Search Results (63)

The construction sector’s drive for sustainability has increased the use of Cross-Laminated Timber (CLT), yet its structural reliability is governed by the integrity of the adhesive bond line. This study evaluates the influence of three one-component polyurethane (PUR) formulations (R1, R2, R3) on the adhesion performance of maritime pine CLT. To isolate adhesive-related effects, lamellas were mechanically classified by modulus of elasticity (MOE) and randomly allocated within stiffness classes. Adhesive characterization through ABES, FTIR, and DSC revealed that R3 exhibited slower cure kinetics (t₀ = 5482 s) but higher thermal stability. Mechanical testing showed that all formulations developed structurally effective dry bonds with shear strengths exceeding 7.1 MPa, with R3 achieving significantly higher dry shear and interlaminar strength. However, 24 h water immersion caused a catastrophic strength reduction exceeding 95% across all formulations, shifting the failure mode from the wood substrate to the adhesive layer. DSC analysis identified glass transition temperatures between 28 °C and 32 °C, which are consistent with the potential for moisture-induced plasticization near service temperatures. These results indicate that while slower-curing formulations like R3 enhance bond quality in dense softwoods due to improved interphase formation, all evaluated PUR systems showed significant vulnerability to saturated conditions, suggesting that adequate moisture protection is essential for maritime pine CLT applications. Full article

Multilayer paper composites have been widely applied in industrial sectors and as sustainable concrete formwork in civil construction. These materials are produced by pressing paper layers bonded with a sodium silicate adhesive; however, their structural performance is often limited by the adhesive’s low mechanical strength. Therefore, in this study, the effects of incorporating 0.5 wt.% nanoclay (NA), nanosilica (NS), and kaolin into sodium silicate on the physical, mechanical, and microstructural properties of the composites were evaluated. The composites were fabricated with 20 layers of recycled kraft paper and a final mass of 65 g/m² of reinforced sodium silicate applied by a glue line. The adhesive was applied using a paper coating machine, followed by pressing at 4.30 MPa. The results showed that the presence of nanomaterials had no measurable effect on the apparent density of the composites; nevertheless, the inclusion of 0.5% NA promoted a 25% increase in toughness. Thus, the use of nanomaterials is efficient at obtaining better-quality composites for numerous technological applications. Full article

Arsenic contamination, mainly in the arsenate (As(V)) form, continues to pose a serious threat to groundwater quality worldwide due to its long-term stability and toxicity at very low levels. Herein, we demonstrate, for the first time, a three-dimensional graphene oxide-based nanocomposite composed of Cu nanoparticle-doped, amino-functionalized UiO-66 (Cu/UiO-66-NH₂) anchored on a graphene oxide framework (Cu/UiO-66-NH₂@GO) as a novel and efficient nanosorbent for the rapid removal of As(V) in groundwater-like solutions. The nanocomposite was characterized by SEM and HRTEM to confirm the hybrid structure and by XRD, N₂ adsorption–desorption isotherms, and XPS to investigate crystallinity, porosity, and surface chemistry. The derived material exhibited a highly dispersed morphology and performed rapid arsenate solid-phase extraction to attain equilibration within 10 min and was effective for a wide pH range of 2–11. The best fit for the kinetic profiles was provided by the pseudo-second-order model. Interestingly, the maximum adsorption capacity of 747.9 mg g⁻¹ at pH 6.8 was achieved, demonstrating the benefits of the complementary pairing of dispersive GO sheets and Zr-MOF adsorption domains with Cu-derived active sites. Mechanistically, the enhanced uptake is ascribed to a combination of effects, including electrostatic pre-concentration, ligand exchange, and inner-sphere complexation at metal-oxo nodes; spectroscopic analysis (XPS and FTIR) suggests that the majority of arsenate is immobilized via a strong Zr-O-As bond at coordinatively unsaturated Zr centers, which is in line with t-ZrO₂-like surface domains formed within the nanocomposite. The embedded GO support inhibits further framework interpenetration and enhances active site availability and mass transport, leading to fast and high-capacity arsenate capture in groundwater samples with related conditions. Taken together, this work presents a powerful design concept that integrates unique GO-supported, Cu-modified UiO-66-NH₂ with Zr-O binding motifs to afford high-rate remediation nanocomposites, providing an excellent platform for next-generation arsenate remediation materials. Full article

Background/Objectives: Follitropin delta is an approved recombinant follicle-stimulating hormone (rFSH) expressed in a human cell line. Correct disulfide connectivity is a critical quality attribute for rFSH, a heterodimeric glycoprotein composed of noncovalently associated α and β subunits and stabilized by an extensive network of intramolecular disulfide bonds. Disulfide characterization is typically performed by mass spectrometry (MS). However, the closely spaced disulfide bonds within the FSH α-subunit are particularly resistant to proteolytic cleavage, complicating conventional MS-based disulfide mapping. Methods: To overcome limitations of MS-based methods, an X-ray crystallography strategy was employed using a ternary complex of the recombinant FSH heterodimer with an anti-FSHα Fab and a stabilizing anti-kappa VHH. Crystals of the desialylated rFSH/Fab/VHH complex were obtained and diffraction data were collected. Results: The structure of recombinant FSH was determined at 2.29 Å resolution. Electron density surrounding cysteine residues in both the α and β subunits was well defined, allowing unambiguous assignment of all intramolecular disulfide bonds in the crystallized protein. The observed cysteine connectivity is fully consistent with the disulfide architecture of FSH from other sources and supports correct folding of the recombinant Follitropin delta. Full article

Sintered nano-silver is widely investigated as a die-attach material for next-generation power electronic modules due to its high thermal conductivity, favorable electrical performance, and stability at elevated temperatures. However, how bonding pressure and joint thickness jointly affect densification, interfacial diffusion, and mechanical reliability has not been systematically clarified, especially under the low-pressure conditions required for large-area SiC and GaN devices. In this work, nano-silver lap-shear joints with three bond-line thicknesses (50, 70, and 100 μm) were fabricated under two applied pressures (1.0 and 1.5 MPa) using a controlled sintering fixture. Shear testing and cross-sectional SEM were employed to evaluate the relationships between microstructural evolution and joint integrity. When the bonding pressure was increased from 1.0 to 1.5 MPa, more effective particle rearrangement and reduced pore connectivity were observed, together with improved metallurgical bonding at the Ag–Au interface, leading to a strength increase from 15.3 to 28.2 MPa. Although thicker joints exhibited slightly higher bulk relative density due to greater heat retention and accelerated local sintering, this densification advantage did not lead to improved mechanical performance. Instead, the lower strength of thicker joints is attributed to a narrower Ag–Au interdiffusion region, which limited the formation of continuous load-bearing paths at the interface. Fractographic analyses confirmed that failure occurred predominantly by interfacial delamination rather than cohesive fracture, indicating that the reliability of the joints under low-pressure sintering is governed by the quality of interfacial bonding rather than by overall densification. The experimental results show that, under low-pressure sintering conditions (1.0–1.5 MPa), variations in bonding pressure and bond-line thickness lead to distinct effects on joint performance, with the extent of Ag–Au interfacial interaction playing a key role in determining the mechanical robustness of the joints. Full article

This review examines strategies to enhance the antifungal properties of commercial soft lining materials (SLMs) through modification with plant-derived oils, extracts, and powders. These natural bioactive compounds act via multiple mechanisms, including disruption of fungal cell membranes, inhibition of biofilm formation, and interference with Candida albicans metabolism, the pathogen causing denture-associated candidiasis. Their incorporation into SLM provides localized antifungal activity at the denture–mucosa interface. The review highlights Aloe vera (aloe), Azadirachta indica (neem), Ocimum basilicum (basil), Melaleuca alternifolia (tea tree), Cocos nucifera (coconut), Allium sativum (garlic), Thymus vulgaris (thyme), and chitosan as notable sources of phytotherapeutics that consistently inhibit C. albicans growth. In addition to antimicrobial effects, studies assessed both intrinsic (hardness, tensile strength, tear strength) and interfacial (bond strength) mechanical properties, as well as surface roughness. Most formulations maintained acceptable mechanical performance and improved surface smoothness. Key limitations include rapid leaching of active compounds, variability in testing methods, and insufficient in vivo and cytotoxicity data. Future research should prioritize the high-quality purification of natural extracts, the isolation of well-defined bioactive compounds, and the design of systems enabling selective and sustained release of these agents, ensuring reproducibility, enhanced stability, and clinical reliability of next-generation bioactive SLMs. Full article

The presented research delivers a comprehensive evaluation of anticorrosive cathodic electrodeposition (CED) coatings through an integrated performance and process capability analysis—an approach that remains extremely limited in the literature, particularly in the context of statistically designed experiments (DoEs) applied to CED systems. This study therefore addresses a notable gap by focusing on the role of polymerization variables in determining coating quality through DoE to quantify the influence on coating thickness uniformity, adhesion integrity and impact resistance, while all other deposition parameters were rigorously controlled. Prior to coating application, all specimens were prepared and conditioned in accordance with ISO 1513:2010. Coating thickness was determined in compliance with ISO 2808:2019, adhesion was characterized by cross-cut methodology according to ISO 2409:2020 and dynamic mechanical resistance was evaluated using a falling-weight apparatus in accordance with ISO 6272-1:2011. The obtained datasets were subjected to statistical capability analysis within the PalstatCAQ environment, providing Cp, Cpk, Pp and Ppk indices in line with ISO 22514-7:2021 and IATF 16949:2016 requirements. Results evidenced non-linear dependencies of thickness formation on curing parameters, with potential capability indices (Cp > 1.8; Pp ≈ 1.4) indicating favorable process dispersion, while performance indices (Cpk < 0.5; Ppk < 0.4) revealed systematic mean shifts and deviations from normality confirmed by Shapiro–Wilk and Anderson–Darling tests. Adhesion testing demonstrated a direct correlation between curing conditions and interfacial bonding, reaching ISO Grade 0 classification. Complementary impact resistance assessments corroborated these findings, showing that insufficient curing induced extensive cracking and delamination. Furthermore, SEM–EDX analysis performed on Sample n.3 of X₂ variable confirmed the chemical integrity and multilayered structure of the CED coating. Full article

The automation of concrete constructions through 3D printing (3DP) has been increasingly developed and adopted in civil engineering due to its promising advantages over traditional construction methods. However, widespread implementation is hindered by uncertainties in quality control, homogeneity, and interlayer bonding, as well as the uniqueness of each printed component. Building upon our prior work in developing 3D-printable self-sensing cementitious materials by incorporating graphite powder and carbon microfibers into a cementitious matrix to enhance its piezoresistive properties, this study aims at enabling condition assessment of cementitious 3DP by integrating the self-sensing materials as sensing nodes within conventional components. Three different 3D-printed strip patterns, consisting of one, two, and three strip lines that mimic the pattern used in fabricating foil strain gauges were investigated as conductive electrode designs to impart strain sensing capabilities, and characterized from a series of quasi-static and dynamic tests. Results demonstrate that the three-strip design yielded the highest sensitivity (${\lambda }_{\mathrm{stat}}$ of 669, ${\lambda }_{\mathrm{dyn}}$ of 630), whereas the two-strip design produced the highest signal quality (SNR_stat = 9.5 dB, SNR_dyn = 10.8 dB). These findings confirm the feasibility of integrating 3D-printed self-sensing cementitious materials through hybrid manufacturing, enabling monitoring of print quality, detection of load path changes, and identification of potential defects. Full article

Towards the creation of a long-lasting and high-performing glulam-product, the optimization of melamine–urea–formaldehyde (MUF) adhesive solutions in order to be in line with worldwide trends of building and cutting-edge material science is a matter of first-priority. However, glulam performance is still highly determined by the efficiency of adhesive bonds, which highlights the necessity of thorough resin and bonding examination. To identify the most effective MUF formulation for structural applications, this study examines the delamination resistance, of spruce three-layer glulam, applying five resins based all on MUF adhesive (EN 14080), differentiating in terms of hardener–resin ratios (1:4 and 1:5) and the applied adhesive amount (1:4 and 1:1) according to ISO 12578. The results revealed that some of the adhesives (A and E) were not suitable for use, the adhesives B and D require further processing, since both achieved a wood failure of 50% in the four applied experiments, while only adhesive C provided almost excellent results in all cases. When the hardener to glue ratio was 1:5 or 1:1, and the application was four times the typical amount of glue, the delamination test requirements were fulfilled, while none of the experiments with a ratio of 1:4 exhibited satisfying adhesion and strength, something that raises concern since this is the ratio recommended by the glulam-production standard. A thorough understanding of MUF adhesive formulations and adhesion mechanisms were approached, which is crucial towards the optimization of wood-based products especially of high-strength requirements as glulam. The hardener-to-glue ratio and the quantity of adhesive were highlighted as crucial factors, underlying the need for accurate formulation and application in structural glulam bonding, while more stringent manufacturing quality control seems to be a necessity. Full article

This study investigates the effects of welding parameters and the addition of a buffer layer on the morphology, microstructure, mechanical properties, and corrosion resistance of the overlay layer during overlay welding. This paper uses Q235 steel as the base material, ER309L as the buffer layer, and ER347 as the overlay layer to conduct process experiments on overlay welding component, aiming to obtain optimal process parameters. The effects of welding line energy and weld bead overlap rate on the morphology, dimensions, and dilution rate of the overlay layer were analyzed. Furthermore, the influence of the presence or absence of the buffer layer on the microstructure, mechanical properties, and corrosion resistance of the overlay layer was investigated. The microstructure and morphology of the overlay layer were characterized by optical microscopy (OM), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). Mechanical and electrochemical tests were also performed to evaluate the mechanical and corrosion resistance properties of ER347 stainless steel weld overlays. The results showed that the optimal process parameters were successfully obtained, which ensured sound weld bead formation while minimizing dilution. The addition of the buffer layer (ER309L) improved the bonding quality of the overlay welding component interface, reduced element dilution in the overlay layer, significantly improved hardness distribution, and reduced sudden changes in hardness in the fusion zone, thereby optimizing the mechanical properties of the ER347 stainless steel overlay layer. After adding the buffer layer, the corrosion current density decreased from 6.23 × 10⁻⁵ A·cm⁻² to 2.21 × 10⁻⁵ A·cm⁻², and the corrosion potential increased from −1.049 V to −0.973 V, effectively reducing the corrosion risk of the overlay component. This study innovatively introduced a buffer layer in the process of overlay welding austenitic stainless steel on low-carbon steel and investigated the impact of the overlay welding process on the overlay layer, thereby contributing to a comprehensive understanding of the overlay welding process from multiple perspectives. Full article

Adhesive bonding has emerged as a transformative joining method across multiple industries, offering lightweight, durable, and versatile alternatives to traditional fastening techniques. This review provides a comprehensive exploration of adhesive bonding, from fundamental adhesion mechanisms, mechanical and molecular, to application-specific criteria and the characteristics of common adhesive types. Emphasis is placed on challenges affecting bond quality and longevity, including defects such as kissing bonds, porosity, voids, poor cure, and substrate failures. Critical aspects of surface preparation, bond line thickness, and adhesive ageing under environmental stressors are analysed. Furthermore, this paper highlights the pressing need for sustainable solutions, including the disassembly and recyclability of bonded joints, particularly within the automotive and aerospace sectors. A key insight from this review is the lack of a unified framework to assess defect interaction, stochastic variability, and failure prediction, which is mainly due complexity of multi-defect interactions, the compositional expense of digital simulations, or the difficulty in obtaining sufficient statistical data needed for the stochastic models. This study underscores the necessity for multi-method detection approaches, advanced modelling techniques (i.e., debond-on-demand and bio-based formulations), and future research into defect correlation and sustainable adhesive technologies to improve reliability and support a circular materials economy. Full article

Segmented timber shells present a novel building system that utilizes modular, planar building components to create lightweight free-form structures in architecture. Recent advancements in the research field of segmented timber shells pursue, among others, two fundamentally opposing research objectives. 1. The modularity of their building components facilitates the reuse of such structures in response to a changing built environment. 2. Advanced developments aim at establishing segmented timber shells as permanent building structures for sustainable architecture. This paper addresses the first research objective through the successful relocation of the BUGA Wood Pavilion in the context of the proposed methodology of Co-Design for circular construction. The methods and results involve integrative design and engineering processes and advanced quality assessment methods, including structural, geodetic, and physical properties for modular timber constructions. The BUGA Wood Pavilion serves as a building demonstrator for the presented research on segmented shells as lightweight, reusable, and durable timber structures. Full article

In recent years, the building insulation layer peeling caused by quality problems has brought about safety hazards to human life. Existing means of non-destructive testing of building insulation layers, including laser scanning, infrared thermal imaging, ultrasonic testing, acoustic emission, ground-penetrating radar, etc., are unable to simultaneously guarantee the detection depth and resolution of the insulation layer defects, not to mention high-precision imaging of the insulation layer structure. A new type of high-precision imaging radar is specifically designed for the quantitative quality inspection of external building insulation layers in this paper. The center frequency of the radar is 8800 MHz and the −10 dB bandwidth is 3100 MHz, which means it can penetrate the insulated panel not less than 48.4 mm thick and catch the reflected wave from the upper surface of the bonding mortar. When the bonding mortar is 120 mm away from the radar, the radar can achieve a lateral resolution of about 45 mm (capable of distinguishing two parties of bonding mortar with a 45 mm gap). Furthermore, an ultra-wideband high-bunching antenna is designed in this paper combining the lens and the sinusoidal antenna, taking into account the advantages of high directivity and ultra-wideband. Finally, the high-precision imaging of data collected from multiple survey lines can visually reveal the distribution of bonded mortar and the bonding area. This helps determine whether the bonding area meets construction standards and provides data support for evaluating the quality of the insulation layer. Full article

This study investigates the thermal and residual stress development in multi-layer lined pipe welding through numerical simulation and experimental validation. The focus is on the weld overlay/liner transition region, a critical area prone to stress concentrations and fatigue crack initiation. Using finite element analysis (FEA) with the Goldak double-ellipsoidal heat source model, the research examines the temperature evolution, residual stress distribution, and deformation characteristics during the welding process. Key findings reveal that the peak temperature in the weld overlay region reaches 3045.2 °C, ensuring complete metallurgical bonding. Residual stresses are predominantly tensile near the three-phase boundary, with maximum von Mises stress observed in the base pipe at 359.30 MPa. This study also employs Response Surface Methodology (RSM) to optimize welding parameters, achieving a 20.5% reduction in residual axial stress and a 58.1% reduction in residual circumferential stress. These results provide valuable insights for optimizing welding processes, improving quality control, and enhancing the long-term reliability of bimetallic composite pipelines. Full article

This paper introduces a high-resolution 77–81 GHz mmWave Synthetic Aperture Radar (SAR) imaging methodology integrating low-cost hardware with modified radar signal characteristics specifically for NDT applications. The system is optimized to detect minimal defects in materials, including low-reflectivity ones. In contrast to the existing studies, by optimizing key system parameters, including frequency slope, sampling interval, and scanning aperture, high-resolution SAR images are achieved with reduced computational complexity and storage requirements. The experiments demonstrate the effectiveness of the system in detecting optically undetectable minimal surface defects down to 0.4 mm, such as bonded adhesive lines on low-reflectivity materials with 2500 measurement points and sub-millimeter features on metallic targets at a distance of 30 cm. The results show that the proposed system achieves comparable or superior image quality to existing high-cost setups while requiring fewer data points and simpler signal processing. Low-cost, low-complexity, and easy-to-build mmWave SAR imaging is constructed for high-resolution SAR imagery of targets with a focus on detecting defects in low-reflectivity materials. This approach has significant potential for practical NDT applications with a unique emphasis on scalability, cost-effectiveness, and enhanced performance on low-reflectivity materials for industries such as manufacturing, civil engineering, and 3D printing. Full article