Search Results (977)

This study presents an integrated surface diagnostic investigation and a diagnostic-driven restoration of the marble sculpture Real Infante Carlo Tito di Borbone (1775), attributed to Giuseppe Sanmartino and preserved at the Royal Palace of Caserta (Italy). Despite the artistic relevance of the sculptor, scientific investigations of his works remain limited. The aim of this work is to characterize surface coatings, identify alteration processes, and support conservation strategies through a multi-analytical approach. The results reveal that the sculpture is composed of calcitic marble covered by an altered organic surface film. Spectroscopic and chromatographic data indicate the presence of lipidic compounds consistent with natural wax, likely associated with previous conservation treatments. An epoxy-based adhesive was also identified, suggesting past restoration interventions. Microbiological analyses detected fungal and bacterial species potentially involved in surface alteration processes. The integration of analytical data enabled the development of a targeted restoration strategy. Cleaning procedures were defined based on the chemical nature of the surface coatings, while structurally stable previous restorations were preserved. A biocide treatment was applied to mitigate biological colonization. This study highlights the importance of surface-oriented diagnostics in understanding coating materials and guiding conservation interventions, providing a methodological framework applicable to marble artworks. Full article

Recycled glass fiber-reinforced polymer (GFRP) powder from decommissioned wind turbine blades offers sustainable reinforcement for wood–plastic composites (WPCs), but its efficiency is limited by poor interfacial adhesion with the polypropylene (PP) matrix caused by surface epoxy residues. In this study, GFRP/WPCs with a fixed formulation of 15 wt% GFRP, 10 wt% wood flour, and 75 wt% PP were used to compare two modification strategies: MAPP compatibilization (1–7 wt%) and H₂O₂ treatment (5–30%). MAPP modification improved the mechanical properties of GFRP/WPCs, with the optimal concentration varying by property: flexural strength reached its maximum (75.45 MPa, +24.7%) at 1 wt% MAPP, while tensile strength (+9.2%), flexural modulus (+20.7%), and impact strength (+18.9%) were maximized at 3 wt% MAPP. H₂O₂ at 10% achieved higher strength gains (tensile: +23.65%, i.e., 26.7 MPa; flexural: +27.93%, i.e., 77.4 MPa; impact: +35.29%, i.e., 16.98 kJ/m²) but moderately reduced flexural modulus. FTIR confirmed up to 71.7% epoxy removal by H₂O₂, exposing cleaner fibers. Both modifications slightly lowered thermal decomposition temperatures but increased char residues and PP crystallinity via enhanced nucleation. SEM showed that MAPP created a compatible interphase, while H₂O₂ enabled direct mechanical interlocking. Surface free energy analysis revealed that MAPP increased polar components, whereas H₂O₂ increased dispersive components. Overall, MAPP offers simpler processing and balanced properties, while H₂O₂ provides superior strength at the cost of some stiffness—providing practical guidance for tailoring recycled GFRP/WPCs for construction and sustainable applications. Full article

This article presents an experimental investigation into the mechanical properties of new laminated bamboo and bamboo–timber hybrid composite materials for construction. A total of thirty-six bamboo and bamboo–timber hybrid composite specimens were manufactured, which include a new configuration that integrates bamboo and pine strips in hybrid bamboo–timber composite members. An interleaved configuration of the hybrid bamboo–timber composites is proposed to enhance stress transfer and interfacial bonding. Such a design can mitigate global hygroscopic and thermal mismatch effects, including composites panel warping and continuous interfacial shear, through redistributing differential strains into small, localized scales. To minimize manufacturing energy demand, cold hydraulic pressing was used to prepare the specimens with bio-epoxy and polyvinyl acetate adhesives (PVAs). The list of experimental tests includes compression parallel to the grain, compression perpendicular to the grain, and flexure. The experimental results revealed that the developed bamboo and bamboo–timber composites outperform the reference materials consisting of commercial engineered bamboo and natural softwood. In particular, the average modulus of elasticity of the hybrid specimens bonded with bio-epoxy adhesive reaches 11.6 GPa (CoV = 13.8%), which is 40 percent greater than that of the tested commercial engineered bamboo specimens (CoV = 15.7%), emphasizing a stiffer and more reliable engineered bamboo. In the case of flexural testing, the hybrid bamboo–timber specimens reach the highest modulus of elasticity, while the engineered bamboo bio-epoxy test series exhibited a modulus of rupture that was 36% higher than that of the commercial engineered bamboo material with a CoV equal to 8%. Full article

As a road repair material, emulsified asphalt offers advantages such as convenient construction, good fluidity, and environmental safety. However, its relatively low strength limits its application range, making performance enhancement a key research focus. In this study, waterborne epoxy resin (WER) was used to modify emulsified asphalt, and the preparation process and performance were systematically investigated. Three types of waterborne epoxy systems were selected, and through compatibility, film-forming performance, and bonding strength tests, the JT waterborne epoxy system was identified as having the best overall performance, with an optimal epoxy-to-curing-agent ratio of 1:0.6. Modified emulsified asphalts with different proportions of WER and styrene–butadiene rubber were prepared. Using fluorescence microscopy, image recognition techniques, and multiple experimental evaluations, the distribution of epoxy resin in the emulsified asphalt was quantitatively analyzed. The results show that the addition of WER significantly improves the bonding strength of emulsified asphalt, with the fastest rate of increase observed in the 5−10% range. However, a comprehensive evaluation considering microstructure uniformity, rheological performance, and water resistance indicates that the optimal overall performance is achieved in the 10−12% range, and the WER content should strictly be controlled below 15% to avoid severe local agglomeration. Meanwhile, the modified water-boiling test reveals that the adhesion between WERAE and aggregates is significantly enhanced, implying a potentially improved resistance to moisture-induced damage under practical service conditions. The standard deviation of area results indicate that when the WER content exceeds 15%, local agglomeration occurs, which is unfavorable for strength development of the modified system; the distribution uniformity results further show that when the WER content is greater than 12%, it negatively affects the uniform dispersion of WER within the emulsified asphalt. Full article

The corrosion-protection performance of zinc oxide-hybrid polymeric coatings is traditionally attributed to the individual contributions of their constituent phases. This study reveals that the calcination temperature of zinc oxide (ZnO) filler is a critical, previously overlooked processing parameter that dictates not only filler crystallinity but also the collective synergistic failure mechanism of the entire coating system. Herein, we demonstrate that incorporating ZnO calcined at 500 °C yields a ternary chitosan–graphene oxide–zinc oxide/epoxy (CS–GO–ZnO/EP) composite coating with a highly compact, dense morphology, minimal internal porosity, and exceptional filler dispersion, as validated by FTIR, XRD, and SEM analyses. The optimized CS–GO–ZnO/EP coating applied to carbon steel exhibits outstanding dry and wet pull-off adhesion strengths, the highest surface hydrophobicity (102.2°), and superior electrochemical barrier protection. Notably, after a 120-h immersion period in an aggressive 3.5 wt.% NaCl electrolyte, the CS–GO–ZnO/EP (500 °C) maintains excellent coating resistance (R_coat = 1.06 × 10⁵ Ω) and a minimized corrosion rate (CR = 0.074 mm/y). This thermal threshold is a key processing window that improves chemical bonding and compatibility between the different parts of the hybrid matrix without causing the severe nanoparticle sintering, phase aggregation, and micro-cracking that happen at 650 °C. This work offers a significant advancement in the design of eco-friendly, high-performance hybrid coatings, demonstrating that precise control of the inorganic phase’s thermal history provides a direct pathway toward superior durability, hydrophobicity, and electrochemical stability for carbon steel protection in aggressive marine environments. Full article

Epoxy/dicyandiamide adhesive film is required for the bonding of polymethyl methacrylate (PMMA) aircraft cockpit edges. An imidazole/alkanolamine composite accelerator was developed to satisfy the requirement of maintaining a bonding temperature below 90 °C for this structure, successfully reducing the curing temperature of the adhesive film from 180 °C to 85 °C. The curing process of the low-temperature curing adhesive film and its hydrothermal aging resistance after curing were investigated using mechanical testing, Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). The results indicate that the curing process of 85 °C for 6 h enables the adhesive film to fulfill the adhesion strength requirements for aircraft cockpit edge applications. The cured adhesive film is found to exhibit limited intrinsic water resistance due to its low crosslinking density. Therefore, external edge sealing is required in practical engineering applications to isolate moisture. This work provides an application-specific one-component epoxy/dicyandiamide adhesive film for the low-temperature flexible bonding of aviation PMMA cockpit edges to PETR, and clarifies its adhesion performance and hydrothermal aging behavior under the target service scenario. Full article

The interfacial adhesion strength of fine lines for flip-chip ball grid array (FCBGA) substrates is highly dependent on the surface desmear process during substrate manufacturing. However, the extremely narrow window for optimal desmear processes limits the improvement of the adhesion strength of fine lines. Herein, a polydopamine-modified epoxy build-up film substrate was fabricated to increase chemical bonding action and broaden the process window. The chemical structure, surface roughness, morphology, surface chemical state, and adhesion strength of the modified substrate were characterized. The results showed that the adhesion strength of the substrates increased from 2.2 N/cm to 4.1 N/cm under suboptimal process conditions. Meanwhile, the effect of the polydopamine deposition time on the adhesion strength of the copper-deposited epoxy resin composite films at the interfaces was systematically investigated; furthermore, the mechanisms and reasons for the increased adhesion strength and interfacial adhesion failure for the copper-deposited epoxy resin composite build-up film substrates were revealed. This work will provide guidance in both theory and experiment to enhance the interfacial adhesion force for advanced substrates in the future. Full article

This study investigates adhesively bonded composite patch repair to enhance the load-carrying capacity of damaged metallic structures, introducing a novel FE-augmented machine learning (ML) framework that addresses the limited availability of experimental data in structural repair applications. To evaluate this approach, aluminum and steel specimens with central fatigue cracks were repaired using glass-fiber/epoxy and carbon-fiber/epoxy composite patches and tested under quasi-static loading at room ($70 \mathrm{F} °$), high ($145 \mathrm{F} °$), and low (−$60 \mathrm{F} °$) temperatures. Finite element (FE) models were then developed in ABAQUS© to predict the failure loads of the patched specimens under varying temperature conditions, showing excellent agreement with the experimental data. The high accuracy of the FE predictions enabled their use as additional training data, effectively augmenting the limited experimental dataset and allowing the development of more robust regression models. Ten machine learning (ML) regression models, including linear regression (LR), polynomial regression (PR), support vector regression (SVR), random forest (RF), gradient boosting (GB), XGBoost (XGB), LightGBM (LGBM), Gaussian process (GP) regression, artificial neural networks (ANNs), and Kolmogorov–Arnold networks (KANs), were trained to predict the failure load of both unpatched and patched specimens as a function of material type, temperature, specimen thickness, crack length, and, for patched specimens, patch type and thickness. The datasets combined a limited set of physical results (75 patched samples: 63 experimental and 12 finite-element; 72 unpatched samples: 27 experimental and 45 theoretical) with Gaussian-mixture-model synthetic samples used only to augment the training data up to 300 samples per case. Under a configuration-grouped, leakage-free nested cross-validation (entire configurations held out for testing, hyperparameters tuned on inner folds only), the best models predicted the failure load of unseen configurations with mean absolute percentage errors of 2.78% (Gradient Boosting, patched, $R^2=0.87$) and 3.33% (Gaussian Process, unpatched, $R^2=0.98$). A paired ablation showed that Gaussian-mixture-model augmentation did not improve accuracy and, for several models, actually reduced it; the final models therefore rely on the real multi-source (experimental, FE, and theoretical) data, with the synthetic pipeline reported as a validated but non-beneficial component for these datasets. Overall, this study provides a novel, data-efficient framework combining experimental testing, FE simulation, and validated regression modeling to predict the performance of adhesively bonded composite patch repairs under varying thermal and mechanical conditions. Full article

Epoxy resin (EP) has been extensively used in electrical insulation systems because of its favorable adhesion, chemical resistance, thermal stability, and dielectric reliability. Nevertheless, the dense three-dimensional network formed during curing generally gives EP a brittle nature, which restricts its use in insulating components that require both mechanical robustness and long-term reliability. In this work, a hydroxyl-terminated hyperbranched polymer (HBP-OH) was synthesized from itaconic acid (IA) and dipentaerythritol (DPE) through an Ax + By polycondensation route and then incorporated into an anhydride-cured epoxy system as a reactive toughening component. The influence of HBP-OH on the structure, mechanical behavior, dielectric response, and DC breakdown strength of the resulting HBP-OH/EP composites was systematically evaluated. The results demonstrate that HBP-OH effectively improves the mechanical performance of EP. At an HBP-OH loading of 9 wt%, the tensile strength increased from 15.00 MPa for pure EP to 33.27 MPa, while the elongation at break and flexural strength reached 6.5% and 88 MPa, respectively. Meanwhile, only a slight reduction in DC breakdown strength was observed at the optimal HBP-OH content. These results indicate that the proposed hyperbranched-polymer modification strategy can improve the toughness and strength of epoxy resin while retaining its dielectric and insulation performance, providing a feasible approach for developing epoxy insulating materials for high-voltage electrical equipment. Full article

Epoxy resins suffer from inherent brittleness, limiting their reliability in impact-resistant structures. This study addresses the dispersion–performance trade-off in nano-alumina (Al₂O₃)/epoxy composites by fabricating specimens with 0–15 wt% filler loadings using an optimized ultrasonic-mechanical dispersion strategy. Quasi-static and dynamic tensile behaviors (600–1600 s⁻¹) were evaluated using a universal tester and a split Hopkinson tensile bar (SHTB) system equipped with high-sensitivity semiconductor strain gauges. Results identify a critical agglomeration threshold at 3 wt%. The 1 wt% composite exhibited optimal quasi-static strength (44.76 ± 0.25 MPa), a 4.0% improvement over the neat epoxy (43.04 ± 0.33 MPa). While all composites showed positive strain-rate sensitivity, nano-Al₂O₃ incorporation generally reduced dynamic strength, except for the 5 wt% composite at intermediate rates. Notably, the 15 wt% composite recovered to 78.49 ± 0.48 MPa at 1600 s⁻¹ due to high-rate energy dissipation mechanisms. Microstructural analysis revealed a transition from brittle cleavage to a hybrid fracture mode dominated by microvoids and localized plastic tearing. This work quantitatively defines the optimal loading window for nano-Al₂O₃/epoxy composites in protective engineering. Full article

Metal centralizers suffer high frictional resistance, high self-weight, and severe pore shrinkage after perforation in deep, highly deviated, and horizontal wells. Targeting the performance demands of adhesive casing centralizers, this study uses epoxy resin as the matrix, introduces amino modification, and regulates inorganic filler composites to prepare an amino-modified epoxy resin composite centralizer material, followed by systematic property tests. The optimal formula of modified epoxy resin:curing agent:UR300 accelerator:amino-modified silica:silicon carbide:alumina is 100:10:1:1:35:20 and delivers superior comprehensive performance. Its compressive strength reaches 136.61 MPa with a Shore hardness of 92.32 HD, low linear expansion, and favorable thermal compatibility with steel casings. Hardness remains stable after 168 h of aging at 150 °C, and the material maintains low friction at ambient and elevated temperatures. After 30-day immersion in acidic, alkaline, and high-salinity fluids, its compressive strength retention exceeds 86% with a slight variation in volume and mass, while adhesion strength reaches 2.667 MPa at a pipe-wall roughness of 12.12 μm. Combining high strength, heat resistance, corrosion resistance, and strong adhesion, the material suits complex downhole conditions and supports the field application of resin composite centralizers. Full article

Thermally sprayed metallic coatings on carbon fiber-reinforced polymer (CFRP) substrates often contain pores and microstructural defects that can reduce adhesion, durability, and protective performance. In this study, a hybrid graphene nanoplatelet (GNP)-fullerene C60 reinforced epoxy coating was applied to HVOF-metallized CFRP, while a carbon nanotube (CNT)-based surface treatment was used to modify surface wettability. Micro-CT and SEM analyses indicated morphological changes consistent with partial coverage of accessible surface-connected defects and modification of the metallized layer surface. Pull-off adhesion strength increased from 320 psi to 650 psi, accompanied by a shift from adhesive to cohesive failure. The optimal nanofiller formulation improved tensile strength from approximately 25 MPa to 56 MPa (124%) and Young’s modulus by approximately 47% compared with neat epoxy. Abrasion testing showed more than 50% reduction in mass loss, and electrochemical impedance spectroscopy indicated improved barrier performance after 200 h of salt spray exposure. CNT surface modification transformed the coating from hydrophilic to superhydrophobic behavior, achieving water contact angles above 155°, delaying ice formation, and reducing ice accumulation. These results indicate that combining hybrid nanocomposite coatings with CNT functionalization can improve mechanical, protective, and surface-functional performance of HVOF-metallized CFRP systems under the laboratory conditions investigated. Full article

Bacterial cellulose (BC) combines high stiffness, low density and a unique three-dimensional fibrillar network, making it a promising bio-based reinforcement for polymer composites. In this study, BC pellicles were cultivated under static, room-temperature conditions in Hestrin–Schramm medium, and purified, freeze-dried and processed into BC/epoxy laminates using wet compression moulding. The processing route was designed to minimise destruction of the native BC architecture, enabling a feasibility assessment of integrating a native BC network into an industrially relevant wet compression moulding process. Specimens were produced according to DIN EN ISO 527-4 at a fixed fibre mass fraction of approximately 8.8 wt%. Scanning electron microscopy (SEM) imaging revealed a predominantly in-plane oriented, channel-like BC network; however, the composites also exhibited inhomogeneities, including dry areas, voids, and resin-rich regions. Mechanical testing demonstrated an increase in Young’s modulus from 2.95 GPa for neat epoxy to approximately 4 GPa for BC-reinforced laminates, whereas the tensile strength of BC-reinforced laminates (approximately 25 MPa) remained below that of the neat epoxy reference. Hence, stiffness was improved while strength remained limited due to process-induced material defects and the low fibre content. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) measurements indicated no substantial differences in thermal degradation behaviour across the investigated processing temperatures. Taken together, these results demonstrate the feasibility of processing BC networks into epoxy laminates and identify impregnation inhomogeneity as a key limitation at this early stage. The work further stresses the need for improved control of BC morphology, drying, and impregnation, as well as improved fibre–matrix adhesion in future studies in order to better harness the structural potential of bacterial cellulose in fibre-reinforced polymer composites. Full article

Marine deck coatings suffer from premature failures such as wear thinning, flaking, and brittle cracking under repeated rolling, abrupt stopping/steering, and high shear loads of heavy equipment due to the imbalance of hardness, strength, toughness, and wear resistance. To address this issue, a rolling load-resistant coating system with an epoxy–amine/epoxy–thiol dual-crosslinked network was constructed using liquid polysulfide rubber (Lp-3) as the key crosslinking modifier, and the effect of Lp-3 content (0–2 wt%) on the comprehensive performance of the coating was systematically investigated. The results showed that the coating achieved the optimal synergy of properties at 1 wt% Lp-3 loading: Shore hardness reached 88.7 HD with the pencil hardness maintained at 8H, adhesion strength increased to 7.2 MPa, Taber abrasion loss significantly decreased to 14.8 mg, tensile strength rose from 5.5 MPa to 12.4 MPa, elongation at break nearly doubled, shear strength reached 10.2 MPa, and the failure mode transformed from brittle cleavage to ductile shear. Mechanistic analysis revealed that the terminal thiol groups of Lp-3 underwent a click reaction with epoxy groups, covalently embedding flexible polysulfide segments into the rigid epoxy network and forming Fe–S interfacial chemical bonds to enhance adhesion. The microphase separation, chain relaxation, and energy dissipation mechanisms effectively blunted crack propagation and alleviated stress concentration, while maintaining sufficient surface hardness and the continuity of the load-bearing skeleton. This work realizes the synergistic optimization of high strength, high toughness, strong adhesion, and excellent wear resistance for marine deck coatings and provides a new strategy and critical technical parameters for the design of functional coatings under heavy-duty dynamic service environments. Full article

Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) polymer electrolytes suffer from low ionic strength and poor mechanical performance. Meanwhile, lithium lanthanum titanate (LLTO) fillers exhibit severe agglomeration and weak interfacial compatibility with the polymer matrix. To solve these problems, 3-glycidoxypropyltrimethoxysilane (KH560) at four different concentrations (1 wt%, 2 wt%, 3 wt%, 4 wt%) was loaded onto polydopamine-modified LLTO (PDA@LLTO). The modified materials were mixed with PVDF-HFP, and composite solid electrolytes were fabricated by the solution casting method. The epoxy groups in KH560 undergo ring-opening reactions with amino and hydroxyl moieties on PDA, while its trimethoxysilane groups crosslink with the polymer matrix, forming a robust “LLTO-PDA-KH560-polymer” interfacial structure. This dual modification markedly improves the dispersion of PDA@LLTO, strengthens interfacial adhesion, and enhances the mechanical and electrochemical properties of the composite electrolyte. All KH560 loadings suppress LLTO agglomeration, and the 3 wt% grafting ratio yields the optimal performance: a uniform and dense microstructure, a room-temperature ionic conductivity of 5.92 × 10⁻⁴ S cm⁻¹, an electrochemical stability window extended to 4.88 V, and a tensile strength over 50% higher than the ungrafted sample. The modified electrolyte effectively inhibits lithium dendrite growth and enhances the cycling stability of solid-state batteries. This work demonstrates that KH560-PDA synergistic modification enables comprehensive performance optimization of composite electrolytes, offering a viable strategy for designing high-performance electrolytes for solid-state lithium-metal batteries. Full article