Search Results (477)

Deep Cretaceous clastic reservoirs in the Kuqa Depression are major targets for natural gas exploration in the Tarim Basin. Recent exploration of the Yageliemu Formation in the Ketan area has revealed considerable resource potential, although reservoir performance is strongly affected by deep burial, compaction, repeated fluid–rock interaction, and pronounced pore-system heterogeneity. Core descriptions, epoxy-impregnated thin sections, cathodoluminescence, scanning electron microscopy, conventional petrophysical measurements, mercury intrusion capillary pressure, and nuclear magnetic resonance data were integrated to evaluate sedimentary fabric, reservoir-space types, pore-throat characteristics, and diagenetic modification. The succession was deposited mainly in a braided river delta plain setting and is dominated by medium sandstone, pebbly sandstone, and fine conglomerate. Overall reservoir quality is poor, with an average porosity of 3.4% and permeability commonly between 0.01 and 0.5 mD. MICP and NMR data distinguish four pore-structure types. From Type I to Type IV, average displacement pressure rises from 0.89 to 11.02 MPa, whereas median throat radius and movable-fluid porosity decline from 0.17 to 0.01 μm and from 2.00% to 0.72%, respectively. Residual intergranular pores constitute the main storage space, while feldspar- and lithic-fragment-dissolution pores provide additional local storage. Fractures contribute little pore volume but can markedly improve connectivity where they remain open or only weakly cemented. The present reservoir heterogeneity reflects the combined effects of sand-body stacking, sandstone–mudstone arrangement, fault-related fracturing, and multistage diagenesis. The most favorable intervals occur in thick, relatively clean stacked sand bodies where residual pores are preserved, dissolution pores remain connected to the throat network, and fractures have undergone limited late-stage filling. Full article

Tight sandstone reservoir effectiveness is governed not by pore volume alone, but by the storage and flow contributions of different pore-throat scales, their structural complexity, and their three-dimensional connectivity. This study investigates tight sandstones of the Benxi Formation deposited in a marine–continental transitional mixed siliciclastic–carbonate setting in the Gaoqiao area, southern Ordos Basin. Petrophysical measurements, red-epoxy-impregnated thin-section petrography, mercury intrusion capillary pressure (MICP), segment-specific fractal analysis of functionally defined pore-throat regimes, X-ray micro-computed tomography (micro-CT), and pore-network modeling (PNM) were integrated. The MICP responses define three pore-throat structure types and two data-derived functional boundaries at 0.708 and 0.141 μm, which separate large-pore-throat-dominated, transitional pore-throat, and fine-throat-limited intervals. Using these nominal boundaries, Type I is strongly dominated by the large-pore-throat interval, which accounts for 88.7% of total mercury intrusion, whereas Type II exhibits a mixed large-to-transitional response, and Type III is characterized by negligible large-pore-throat intrusion and pronounced fine-throat restriction. Perturbing both functional boundaries by ±5% and ±10% does not alter these principal functional distinctions, although samples close to the second boundary exhibit the expected local transitional sensitivity. Among the three segment-specific fractal parameters, the fine-throat fractal dimension, D_B, shows the strongest association with median capillary pressure (r = 0.834, p < 0.001) and remains significantly related to displacement pressure, median pore-throat radius, and permeability, whereas D_T shows no significant linear correlation with the tested petrophysical and MICP parameters. The fractions of the largest connected pore cluster in representative Type I–III samples are 90.26%, 72.56%, and 64.65%, while their PNM permeabilities decrease successively from 64.32 mD to 0.850 and 0.121 mD. Together, these results indicate that, for the investigated samples, reservoir effectiveness reflects the combined influence of pore-throat size configuration, segment-specific structural complexity, and three-dimensional network connectivity. Full article

A new, heavy-metal-catalyst-free epoxy vitrimer system modified with a liquid crystalline epoxy resin (LCER) is presented. A critical innovation in this work was the replacement of conventional toxic transesterification catalysts, such as zinc compounds, with an excess of a bio-based compound: glycerol. Two anhydrides, maleic anhydride (MA) and phthalic anhydride (PA), were evaluated as curing agents to determine their impact on the thermal and self-healing properties of the resulting networks. The study revealed that the systems cured with an aliphatic anhydride exhibited superior self-healing characteristics compared to their aromatic counterparts. Moreover, the use of MA allowed for a lower curing temperature. Differential scanning calorimetry (DSC) was employed to analyze the thermal behavior of the resin and its compatibility with the epoxy vitrimer network, as well as the curing process itself and the thermal characteristics of the obtained polymer network. Hot-stage-polarized optical microscopy (HS-POM) was used to confirm the formation of liquid crystalline phases of the LCER and to track the healing process. Furthermore, it was observed that in selected formulations, the addition of LCER itself was sufficient to induce self-healing capabilities without the necessity of adding multi-hydroxyl alcohol. Full article

This study focuses on the deposition of nickel thin-films onto glass fiber fabric via DC magnetron sputtering and explores their potential for broadband microwave absorption applications. A total of twelve laminate samples were prepared by integrating the coated fabrics with epoxy resin, with sputtering powers ranging from 0.5 to 2 kW and deposition times ranging from 10 to 90 min. The microstructure, surface resistance, electromagnetic parameters, and microwave absorption performance were systematically characterized using SEM, XRD, four-point probe measurements, and vector network analysis, supplemented by the Lorentz model fitting and simulation validation. The results indicate that the nickel coatings exhibit a non-uniform arc-like morphology, with preferential growth along the (111) crystallographic plane, while the (200) and (220) planes form under specific conditions. The surface resistance reaches up to 10⁸ Ω·m, suggesting the absence of a continuous conductive network. Electromagnetic parameter analysis reveals that the laminates display dielectric-loss-dominated microwave absorption, and the Lorentz fitting identifies double resonance peaks under prolonged or high-power sputtering. The addition of a dielectric matching layer further enhances the absorption performance. All samples achieve wideband absorption within the Ku-band. Notably, the samples prepared at 1 kW for 30 min and at 1 kW for 90 min both exhibit a reflectivity of ≤−10 dB across the entire 8–18 GHz frequency range. The experimental results are in good agreement with simulations. The bulk density of the laminates is approximately 1.8 g/cm³. These findings confirm that magnetron-sputtered nickel-coated continuous glass fiber fabrics hold considerable promise for wideband microwave absorption applications. Full article

This study investigates the degradation behavior of decommissioned wind turbine blade composites in organic fluid systems, with particular focus on the subcritical acetic acid route. Supercritical acetone and supercritical n-butanol were used as screening media, while retired-blade glass fiber-reinforced polymer (GFRP) composites and laboratory-prepared glass fiber/epoxy composites were used to compare resin removal and fiber recovery behavior. The screening results showed that supercritical acetone and supercritical n-butanol caused partial matrix degradation but left visible organic residues on recovered fibers, whereas subcritical acetic acid produced cleaner fiber surfaces under lower-pressure conditions. The effects of temperature and reaction time were then analyzed in the subcritical acetic acid system. At 280 °C for 60 min, the epoxy resin degradation rate reached 99.81%, and the recovered glass fibers retained 96.49% of their tensile strength. Gas chromatography–mass spectrometry (GC–MS) analysis indicated that the liquid products mainly contained phenols, esters, and other oxygenated organics, with bisphenol A derivatives as representative components. These products suggest a coupled degradation process involving epoxy network swelling, bond cleavage, fragment release, and secondary acetylation in acetic acid. The boiling-point difference between acetic acid and the main degradation products, together with the product distribution obtained after recovered-acid addition, indicates the potential of acetic acid reuse. These findings support subcritical acetic acid as a promising medium for resin removal and glass-fiber recovery from decommissioned wind turbine blade composites. 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

This review provides an overview of the latest advances in bionic vascular self-healing cement, focusing on vascular design, fabrication, selection of healing agents, transport and curing mechanisms, and performance evaluation methods. Compared to systems based on microcapsules and microorganisms, vascular networks enable directed and efficient transport of healing agents and repeated healing; however, the presence of hollow channels results in an inevitable loss of mechanical properties. Additive manufacturing, in situ printing based on Pickering emulsions, and direct printing of cement-based or multi-material systems have enhanced geometric flexibility and scalability. However, issues such as channel quality, polymer-cement interface stability, and on-site quality control remain unclear. Regarding the selection of healing agents, epoxy resin systems are generally more suitable for structural healing, polyurethanes are suitable for rapid sealing and wide or irregular cracks, while silicate healing agents are suitable for healing where cement compatibility and durability are prioritized. The most critical research gap lies in the lack of standardized, full-scale, multi-cycle, and long-term environmental validation, which limits the practical engineering application of vascular self-healing technology. Future research should prioritize the integrated design of various performance metrics, the long-term durability of polymers, standardized benchmark testing, and validation based on actual service 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

Aramid nanofibers (ANFs) inherit the exceptional properties of the bulk counterparts, while introducing a large specific surface area and excellent processability. However, the strong inter-fibrillar interactions and tendency to agglomerate hinder their high-content incorporation into polymer matrices. Here, we report a one-pot reprotonation–compounding strategy for fabricating aramid nanofiber-reinforced poly(vinyl alcohol) (ANF–PVA) composite films, where the ANF dispersion was mixed with polymers during the protonation process to form a continuous 3D network in the ANF-PVA film. The optimized film with a loading of 20 wt% ANFs exhibited a tensile strength of 122.2 MPa and a toughness of 28.36 J m⁻³. Furthermore, the high ANF loading enabled versatile applications. A robust ANF-PVA hydrogel, prepared via salt-induced gelation, delivered 132% enhancement in tear strength and 38.2% increase in cyclic compressive strength compared with the PVA hydrogel. Moreover, inspired by the “brick-and-mortar” architecture of natural nacre, the fully organic ANF-PVA film was incorporated into carbon fiber/epoxy laminates, with a configuration of one nacre-inspired film per five prepreg plies, achieving a 36.5% improvement in impact toughness and minimal loss in flexural strength. This scalable reprotonation–compounding approach provides a general route for producing high-loading ANF-based composites, paving the way for the broader utilization in advanced materials. Full article

A cure-dependent viscoelastic constitutive model is developed to describe the stress response of epoxy resin during curing. The progressive formation of the load-carrying network is represented phenomenologically through cure-dependent equilibrium and Maxwell-branch stiffness functions. A one-dimensional history-integral equation is derived and extended to non-isothermal conditions by incorporating temperature-dependent stiffness and reduced-time effects. Explicit stress-increment equations are then obtained for one-dimensional and three-dimensional isotropic materials and implemented in ABAQUS through a UMAT. Two idealized numerical cases are used to verify the consistency between the UMAT results and direct constitutive calculations. An illustrative encapsulation model further shows that different assumptions regarding the curing-dependent stiffness factor produce substantial differences in peak and final stresses. An additional cooling-rate sensitivity analysis shows that increasing the cooling rate increases the magnitude of the final compressive stress because less time is available for viscoelastic relaxation. A formal tensorial extension is also provided for anisotropic thermosetting materials, although it is not numerically assessed. The present results constitute constitutive and numerical verification rather than material-specific experimental validation. 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

Lead-free polymer composites containing high-atomic-number fillers are promising alternatives to conventional lead shielding for nuclear medicine applications. In this study, Bi₂O₃-, WO₃-, and hybrid Bi₂O₃/WO₃ nanoparticle-filled epoxy resin composites were fabricated and evaluated for attenuation of the 140 keV photons emitted by technetium-99m (Tc-99m). The synthesized Bi₂O₃ and WO₃ nanoparticles exhibited hydrodynamic diameters of 638.2 ± 11.3 and 404.2 ± 3.2 nm, respectively, with polydispersity indices below 0.30 and zeta potentials of −33.73 ± 0.63 and −32.47 ± 0.75 mV, indicating acceptable dispersion characteristics and colloidal stability. SEM–EDX confirmed successful incorporation of Bi- and W-containing phases into the epoxy matrix, while the XRD and FTIR analyses verified retention of the crystalline metal oxide phases and the principal chemical structure of the cured epoxy network. Tensile testing revealed a composition-dependent strength–ductility relationship, with the Bi₂O₃-filled composite exhibiting the highest tensile strength among the developed formulations and the hybrid composite showing the greatest elongation at break. XCOM and Phy-X/PSD simulations demonstrated that increasing high-Z filler content enhanced the mass and linear attenuation coefficients and reduced the half-value layer, tenth-value layer, and mean free path. Experimental shielding performance was evaluated using Hp(10) measurements with optically stimulated luminescence dosimeters positioned on an anthropomorphic thorax phantom under a fixed Tc-99m exposure geometry. The transmitted dose decreased with increasing filler loading, and nanoparticle-filled formulations generally outperformed the corresponding conventional-particle composites. The hybrid 75:25 Bi₂O₃/WO₃ NP composite exhibited the lowest mean Hp(10) value of 0.016 µSv, corresponding to a 50% reduction relative to the lead reference under the investigated geometry. The combined structural, mechanical, computational, and dosimetric results demonstrate that hybrid filler design enables simultaneous optimization of attenuation efficiency and mechanical tolerance. These findings identify the Bi-rich hybrid epoxy composite as a promising lead-free material for customized shielding components, including vial holders, syringe-shield housings, protective panels, and workstation accessories used during Tc-99m handling in nuclear medicine. 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

Epoxy resin (EP) exhibits pronounced intrinsic brittleness arising from the highly crosslinked network formed after curing, thereby restricting its application in load-bearing structures. Although TiO₂ nanoparticles possess the potential for impact-strength improvement, they are highly prone to aggregation, which compromises stress-transfer efficiency within the composite. To overcome this challenge, a ball-milling strategy is adopted to anchor TiO₂ nanoparticles onto three-dimensional graphene oxide (3DGO), leading to the successful fabrication of a 3DGO@TiO₂ hybrid filler. At an ultralow loading of 0.03 wt%, the 3DGO@TiO₂ epoxy resin composite shows a 221.5% increase in impact strength to 19.55 kJ/m² and 33.53% and 32.34% increases in tensile and flexural strength to 64.32 MPa and 96.17 MPa, respectively, relative to neat EP. Morphological analyses indicate that the 3DGO spatial confinement reduces TiO₂ aggregate characteristic length by 55.1% from 1123 nm to 504 nm. Molecular dynamics simulations show that the hybrid filler decreases fractional free volume to 17.6%, induces denser matrix packing, and increases the calculated physical interfacial energy to 1023 kcal/mol, which is 2.2 times that of the pure TiO₂ epoxy resin system. This work confirms that 3DGO simultaneously optimizes nanofiller dispersion and physical confinement, offering a novel strategy for high-performance epoxy composites at ultralow loadings. Full article

The development of sustainable polymer composites reinforced with renewable resources and advanced nanomaterials has attracted considerable attention for multifunctional engineering applications. In this study, an environmentally friendly epoxy-based biocomposite (EBC) reinforced with coconut shell powder (CSP) and graphene nanopowder (GNP) was successfully produced through a casting process. CSP was employed as a bio-based filler, while GNP was incorporated at concentrations ranging from 0 to 0.75 wt.% to improve the overall performance of the composites. The effects of GNP loading on bulk density, tensile strength, elongation at break, Shore D hardness, thermal conductivity, dielectric properties, thermal stability, mechanical and microstructural characteristics were systematically investigated. The results demonstrated that the incorporation of GNP significantly enhanced the multifunctional properties of the improved EBCs. Bulk density increased from 1137.5 to 1143.1 kg m⁻³ with increasing GNP content. The optimum tensile strength of 28.6 MPa and Shore D hardness of 77.4 were achieved at 0.45 wt.% GNP, indicating effective stress transfer and strong interfacial interactions between the epoxy matrix, CSP, and GNP. Thermal conductivity increased from 0.110 to 0.149 W m⁻¹ K⁻¹, while the dielectric constant increased from 3.06 to 4.25 with increasing GNP concentration. Thermogravimetric analysis revealed improved thermal stability and enhanced char formation in graphene-containing composites. FTIR analysis confirmed that graphene acted primarily as a physical reinforcement without altering the fundamental chemical structure of the epoxy network. SEM and EDX investigations demonstrated improved structural compactness, homogeneous filler dispersion, and successful graphene incorporation. The findings indicate that GNP and CSP reinforced EBCs possess significant potential for lightweight structural materials, thermal management systems, dielectric components, and sustainable multifunctional engineering applications. Full article