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The research examines the outcomes of shear and flexure testing on reinforced concrete beams made from steel and polypropylene fibre. As well as assessing the impact of fibre in this structural integrity with shear strengthening ratios, certain elements in the characteristics of the cement that is both new and hardened are presented. 14 square beams being put into practice. Tests were made. There were beams produced from 7 distinct mixing dimensions, depending on the kind and the fibre content. For each composite mix there were two beams: one with and the other without stirrups. The primary changes caused by the introduction of fibres were enhanced shear strength, rigidity (especially after the first breaking stage) and ductility. The characteristics of hard concrete (tensile strength, compressive strength and elasticity modules), longitudinal reinforcement concrete, stresses in stirrups, were other factors utilized for the analysis of performance (at the compression and web zone).

Explosive cladding is known for its ability to join a wide variety of metals that other welding methods cannot do. In this present work, the weldability of aluminium alloy and mild steel plates and their bonding strength through an explosive cladding process investigation is performed. Experiments are conducted in the open air using Gelatin (SG-90) variety explosive having a detonation velocity of 3400 m/sec. Experimental trials for single replications were adopted. Ram tensile test has been carried out to determine the bonding strength. The effects of angle of inclination, loading ratio and stand-off distance on the weld strength were analyzed. The possibility of obtaining a sound weld depends on the limiting conditions of the above parameters. The microstructure of the explosive clad joints is studied for varying process parameters which shows a wavy profile that produces higher strength. The strength of the weld in both tensile and shear strength obtained is good and is within the acceptable range. An increase in strength of welded joints is obtained for higher parameter range.

ObjectivesThe aim was to investigate shear bond strengths and failure modes of four self-etch bonding agents to bovine dentin and enamel and to compare evaluation of data sets with or without exclusion of cohesive failure specimens.MethodsComposite-cylinders were bonded perpendicularly to bovine dentin and enamel surfaces. Shear-strengths were measured 24 h post-bonding of: Scotchbond Universal® (SBU, 3 M), OptiBond™ XTR (OBXTR, Kerr), OptiBond™ universal (OBU, KaVo-Kerr) and Prime & Bond active® (PBA, Dentsply-Sirona). Analysis of overall data was made via a linear mixed-model. This was repeated after exclusion of specimens associated with cohesive failures.ResultsWhen both adhesive and cohesive failures were considered, OBU and OBXTR showed comparable dentin and enamel bond strengths, whereas lower strengths were found on enamel for SBU (p < 0.001) and PBA (p = 0.015). For OBXTR higher shear strengths were measured for specimens associated with cohesive failures. When cohesive failures were excluded, the majority of shear bond strengths of adhesive failure specimens were only slightly different from overall results. However, uniquely with OBXTR dramatically lower shear bond strengths were found for dentin substrate.SignificanceAfter exclusion of cases with cohesive failures OBXTR adhesive fell behind other materials in the sequence of average shear strengths. This did not reflect the actual performance of the material. Therefore, in statistical analysis we do not recommend exclusion of data based on a specific fracture mode.

To develop a multifunctional orthodontic adhesive (QDA) using ZnO quantum-dots (ZnQDs) as modifier and investigate the antibacterial capability, fluorescence property as well as biocompatibility and bonding property.ZnQDs were synthesized using sol-gel method. XPS, XRD, FT-IR, HRTEM, SAED, DLS and spectrofluorimetry were used to characterize ZnQDs. ZnQDs were incorporated into Transbond XT adhesive paste with 20 %, 30 %, 40 % mass fraction, respectively, to form the multifunctional adhesives (QDAs). Antibacterial capability was evaluated with MTT kit, CFU count and Live/Dead Bacterial Staining Kit. Ultraviolet photography and spectrofluorimetry were used to confirm the fluorescence property of QDAs. Biocompatibility assay was performed on gingival fibroblasts and subcutaneous tissue of rats. Softening in solvent rate, shear bond strength and degree of conversion (DC) were measured.The synthesized ZnQDs presented excellent crystallinity and fluorescence properties. MTT assay, CFU count and CLSM analysis indicated that QDAs had significant antibacterial activity compared with Transbond XT adhesive paste. CCK-8 assay and Live/Dead cell staining analysis denied the cytotoxicity of QDAs and histological analysis proved that QDAs all had no inflammatory irritation to subcutaneous tissue. Softening in solvent, shear bond strength and DC evaluations indicated that 20 % mixing ratio of ZnQDs could enhance the resistance to degradation without influencing the bond strength and DC. Ultraviolet photography and spectrofluorimetry analysis proved the fluorescence capability of QDAs.ZnQDs can impart antibacterial and fluorescence properties to orthodontic adhesives without affecting biocompatibility and bonding performance. QDAs can be multifunctional orthodontic adhesives to reduce bacterial adhesion around brackets and help orthodontists remove residual adhesives precisely when needed.

This split-mouth randomized clinical trial aimed to evaluate the influence of dental enamel deproteinization with sodium hypochlorite on orthodontic accessories breakages using 2 orthodontic adhesives.Forty patients with indications for orthodontic treatment with fixed appliances were randomly divided into 2 groups according to the orthodontic adhesive used: Transbond XT (3M Unitek, Monrovia, Calif) (n = 20) and Orthocem (FGM Dental Products, Joinville, Santa Catarina, Brazil) (n = 20). A split-mouth trial was conducted in the maxillary teeth; the deproteinization process with 5% sodium hypochlorite was performed on the experimental side. The opposite side served as a control without deproteinization. The primary outcome was the number of orthodontic accessories breakages. The randomization was performed using the BioStat software (AnalystSoft Inc, Walnut, Calif). Single-blind was applied for patients. Orthodontic accessories were bonded according to the manufacturer's instructions. The accessories breakages were followed during the first 6 months of treatment. Intergroup comparisons were performed with t tests and 1 and 2-way analysis of variance.Thirty-nine patients concluded the trial. The Transbond XT group comprised 20 patients (9 male, 11 female), with a mean age of 20.77 ± 6.44 years. The Orthocem group included 19 patients (9 male, 10 female), with a mean age of 23.14 ± 7.98 years. The application of sodium hypochlorite before bonding did not influence the number of orthodontic accessories breakages (P = 0.867). The type of adhesive used, associated or not with the deproteinization, did not affect the number of orthodontic accessories breakages (P = 0.929).Enamel deproteinization with 5% sodium hypochlorite did not impact the number of orthodontic accessories breakages. In addition, the 2 bonding adhesives used showed similar clinical results, with or without the enamel deproteinization.The trial was registered at ensaiosclinicos.gov.br, ReBEC (no. RBR-39ntmjk).The protocol was not published before trial commencement.This research did not receive any grant from funding agencies.

High-performance ballistic fibers, such as aramid fiber and ultra-high-molecular-weight polyethylene (UHMWPE), are commonly used in anti-ballistic structures due to their low density, high tensile strength and high specific modulus. However, their low modulus in the thickness direction and insufficient shear strength limits their application in certain ballistic structure. In contrast, carbon fiber reinforced epoxy resin matrix composites (CFRP) have the characteristics of high modulus in the thickness direction and high shear resistance. However, carbon fibers are rarely used and applied for protection purposes. A hybridization with aramid fiber reinforced epoxy resin matrix composites (AFRP) and CFRP has the potential to improve the stiffness and the ballistic property of the typical ballistic fiber composites. The hybrid effects on the flexural property and ballistic performance of the hybrid CFRP/AFRP laminates were investigated. Through conducting mechanical property tests and ballistic tests, two sets of reliable simulation parameters for AFRP and CFRP were established using LS-DYNA software, respectively. The experimental results suggested that by increasing the content of CFRP that the flexural properties of hybrid CFRP/AFRP laminates were enhanced. The ballistic tests’ results and the simulation illustrated that the specific energy absorption by the perforation method of CFRP achieved 77.7% of AFRP. When CFRP was on the striking face, the shear resistance of the laminates and the resistance force to the projectiles was promoted at the initial penetration stage. The proportion of fiber tensile failures in the AFRP layers was also enhanced with the addition of CFRP during the penetration process. These improvements resulted in the ballistic performance of hybrid CFRP/AFRP laminates was better than AFRP when the CFRP content was 20 wt% and 30 wt%.

This double in vitro study and randomized clinical trial aimed to investigate the bonding failure rates of orthodontic brackets after enamel pretreatment with agents showing different particle sizes.For the in vitro study, 80 bovine teeth were randomly divided into 4 groups according to the pretreating method used and their particle sizes: erythritol (14 μm), glycine (18-22 μm), sodium bicarbonate (70 μm), and no pretreatment. Scanning electron microscopy microphotographs were performed after pretreatment. Then, brackets were bonded, and shear bond strength was calculated. For the clinical study, agents with low (erythritol) and high (sodium bicarbonate) particle sizes were chosen. Twenty consecutive patients willing to start fixed orthodontic treatment with vestibular stainless steel brackets were enrolled. Patients were randomly divided into 2 groups following a split-mouth design. Group A underwent a 5-second enamel pretreatment procedure with erythritol for teeth belonging to maxillary left and mandibular right quadrants, whereas the remaining quadrants were pretreated for 5 seconds with sodium bicarbonate powder. In group B, quadrants were inverted. Then, brackets were bonded on the vestibular surfaces of teeth, and patients were visited monthly for 12 months to assess bond failures. Periodontal evaluation of probing pocket depth, bleeding on probing, plaque index, and papilla bleeding index was conducted before bonding and after 1, 3, 6, and 12 months.The in vitro study showed that erythritol and control presented significantly higher shear bond strength values for other agents. Bicarbonate showed the lowest values. In the clinical study, 20 patients (aged 16.4 ± 3.9 years) were enrolled, and all completed the study. Erythritol showed a significantly lower failure rate (3%) than sodium bicarbonate (7.5%). Kaplan-Meier survival plots showed statistically significant differences in risk of failure between the 2 groups during the 12-month follow-up.Enamel pretreatment with erythritol can be a viable technique to reduce failure rates of orthodontic brackets.The trial was not registered.The protocol was not published before trial commencement.No funding or grant was received for this research.

Due to native character of thermal expansion coefficient (CTE) mismatch between Cf/SiC and GH3536, achieving high strength joint was a huge challenge for Cf/SiC-GH3536 joints. Herein, a composite filler metal of Ag-Cu-Ti + Sc2(WO4)3 was developed to join Cf/SiC and GH3536. This work introduced Sc2(WO4)3 to Ag-Cu-Ti system as a negative thermal expansion (NTE) reinforcing phase to release joint residual stress. Sc2(WO4)3 was evenly distributed in the brazing seam and reacted with Ti to form Ti3O5 reaction layer. The results of finite element analysis showed that the residual stress of the joints was effectively released by introducing Sc2(WO4)3 reinforcing phase, and the mises stress was decreased from 447 to 401 MPa. The maximum shear strength of the Cf/SiC-GH3536 joint brazed with Ag-Cu-Ti + 6 vol% Sc2(WO4)3 filler alloys was 64 MPa, which was about 2.6 times higher than that of Ag-Cu-Ti alloys. The results of this study provide a promising strategy for the introduction of new Sc2(WO4)3 reinforcing phase in Ag-Cu-Ti system, and improve the reliability and feasibility of composite brazing alloy in brazing filed.

The exploration towards cost-effective filler metal for ceramics joining has always been the key issues for ceramics joining. Herein, we reveal that the Al metal prefers to spread on the ZrO2 based ceramic under the air heating condition, due to the geometric limit effects by in-situ formed dense Al2O3 surface. Inspired by this, the joining of ZrO2 based ceramics was realized in air with Al metal as filler, through the diffusion of Al towards ceramic side. The Al element can induce obvious interfacial bonding effect on Al2O3 layer and ZrO2 ceramic, where the hybridization among the Al-p, Zr-d and O-p orbitals plays a key role. The in-situ formed Al2O3 layer on Al filler surface is vital for forming the fine interface (shear strength of ∼36 MPa), which results in the relief of lattice mismatch and peak stress at ceramic-filler metal transition interface.

To improve the Al/Mg bimetallic interface, La was added into the Al/Mg bimetallic interface manufactured by a compound casting process. The effect of La addition on the microstructure, mechanical properties and fracture behavior of the Al/Mg bimetallic interface and the formation mechanism of the interface were studied in detail. Al11La3, Al8Mn4La, Al20Ti2La, and other rare earth precipitates (RE precipitates) preferentially precipitated at the interface with La addition, while the number of the Al11La3 and Al8Mn4La located in eutectic structure area (E area) gradually increased and aggregated in the interface with the increase of the La content. Besides, the matrix structure in different areas of the Al/Mg interface changed in different degrees, and the eutectic structure and primary γ (Mg17Al12) dendrites in the E area were refined, but the intermetallic compounds area (IMC area) had no obvious change. With the addition of the La, the interface was strengthened under the comprehensive effect of refinement strengthening and precipitation strengthening from the E area. When the La content increased to 1.0%, the shear strength of the Al/Mg bimetal reached the maximum of 51.54 MPa, which was 30.95% higher than the group without La addition. However, with the further increase of the La content, the large area aggregation of the Al11La3 and Al8Mn4La occurred in the interface, leading to the separation of the matrix structure of the E area and the decrease of the shear strength of the Al/Mg interface.

To investigate the effect of silane contents on their chemical interaction with 10-methacryloyloxydecyl-dihydrogen phosphate (MDP), and affecting the bonding of MDP to zirconia by time-of-flight secondary ion mass spectrometry (TOF-SIMS) and solid-state nuclear magnetic resonance (SSNMR) spectroscopy.Zirconia (Cercon ht, Dentsply) slabs were prepared and fully sintered. Experimental primers SE-5 and SE-10 were formulated by adding 5 wt% and 10 wt% γ-methacryloxypropyltrimethoxysilane to an MDP-based primer SE BOND (SE), respectively. SE, SE-5, and SE-10 were applied on the assigned zirconia slabs. The chemical compositions on the surface and adhesive interfaces were examined by TOF-SIMS in a depth-profiling mode. Hydrophilicity and resin affinity of treated zirconia were analyzed. The bond strengths to resin cylinder were examined either after 24-h storage or thermocycles. In addition, zirconia powders treated with three primers were assessed by SSNMR spectrometry for the adsorption of MDP.TOF-SIMS analysis showed that SE treatment generated the greatest amount of P-O-Zr related ions, which reduced in SE-5 and SE-10 groups. The 3D ion-images illustrated the generation of ZrOMDP adsorption onto zirconia via P-O-Zr ionic bond promotes bonding with resin. The silane enhances the hydroxylation of zirconia and impairs the adsorption of MDP, but does not adversely affect the bond durability.

For estimating the long-term stability of underground framework, it is vital to learn the mechanical and rheological characteristics of rock in multiple water saturation conditions. However, the majority of previous studies explored the rheological properties of rock in air-dried and water saturated conditions, as well as the water effects on compressive and tensile strengths. In this study, andesite was subjected to direct shear tests under five water saturation conditions, which were controlled by varying the wetting and drying time. The tests were conducted at alternating displacement rates under three vertical stresses. The results reveal that the shear strength decreases exponentially as water saturation increases, and that the increase in shear strength with a tenfold increase in displacement rate is nearly constant for each of the vertical stresses. Based on the findings of the shear tests in this study and the compression and tension tests in previous studies, the influences of both water saturation and loading rate on the Hoek-Brown failure criterion for the andesite was examined. These results indicate that the brittleness index of the andesite, which is defined as the ratio of uniaxial compressive strength to tensile strength, is independent of both water saturation and loading rate and that the influences of the water saturation dependence and the loading rate dependence of the failure criterion can be converted between each other.

Surface structure of C/C composites has been regulated through electrochemical corrosion at room temperature to modify the residual stress and improve the joining strength when brazed to Nb. The unique crevice corrosion in C/C composites is investigated to reveal the change of corrosion depth and fiber size. The interlacing zone of carbon fiber reinforced brazing alloy replaces the reaction layer in the original joint. Joining area is increased dramatically and the continuous crack will be hindered. The interlacing zone eliminates the stress concentration and relieves the residual stress through reducing the property mismatch. All advantages contribute to the joining quality of C/C Nb. Shear strength of C/C Nb joint with 80 μm depth reached 37.7 MPa, which was 1.2 times higher than that of original joint. Surface structure design of C/C composites not only expands the application in structure component, but also exhibits the promising application in energy field.

A novel carbonized phenolic formaldehyde resin (PF) resin-coated Ni foam was used as an interlayer for brazing carbon fiber reinforced carbon composites (C/C) and Nb using a Ti–Ni filler. At first, uniformly distributed carbonaceous laminae with different mass fractions on the Ni foam surface were acquired after the carbonization process by controlling the concentration of the PF solution. Afterwards, the obtained carbonaceous laminae covered Ni foam composite (C-Nif) was applied as an interlayer for brazing C/C and Nb via an assembly of C/C/Ti foil/Ni foil/C-Nif interlayer/Ti foil/Nb. The morphologies and microstructures of the carbonization product and the interfacial microstructures of the joints were investigated. The brazing mechanism has been elaborated in detail. With the help of the interconnected porous structure of the Ni foam, the distribution of the in-situ formed (Ti,Nb)2Ni particles, (Ti,Nb)C ring reinforcements as well as the Nb solid solution were uniformly obtained throughout the brazing seam. As a result, the joint residual stress was effectively released and consequently, the joint shear strength at elevated temperature (1000 °C) reached up to 33 MPa, which is 4.5 times higher than the directly brazed joint without an interlayer.

The wettability of 3 mol% yttria-stabilized zirconia (3YSZ) by molten Cu was noticeably improved by applying a direct current (DC). Furthermore, robust brazing of 3YSZ to a GH3128 superalloy using a Cu filler was achieved within seconds at 1100 °C with the assistance of a DC. When the DC flowed from 3YSZ to GH3128, the shear strength of the joints reached 225 ± 20 MPa at 1 s of energization and increased to 330 ± 30 MPa at 5 s of energization. The formation of Cu51Zr14 at the 3YSZ/Cu interface, the dissolution of Ni into the Cu filler, the dispersive distribution of fine granular (Mo, Cr, W)(Ni, Cu) in the brazing seam and the relief of residual stress by ductile (Cu, Ni) solid solution were crucial for achieving the high-strength joints. This work provides a novel and economical method for ultrafast brazing of zirconia to metals.

The effects of heat treatment on the mechanical properties of plain-woven SiC/SiC composites at 927 °C and 1200 °C in argon were evaluated through tensile tests at room temperature and at elevated temperature on the as-received and heat-treated plain-woven SiC/SiC composites, respectively. Heat treatment can improve the mechanical properties of composites at room temperature due to the release of thermal residual stress. Although heat treatment can damage the fiber, the effect of this damage on the mechanical properties of composites is generally less than the effect of thermal residual stress. Heat treatment will graphitize the pyrolytic carbon interface and reduce its shear strength. Testing temperature will affect the expansion or contraction of the components in the composites, thereby changing the stress state of the components. This study can provide guidance for the optimization of processing of ceramic matrix composites and the structural design in high-temperature environments.

In this work, porous Si3N4 ceramics were successfully and ultrasonically soldered using Sn9Zn2Al solder through sonocapillary and cavitation. Si3N4 ceramics were first ultrasonically wetted and then soldered. The results show that porous Si3N4 ceramics can be wetted in the air within extreme short time of 10 s under ultrasonic. The capillary filling distance of the solder into the ceramic micro-channels achieves a value of 60 μm within 10 s and increases with prolonged ultrasonic time and high ultrasonic power. The infiltrated solder tightly bonded with the ceramic rod. The shear strength of the joint increases at prolonged ultrasonic time and becomes stable after 60 s. A geometric model is built to analyze the infiltration mechanism of the solder, and the result shows that the acoustic pressure inside the solder can reach 4 MPa, which is much higher than the pressure (0.32–1.4 MPa) needed for the sonocapillary action. The wetting mechanism of the solder to the ceramic is analyzed based on the cavitation bubble dynamics calculation. The high liquid velocity, pressure and temperature caused by the collapse of the cavitation bubble serve as the main factors that wet the ceramic.

To determine whether the composition of universal adhesives and the use of silane coupling agents could affect the fatigue strength of composite repair.Composite samples were aged in water at 37 °C for 90 days and bonded to fresh composite to produce twin-bonded bar-shaped composite specimens (2 × 2 × 12 mm). Five universal adhesives, a multistep composite repair system and a hydrophobic solvent-free resin associated to a separate silane coupling agent application were used for bonding. Composite samples were tested under 4-pointflexure initially at quasi-static loading (n = 12) followed by cyclic loading (n = 25). The stress-life fatigue behavior was evaluated following the staircase method at 4 Hz. The unfractured side of cyclic loaded beams were evaluated under SEM to determine crack initiation sites. Fatigue data was analyzed by ANOVA and Tukey test and Wilcoxon Rank Sum Test (α = 0.05).Bonding protocols were unable to restore the cohesive strength of the nanofilled composite (p 0.05). Fatigue testing was more discriminative to reveal discrepancies in composite repair than conventional quasi-static loading. While the composition of universal adhesives affected composite repair potential, the highest endurance limits occurred for the separate silane coupling agent application. Crack propagation sites were mostly located on the aged composite surface.Although a trend for simplification invariably overruns current adhesive dentistry, composite repair using solely universal adhesives may result in inferior repair potential. The additonal use of silane coupling agents remains as an important procedure in composite repairs.

Geocomposites are extensively used in asphalt pavements as they provide significant long-term pavement benefits. Indeed, when correctly installed, geocomposites enhance road pavement performance thanks to their waterproofing properties, stress absorbing membrane interlayer (SAMI) action and improved mechanical strength of the pavement. Nevertheless, the presence of an interlayer causes de-bonding effects that negatively influence the overall pavement characteristics. This paper presents an experimental investigation aimed at comparing the interlayer bonding characteristics of four different geocomposites with an unreinforced reference configuration, laid on an Italian motorway section, in which the reinforcement depth and the lower layer surface condition (milled or new) were also varied. Interlayer shear strength (ISS) was measured, on both cores and laboratory produced specimens, through Leutner and Ancona Shear Testing Research and Analysis (ASTRA) equipment. The ISS results showed that geocomposites can be successfully applied directly on milled surfaces. Moreover, the application of a normal stress, as in the ASTRA device, tends to mitigate any difference related to the specimen heterogeneity. Finally, existing laws, which correlate the results obtained with different shear equipment on unreinforced interfaces, were generalized by considering the presence of geocomposites and the corresponding ISS specification limits were proposed for both ASTRA and Leutner test.

The cyclic properties of geosynthetic soil interface are crucial for reinforced soil structures subject to seismic loading. A series of cyclic direct tests under cyclic normal loading was conducted on geogrid-gravel interface. The relationship among the amplitudes of cyclic normal loading and shear displacement and frequencies in the horizontal and vertical directions with interface shear strength and volume change was investigated. Test results showed that the relative time shift, shear stiffness, and enhance coefficient increased with increasing amplitude of cyclic normal loading. The interface exhibited shear hardening and softening with increasing amplitude of shear displacement. The vertical displacement decreased with increasing amplitude of cyclic normal loading but increased with increasing amplitude of shear displacement. Furthermore, three patterns were analysed for different frequencies in two loading directions. The value of vertical displacement was largest when the normal loading impact frequency was larger than the cyclic horizontal shear frequency, and smallest at equal frequencies in two loading directions. The shear stiffness was positively correlated with the amplitude of cyclic normal loading. However, it was negatively correlated with the amplitude of shear displacement. The value of the damping ratio was smallest under constant normal loading at a shear displacement amplitude of 0.5 mm.

To extend the application of the SiO2f/SiO2 composites, self-joining process is indispensable. Reliable self-joining of SiO2f/SiO2 composites was achieved by Bi2O3–B2O3–ZnO glass. With a low glass transition temperature, the onset temperature of residual stress is much lower than that of active brazing. In addition, bismuth glass exhibits a good wettability on the surface of SiO2f/SiO2 composites. When the joints were brazed at 750 °C/30 min, the average shear strength of the joints reached 21.2 MPa, reaching 77.8% of the shear strength of SiO2f/SiO2 composites. This technology can effectively fill the bank of self-joining of SiO2f/SiO2 composites.

Reactive air brazing of Si3N4 ceramic was successfully achieved by using Ag-CuO filler metal. The effects of CuO content on the wettability of Ag-CuO/Si3N4 system and the shear strength of Si3N4/Si3N4 joint were investigated, and meanwhile the interfacial behavior was analyzed and discussed. Moreover, the work of adhesion, interfacial energy, and electronic properties of Ag/Si3N4, Ag/CuO and Ag/SiO2 interfaces were evaluated by first-principles calculations. The Ag-CuO/Si3N4 system transforms from no-wetting into wetting due to the oxidation of Si3N4 substrate and the formation of SiO2 layer on the substrate surface. The maximum average joint shear strength of over 50 MPa is obtained as the CuO content is 8 at.%. Compared with the Ag(111)/Si3N4(0001) interface, the Ag(110)/CuO(001) and Ag(110)/SiO2(001) interfaces show stronger interfacial bonding due to the formation of Ag-O ionic bond, indicating that the addition of CuO and the formation of SiO2 contribute to the enhancement of interfacial bonding.

Due to the mismatched impact parameters between the velocity and the angle, a joint with an unbonded zone in the middle and the microdefects at the interface was fabricated by magnetic pulse welding (MPW). In this study, an oblique angle in the working zone was prefabricated to make an inclined-wall field shaper (FS) for MPW and thereby improve the quality of the joint. The effects of the span and size of the inclined wall on the impact parameters were evaluated by numerical simulations. With increasing span, the location where the maximum impact velocity occurred approached the free end of the joint. With increasing size of angle, the initial impact angle evidently increased. The microstructure indicated that the flat interface was changed into the wavy one, and the thick transition layer with microdefects could be removed using an inclined-wall FS. The double bonding zone was changed into the single one, which formed a continuous range with a length of above 3 mm where the impact parameters matched with each other. The length of the unbonded zone in the initial collision zone decreased from about 1 mm to 0.3 mm via using an inclined-wall FS with the span of 6.4 mm and the size of 5°. Shear test results showed that the zones with high strength were merged in the initial collision region. The maximum shear strength of about 81 MPa could be obtained using an inclined-wall FS with the size of 3° and the span of 6.4 mm, which was increased by 33% higher than that without an inclined wall.

InSn-50Ag composite solder joints doping Ni-coated carbon nanotubes (Ni-CNTs) were fabricated by transient liquid phase (TLP) bonding, and then the effect of Ni-CNTs contents (x = 0, 0.01, 0.03, 0.05, 0.07, 0.1 wt%) on the microstructure and shear property of the composite solder joints was examined. The results showed that the microstructure of Cu/InSn-50Ag-x(Ni-CNTs)/Cu composite solder joints consisted of the interfacial region bamboo-type Cu3(In, Sn), solder center region Ag3In, Ni3Sn4, Ag particles and Ni-CNTs. The appropriate amounts of Ni-CNTs (about 0.07 wt%) are conducive to form a compact composite solder joint and restrain the growth of interfacial Cu3(In, Sn) IMC layer, and the morphologies of IMC layer are determined by Ni-CNTs suppressing atom diffusion and IMC grain orientation. The shear strength of composite solder joints relates to Ni-CNTs content, and the maximum shear strength reaches 42 MPa of Cu/InSn-50Ag-0.07(Ni-CNTs)/Cu. It is regulated by uniform distribution of Ni-CNTs, refined Ag3In grains and interface IMC layer with near-continuous voids. The fracture of the composite solder joints doped Ni-CNTs occurred near to the boundary between the interfacial IMC layer and solder center region, the fracture mechanism is ductile fracture.

This study focuses on the transient liquid phase (TLP) bonding of DD5 single-crystal superalloy to CrCoNi-based medium-entropy alloy (MEA) using a BNi-2 filler alloy. The microstructure and mechanical properties of the TLP-bonded DD5/MEA joint were evaluated, and the microstructural evolution mechanism was investigated. The formation of the isothermal solidification zone (ISZ) depended on the diffusion of the melting-point depressants (Si and B elements) from the liquid filler into the DD5 and MEA substrates, as well as the dissolution of the substrates. Boron diffused along the γ channel of DD5 and reacted to form M5B3 boride, herein referred to as the diffusion-affected zone (DAZ I). Similarly, the Cr5B3 boride precipitated in the Ni-rich MEA matrix adjacent to the MEA substrate (i.e., DAZ II). Additionally, a coherent orientation of [0]BCT // [0 1 1]FCC and (0 0 2)BCT // (2 0 0)FCC was detected between M5B3 boride with a body-centered tetragonal (BCT) structure and the face-centered cubic (FCC) matrix. The performance of the joint was dominated by the properties of the bonding seam. As the bonding time increased from 20 to 80 min, the athermal solidification zone (including eutectic microstructure) was gradually replaced by the ISZ exhibiting excellent plastic deformation capability, and the shear strength of the joint was improved. The maximum shear strength (752 MPa) was achieved when the eutectic-free joint was bonded at 1050 °C for 80 min. The fracture morphology revealed a mixture mode, indicating the initiation of cracks in the DAZ II, mainly propagating in the ISZ, and passing through the DAZ I.

Stainless steel reinforcing rebars and prestressing strands are viable alternatives to carbon steel materials for prestressed concrete structures in extremely aggressive environments. They offer better durability and require less maintenance. This study experimentally investigated the transfer length and prestress losses of 15.2-mm- (0.6-in.-) diameter Duplex High-Strength Stainless Steel (HSSS) strands as well as the shear and flexural behavior of two full-scale 12.8-m- (42-ft-) long AASHTO Type II concrete girders prestressed with HSSS strands and reinforced with duplex stainless steel rebars. The girders were made composite by adding a deck slab. One girder was tested in shear at both ends while the other girder was tested in flexure. Experimental shear and flexural behavior of the girders exhibited a constant increase in load carrying capacity up to failure. The failure mode for the shear tests was web shear, and for the flexural test was rupture of the HSSS strands. Both girders tested in shear and flexure failed in a progressive manner as they exhibited adequate warning through noticeable deflection, excessive cracking, and large reserve strength from first cracking to failure. The applicability of AASHTO LRFD provision for stainless steel reinforcing materials was investigated. AASHTO LRFD equations for flexural resistance were modified to cover rupture of strand failure mode. Experimental shear strength and flexural strength of the girders were greater than the predicted values by AASHTO shear equations and modified AASHTO flexural equations, respectively.

The primary objective of the current investigation is to evaluate the low-velocity impact behaviour and mechanical properties of low volume fibres reinforced self-compacting concrete made with 30% GGBS as a replacement of cement with a water powder ratio of 0.3. The steel, basalt and glass fibres of length 22 and 30 mm with low volume fractions of 0.25, 0.5 and 0.75% are used for this investigation. The self-compatibility of concrete is confirmed by testing the slump flow test. The addition of fibers reinforced in the concrete decreases flow as compared without fibers reinforced conrete, flow value decreased in basalt and glass as compare to steel fiber reinforced concrete. The compressive, flexural, split tensile strength and low-velocity impact resistance, shear strength were conducted after 28 days of water curing. The experimental results show that the compressive strength is only a marginal strength improvement was observed in the steel fibre reinforce self-compacting concrete mixes. The high tensile, flexural, shear strength were observed in 30% replacement of GGBS with 0.75% of steel fibres of 30 mm length. The results of the experiments express that incorporation ratio of steel fibre reinforced concrete improves the strength, remarkably tensile, flexural and shear strength as compared with the control and other fibers reinforced concrete. A significant improvement was observed in impact energy of steel fibrous reinforced concretes as compared with the control mix of self compacting concrete. The results demonstrate that use of steel fiber is reinforced in the self compacting conrete including ground granulated blast furnance slag, the impact energy and the ductility characterstics of the self compacting fiber reinforced concrete are noticeably increased.

This study provides a review of the research on the interfacial shear strength (IFSS) of the carbon nanotube (CNT) reinforced polymer composites. The IFSS reflects the efficiency of transferring load between the reinforced fiber and its surrounding matrix, which plays a critical part in determining the characteristics of the composite. The review focuses on the experimental as well as theoretical/modeling studies of the CNT and the polymer matrix interface. The major techniques required for the measurement of the IFSS of the composites have been discussed. The methods to enhance the shear strength at the interface along with the functionalization of CNT and the advantages and disadvantages have been explained in detail. Moreover, the review presents some of the research opportunities associated with IFSS for the growth and enhancement of the mechanical properties of the CNT-reinforced polymer nanocomposites.

AlN ceramic was successfully wetted and then joined with nonactive Sn9Zn eutectic solder assisted by ultrasonication in air. The effect of ultrasonic time on the formation of joint was studied. Results indicated that the defect-free joint can be obtained at an ultrasonic time of 5 s. Two regions, namely, AlN/Sn (s,_s) and AlN/Zn (s,_s), were found in the bonding interface. Zn and O accumulated in the AlN/Sn (s,_s) interface. An amorphous and nanocrystalline layer of ZnO formed in the hard-wet AlN surface. And Zn (s,_s) directly bonded with AlN. The low temperature and fast bonding of the AlN was attributed to the high pressure and temperature caused by cavitation effect. The shear strength of the joint increased from 10.6 MPa to 30.7 MPa when the ultrasonic treatment time increased from 5 s to 150 s. With the prolongation of ultrasonic time, more AlN ceramic particles entered the solder and acted as the reinforcing phase.

This paper investigates the accuracy of different design equations given in design specifications and literatures in determining the block shear strength of the lean duplex stainless steel fillet welded connections with base metal fracture. It points out the problem inherent in the block shear provision specified in the North American cold-formed design specification, which does not consider shear strain hardening. The previous test results have found that full shear strain hardening can be assumed for the carbon steel and ferritic stainless steel welded connections, but not applicable to the thin-walled lean duplex stainless steel welded connections with a higher ratio of the tensile strength to yield stress. Based on the results of finite element analysis including ductile damage simulation, this study reveals that the block shear strength of the lean duplex stainless steel specimens can be determined accurately using the mean between the shear yield stress and the shear ultimate stress. This paper also investigates the effect of stress triaxiality incorporated in the block shear equations found in the literature through comparative analysis with the bolted connection. The effect is shown to be negligible for the thin-walled lean duplex stainless steel welded connection, although higher stress triaxiality is developed in welded connection than in bolted connection. This paper recommends a block shear equation assuming the normal tensile stress in the net area in conjunction with partial shear strain hardening. The recommended equation was found to be more accurate than other equations for determining the block shear strength of the thin-walled lean duplex stainless steel welded connections.

In the present study, value added and environment-friendly adhesive material is prepared from post-consumer (used) expanded polystyrene (PCEPS) for possible applications. The physico-chemical properties of the prepared adhesives, such as, solubility, viscosity, shear strength/bonding strength, moisture content are estimated as per the standard procedures. The study shows that PCEPS is sufficiently soluble in various solvents, such as, m-xylene, n-BA, THF, MEK etc. Various substrate materials, such as, paper, wood, cement and clay bricks, and ceramic tiles are considered to check the suitability of the prepared adhesive to bind them. The study indicated that the prepared adhesive (PCEPS-MEK) is suitable to bind various substrate materials mentioned above. The study further extended to bind the metal (iron) substrates with PCEPS adhesive. From the results, it is noticed that PCEPS adhesive offered lower bonding strength over commercial adhesive Araldite. Therefore, the study furthermore extended to improve the PCEPS adhesive bonding strength using two different additives. The result implied that the bonding strength of the EPS adhesive decreased drastically with the increase of Additive-1 (A1). However, the bonding strength of EPS adhesive increased in presence of Additive-2 (A2) and its loading. Around 69% increment in bonding strength of PCEPS adhesive is obtained when the Additive-2 loading is increased up to 50 wt% under present experimental conditions. Therefore, Additive-2 can be used as one of the suitable additives to improve the PCEPS adhesive properties especially bonding strength.

Martensitic stainless steels (MSS) are often used to manufacture fasteners such as bolts that are used to secure critical components operating at high temperature environments. Particularly, it is often observed that AISI 431 MSS bolts fractured by shear when force is applied to untighten it during maintenance. This experimental study aims to investigate the shear strength and hardness of AISI 431 MSS after subjected to high temperature heating and deduce the failure mechanism of the material when shear load is applied. Double shear test and hardness test were conducted on numerous AISI 431 MSS rod samples after subjected to heating that ranged from room temperature (RT) to 900 °C while fracture morphology was studied by means of Field Emission Scanning Electron Microscope (FESEM). Results showed that shear strength after heating was almost consistent with little changes up to 500 °C followed by a slight degradation of strength between 500 °C and 700 °C. As for the heating above 700 °C, a significant increase in strength was observed. Adding on, the notable decrease of hardness between 500 °C and 700 °C suggested that this is the tempering temperature region where ductility is enhanced. Fracture morphology showed that failure is contributed by a mixed mode of brittle and ductile failure with ductile failure by dimple rupture being the final failure mechanism.

In this work, we developed a new β-LiAlSi2O6/Mg2SiO4 glass-ceramic interlayer to join dense Si3N4 and porous Si3N4 ceramics for high-temperature applications. The microstructure and phases of the joint were investigated using systematic analysis methods and the mechanism for the interfacial bonding was proposed. The double crystalline phases of β-LiAlSi2O6 and Mg2SiO4 precipitated in the joint seam during the joining process, forming a novel glass-ceramic interlayer with high crystallinity. Due to the good wettability of liquid glass on porous Si3N4, a gradient and dense infiltration layer was formed in porous Si3N4 and reinforced it, which improved the mechanical strength of the whole joint. In this case, the shear strength of the joint reached 78 MPa, and it could still maintain 74 MPa up to 850 °C, which fully demonstrated the high-temperature resistance of the joint.

An experimental investigation into the shear behavior of Glass Fiber Reinforced Polymer (GFRP) reinforced concrete beams is presented. The study also looks at the effectiveness of shear strengthening of such beams using externally-bonded Carbon Fiber Reinforced Polymer (EB-CFRP) sheets and investigates the possibility of interaction between internal and externally bonded shear reinforcement. A total of 18 beams, 2.4 m long with a rectangular cross-section of 300x200, reinforced with GFRP bars and stirrups were tested. Three types of concrete were used in this study; ordinary Portland cement (OPC) concrete, Fiber Reinforced concrete (FRC), and Geopolymer concrete (GPC). Six beams, two for each concrete type, severed as control while the other twelve were strengthened using “U” shape EB-CFRP sheets. The CFRP sheets were placed in two different arrangements, above and in-between internal stirrups locations. The results indicate that GFRP is a viable reinforcement for GPC, OPCC, and FRC, whereas EB-CFRP proves to be a feasible strengthening technique for such composite systems. The gain in shear strength for EB-CFRP strips beams on the location of internal stirrups is 5–10% lower as compared to the other arrangement. The difference in the strength gain may indicate a possible interaction between the internal and external shear reinforcement.

The superplastic forming/diffusion bonding (SPF/DB) process has been proved to be an effective way to fabricate multi-layer integrated structures. During this study, a hollow structure with two stiffeners was manufactured by SPF/DB process using TA7 titanium alloy. The tensile behavior of the alloy was investigated by undertaking uni-axial tensile tests at high temperature, with results showing that the maximum elongation was 199.8% at 870 °C/0.001 s−1. Diffusion bonding experiments utilizing TA7 titanium alloy were conducted at different temperatures. The shear strength of DB joints at 880 °C and 900 °C were 568.4 MPa and 569.1 MPa, respectively. Based on the superplastic properties, a finite element simulation of the hollow structure was carried out, with results showing that this could be fabricated by the DB/SPF process. Finally, fabrication of this hollow structure was successfully demonstrated by DB at 880 °C/2 MPa/1 h and SPF at 870 °C with a target strain rate of 0.001 s−1. Thickness measurements indicated that the maximum reduction in thickness was approximately 10% and occurred at the short stiffener. The experimental result was less than the predicted reduction from the finite element simulation. When comparing the tensile strength and elongation of the initial material, the reduction in the manufactured material was 9.4% and 0.4%, respectively. The microstructure was characterized and the average grain size was measured to increase from 7.5 μm to 14.8 μm.

This article conducts a theoretical and experimental analysis of three dimensional (3D) finite element (FE) model to anticipate the shear strength, load–deflection, and crack pattern of fourteen Hybrid Glass Fiber Reinforced Polymers (GFRP)/Steel Bars in Reinforced Concrete Beams without stirrups by ANSYS. The reinforced concrete beams are simply supported. All beams cross-sections were of 120 mm breadth and variable depth; the overall length was 2300 mm with a clear span of 2000 mm without stirrups. In this paper, the adopted variables are; concrete compressive strength ( f c ' ), shear span to depth ratio (a/d), depth of beam (d), and the reinforcement ratio (ρ). In hybrid GFRP/steel reinforced concrete beams, the experiments demonstrate a significant improvement in ductility and an apparent decrease in deflection and deformation of the beams. In contrast, during cracking initiation and propagation, better performance is found in hybrid GFRP/steel reinforced concrete beams. A comparison is conducted between the results of the ANSYS and the experiment to ensure that the finite element model is accurate. Additionally, each parameter's effect was described and compared to experimental results. The FE models’ theoretical conclusions are in acceptable agreement with the experimental outcomes.

In this study, the investigation of effective stresses of Titanium Grade 5 feedstock material during the continuous forming process has been carried out. The numerical simulation has been carried out through a finite element tool DEFORM-3D. The experimental plan and design have been carried out by using Response Surface Methodology (RSM) on MINTAB platform by considering extrusion wheel velocity and feedstock temperature as main extrusion parameters. Effective-stresses of Ti-6Al-4 V alloy have been investigated to understand the deformation behavior for further more applicability of feedstock material in the modern industrial sector and to keep the shoe and other components of the CONFORM machine safe. It has been found that the effective-stress of feedstock material is high in the biting - deformation region and then gradually decreases towards the flowing direction of the material. It has been observed that as the feedstock temperature increases, the value of effective stresses which occur in other region decreases to some extent. So, the result concludes that increasing extrusion wheel velocity and feedstock temperature of alloy will reduce the shear strength of feedstock material during the continuous forming process. Therefore, the load requirement for deformation can be reduced. Moreover, the wear of extrusion shoe which is one of the most important elements can also be minimized thereby enhancing the life of extrusion shoe material.

Over the past decade, Polyvinyl Chloride (PVC) stay-in-place formwork has become a popular alternative for conventional formwork in concrete construction industry due to its relatively lower cost of construction and ease of assembly. The PVC panels are joined using connectors and serve as a permanent formwork into which fresh concrete is poured to form composite PVC encased concrete walls. This study has experimentally investigated the effects of using macro-synthetic fibre reinforced concrete on the interface shear strength of composite PVC encased walls in comparison with composite PVC encased walls filled with conventional plain concrete and reinforced concrete. Nine composite PVC encased concrete wall specimens were cast and tested using direct shear tests. Based on the load–deflection curves obtained from the direct shear tests, the maximum shear loads and interface shear strength values were determined for three different cases including i) test specimens filled with plain concrete, ii) test specimens filled with macro-synthetic fibre reinforced concrete, and iii) test specimens filled with reinforced concrete. The determined parameters as well as the measured load–deflection curves for the three cases were compared and the final findings have been discussed. Based on the outcomes of this study, it has become apparent that the tested composite PVC encased macro-synthetic fibre reinforced concrete wall specimens can noticeably exhibit higher interface shear strength values compared to the tested wall specimens filled with plain concrete. Since AS 3600 (2018) does not prescribe the shear plane surface coefficients for determining the interface shear strength of composite PVC encased concrete walls, in order to enable structural designers to determine the interface shear strength for those panels using AS 3600 (2018), those coefficients have been extracted from the test results for the three mentioned cases and proposed for practical applications.

This paper presents a semi-empirical model to estimate the ultimate shear strength of steel fiber-reinforced concrete (SFRC) beams without shear reinforcement using the gene expression programming (GEP) technique. An extensive, reliable dataset consisting of the data of 266 SFRC beams with no stirrups was established for the development of this model. The most effective variables including the compressive strength ( f c ' ), ratio of shear span-to-effective depth ( a / d ), ratio of flexural reinforcement ( ρ ), and fiber factor ( F ) were employed as input parameters in the GEP-based modeling. The accuracy of the proposed model was verified by its ability to predict a portion of data that had not been used in the training phase. Moreover, the performance of the model was evaluated using different statistical criteria. Sensitivity analysis and parametric studies were conducted on the proposed model to determine its ability to correctly consider the effect of input parameters for predicting the ultimate shear strength. In addition, the proposed model was compared with some other models proposed in the literature, and it was found that the proposed model demonstrates the best performance and accuracy among the considered shear strength prediction models.

In the UHPC-steel composite bridge deck, the thickness of UHPC layer is usually only 40–50 mm, so short headed studs are used for shear connection of the interface between UHPC and steel deck. In this paper, the refined finite element (FE) model of push-out specimen is established to explore failure mode of the stud connection, damage concentration location of UHPC and load-slip behavior of UHPC-steel interface. Verified against the existing test results, FE parameter analysis is conducted, and shear strength formula and load-slip relationship of short headed stud embedded in UHPC are proposed. With the consideration of reduction effect of group studs, the shear strength formula of single stud can be used to simplify the calculation safely. A nominal shear stress S-N curve with 95% survival probability is proposed, fitted by the International Institute of Welding (IIW) recommended method. Based on the fracture mechanics method, a fatigue life evaluation formula of stud under influence of multiple factors is established. By the comparative analysis between the proposed formulas and the existing codified formulas for stud connection in ordinary concrete, the recommended formula for the fatigue strength of stud in UHPC is proposed.

Background: This study aimed to evaluate the effect of the combination of zinc oxide nanoparticles (NPs) and chitosan NPs on the shear bond strength (SBS) of composites used for orthodontic bonding. Methods: Four groups of composites (n = 10), containing 0%, 1%, 5%, and 10% w/w NP fillers, respectively, were used to bond brackets to the surfaces of 40 intact bovine incisors. After 1000 rounds of thermal cycling at 5°C–55°C, all specimens were mounted in acrylic blocks. The SBS was tested using a universal testing machine, and the adhesive remnant index scores were registered using a stereomicroscope. Data were statistically analyzed using a 1-way ANOVA and the Kruskal–Wallis test. Results: The highest value of mean SBS was found in the control group, and the lowest value was found in the group with composite containing 10% NPs. The adhesive remnant index did not differ significantly among the groups (P = 0.823). Conclusions: Incorporation of 1% and 5% zinc oxide and chitosan NPs had no effect on the SBS of composite, and the obtained SBS values were similar to that of the control group.

Although the shear behaviors of silt–structure interfaces are critical in engineering practice, they have not been extensively investigated systematically. In this study, the influence of the silt water content and interface roughness on the shear behaviors of silt–cement mortar interfaces is investigated. Forty–eight silt–cement mortar structure interface tests and 18 silt direct shear tests were carried out. The results indicated that as the water content of the silt gradually increased to saturation, the interface shear stress–displacement curves changed from strain softening to strain hardening, and the interface shear strength decreased significantly. The shear strength of the rough interface was found to be significantly greater than of the silt, and the shear strength of the smooth interface was found to be lower than that of the silt. The interface shear strength gradually increased with the surface roughness, but the increase tended to be gentle. A large shear deformation was observed, and this increased with the decrease in soil water content and the increase (up to a point) in interface roughness. A model of the interface shear strength between unsaturated soil and structures considering the influence of water content and interface roughness was established and verified.

Ultra high-performance concrete (UHPC) is becoming a promising solution in steel–concrete composite bridges to improve the structural performance and durability of bridge decks. In contrast with conventional concrete, the excellent properties of UHPC allow for thinner and lighter designs with more efficient connections. In this study, the feasibility of large-diameter (30 mm) stud connection in thin UHPC slab was investigated to fully utilize the mechanical advantages of UHPC. The proposed composite structures employed large-diameter short stud (aspect ratio of 2.0) and UHPC slab as thin as 75 mm. Push-out tests were performed on 15 specimens with varying stud length, diameter and slab thickness. The use of large-diameter studs significantly increased the shear strength and ensured desirable failure mode of stud fracturing. The reduction of slab thickness from 150 to 75 mm resulted in little change to the shear strength, but splitting cracks appeared on the outer slab surface. Marginal effect on the shear strength was observed for large-diameter studs as the stud aspect ratio decreased from 4 to 2 and the cover thickness was reduced to 15 mm. The test results showed two main failure modes, including stud fracture via local crushing and stud fracture with UHPC pry-out. Finite element model was established to further study the stud-UHPC composite mechanism. These findings demonstrated the suitability of using short large-diameter stud and thin UHPC slab to reduce the self-weight and improve shear performance of composite structures.

Widely used formaldehyde-based resins for modern wood-based panels are toxic to humans and the environment. Geopolymer-based adhesives (GA) are abundant environmentally inorganic materials with wide applications in engineering fields. However, the modification and design of GA with excellent properties for practical applications remain a major challenge. Here, calcium chloride (CaCl2) solution was used to coat the wood surface, which quickly polymerized in situ with the geopolymer to form calcified geopolymer during hot-pressing, leading to the construction of a robust geopolymer/wood bonding interface. The formation mechanism of the reinforced interface between wood and geopolymer was characterized, and the wet shear strength and flammability were evaluated based on the binding application of plywood. The calcified geopolymer can achieve the dual effects of blocking the penetration of lye and promoting in situ reinforcement during hot-pressing, which effectively eliminates the impact of the weak interface layer of the alkali/wood and reorganizes the microstructure of the geopolymer/wood bonding interface. The wet shear strength of plywood with a 2.0 mol/L CaCl2 solution loading was increased from 0.45 MPa to 0.87 MPa, an increase of 93% compared with the pristine samples. The inherent flame retardancy of geopolymers contributed to a 42.6% reduction in the first peak of the heat release rate and a decrease of 28.9% in the total heat release compared with industrial urea-formaldehyde resin. This resulting GA, which was prepared by a facile and green method with markedly increased wet shear strength and inherent flammability, may have potential applications in functional wood-based composites and be used as a replacement for formaldehyde-based adhesives.

The Al2O3 ceramic and Kovar 4 J34 alloy were effectively bonded by vacuum brazing by using an Ag-based filler metal with a composition of Ag-5Cu-1Al-1.25Ti (wt%). The typical interfacial structure of the Al2O3/Kovar 4 J34 joint brazed at 960 °C for 10 min was determined as Al2O3/Ti3(Cu, Al)3O/Ag(s, s) + Cu(s, s) + disperse AlCu2Ti/Ti2Ni + TiFe2/Kovar. The brazing parameters were observed to have a decisive effect on the microstructure evolution and variation of the mechanical properties of the Al2O3/Kovar 4 J34 brazed joints. The maximum shear strength of the brazed joints could reach 150 MPa, and the failure primarily occurred in the ceramic substrate and Ti3(Cu, Al)3O reaction layer. Moreover, the microstructural stability of the Al2O3/Kovar 4 J34 brazed joints at elevated temperatures was also investigated. After thermal cycling at 600 °C for 3 h, the interfacial structure of the brazed joint did not change obviously except for the thickening of the reaction layer, and the joint shear strength remained at 130 MPa. However, the average shear strength of the joint under the testing temperature of 600 °C was reduced to 73 MPa, and the fracture propagated along the Ag matrix of the brazing seam due to the softening of silver.

To prepare large-sized and complex-shaped components, the feasibility of direct diffusion bonding of (Hf0.2Zr0.2Ti0.2Ta0.2Nb0.2)C high-entropy ceramic (HEC) and its diffusion bonding with a metallic Ni foil was investigated, and the interfacial microstructure and mechanical properties of HEC/HEC and HEC/Ni/HEC joints were analyzed. For the direct diffusion bonding, reliable joints with a shear strength of 146 MPa could be achieved when the bonding temperature reached 1500 °C under a pressure of 30 MPa. By introducing a metallic Ni foil as the interlayer, the HEC was successfully bonded at the diffusion temperatures from 1150 °C to 1250 °C under 10 MPa through the formation of Ti2Ni compound phase. Meanwhile, the HEC(Ni) phase formed by the diffusion of Ni into HEC and Ni(s, s) bulks precipitated in the bonding transition zone. The maximum joint shear strength of 151 MPa was obtained by optimizing the Ni-foil thickness, bonding temperature, and holding time.

This paper describes a simple analytical tool for the calculation of the shear strength of r.c. rectangular members with shear reinforcement and subjected to only truss mechanism. The proposed method considers simplified stress fields and evaluates the shear strength of members subjected to axial force, bending moment and shear force by means of the application of the static theorem of limit analysis. Unlike most of the formulations proposed in codes and in other research studies, the proposed method considers a single physical model to explain the resistance to axial force, bending moment and shear force, and simultaneously satisfies the equilibrium under all the above internal forces. The paper identifies basic points of the N-M-V ultimate domain and reports relations and procedures to calculate the values of the internal forces of these points as well as the internal forces of the points in between. The method is applied to a set of beam and column members and a comparison is drawn between the shear strength resulting from the simplified method and that from a more complex non-linear mathematical program proposed in the past by the same author. Finally, to prove the value of the method and define the field of reliable application, the proposed method is applied to members tested in laboratory by other researchers and characterised by different geometric and mechanical properties. The obtained results are also compared with those deriving from other methods present in the literature.

Purpose: To evaluate the push-out bond strength (PBS) and failure mode of single adjustable (SAP) and customized (CP) posts cemented to root canal dentin using conventional (RelyX Ultimate) or self-adhesive (RelyX U200) dual-cure resin cements. Methods: Herein, 40 bovine mandibular incisors were divided into four groups (n = 10): SAP cemented with RelyX Ultimate (SAP-UT), SAP cemented with RelyX U200 (SAP-U2), CP cemented with RelyX Ultimate (CP-UT), and CP cemented with RelyX U200 (CP-U2). PBS and failure modes were analyzed. Three-way repeated measures ANOVA test followed by Tukey’s test and Fisher–Freeman–Halton exact test were used for data analysis (α = 5%). Results: The PBS values for SAP (p .05). When conventional resin cement was used, the SAP showed significant differences compared to CP (p

Summary Objective This study aimed to evaluate the failure incidence of brackets with at least six months follow-up between self-etch primer and conventional etch/primer, as well as to investigate the clinical duration of the bonding process and the amount of adhesive remnant index (ARI). Methods Electronic search was conducted in databases including PubMed, Scopus, Web of Science, ProQuest, ClinicalTrials.gov, and ICTRP (International Clinical Trials Registry Platform). The electronic search targeted only randomized clinical trials and was limited from January 2000 to June 2021. Delphi list is used to evaluate the risk of bias and Stata Version14.2 software was used. This systematic review was conducted according to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) and recorded on the Ethics Committee of Research Institute of Dental Sciences, SBMU (IR.SBMU.DRC.REC.1398.240). Results Out of 2288 extracted studies, 30 of them entered the full-text evaluation process. According to the inclusion criteria, 15 studies entered this systematic review. Containing 607 participants and 10,563 brackets/teeth. All the included studies were of randomized clinical trials (RCT) design with either parallel or split-mouth design. Comparing the two groups, the risk difference effect (RD) = 0.007 CI 95% (−0.004,0.018) indicated a neglectable difference in the risk of bracket failure during treatment between the two groups. The index I2 = 53.9% indicated moderate heterogeneity in the results. Furthermore, the P-value = 0.007 indicated statistical insignificance between the two interventions in terms of failure rate. The clinical duration of bonding time analysis were equal to SMD _Cohen = −2.67 CI95% (−3.49, −1.85), which indicated a statistically significant reduction in clinical process time, using the self-etch primer. Data synthesis for adhesive remnant index could not be conducted due to heterogeneity among included studies. Conclusions There was no difference between the self-etch primer and conventional etch/primer in bracket debonding at a medium level of evidence, However, there was statistically significant reduction in clinical bonding time using self-etch primer.