AbstractObjectives This study aimed to investigate the adhesion of veneering composite to metal-free computer-aided design/computer-aided manufacturing (CAD/CAM) materials with different compositions after surface conditioning and application of adhesive resins.Materials and Methods A total of one hundred and sixty specimens were divided into four groups (n = 40) manufactured either from polyetheretherketone (PEEK; KERAstar PEEK), polyetherketoneketone (PEKK; Pekkton), fiber-reinforced composite (FRC; Trinia), or high-impact polymer composite (COMP; Bredent HIPC) CAD/CAM discs. Each group was then randomly subdivided into four different subgroups of adhesive systems (n = 10) as Visiolink (Bredent), Single Bond Universal (3M), G-Premio BOND (GC), and OptiBond Universal (Kerr). The shear bond strength (SBS) of each specimen with veneering composite material was tested with a universal testing machine following thermocycle aging (5000 times). The modes of failure resulting from the tests were determined with scanning electron microscope (SEM), dispersive spectroscopy (EDS), and analytical imaging. The data were statistically analyzed with two-way ANOVA and Bonferroni post hoc tests (alpha = 0.05).Results The highest SBS values among all groups were found for the COMP material (20.28 ± 2.08 MPa) with OptiBond Universal adhesive, while the lowest for the PEEK material (10.33 ± 2.47 MPa) with G-Premio BOND. The most common failure mode for the PEEK and PEKK specimens was adhesive failure, for the FRC and COMP groups mixed failures were common.Conclusions Bond strength values of at least 10 MPa were achieved for all tested between metal-free CAD/CAM materials and adhesive resin application.

AbstractSurface modification of polyester fabric was done using dielectric barrier discharge (DBD) with the aim of improving the adhesion properties using polyurethane (PU) polymer as an adhesive. The change in adhesion strength with respect to various plasma powers and treatment durations was examined. For analysing the adhesive bond strength of the coated fabric the T-peel off strength was investigated. After plasma treatment, an improvement in adhesion was observed compared to the untreated sample. The effect of oxygen gas on adhesion with PU adhesive was also studied. Surface wettability after plasma treatment was studied by wicking measurements. Changes in surface morphology were analysed using a scanning electron microscope (SEM) and an atomic force microscope (AFM). X-ray photoelectron spectroscopy (XPS) and ATR-FTIR were used to study the surface chemistry of plasma-treated samples. SEM, AFM, and XPS results reveal the surface roughening and incorporation of functional groups, such as C–O, C–OH, O–C=O, and COOH. No adverse effect on the mechanical strength of the plasma-modified polyester fabric was seen.

AbstractThe pull-out test was performed in this study to investigate the bond performance between basalt fiber reinforced polymer (BFRP) bars and recycled concrete. Three factors were considered: aggregate size (5–10 mm, 11–15 mm, and 16–20 mm), bond anchorage length of bars (3D, 5D, and 7D), and the recycled aggregate replacement rate (0%, 30%, 60%, and 100%). The bond–slip mechanism, failure mode, bond stress distribution, and bond–slip curves were all analysed. Based on the results, it was found that situations with a high recycled aggregate replacement rate, large aggregate particle sizes, or long bond lengths have an increased likelihood of experiencing splitting failure. As the aggregate size increases, the bond strength between the BFRP bars and the concrete would also increase, in ordinary concrete, a 22.54% increase was observed, whereas in recycled concrete, the maximum increase reached 48.20%. The effect would be more pronounced on recycled concrete compared to ordinary concrete, and it would also be more significant in specimens with BFRP bars compared to steel bars. Additionally, the optimal bond anchorage length was determined to be 5D. The bond strength exhibited a trend of decrease followed by an increase as the recycled aggregate replacement rate increased. The maximum reduction of 59.7% in bond strength was observed when the replacement rate of recycled aggregate reached 60%. Moreover, when the replacement rate of recycled aggregate increased to 100%, there was a decrease of 19.05% in bond strength compared to the specimen without recycled aggregates. Based on the experimental test data and existing models, an improved two-stage bond–slip constitutive model was proposed.

AbstractDue to their remarkable advantages, composite adhesively bonded joints are intensively used in many engineering fields. There are many investigations performed by researchers to study the fracture behavior of the adhesively bonded joints. However, there exist discrepancies between the numerical predictions and the experimental results in some cases. This paper reports an investigation on the finite fracture behavior of composite adhesively bonded joints subjected to four-point bending. Experiments are performed for composite adhesively bonded joints with four different configurations. The fracture behavior is observed experimentally by utilizing a high-speed camera. The failure analysis employing the energy-stress coupled criterion is performed. The experimental results are compared with the numerical predictions by using an experimental-based approach where both geometric nonlinearity and interfacial energy are considered. Numerical illustrations are carried out to assess the effect of interface energy, geometric nonlinearity, joint type and dimensions on the fracture behavior of the considered bonded joints.

AbstractThe present experimental study introduced NTA-WAAM system for fabricating thin-layered structures using ER70S-6 wire. The study is directed towards determining the Sw in the manufactured parts, considering varying level of TS (0.17, 0.19, and 0.24 m/min) and BL (2, 3, 7 layers). The Sw is computed through image processing using canny edge detection method. Increasing the BL from 2 to 7 and reducing TS from 0.24 to 0.17 m/min, the resulting Sw is increased from 1.05 to 2.69 mm. So with high BL, TS should be more to suitably control the Sw because of high heat dissipation and low fluidity of molten pool. In addition to the morphological attributes, microstructural evolution, XRD, Rietveld refinement, tensile, and wear testing are incorporated to present the feasibility and stability of part fabricated through NTA-WAAM. Crystallite size, dislocation density, and residual stress are computed through XRD. It is observed that when approaching the top section from bottom zone of deposition, crystallite size is reduced from 23.43 to 21.85 nm, whereas dislocation density (2.83 × 1012 to 6.52 × 1012m−2) and residual stress (−263.72 to −300.12 MPa) are increased. It indicates the adverse effect of crystallite size towards dislocation density and residual stress, which is primarily attributed to varying level of heat transfer during deposition. The deposit exhibits an ideally refined crystal structure than initial filler wire as χ2≈1 (from Rietveld analysis). Compressive residual stress development further improves the fabricated part’s tensile characteristics. Formation of equiaxed dimples, characterises the ductile failure phenomena, whereas the enhancement in their dimensions reflects the improvement in ductility.

AbstractThe present in vitro study evaluated the effect of titanium nanotubes (nTiO2) application on high translucent zirconia (Copra Supreme, Whitepeaks) on shear bond strength values with different self-adhesive resin cements (Panavia V5, G-Cem One, and Variolink Esthetic DC). One hundred and forty-eight specimens were prepared and randomly divided into four groups (n = 37) according to surface treatment groups (air-abraded sintered zirconia, air-abraded pre-sintered zirconia, application of nTiO2 on zirconia, and application of nTiO2 on air-abraded zirconia). nTiO2 were produced by alkaline hydrothermal synthesis, mixed with isopropyl alcohol (50 wt%), and applied on pre-sintered zirconia. The surface roughness (Ra) was examined. Sintered surfaces were characterized by field emission scanning electron microscope (Fe-SEM), and energy-dispersive X-ray spectroscopy (EDS) analysis. Surface treatment groups were randomly divided into three subgroups according to self-adhesive resin cement (n = 12). Luting procedures were performed and specimens were stored in water at 21 °C for 6 months before the shear bond strength test. Data were analyzed by one-way ANOVA and two-way ANOVA. Fe-Sem images and EDS confirmed the incorporation of nTiO2 on zirconia. Surface treatment methods affected the Ra of zirconia (p .05).

AbstractThe influence of multi-walled carbon nanotube (MWCNT) content on the melting properties, wettability, microstructure, and intermetallic compounds (IMCs) of Sn-58Bi-xMWCNT (x = 0, 0.01, 0.02, 0.03, 0.05, and 0.10 wt.%) and the effects of MWCNT on the tensile strength of Cu/Sn-58Bi-xMWCNT/Cu solder joint were analyzed. The results show that MWCNT addition at a small trace amount into Sn-58Bi solder could increase the spreading area of Sn-58Bi solder, refine the solder matrix microstructure, inhibit the growth of interfacial IMCs, and significantly improve the tensile strength of Sn-58Bi solder joints. However, the melting point and melting range remained the same or slightly changed. The wettability of Sn-58Bi alloys increased first and then decreased with the addition of MWCNT. The spreading area and the tensile strength of solder joint were the maximum when the MWCNT content was 0.01 wt.%, and they were 42.23 mm2 and 50.07 MPa, respectively. The reason may be related to the improved microstructure of solder alloys and the morphology of IMCs due to MWCNT addition at trace level.

AbstractElectrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and gravimetric analysis techniques were used to evaluate the ability of Lippia javanica leaf extract to inhibit aluminium (Al) corrosion in 1 M HCl solution. The formation of the protective film was confirmed using Ultraviolet-visible spectroscopy (UV–Vis), Fourier transform-infrared spectroscopy (FTIR) and contact angle studies. According to EIS, the presence of L. javanica extract in the acidic solution decreased the corrosion current density (icorr) and the double-layer capacitance (Cdl) due to the formation of a protective adsorption layer on the Al surface. PDP curves revealed anodic polarization passivation of the Al substrate, a well-known property of a highly entropic alloy like Al. Gravimetric results showed that the maximum protective efficacy of the L. javanica extract was 91.89% when the optimal concentration of the extract was 800 ppm. The contact angle increased to 123° in the presence of ALJPE, indicating the hydrophobic nature of the Al surface due to the formation of a protective film. The FTIR spectra revealed the involvement of C=O, C=C, O–H, =C–O–C, S=O, and C–H during the adsorption process, leading to the formation of ALJPE–Al3+ protective complexes. It was discovered that the adsorption mechanism of the extract on the Al surface follows the Langmuir adsorption isotherm description process. Using density functional theory (DFT), different dsorption positions were studied, finding that verbascoside preferentially binds to the Al(111) surface via the phenylethanoid group, with the oxygen atom close to the Al surface, leading to a binding energy of 114.620 kcal/mol.

AbstractTo decrease impacts on the environment and maintain competitiveness in the market, various industries (for example, fabrication and construction) are concentrating on minimizing material and energy usage. Aluminium (Al) and its alloys are contending possibilities for various complex applications to meet these industrial needs since they have improved qualities like good weight-to-strength ratios. Fusion welding causes the joints to deteriorate while joining Al. Friction stir welding (FSW) or friction Stir Processing (FSP) creates joints below melting point temperatures, eliminating the drawbacks of excessive heat input but necessitating an increase in the joint’s final characteristics. Nanoparticle reinforcement is an emerging field that provides great methods to create composite joints with improved joint characteristics. The surface attributes of composite joints can be improved, including hardness, strength, corrosion resistance, and wear resistance. This paper critically reviews the work carried out in the field of FSW/FSP welding AA5083 and AA6082 with carbide and oxide as reinforced nanoparticles. Further trends in nanoparticle reinforcement, oxide and carbide effect on welding parameters, microstructural formation, and mechanical properties are being analyzed. Analysis shows that the diffusion of the reinforcing nanoparticles, which affects the joint characteristics, is significantly influenced by FSW/FSP parameters. Additionally, the dispersed nanoparticles enhance joint characteristics and help refine grains. The kind, quantity, & size of reinforced nanoparticles and the welding conditions greatly influence the joint characteristics and microstructures in similar and different Al welds. Finally, prospects for a reinforced FSW are examined, followed by a look ahead and concluding notes.

AbstractThis study explores the potential benefits of gas metal arc (GMA) welding for ASME SA387-Gr.11-Cl.2 steel, with a focus on ensuring humane and environmentally friendly welding techniques. Metal-cored filler wire (MCFW) was tested on 6 mm thick ASME SA387-Gr.11-Cl.2 steel plates using MEGAFIL 237 M. Current (A), voltage (V), and gas flow rate (GFR) were tuned to get optimal results during welding, which was performed at 100 A, 13 V, and 21 L/min, respectively. Subsequently, visual inspection confirmed the absence of surface defects in the as-welded plates. In addition, macroscopic metallography analysis confirmed the satisfactory weld bead geometry (WBG). Microstructural variations were analyzed using optical microscopy, and microhardness measurements were taken to validate the results. Furthermore, the as-welded plates were heat treated before being examined for microstructure and microhardness. Comparative analysis of microstructure and microhardness values showed that the weld zone of as-welded plates exhibited a lanky martensitic configuration, while the heat-treated plates demonstrated a finer and more irregular distribution of the unaltered martensitic structure. These findings were further supported by respective hardness values of 1887.4 HV and 262.4 HV for the as-welded and heat-treated plates. By exploring the optimized use of metal-cored filler wire in GMA welding for ASME SA387-Gr.11-Cl.2 steel, this research aims to achieve welding practices that meet both technical requirements and environmental considerations, ensuring a humane approach to welding processes.

AbstractThis paper investigates the influence of the loading arrangement of double cantilever beam (DCB) test on the computed fracture resistance parameters of a structural adhesive. Aluminium joints were tested on three conventional loading arrangements from the BS ISO 25217:2009. We have found that the compliance of different loading arrangements can lead to significant differences in the fracture resistance computed using the cross-head displacement of the tensile-testing machine, even after considering the take-up of play and machine-compliance effects. In contrast, using the digital image correlation to measure the load-line displacement results in fracture resistance that is essentially independent of the loading arrangement. This finding was confirmed using three different data-reduction schemes, which yielded almost identical values of fracture resistance (less than 1% difference). Furthermore, direct identification of the traction-separation law at the crack tip was performed using Savitzky–Golay filter to compute the derivative of the J integral with regard to normal separation. Again, no significant influence of the loading arrangement was found since identified values of the separation at the peak traction and maximum separation are in excellent agreement. The identified maximum separation can be used as a threshold value of the relative deflection of the DCB arms to automatically determine the crack-tip position.

AbstractThis article presents a detailed systematic review on the current developments in the machining of superalloys. Superalloys have extensive high temperature applications and research has been conducted in various machining processes. The conventional and nonconventional processing of superalloys is an emerging research area and needs attention. This systematic literature survey intends to consolidate, review, and critically highlight the machining aspects carried out in this field. Bibliometric analysis using BibExcel is conducted to capture new insights in the focused field of research. Articles published since 1991 on material processing of superalloys are listed and referenced. Article statistics on each class of publications have been highlighted. A citation analysis is also reported and the articles with the highest impact are identified. Geographical mapping reveals the role of universities and institutions in the focused research. Gephi is used to identify the key research clusters and topics. Seven prominent clusters were identified and articles in each research cluster have been elaborated. A quality versus quantity analysis of the various publications is done. Present state of art in the focused research and the future directions on the material processing of superalloys based on the review are reported.

AbstractIn this paper, a novel rubber nanocomposite containing phenyl-vinyl-methyl-polysiloxane (PVMQ) and ethylene propylene diene monomer (EPDM) was produced during a two-roll mill procedure for mechanical applications. For this purpose, ethylene propylene diene monomer-grafted-maleic anhydride compatibilizer (EPDM-g-MAC) and graphene oxide (GO) was used as a compatibilizer and reinforcements to make a uniform composite. To study mechanical and physical characterizations, dynamic mechanical thermal analysis (DMTA), rheology, morphology, and curing characterizations of nanocomposites were investigated, which showed that compatibilizer makes GO dispersion uniformly. An electrical resistivity test was performed to study the electrical conductivity of the nanocomposites. The results indicate that the samples with higher GO content had a response to the electrical current. The curing study indicates that, by increasing the GO nanoparticles in the presence of EPDM-g-MAC, the curing properties are enhanced as well as mechanical properties by improving the bonding among GO, compatibilizer, and matrix [tensile strength (54%), modulus (68%), elongation-at-break (67%), hardness (81%), and fatigue (51%)]. FE-SEM and TEM images demonstrated that, by increasing GO nanoparticles in the presence of compatibilizer, the mean diameter of EPDM decreased in the substrate, which consequently increased the mechanical properties. The changes in surface temperature were investigated with constant voltage (75 V), which indicates that by increasing GO nanoparticles and electrical conductivity, the surface temperature increased significantly. The results of practical experiments showed good agreement with the theoretical results.

AbstractIn order to improve the poor hydrophobicity and single repair conditions of traditional self-healing polyurethane coatings, prepolymers were synthesized with bio-based polyol castor oil (CO), self-made alkyl aryl modified silicone polyols (Si-OH) and isophorone diisocyanate (IPDI), and 4,4'-dithiodianiline (ODD) was used as chain extender containing dynamic disulfide bond, 4-methylumbelliferone (4-MU), as a bio-based end capping agent with reversible ring structure, was polymerized step by step to prepare a photothermal responsive bio-based superhydrophobic self-healing poly(siloxane-urethane) coating (PUSi). In this paper, the effect of the amount of alkyl aryl modified silicone polyol (Si-OH) on the properties of PUSi was studied. The results showed that PUSi with different alkyl aryl modified silicone polyol additions could achieve self-healing under heating, UV irradiation and infrared light irradiation, and the maximum repair efficiency could reach 91% through optical microscope (OM), 3D profilometer and universal testing machine; The contact angle meter proved that the introduction of alkyl aryl modified silicone polyol greatly improved the hydrophobicity of PUSi, and the maximum water contact angle was 162°. The coating has broad application prospects in the fields of self-cleaning fabrics, super hydrophobic surfaces, special protective clothing and so on.

AbstractThe coating materials Polyaniline (PANi), Polyaniline-TiO2, and Chitosan-Polyaniline-TiO2 ternary nanocomposite (CPT) were separately synthesized by chemical oxidative polymerization with ammonium persulphate as an oxidant in a hydrochloride aqueous medium. The synthesized materials were characterized by FT-IR, XRD, SEM, and TEM. The FT-IR and XRD result adequately established the interaction between chitosan, PANi, and TiO2 NPs. Microstructural studies revealed significant variation in the morphologies of PANi, PANi-TiO2, and chitosan-polyaniline-TiO2 nanocomposite and embedment of TiO2 NPs in the polymer matrix. The coating materials PANi, PANi-TiO2, and CPT were mixed with epoxy resin (10%) and subsequently, cast on low carbon steel (LCS) using NMP as solvent and triethyl tetra amine as curing agent. The anti-corrosion properties of coated specimens in 3.5 wt.% NaCl solution was evaluated using EIS studies, PDP, Salt spray test, water uptake test, immersion test, and SEM. Results of corrosion tests revealed superior corrosion protection offered by CPT ternary nanocomposite coating to LCS in 3.5 wt % NaCl solution compared to PANi and PANi-TiO2 nanocomposite coatings.

AbstractThe objective of this study is to replace steel-phosphating treatments with self-assembled monolayers (SAMs), in this case, of phosphonic acids. Two industrial applications are targeted: obtaining an adhesion primer between steel and paint or lubricating stainless steel for mechanical applications, such as stamping; research has been conducted using alkyl phosphonic acids. The carbon chain length and terminal function are changed to obtain the best properties depending on the application.

AbstractThe moisture resistance of friction-welded wood joints can be improved by applying bio-based bonding additives. Several biomolecules including tannic acid, organosolv lignin from hardwood, kraft lignin from softwood, and derivates thereof, were investigated regarding their applicability as bonding additives in the friction welding process. Welding with kraft lignin showed significantly increased moisture stability after 24 h water immersion. An average wet bond strength of 1.5 MPa compared to 0.38 MPa of untreated spruce was obtained. Modification of kraft lignin through succinylation, acetylation or depolymerisation led to no further improvement in moisture stability. Depolymerised kraft lignin resulted in an even higher delamination rate of the samples during water immersion than untreated samples. Structural analysis of the lignin variations by FTIR-ATR, GPC and 31P NMR in combination with thermal analysis by TGA and DSC showed the impact of various structural and chemical features on the thermal behaviour and intermolecular interactions of the applied lignin.

AbstractThe development of a biodegradable adhesive that uses waste from industry will bring enormous economic, social, environmental, and health benefits. Many laboratories around the world conduct research on the development of natural adhesives that can replace those based on toxic formaldehyde. Works in this area are also carried out by Sestec Polska Sp. z o. o, an example of which is the Sestec B0021G adhesive. This product belongs to the family of animal protein-based adhesives and is dedicated to particle board (PB) production (classes P1–P5 according to EN 312). This work presents the results obtained during the preparation of boards based on Sestec B0021G protein adhesive, manufactured with the use of variable production parameters, and assesses the influence of these parameters on the properties of the obtained products. The emphasis was especially on presenting the impact of production parameters on the PB strength and water resistance. The tests were carried out using different densities (560–800 kg/m3), pressing temperatures (150–230 °C), amounts of adhesive (7–15% in the surface layer and 5–13% in the core layer) and specific press times (5–13 s/mm). The boards showed excellent mechanical properties and water resistance. Higher PB classes were obtained under standard production conditions. Eventually, the obtained results showed that the binder can be used to produce all classes of PB products P1 to P7, and not only P1-P5 as initially assumed.

AbstractIndirect restorations made of resin composite materials are increasingly used yet there is no consensus in the literature on how different luting strategies influence the bond strength. The aim of this was to study the influence of luting strategy and aging on the adhesion of indirect restorations on dentin. Bovine incisors (N = 120) received conical cavities and filled them with resin composite. The cone sets were divided into 8 groups (n = 15 each) and the cylinders were cemented according to: ‘Luting strategy’ (U200: Self-adhesive cement resin; ULT: Scotchbond Universal + RelyX Ultimate; SB2: Phosphoric Acid + Adper Single Bond 2 + RelyX ARC; SBMP: Phosphoric Acid + Scotchbond Multi-purpose + ARC) and ‘Aging’ (Tc: With thermocycling/10.000 cycles: 5–55 °C; Without thermocycling). The specimens were subjected to a Push-out Bond Strength (σ) (100 kgf; 0.5 mm/min). Stereomicroscope and scanning electron microscopy (SEM) images were made to classify the failures. Data (MPa) were submitted to two-way-ANOVA, Tukey (α = 5%), and Weibull tests. ANOVA revealed that ‘luting strategy’ and ‘aging’ were statistically significant. When the factor ‘TC’ was evaluated separately, the TC groups presented higher bond strength than the unaged groups. As for the non-thermocycling groups, the different luting strategies had no statistical difference, except for the SB2 group, which was lower than ULT. Among all groups, TC, U200_Tc, SBMP_Tc, and ULT_Tc were statistically similar and significantly higher than that of the SB2-Tc group. The Weibull modulus was statistically different among the groups but characteristic strength was significant. Mixed failures were predominantly observed. Self-conditioning strategy promoted higher bond strength than the two-step conventional strategy but after thermocycling, the two-step conventional strategy presented the worst performance among the experimental groups.

AbstractThe Uncaria Cordata as corrosion inhibitors for mild steel (MS) in a 1.0 M hydrochloric acid (HCl) solution. The EIS, polarization, and LPR measurements were used as experimental measurements to confirm the anti-corrosion performances of the Uncaria Cordata at room temperature. The corrosion inhibitors, even at a low dosage range, achieved inhibition efficiencies to a maximum of 97.0% for 400 ppm of Uncaria Cordata. Surface morphology via AFM and SEM/EDX was carried out to validate the presence of protected film and an optimum concentration of each extract above the metal’s surface in the corrosive acidic solution. The ΔGoads value − 19.70 kJ/mol proved a spontaneous merge of physical and chemical adsorption by the extract compounds at the interface of MS and the HCl solution. DFT was governed to accommodate the elevated inhibition efficiency upshot obtained by the electrochemical tests and recommend a synergy mechanism for most of the adsorbed active compounds in Uncaria Cordata inhibitors with the MS surface. Monte Carlo simulation indicates three active compounds, namely 1, 2, and 8, found to have parallel adsorption on MS. This encourages the highest surface coverage and shields the MS surface from the intrusion of corrosive agents.