead foams’ interfaces had effectively bonded. A high tensile strength of 1.80 MPa and an elongation at break of 360.1% were reached in the METPU sample with a density of 0.35 g/cm 3 . A 200-fold cyclic compression measurement verified that the compressed METPU sample could recover more than 95% both in stress and modulus, after 6 days of relaxation. This suggested the presence of excellent interbead bonding in the ETPU bead foams. Based on the differential scanning calorimetry (DSC) results, we proposed that a formation mechanism for interbead bonding during the ETPU steam-molding process existed. [ABSTRACT FROM AUTHOR]

Coplanar capacitance imaging is a detection technique based on the sensitive field mechanism, which can display 2D or 3D medium distribution images in real time. In order to achieve the visual detection of adhesive deffects in aeronautical insulating composites, a imaging algorithm based on Kalman filter is proposesd based on the analysis of of uniplanar capacitance imaging model and image reconstruction principle, and the optimal estimate is achieved by adjusting the degree of dependence on the estimated and measured capacitance values continuously. The validity and feasibility of the proposed algorithm are verified through experiment. Compared with traditional imaging algorithm, the proposed image reconstruction algorithm greatly improves the image reconstruction precision of adhesive defect. [ABSTRACT FROM AUTHOR]

Adhesive bonding is becoming more increasingly important in joining of structural elements. In civil engineering, there is a growing interest in connection by adhesive bonding in steel-concrete flexural members. This study concerns the guided wave propagation technique applied to condition assessment of an adhesive connection between a steel member and a concrete beam. Various states of degradation were considered by producing several laboratory samples differing in the placement and the length of the adhesive bond. Piezoelectric transducers were used to excite and to register signals of propagating waves. In addition, the finite elements method was used to simulate propagation of guided waves at the bond-line between steel and concrete. Results for the beam with perfect bonding were compared with results obtained for beams with partially degraded connections. The influence of the length of damaged bond and its position on registered signals was investigated. [ABSTRACT FROM AUTHOR]

Recycling and reuse of wood-based panels has been attracting great attention since it is an environmentally friendly means of managing wood waste. The recycled wood-based panels usually still contain adhesive residue. In the current research, the impact of urea-formaldehyde (UF) resin, one of the most widely used adhesives, on recycling and reconstitution of wood-based products has been evaluated by adding cured UF resin particles into a new adhesive system. The morphology, chemical structure, curing behavior, and bonding quality of an adhesive system containing 0–6% previously cured resin particles of varied sizes (< 600 μm) were investigated and compared to those properties of a regular adhesive without any impurity. Three-ply plywood glued with a UF adhesive containing 0–10 wt% previously cured resin of varied particle sizes (< 600 μm) were prepared and characterized. The results indicated that the resin residue could significantly affect the curing behavior and bonding quality of the new adhesive system. Higher content and greater size of the particles caused more severe deterioration in the bonding strength. [ABSTRACT FROM AUTHOR]

Thermally modified and unmodified beech veneers in untreated and plasma-treated state were immersed in melamine solution at different concentrations. The plasma pre-treated veneers exhibited significantly higher melamine loads than the untreated veneers at equal impregnation duration. Subsequently the veneers were manufactured into 5-layer plywood boards; the plywood samples then underwent an extreme testing procedure based on DIN-EN 314-1/2 in order to proof the bonding quality by means of shear strength. The plywood boards made of plasma pre-treated veneers exhibited up to 2.7-fold improvement in shear strength compared to plywood made of untreated veneers. Results differed markedly based on material (unmodified/thermally modified veneer) and concentration of melamine solution. [ABSTRACT FROM AUTHOR]

Three types of titanium clad steel sheets were fabricated by a hot-roll bonding process at different rolling reductions (40%, 55%, and 65%). The specimens with stacking sequences of TA1/steel/TA1, TA1/T2/steel/T2/TA1 and TA1/BAg-8/steel/BAg-8/TA1, corresponding to Ti/steel clad composites bonded without a filler, with a red copper filler, and with a BAg-8 filler, are referred to here as Ti-steel, Ti-T2-steel, and Ti-Ag-steel, respectively. The Ti-steel specimen was prepared by direct hot-roll bonding with its four sides welded by arc welding, while the Ti-T2-steel and Ti-Ag-steel specimens were prepared by a combined brazing and hot-roll bonding process, named as a brazing-rolling process. These three types of as-roll bonded specimens were subjected to heat treatments, under 65% rolling reduction. The bonding quality, interface structure evolution, and mechanical properties of the clad composites were systemically studied. The results showed that the reduction in the shear strength of Ti-T2-steel under 65% rolling reduction was due to the poor interface components. The presence of brittle intermetallic compounds (IMCs) and the rapid increase of α-β Ti at the interface of Ti-T2-steel with increasing temperature were regarded as the key factors influencing interfacial failure. The formation of the TiFe 2 phase at 800 °C for Ti-Ag-steel provided major sites for the nucleation and propagation of cracks during the tensile tests, leading to interfacial delamination. The experimental elongation values of these three types of clad composites were enhanced significantly at all heat-treatment temperatures compared with the calculated elongation values using the rule of mixture (ROM). In addition, the experimental values of yield strength (YS) decreased while those of the ultimate tensile strength (UTS) increased for Ti-Ag-steel, in contrast with the corresponding values by ROM, suggesting the favourable formability of the clad composite by lamination owing to low yield ratio. [ABSTRACT FROM AUTHOR]

Through using a novel micro-coating metal additive manufacturing (MCMAM) process in this study, the forming characteristics of the multilayer single-pass specimens were investigated. The forming defects including the porosity and the bonding quality between layers were analyzed. Moreover, we also attempted to study the effect of process parameters such as flow rate, deposition velocity, and layer thickness on the forming morphology. Based on the results, the optimization of process parameters was conducted for the fabrication of thin-wall MCMAM. Finally, estimation criteria for the integrity of the interfacial bond were established. [ABSTRACT FROM AUTHOR]

Edge-glued panels are composed by the lateral and top gluing with adhesives of solid battens. These panels use small pieces of wood, offering an optimal usage of forest resources and the development of higher value-added products. The adhesive generally used to produce the panels are the synthetic ones (PVA or EPI). The polyurethane derived from castor oil may arise an alternative to replace the adhesives derived from non-natural origin, because it has no solvent in its composition, is a biodegradable material and it comes from a renewable resource. The bonding quality of this panel was performed according to BS EN 13353, which specify the minimum resistance values for panels under different humidity and temperature conditions applied to the international market. In this context, the aim of this paper was to evaluate the lateral gluing quality of Pinus taeda panels using the polyurethane derived from castor oil, as well as assess the pressing time effect on the bonding quality. The adhesive was applied into the battens surface in weight of 180 g/m. The panels were put into a cold press machine for 1, 2, 4, 8 and 24 h, totalizing five conditions and eight together/replications. The bonding quality of this panel was performed according to BS EN 13353 and BS EN 13354, under different humidity and temperature conditions. The results were submitted to statistical analysis by outlier tests, normality test, homogeneity variance, analysis of variance and mean comparison, all with 95 % reliability. The polyurethane showed acceptable values to EN-13353 for 4 h in the press machine. The test for critical humidity and temperature conditions showed a reduction in the adhesive bond strength, but still acceptable to EN-13353. Under these circumstances, it is concluded that the polyurethane derived from castor oil may be an alternative to produce lateral glued panels for dry conditions and internal and external applications for humid conditions. [ABSTRACT FROM AUTHOR]