Search Results (154)

The stability of shield tunnel segmental linings is highly sensitive to the lateral pressure coefficient, especially under weak, heterogeneous, and variable geological conditions. However, the mechanical behavior of steel plate-reinforced linings under such conditions remains insufficiently characterized. This study aims to investigate the effects of varying lateral pressures on the structural performance of reinforced tunnel linings. To achieve this, a custom-designed full-circumference loading and unloading self-balancing apparatus was developed for scaled-model testing of shield tunnels. The experimental methodology allowed for precise control of loading paths, enabling the simulation of realistic ground stress states and the assessment of internal force distribution, joint response, and load transfer mechanisms during the elastic stage of the structure. Results reveal that increased lateral pressure enhances the stiffness and bearing capacity of the reinforced lining. The presence and orientation of segment joints, as well as the bonding performance between epoxy resin and expansion bolts at the reinforcement interface, significantly influence stress redistribution in steel plate-reinforced zones. These findings not only deepen the understanding of tunnel behavior in complex geological environments but also offer practical guidance for optimizing reinforcement design and improving the durability and safety of shield tunnels. Full article

In response to growing global concerns about plastic waste, the development of efficient recycling technologies for thermoplastics has become increasingly important. Polypropylene (PP), a widely used commodity resin, is of particular interest because of the urgent need to establish sustainable material circulation. However, conventional mechanical property evaluations of injection-molded products typically require dedicated specimens, which involve additional material and energy costs. As described herein, we propose a simplified mechanical model to derive Poisson’s ratio and critical expansion stress directly from standard uniaxial tensile tests of molded thermoplastics. The method based on the true stress–true strain relationship in the small deformation region was validated using various thermoplastics (PP, POM, PC, and ABS), with results showing good agreement with those of the existing literature. The model was applied further to assess changes in mechanical properties of Homo-PP and Block-PP subjected to repeated extrusion. Both materials exhibited reductions in elastic modulus and critical expansion stress with increasing extrusion cycles, whereas Block-PP showed a slower degradation rate because of thermo-crosslinking in its ethylene–propylene rubber (EPR) phase. DSC and chemiluminescence analyses suggested changes in stereoregularity and radical formation as key factors. This method offers a practical approach for evaluating recycled PP and contributes to high-quality recycling and material design. Full article

Three-dimensional printing is rapidly growing in applied dentistry. In order to print faster, increase workflow, and minimize the consumption of resin material, it is important to use the right printer and the correct printing orientation. The objective of the present report is to analyze the flexural strength of specimens realized with two different dental light-curing resins (Keyguide and C&B) obtained from two different Digital Light Processing (DLP) 3D printers. Different printing orientations (0°, 45°, and 90°) were evaluated. 3D Builder, MeshMixer, RayWare, and Chitubox software were used to design the resin specimens. A total of 15 Keyguide and 15 C&B specimens in the shape of a rectangular parallelepiped, with dimensions of 2 mm × 2 mm × 25 mm, were obtained with the Sprintray Moonray S 3D printer, and the 15 Keyguide and 15 C&B specimens presented the same characteristics as those printed using the Moon Night printer. Prior to sample printing, a calibration protocol (tolerance test and dimensional accuracy test) was performed using RayWare software. This procedure allowed compensation for resin shrinkage or expansion, thus ensuring dimensional consistency in all printed samples. Each resin specimen, after printing and post-processing (MoonWash 2 and MoonLight 2), was subjected to a mechanical test with a universal testing machine. After breaking the specimen, the flexural strength values were recorded with computer software (Bluehill, Instron Corporation, Canton, MA, USA). According to the results obtained, the printing orientation of the specimens does not affect the flexural strength of the two materials examined. However, at the maximum load, some differences emerged for both materials printed with the Moon Night printer, depending on their build angle. Both light-cured resins tested had a higher maximum load resistance when printed with the newer Moon Night printer. This result could be due to the Moon Night printer’s better construction characteristics compared to those of the Sprintray or to issues related to the dimensional calibration of the specimens. Full article

The growing demand for sustainable materials with tunable thermal and structural properties has driven the development of composites reinforced with natural fibers in additive manufacturing (AM) technologies. This study investigates the thermal and chemical behavior of polymer composites produced via Digital Light Processing (DLP), an AM technique based on vat photopolymerization that stands out for its high resolution, dimensional control, and superior speed compared to methods such as FDM and SLA. Samples were manufactured with a UV-curable acrylate resin reinforced with jute fibers (Corchorus capsularis) in mass fractions of 0%, 2%, 2.5%, and 3% in solid geometries (CS-). TGA indicated a 4% reduction in the initial degradation temperature with increasing fiber content, from 326.3 °C (CS-0) to 313.2 °C (CS-3.0). TMA revealed a reduction of up to 19% in the coefficients of thermal expansion, indicating greater dimensional stability. The DMA indicated a 16.9% decrease in the storage modulus with 3% fibers, evidencing changes in the viscoelastic response. FTIR detected additional bands at 3340 cm⁻¹ and 1030 cm⁻¹, related to O–H and polysaccharides, confirming a fiber–matrix chemical interaction. These results demonstrate the potential of jute as a sustainable reinforcement in photopolymerizable resins, paving the way for ecological and functional applications in 3D-printed composites. Full article

Alcalá de Ebro is located 35 km northwest of the city of Zaragoza, on the right bank of the Ebro River at the outlet of a ravine (Juan Gastón) towards the river, with a catchment area of more than 230 km². Over time, urbanisation and agricultural development have eliminated the last stretch of the drainage channel, and these water inputs have been channelled underground, filtering through the ground. This section of the Ebro Valley rests on a marly tertiary substratum, which promotes dissolution-subbing processes that can lead to sinkholes. The ground tends to sink gradually or suddenly collapse. Many studies have been carried out to understand not only the origin of the phenomenon but also its geometry and the area affected by it in the town of Alcalá de Ebro. In this sense, it has been possible to model an area around the main access road, where numerous collapsing sinkholes have been found, blocking the road and affecting houses. It also affects the embankment that protects the town from the floods of the river Ebro. These studies have provided specific knowledge, enabling us to evaluate and implement underground consolidation measures, which have shown apparent success. Several injection campaigns have been carried out, initially with expansion resins and finally with columnar development, using special low-mobility mortars to fill and consolidate the undermined areas and prevent new subsidence. These technical solutions propose a method of ground treatment that we believe is novel for this type of geological process. The results have been satisfactory, but it is considered necessary to continue monitoring the situation and to extend attention to a wider area to prevent, as far as possible, new problems of subsidence and collapse. In this sense, the objective is to continue the control and monitoring of possible phenomena related to subsidence problems in the affected area and its immediate surroundings, to detect and, if necessary, anticipate subsidence or collapse phenomena that could affect the body of the embankment. Full article

Fructooligosaccharides (FOSs) are carbohydrates of high nutritional value with various prebiotic properties. Optimizing their production process is of significant interest for expanding commercial-scale production. This review discusses the properties and potential applications of FOSs, addressing production challenges and providing an economic market analysis. Bibliometric analysis of data concerning the functional properties, production, purification, and applications of FOSs revealed an over 87% increase in the number of worldwide publications from 2012 to 2022, rising from 88 to 165. Furthermore, contributions from ninety-three countries were identified up to 2024, with Brazil ranking first, with 326 publications. Furthermore, Aureobasidium sp. and Aspergillus sp. have shown the best results for FOS production, with reported conversion in the order of 0.66 g FOS/g sucrose. Nevertheless, the formation of by-products or co-products requiring separation from the medium remains a challenge. Activated carbon, cation exchange resins, and zeolites are highlighted as key adsorbents, with the adsorption process achieving FOS purity exceeding 90%. Furthermore, membrane technology is identified as a more efficient and promising separation method. Addressing these limitations will facilitate the further expansion of the growing global FOS market, promoting a sustainable approach and their integration with biorefineries, which can enable the development of a wider range of value-added products. Full article

The thermal protection system of a re-entry vehicle requires a high-heat-resistant heat shield to protect the spacecraft. Most of the ablative materials developed so far have high heat resistance but have technical issues such as long production times. In this study, we propose a new ablative material (LATS/PEEK) consisting of PEEK and carbon felt as a material that can solve these problems. PEEK has excellent properties such as a short production time and its ability to be produced using 3D printer technology. In addition, PEEK can be molded with a variety of fusion bonding methods, so it is possible to mold the heat shield and structural components as a single structure. However, heating tests conducted in previous research have confirmed the expansion phenomenon of CF/PEEK produced by 3D printers. The expansion of the ablative material is undesirable because it changes the aerodynamic characteristics during re-entry flight. Therefore, the purpose of this research is to clarify the mechanism of the expansion phenomenon of the ablative material based on PEEK resin. Therefore, we conducted thermal gravimetric analysis (TGA) and thermomechanical analysis (TMA) and concluded that the expansion phenomenon during the heating test was caused by the pressure increase inside the ablative material due to pyrolysis gas. Based on this mechanism, we developed a new 3D LATS/PEEK with a structure that can actively release pyrolysis gas, and we conducted a heating test using an arc-heating wind tunnel. As a result, it was found that 3D LATS/PEEK had less expansion and deformation during the heating test than CF/PEEK manufactured using a 3D printer. Full article

This study investigates the effect of hygrothermal environments on the compressive properties of three-dimensional four-directional braided composites through experiments and finite element simulations, revealing the degradation behavior under various hygrothermal conditions. The results indicate that the moisture absorption behavior of the material conforms to Fick’s law. The longer the hygrothermal aging duration and the higher the temperature, the more significant the reduction in compressive performance, as evidenced by the continuous decline in ultimate stress. The hygrothermal environment primarily affects material performance through moisture absorption and thermal expansion characteristics of the epoxy resin, while the carbon fibers exhibit high stability in such conditions, maintaining the integrity of the three-dimensional four-directional structure. Microscopic observations reveal that hygrothermal aging exacerbates damage at the resin–fiber interface, leading to more pronounced stress concentration. Finite element simulations further quantify the internal stress distribution under hygrothermal conditions, demonstrating that moisture-induced expansion stress is more significant than thermal expansion stress, providing theoretical support and design guidance for improving the performance of composites in extreme environments. Full article

Silicon could revolutionize the performance of lithium-ion batteries (LIBs) due to its formidable theoretical gravimetric capacity, approximately ten times that of graphite. However, huge volume expansion during charge/discharge processes and poor electronic conductivity inhibited its commercialization. To address the problems, new carbon-silicon core-shell microparticles have emerged for prospective anodes in LIBs. In this study, we develop a core-shell structure by using hard carbon derived from phenolic resin as the core and nano silicon/pitch coating as the shell to the resulting HC@Si-P composite anode. A composition-optimized 20 wt.% pitch coated-Si/HC composite anode delivers superior cycling stability over 200 cycles under 1 A/g current density, showing a 398 mAh/g capacity. At 5.0 A/g current density during charge and discharge processes, the reversible capacity reaches 215 mAh/g. Upon reducing the current density to 0.1 A/g, the capacity remains high at 537 mAh/g. Impedance testing shows that after pitch coating, the RSEI impedance decreases and the diffusion coefficient of HC@Si-P increases. Moreover, the facile and scalable preparation technique is encouraging for the potential practical application of silicon-based anode materials of this type in the upcoming generation of LIBs. Full article

This study investigates the novel role of yarn-level fibre hybridisation in tailoring thermomechanical properties and thermal residual stress (TRS) fields in the resin at both micro- and meso-scales of 3D orthogonal-woven flax/E-glass hybrid composites. Unlike previous studies, which primarily focus on macro-scale composite behaviour, this work integrates a two-scale homogenisation scheme. It combines microscale representative volume element (RVE) models and mesoscale repeating unit cell (RUC) models to capture the effects of hybridisation from the fibre to lamina scale. The analysis specifically examines the cooling phase from a curing temperature of 100 °C down to 20 °C, where TRS develops due to thermal expansion mismatches. Microstructures are generated employing a random sequential expansion algorithm for RVE models, while weave architecture is generated using the open-source software TexGen 3.13.1 for RUC models. Results demonstrate that yarn-level hybridisation provides a powerful strategy to balance mechanical performance, thermal stability, and residual stress control, revealing its potential for optimising composite design. Stress analysis indicates that under in-plane tensile loading, stress levels in matrix-rich regions remain below 1 MPa, while binder yarns exhibit significant stress concentration, reaching up to 8.71 MPa under shear loading. The study quantifies how varying fibre hybridisation ratios influence stiffness, thermal expansion, and stress concentrations—bridging the gap between microstructural design and macroscopic composite performance. These findings highlight the potential of yarn-level fibre hybridisation in tailoring thermomechanical properties of yarns and laminae. The study also demonstrates its effectiveness in reducing TRS in composite laminae post-manufacturing. Additionally, hybridisation allows for adjusting density requirements, making it suitable for applications where weight and thermal properties are critical. Full article

The adhesive–resin composite pair has been the cornerstone of direct restorations in dentistry for many years. Resin composites are traditionally classified in three ways based on their inorganic structure, their organic composition and their viscosity. While these classifications have long been associated with the optical, mechanical, and clinical properties of resin composites, recent studies indicate that this classification is not always valid. In recent years, a significant expansion of the range of clinical resin composite families has occurred, each with varying degrees of validation through in vitro and clinical studies. As a result, new resin composites with distinct structures, viscosities, and clinical indications have emerged. Despite this progress, a formal classification of the clinical features of all resin composites is still lacking, leading to terminological inconsistencies in research and potential confusion among clinicians. This brief review, supported by an exhaustive search of the dental literature, proposes a new clinical classification system for resin composites based on their key clinical features to help clinicians and researchers easily identify the key clinical characteristics of formulations. This modular classification, encompassing eight main families and 14 characteristics, is particularly suited to future developments, as current trends aim to simplify procedures by integrating multiple formulations into single products. Full article

The relationship between thermodynamic entropy generation and free volume changes during the tensile deformation of epoxy resin was investigated. Thermodynamic entropy generation was evaluated using differential scanning calorimetry (DSC) for samples at various strain levels, while free volume changes were measured with positron annihilation lifetime spectroscopy (PALS). Volumetric strain was assessed through the digital image correlation (DIC) method. The results showed that both thermodynamic entropy and free volume increase during tensile deformation, and the average free volume radius becomes more uniform. It was observed that thermodynamic entropy generation and free volume each exhibit a linear relationship with volumetric strain. Additionally, thermodynamic entropy generation increased linearly with free volume. These findings suggest that the increase in thermodynamic entropy during tensile deformation is attributed to irreversible changes, such as the expansion of free volume within the material. Full article

Proanthocyanidins have received extensive attention due to their high functional value, but their sources are limited. Therefore, this experiment studied the preparation, biological activities, and characterization of proanthocyanidins from Chinese jujube (Ziziphus jujuba Mill. cv. Muzao) at different periods, aiming to explore a new source of proanthocyanidins and enhance their utilization value. Through ultrasonic-assisted enzymatic extraction, the optimal extraction conditions for PC from Muzao were determined, yielding a proanthocyanidin content of 2.01%. Purification using AB-8 macroporous resin increased the proanthocyanidin content by 11 times. The bioactivity results indicated that proanthocyanidins demonstrated significant in vitro antioxidant activity (scavenging rate ≥ 83.4%) and blood glucose-lowering activity (inhibition rate ≥ 84.7%). Both activities decreased with maturity, while the degree of polymerization also exhibited a positive effect. Mass spectrometry identified a total of 102 compounds, with cyanidin-based compounds being the most abundant, comprising 28 species. The comprehensive research results indicate that the oligomeric proanthocyanidins extracted, purified, and isolated from Muzao during the young fruit stage exhibit diverse biological activities and are abundant in content. They can be utilized for the extraction and purification of proanthocyanidins, offering a reference for the expansion of natural sources of proanthocyanidins and the development of functional foods. Full article

Starch foam has attracted significant attention as an alternative to expanded styrene (EPS) foam owing to its abundance and biodegradability. Despite these merits, its limited thermal insulation and flexibility compared to EPS have hindered its utilization in packaging. Herein, we report the effect of blending with starch/PBAT on foaming behavior and physical properties during foaming processing. We fabricated a starch/PBAT blend with systematically controlled blending ratios (0, 10, 15, 20, and 25 wt%) to analyze their effect on the interaction and characteristics of blended foam. The blending of starch and PBAT significantly reduced complex viscosity, enhancing resin flow during the foaming process. This improvement in resin flow led to increases in expansion ratio while reducing density and cell wall thickness. The thermo-insulation performance improved to 0.043 W/mK with 20 wt% of PBAT due to the enhanced expansion ratio and cell morphology. Additionally, the flexural strain at break improved significantly from 2.8 ± 0.6% to 9.6 ± 1.0% with increasing PBAT content. Enhanced water resistance was also observed, demonstrated by a reduction in water absorption and an extension of dissolution time. Overall, these findings underscore the potential of starch/PBAT foam to improve the thermal-insulating property, flexibility, and water resistance while maintaining their biodegradability and sustainability. Full article

Due to the significance of carbon utilization and storage, CO₂ huff and puff is increasingly receiving attention. However, the mechanisms and effects of CO₂ huff and puff extraction in medium to deep saturated heavy oil reservoirs remain unclear. Therefore, in this study, by targeting the medium to deep saturated heavy oil reservoirs in the block Xia of the Xinjiang oil field, measurements of physical properties were conducted through PVT analysis and viscosity measurement to explore the dissolution and diffusion characteristics of CO₂-degassed and CO₂-saturated oil systems. Multiple sets of physical simulation of CO₂ huff and puff in medium to deep saturated heavy oil reservoirs were conducted using a one-dimensional core holder to evaluate the EOR mechanism of CO₂ huff and puff. The results demonstrate that the solubility of CO₂ in degassed crude oil is linearly correlated with pressure. Higher pressure effectively increases the solubility of CO₂, reaching 49.1 m³/m³ at a saturation pressure of 10.0 MPa, thus facilitating oil expansion and viscosity reduction. Meanwhile, crude oil saturated with CH₄ still retains the capacity to further dissolve additional CO₂, reaching 24.5 m³/m³ of incremental CO₂ solubilization at 10.0 MPa, and the hybrid effect of CO₂ and CH₄ reduces oil viscosity to 1161 mPa·s, which is slightly lower than the pure CO₂ dissolution case. Temperature increases suppress solubility but promote molecular diffusion, allowing CH₄ and CO₂ to maintain a certain solubility at high temperatures. In terms of dynamic dissolution and diffusion, the initial CO₂ dissolution rate is high, reaching 0.009 m³/(m³·min), the mid-term dissolution rate stabilizes at approximately 0.002 m³/(m³·min), and the dissolution capability significantly decreases later on. CO₂ exhibits high molecular diffusion capability in gas-saturated crude oil, with a diffusion coefficient of 8.62 × 10⁻⁷ m²/s. For CO₂ huff and puff, oil production is positively correlated with the CO₂ injection rate and the cycle injection volume; it initially increases with the extension of the soak time but eventually decreases. Therefore, the optimal injection speed, injection volume, and soak time should be determined in conjunction with reservoir characteristics. During the huff and puff process, the bottom hole pressure should be higher than the bubble point pressure of the crude oil to prevent gas escape. Moreover, as the huff and puff cycles increase, the content of saturates in the oil rises, while those of aromatic, resin, and asphaltene decrease, leading to a gradual deterioration of the huff and puff effect. This study provides a comprehensive reference method and conclusions for studying the fluid property changes and enhanced recovery mechanisms in medium to deep heavy oil reservoirs with CO₂ huff and puff. Full article