Search Results (4,580)

Carbon fiber-reinforced resin matrix composites (CFRC) are extensively used in aerospace, automotive manufacturing, and sports equipment. However, the brittle nature of the resin matrix causes CFRC to exhibit severe vibrations and noise under dry friction conditions. Enhancing the intrinsic damping properties of the resin matrix serves as a fundamental and effective strategy to mitigate vibration and noise radiation in composite components. This study systematically investigates high-temperature co-curing damping composites using co-curing technology, aiming to improve the mechanical performance and damping characteristics of traditional fiber-reinforced epoxy resin composites. A novel carbon fiber-reinforced terminal carboxyl nitrile epoxy pre-polymer composite material demonstrates both stable chemical properties and excellent high-temperature resistance. Through formulation adjustments, the curing temperature and time of epoxy resin are matched with those of the terminal carboxyl nitrile epoxy pre-polymer. The performance of epoxy carbon fiber composites was evaluated through tensile tests, flexural tests, impact tests, infrared spectroscopy, thermogravimetric analysis, dynamic mechanical analysis, scanning electron microscopy, and X-ray diffraction. Results show that blending epoxy resin with terminal carboxyl nitrile liquid rubber enhances energy dissipation by increasing intermolecular friction and hydrogen bonding interactions. The damping ratio of epoxy resin-based carbon fiber composites reaches as high as 1.67%. Tensile strength, flexural strength, and impact strength reach 1968 MPa, 1343 MPa, and 127 kJ/m², respectively. The addition of terminal carboxylated nitrile liquid rubber facilitates the formation of continuous friction membranes, enhancing friction stability. Tensile tests demonstrate that carbon fiber composites containing 25% terminal carboxylated nitrile liquid rubber outperforms other formulations. As evidenced by impact tests, the performance of the prepared composites is superior to that of other configurations. Dynamic mechanical analysis indicates that the 25% rubber-containing composites exhibit enhanced damping characteristics and higher loss modulus. Experimental results confirm that this study advances the development of functional composites for vibration reduction and noise control applications. Full article

Thermoplastic hybrid composites reinforced with flax and glass fibers offer a sustainable, high-performance alternative for structural applications by balancing stiffness and energy absorption. This study investigated the impact of low-pressure plasma treatment on the thermal, mechanical, and microstructural properties of two polypropylene-based laminate configurations, PFGFP (polypropylene–flax–glass–flax–polypropylene) and PFGGFP (polypropylene–flax–glass–glass–flax–polypropylene), to optimize fiber–matrix interfacial adhesion. Materials were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), tensile testing, and scanning electron microscopy (SEM). The plasma treatment significantly enhanced the lignocellulosic fibers’ surface energy, reducing the flax contact angle from 93.5° to 56.1°. DSC analysis revealed a matrix crystallinity of 35.41%, while TGA confirmed flax thermal stability up to 250 °C. The PFGFP configuration exhibited superior mechanical performance (Tensile strength = 61.69 MPa; Young’s modulus = 518.62 MPa), attributed to its symmetric architecture and efficient fiber impregnation. Conversely, PFGGFP showed reduced strength and microstructural voids due to incomplete wetting in dense reinforcement regions. These findings conclude that the synergy between plasma surface modification and optimized laminate architecture is critical for the design of high-performance sustainable composites, providing an objective basis for improving interfacial compatibility in hybrid systems. Full article

The cement industry is central to sustainable manufacturing due to its high energy demand and associated CO₂ emissions. In cement production, a substantial share of electrical energy is consumed in the clinker grinding circuit, where Blaine fineness (specific surface area, cm²/g), a key quality output, affects both cement performance and specific energy consumption. However, laboratory Blaine measurements are typically available with a 30–60 min delay, which limits timely process interventions and may promote conservative operating practices (e.g., precautionary over-grinding) to secure quality. This study develops machine-learning models to predict the finished-product Blaine fineness (Blaine-F) from routinely recorded industrial quality-control inputs, including XRF-based oxide composition, derived chemical moduli (lime saturation factor, LSF; silica modulus, SM; alumina modulus, AM), laser-diffraction particle-size distribution descriptors (Q10/Q50/Q90 corresponding to D10/D50/D90 percentile diameters; and R3 residual fractions at selected cut sizes), and intermediate in-process fineness (Blaine-P). The models were trained on over 200 finished-product samples obtained from the quality-control laboratory information management system (LIMS) of Seza Cement Factory (SYCS Group, Turkey). Ridge regression, Random Forest, XGBoost, LightGBM, and CatBoost were tuned using RandomizedSearchCV with five-fold cross-validation and evaluated on a held-out test set using MAE, RMSE, and R². The results show that the linear baseline provides limited explanatory power (Ridge: R² ≈ 0.50), consistent with the strongly non-linear behavior of the grinding–separation system, whereas tree-based ensemble methods achieve higher predictive accuracy. XGBoost yields the best overall performance (R² = 0.754; RMSE = 76.9 cm²/g), while Random Forest attains R² = 0.744 with the lowest MAE (61.7 cm²/g). Explainability analyses indicate that Blaine-F is primarily influenced by the fine-tail PSD descriptor Q10 (D10 particle size) and the intermediate fineness Blaine-P, whereas chemistry-related variables (e.g., LSF and SiO₂, and particularly SM) provide secondary yet meaningful contributions. These findings support the use of the proposed model as a virtual sensor to reduce decision latency associated with delayed laboratory Blaine measurements and to enable tighter fineness targeting. Potential energy and CO₂ implications should be quantified using site-specific, plant-calibrated relationships between kWh/t and Blaine fineness, rather than inferred as measured outcomes within the present study. Full article

In this study, we develop bio-epoxy composites incorporating bio-oils obtained from the pyrolysis of almond and walnut shells at 400 °C and 600 °C, with the aim of evaluating their potential as renewable precursors for epoxy resin modification. The influence of pyrolysis temperature on bio-oil yield and chemical composition is examined to identify phenolic-rich fractions relevant to epoxy curing. Bio-oil production increased with temperature, reaching 40.46% for walnut shells and 36.84% for almond shells at 600 °C. Chemical analysis revealed that aromatic compounds, particularly phenolics, were the major constituents associated with epoxy curing reactivity. For walnut hulls, the total aromatic fraction increased from 30.4% at 400 °C to 35.2% at 600 °C, while almond hulls showed an increase from 23.8% to 26.1% over the same temperature range. Incorporation of bio-oil into the epoxy matrix promoted three-dimensional network formation through reactions between epoxy groups and the functional moieties present in the bio-oil, resulting in a higher cross-linking degree, Young’s modulus, and tensile strength. However, compared to neat epoxy, the bio-oil-modified systems exhibited reduced storage modulus (E′) and glass transition temperature (Tg), attributed to the plasticizing effect of lighter oxygenated species. Overall, although bio-oil incorporation decreases Tg and cross-linking degree, it still provides a viable pathway toward partially bio-based epoxy resins with enhanced stiffness and competitive mechanical performance. Full article

Zirconia-based ceramics find wide application in engineering due to their very high hardness, resistance to elevated temperatures, and high fracture toughness. Among stabilizers of the advantageous tetragonal zirconia phase, yttria allows for better grain size refinement than ceria does; thus, Y₂O₃ is the most widely used. In the present study, comparative analysis was performed for yttria-stabilized zirconia (YSZ) and ceria-stabilized zirconia (CSZ) in terms of sinterability, densification, and mechanical properties, including hardness and resistance to plastic deformation. The results proved that CSZ sintered in similar conditions as YSZ exhibits similar properties, including an elastic modulus of 200–220 GPa and H/E of 0.070–0.076. In particular, the hardness of the ZrO₂–5 wt% CeO₂ ceramic appeared to be 14.6 ± 0.5 GPa, close to that of ZrO₂–3 wt% Y₂O₃, which was 14.20 ± 0.74 GPa. However, SiC addition to ZrO₂–5 wt% CeO₂ composites increased hardness substantially up to 16.8 ± 0.8 GPa. Moreover, the fracture toughness of CSZ was 2.5 times higher than that of YSZ sintered under identical conditions. Thus, CeO₂ can be a good, cheaper alternative to the traditionally used Y₂O₃ stabilizer for submicron-grained tetragonal zirconia ceramics. Full article

The application of bioactive polysaccharides from medicine–food homology sources in the food industry still poses a significant challenge. This study investigated the effects of ultrasonically modified polysaccharides from Dendrobium officinale on the physicochemical properties of plant-based yogurt. The Dendrobium officinale polysaccharides were treated with ultrasound at varying power levels (200–600 W) and durations (20–40 min). The modified polysaccharides (0.5%) were then incorporated into soy-protein-isolate-based (5%) yogurt, and the resulting composites were characterized in terms of their structural and functional properties. Results showed that optimal treatment (400 W, 20 min) reduced the particle size of the polysaccharides while enhancing their hydrophilicity and hydroxyl group exposure. The incorporation of these modified polysaccharides into SPI gels promoted probiotic growth, lowered the gel pH, and facilitated the formation of protein gel. Consequently, the resulting gels exhibited a denser microstructure, along with superior gel strength, water-holding capacity, apparent viscosity, storage modulus, deformation resistance, and antioxidant activity (scavenging DPPH and ABTS radicals). These findings suggest that ultrasonic treatment not only modifies polysaccharides from Dendrobium officinale to enhance their bioactivity but also augments their capacity to facilitate protein gel formation. This work provides the evidence that ultrasound-modified polysaccharides from Dendrobium officinale can simultaneously act as prebiotic stimulators and structural reinforcements, offering a novel strategy for designing high-quality plant-based yogurts. Full article

A novel Lithium triflate-incorporated Solid Polymer Electrolyte (SPE) has been developed by using the optimized blend of Ghatti Gum (GG) and Xanthan Gum (XG) with a biodegradable synthetic polymer, Polyvinyl alcohol (PVA), ethylene glycol as a plasticizer, and formaldehyde as a cross-linker for energy storage applications. They are examined by X-ray diffraction, Fourier transform infrared spectroscopy, and electrochemical impedance analysis. The frequency-dependent conductivity adheres to Joshner’s universal power law, with the TF10 composition achieving the higher ionic conductivity of 2.73 × 10⁻⁵ S cm⁻¹. Temperature-dependent conductivity confirms Arrhenius-type behavior and shows a low activation energy of 0.15 eV that supports facile ion transport. The conduction process in TF10 follows the Correlated Barrier Hopping (CBH) model. Dielectric and modulus investigations indicate relaxation dynamics with the shorter relaxation time (6.45 × 10⁻⁶ s) from tangent loss spectra. From the SEM analysis, the uniform distribution and the porous nature of the electrode activated carbon are confirmed. A supercapacitor is assembled with TF10 displays electric double-layer capacitive features, delivering a specific capacitance of 7.1 Fg⁻¹ at 15 mVs⁻¹. Charge–discharge analysis reveals energy and power densities of 2.52 Wh kg⁻¹ and 2500 W kg⁻¹, respectively, for the supercapacitor. Full article

The rising environmental concerns over cement-based construction materials have led to the development of sustainable alternatives. Among these, geopolymers represent a promising class of low-carbon binders offering environmental benefits and competitive mechanical properties; however, their intrinsic brittleness limits their tensile and post-cracking performance. This study investigates the adoption of flax fibers as natural reinforcement to enhance ductility and post-peak behavior of metakaolin-based geopolymers. The performance of metakaolin-based geopolymers with flax fibers (MKFLAX) was experimentally evaluated in terms of strength, stiffness, toughness, and failure behavior. The addition of flax fibers enhanced ductility, toughness, and post-peak load-carrying capacity while slightly improving stiffness due to the bridging of cracks and the fiber pull-out mechanism. In comparison with the available literature on sisal, flax, and jute fibers, flax fibers showed improved performance due to the better dispersion within the matrix and higher tensile modulus. These findings highlight that flax fiber-reinforced metakaolin geopolymers show enhanced post-cracking behavior at the laboratory scale and could be of interest for sustainable cementitious materials, subject to further validation at the structural scale. Furthermore, a nonlinear finite element model was adopted based on damage mechanics to simulate the damage localization, stress–strain response and post-peak behavior of geopolymer composites. The numerical results showed a reasonable agreement with the experimental trends, particularly in the elastic and early softening phases. The findings are limited to the studied material system, fiber content, and small-scale samples and should be viewed as trend-level observations rather than generalized performance claims. Full article

Background/Objectives: Bulk-fill (BF) resin-based composites (RBCs) have become increasingly popular due to their efficient placement. However, there is a lack of comprehensive performance comparisons among commercially available BF RBCs. In standardized curing conditions, this study aimed to compare the mechanical performance, water sorption and solubility, surface roughness, and color stability of commercially available BF RBCs with different consistencies (flowable and packable). Methods: Ten BF RBCs, along with a conventional RBC (control), were evaluated. Flexural strength and elastic modulus were measured using a three-point bending test. Water sorption and solubility were assessed after 28-day water storage. Color (ΔE₀₀) and surface roughness (ΔRa) changes were measured after 28-day immersion in water, Pepsi, or coffee. One-way ANOVA and Tukey’s tests analyzed the data. Results: 3M Flow, Shofu Bulk, and Ivoclar Flow revealed lower strength (p < 0.001) compared to 3M Bulk (132.17 ± 12.54 MPa) and the control (124.56 ± 15.60 MPa). Shofu Bulk (24.68 ± 12.55 µg/mm³) and Ivoclar Flow (27.11 ± 6.27 µg/mm³) were the least affected by water sorption. While Shofu Bulk (13.98 ± 11.39 µg/mm³), Ivoclar Flow (20.28 ± 6.64 µg/mm³), and SDR (20.84 ± 9.74 µg/mm³) exhibited the lowest solubility (p < 0.01). After water and Pepsi immersion, FGM Bulk showed a significant color change compared to 3M Bulk and Ivoclar Bulk (p < 0.05). Following coffee immersion, Shofu Bulk (17.38 ± 1.82) revealed significant color changes (p < 0.001). Increased surface roughness was observed in 3M Bulk and Ivoclar Bulk after water immersion, Shofu Bulk after Pepsi immersion, and FGM Bulk after coffee immersion. Conclusions: BF RBCs exhibit notable variability in their intrinsic properties. 3M Bulk and Control showed the highest strength, while Shofu Bulk had significant color changes. Full article

In this research, Fe-P scaffolds were successfully fabricated by the powder metallurgy method for the first time, using NaCl as the space holder for bone tissue engineering applications, with apparent porosities of approximately 70%. The Fe₃P powder was successfully synthesized by the mechanochemical method under an argon atmosphere using an initial mixture of Fe and P powders. The XRD patterns show that Fe₃P was obtained after sintering the milled powders at 1000 °C. Fe, Fe₃P, and Fe-50 wt% Fe₃P composite scaffolds and bulk pellets were prepared by sintering the milled powder at 1000 °C. Furthermore, the mechanical properties (compression strength) and bioactivity of the Fe-P scaffolds were determined. According to the compression test results, the composite scaffold showed higher compressive strength, lower fracture strain, and higher elastic modulus than the Fe and Fe₃P scaffolds, indicating that adding Fe₃P to Fe improves the mechanical properties. Moreover, among the scaffolds prepared by sintering at 1000 °C, the Fe scaffold exhibited the highest corrosion rate compared to the Fe₃P and composite samples, while the corrosion resistance of the composite sample was 3 times higher than that of the Fe sample. The ICP analysis showed that the amount of Fe released from the bulk pellets during soaking in PBS solution after four weeks was 3220 μg/dL, 4003 μg/dL, and 4774 μg/dL for the composite, Fe₃P, and Fe samples, respectively. The composite sample showed the highest cell viability, while the Fe sample had the lowest. The compressive strength (12.62 MPa) and fracture strain (5.98%) of the porous sintered composite scaffold at 1000 °C were within the range of trabecular bone, while the compressive strength of the composite sample was 17 times higher than that of the Fe sample. Furthermore, the MTS test showed that all the samples had good viability, while the composite sample had the best cell viability. The scaffolds were not cytotoxic. It can be concluded that the mechanical and biological properties of the composite sample were superior to those of the Fe and Fe₃P samples and that it may be a promising candidate for bone tissue engineering applications, especially for trabecular bone replacement. Full article

Titanium-based alloys are widely used in dental implantology; however, the mechanical limitations of commercially pure titanium (cpTi) and unresolved concerns regarding stress shielding remain. This study evaluated the structure–property–function relationship of a novel β-type titanium–niobium–zirconium (Ti–Nb–Zr; TNZ) alloy for dental implant applications. Laboratory testing assessed the elemental composition, tensile properties, and fatigue resistance of the cpTi, compared with modified Grade 4 cpTi (MG4T). In parallel, a randomized, single-blind, controlled clinical trial was conducted over 12 months to compare the clinical performance of TNZ and MG4T implants under functional loading. A total of 80 participants (mean age: 54.2 years; 43 females, 37 males) were enrolled, with 77 completing the 12-month follow-up (TNZ: n = 38; MG4T: n = 39). Clinical outcomes included implant success and survival, peri-implant soft tissue parameters, marginal bone levels, fractal dimension (FD) analysis of trabecular bone, and adverse events. TNZ implants demonstrated superior fatigue resistance without an increase in the elastic modulus relative to MG4T. Clinically, both groups achieved 100% implant success and survival, with no implant-related adverse events. FD analysis revealed time-dependent bone remodeling without evidence of pathological adaptation. These findings support the functional viability of TNZ as a mechanically robust, biocompatible implant material. Further long-term, multicenter trials are warranted to confirm sustained clinical benefits and broader applicability. Full article

The aim of this study is to experimentally evaluate the damage mechanisms occurring in the adhesive-bonded regions of glass fiber-reinforced polymer (GFRP) and carbon fiber-reinforced polymer (CFRP) composites, which are widely used in marine and offshore wind turbine applications, under environmental conditions. In particular, this study focuses on the degradation caused by long-term seawater exposure and its effects on the bending behavior and load-carrying capacity of adhesive joints. For this purpose, the specimens were prepared in accordance with ASTM D5868-01, using 7-layer GFRP and 8-layer CFRP laminates. Single-lap adhesive joints were fabricated. To simulate marine environmental conditions, the single-lap adhesive joints were immersed in natural seawater obtained from the Aegean Sea (22 °C temperature and 3.3–3.7% salinity) for 1, 2, and 3 months in separate containers. Three-point bending (3PB) tests were performed on specimens representing marine applications, while four-point bending (4PB) tests were conducted on specimens representing offshore wind turbine blade structures. The results quantitatively revealed the influence of seawater on adhesive-bonded composite joints. In 3PB tests, the reductions in the Young’s modulus of GFRP specimens after 1, 2, and 3 months of exposure were measured as 5.94%, 8.90%, and 12.98%, respectively. For CFRP specimens, degradation was more limited, with corresponding reductions of 1.28%, 3.39%, and 3.74%. A similar trend was observed in 4PB tests representing offshore wind turbine applications, where GFRP joints exhibited modulus reductions of 3.15%, 6.42%, and 9.45%, while CFRP joints showed reductions of 1.29%, 2.62%, and 3.48% for the same exposure durations. Overall, the findings demonstrate that CFRP composites exhibit more stable mechanical behavior under environmental exposure, whereas GFRP structures undergo more pronounced performance losses, particularly in moisture- and salt-rich environments. These results highlight the critical importance of material selection for long-term durability in offshore composite structures. The outcomes of this study contribute to a better understanding of the damage processes occurring in composite adhesive joints under environmental conditions and provide a scientific basis for developing more reliable design and material selection strategies in both the marine and wind energy sectors. Full article

Multi-composite activated neural network operators can be understood as positive linear operators, allowing them to be analyzed using standard, established theory. Formed by composing multiple general activation functions, these operators act upon continuous real-valued functions defined on a compact interval. This work presents a quantitative analysis of how quickly these operators converge to the unit operator. Utilizing general inequalities based on the modulus of continuity—applicable to either the function itself or its derivative—this study establishes both uniform and Lp approximation results. Furthermore, the analysis incorporates the convexity of functions to produce related, specific results. Full article

Alginate, primarily sodium alginate, is a biopolymer derived from brown algae or bacterial sources that forms hydrogels via ionic crosslinking with certain divalent cations. Its incorporation into soils, earthen materials, cementitious composites, and asphalt mixtures improves mechanical performance and durability. This review collates recent advances in alginate-based treatments for geotechnical and construction applications, highlighting how alginate dosage, substrate type, gelation method, mixing strategy, and curing regime influence mechanical strength, physical properties, and self-healing efficiency. In soil stabilization, alginate treatments increase unconfined compressive strength (UCS) by 0.2–1.5 MPa in sand, with some studies reporting increases of over 2 MPa. Reported UCS improvements in alginate-treated clayey soils generally fall within the range of 50–150% compared to untreated samples, although isolated studies document increases exceeding 200%, depending on material composition and curing conditions. In cementitious systems, alginate-based capsules and hydrogels facilitate self-healing, achieving high closure rates of 70–100% for microcracks <0.4 mm, with some studies achieving complete sealing of macrocracks up to 4 mm while also recovering significant mechanical strength. Depending on dosage and formulation, alginate can also serve as a viscosity-modifying admixture, increasing the plastic viscosity and yield stress of the fresh mix, with this thickening effect becoming pronounced at dosages above approximately 0.1 w/w% by cementitious binder mass. For asphalt pavements, alginate-encapsulated rejuvenators facilitate high healing efficiency under cyclic loading and thermal cycling; rheological tests confirm elevated complex modulus and improved viscoelastic response. This review also synthesizes an explanatory framework for the divergent results found in the literature, advocates for standardized experimental protocols and material characterization, and outlines future research directions to advance alginate as a suitable alternative to conventional stabilizers. Full article

The development of natural biopolymers to improve the structural and textural defects of whey protein in acidic dairy products is of great interest. This study investigated the interaction between Phellinus linteus polysaccharides (PLPs) and heat-induced polymerized whey protein (PWP), and its application in goat milk yogurt. The physicochemical properties and interaction mechanisms of PWP-PLP composite hydrogels (with 1–4% PLP) were characterized using particle size, DSC, and synchronous rheology and Fourier transform infrared spectroscopy. The results show that PLP increased hydrogel particle size, absolute zeta potential (from −34.98 mV to −42.26 mV), and denaturation temperature (from 102.33 °C to 112.57 °C), indicating the enhanced stability. SR-IR analysis revealed intensified hydrogen bonding and protein secondary structure rearrangement. Incorporated into yogurt, the optimal composite (10% PWP with 3% PLP) significantly improved water-holding capacity (by 20–30%), storage modulus (G′), and produced a denser microstructure with superior texture. This work demonstrates that PLP is an effective natural modifier for constructing stable protein–polysaccharide hydrogels to enhance yogurt quality. Full article