Search Results (506)

Fused deposition modeling (FDM) provides a flexible manufacturing route for continuous fiber-reinforced thermoplastic composites, but weak interlaminar bonding and the trade-off between load-bearing capacity and deformation capability still limit their structural applications. In this study, multi-scale carbon/Kevlar fiber hybridization was introduced into acrylonitrile butadiene styrene (ABS)-based composites by combining continuous carbon fiber (CCF) or continuous Kevlar fiber (CKF) with short carbon fiber-filled ABS (ABS/SCF) or short Kevlar fiber-filled ABS (ABS/SKF). Four hybrid configurations and two continuous-fiber baseline composites were fabricated by FDM and evaluated through three-point bending tests, floating roller peel tests, peeled-surface SEM observations, and Rule-of-Mixtures-based hybrid effect analysis. The flexural results showed that short-fiber-filled matrices improved the flexural properties of both CCF- and CKF-based composites, but the degree of improvement depended on the fiber combination. Among the investigated configurations, CCF + ABS/SCF exhibited the highest flexural modulus and strength, which were 34.31% and 27.26% higher than those of CCF + ABS, respectively. For the CKF-based composites, CKF + ABS/SCF increased the flexural modulus and strength by 31.51% and 26.78%, compared with CKF + ABS, while maintaining the progressive deformation behavior associated with Kevlar reinforcement. The peel results showed that all hybrid composites had higher interlaminar peel resistance than their corresponding baselines, with increases ranging from 18.66% to 54.42%. The peeled-surface SEM observations indicated that the short-fiber-filled matrices changed the crack-propagation features, with more matrix tearing, fiber pull-out, and irregular peeling areas. The RoM-based comparison showed that the measured flexural properties of all hybrid configurations were higher than the corresponding RoM reference values. Overall, CCF + ABS/SCF was more suitable for improving stiffness and load-bearing capacity, whereas CKF + ABS/SCF showed a more balanced response in terms of flexural performance, interlaminar peel resistance, and progressive deformation behavior. Full article

3D-printed continuous carbon fiber-reinforced polylactic acid (CF/PLA) composites combine the high load-bearing capability of continuous fibers with the structural design freedom of additive manufacturing, showing broad application prospects in lightweight complex structures. However, the chemically inert surface of carbon fibers and their insufficient interfacial compatibility with the PLA matrix lead to inefficient interfacial load transfer, thereby limiting the mechanical performance of the composites. In this study, a waterborne polyurethane (WPU)-based sizing treatment was applied to carbon fibers to enhance the fiber–matrix interface of 3D-printed continuous CF/PLA composites. The WPU sizing layer increased fiber-bundle cohesion and introduced a transition region between CF and PLA through possible hydrogen bonding, dipolar interactions, and physical adhesion. When the nominal WPU concentration was 5 wt%, the apparent interfacial shear strength reached 1.31 MPa, representing an improvement of approximately 65% compared with ACF/PLA. The three-point flexural strength reached 69.76 MPa, which was 55.3% higher than that of the ACF/PLA composite. These results indicate that WPU sizing is an effective and scalable interfacial regulation strategy for improving the mechanical properties of 3D-printed continuous CF/PLA composites. Full article

This experiment aimed to explore the effects of different doses of compound probiotics (a 1:1:1 mixture of Saccharomyces cerevisiae, Lactobacillus acidophilus, and Bacillus subtilis) added to the diet on pregnant sows and weaned piglets. The experiment was carried out in two stages. Experiment with pregnant sows: thirty-six second-parity Large White sows at 80 d of late gestation were randomly divided into a control group, experimental group I, and experimental group II. The control group was fed a basal diet, while experimental groups I and II were fed the basal diet supplemented with 2 g/kg and 3 g/kg of compound probiotics, respectively. The pre-experiment lasted 7 d, and the formal experiment continued until the end of lactation. The results showed that the numbers of live piglets per litter, healthy piglets per litter, litter birth weight and litter weaning weight in the experimental groups were significantly higher than those in the control group (p < 0.05). Colostrum IgG concentration in experimental group I was significantly higher than that in the control group and experimental group II (p < 0.05). Compound probiotics significantly increased colostrum immunoglobulin levels (p < 0.05). The concentrations of ammonia, carbon dioxide and PM2.5 in the barns of the experimental groups all showed a decreasing trend. Experiment with weaned piglets: a total of 160 Landrace × Yorkshire crossbred weaned piglets at 30 d of age with an initial body weight of (8.01 ± 0.13) kg were randomly assigned to four groups. The control group was fed a basal diet, while the treatment groups were supplemented with 2, 3, and 4 g/kg of compound probiotics, respectively. The results indicated that average daily gain and average daily feed intake in experimental group III were significantly higher than those in the control group, while the feed-to-gain ratio and diarrhea rate were significantly lower (p < 0.05). The apparent digestibility of crude fiber was significantly higher than that in the control group (p < 0.05), and serum IgA was significantly higher than in the other groups (p < 0.05). In conclusion, dietary supplementation with 2 g/kg compound probiotics for sows in late gestation showed the optimal effect, improving reproductive performance, colostrum immune indices and reducing harmful gases in the barn. For weaned piglets, supplementation with 4 g/kg compound probiotics improved growth performance, nutrient digestibility and serum immune indices. Full article

Viscose-derived carbon fibers (VDCFs) are lightweight and flexible textile materials with strong potential for electromagnetic interference (EMI) shielding; however, their performance is governed by surface chemistry. This study aims to tailor the functional properties of VDCFs via process-driven sulfurization. The fibers were treated with sulfur vapor at 400–800 °C under argon, followed by rapid quenching, enabling controlled sulfur incorporation (0.5–12 mmol g⁻¹). Structural and chemical analyses (XRD, SEM–EDS, ATR–FTIR, and TPD–MS) revealed temperature-dependent sulfur incorporation and evolution of sulfur-containing surface functionalities. Sulfurization at 400–500 °C favored the formation of thermally labile sulfur species, tentatively assigned to mercapto-, sulfide-, and polysulfide-type groups, whereas higher treatment temperatures promoted more thermally stable sulfur-containing functionalities associated with the carbon framework. Two desorption regimes (120–250 °C and 250–500 °C) indicate the coexistence of weakly and strongly bound sulfur species. Importantly, sulfurization preserved fibrous morphology while increasing surface roughness and defect density, enhancing interfacial activity. The treatment temperature was identified as the key factor controlling sulfur loading and distribution, with sulfur content continuing to decrease above 600 °C, albeit at a reduced rate. Electromagnetic characterization in the X-band (8–12 GHz) showed a transition toward reflection-dominated EMI shielding, with reflectivity increasing from 87% for pristine fibers to 94–95% for sulfurized samples at 10 GHz, accompanied by corresponding decreases in transmission and absorption. These results demonstrate a clear processing–structure–property relationship and highlight sulfur-functionalized VDCFs as efficient textile components for EMI shielding. Full article

The influence of double continuous cold rolling followed by annealing on the texture evolution and mechanical properties of a commercial low-carbon ferritic steel was investigated. Ultrathin sheets (final thickness 0.22 mm) were produced through a two-stage cold rolling process with intermediate and final annealing at 690 °C for 35 s, followed by light temper rolling at 100 °C for 20 s. Texture evolution was characterized using Electron Backscatter Diffraction (EBSD) with Orientation Imaging Microscopy (OIM), producing pole figures and orientation distribution functions (ODFs). Mechanical properties were evaluated through Vickers microhardness and ultimate tensile strength measurements obtained from three independent locations per sample. Quantitative ODF analysis (φ₂ = 45°) revealed that γ-fiber ({111}//ND) intensity increased after each cold reduction stage and decreased after annealing due to recrystallization. The α-fiber (110/RD) and cube components (001//RD) showed a slight increase after annealing. The final ultrathin sheet exhibited moderate γ-fiber intensity (≈3 M.R.D), low Vickers microhardness (100–150 HV), and tensile strength (400–450 MPa). These results demonstrate controlled evolution of texture and microstructure during double cold rolling and annealing, providing a basis for future studies on forming-related behavior without directly assessing formability. Full article

The application of continuous carbon fiber (CCF) can reinforce the mechanical properties of 3D-printed parts, but the effect of reinforcement layer distribution on composite performance remains unclear. This study investigates the effect of concentrated and separated distributions of CCF layers with different numbers of reinforcement layers. Tensile and flexural tests are conducted in accordance with ASTM D5083 and ASTM D790, respectively. Under the conditions of a solid-filled matrix (Onyx) and 0° CCF deposition, both concentrated and separated CCF layers improve several mechanical properties. Compared with pure Onyx, one-layer CCF increases the tensile modulus by about six times and more than doubles the tensile strength. Increasing the CCF volume leads to further increases in these properties. With concentrated three-layer CCF, the tensile modulus and tensile strength reach 7.153 ± 0.090 GPa and 109.045 ± 5.124 MPa, respectively. For flexural properties, separated two- and three-layer CCFs significantly improve the tangent modulus of elasticity from 0.467 ± 0.106 GPa for pure Onyx to 2.246 ± 0.333 GPa and 3.394 ± 0.081 GPa, respectively. This study also compares the tensile and flexural strength-to-weight ratio of all specimen groups and analyzes the failure mechanisms based on macroscopic fracture appearance. The results can provide guidance for selecting appropriate CCF layer distribution strategies to reinforce composites in different applications. Full article

Adhesive joints typically require high safety factors, as their mechanical performance is highly sensitive to environmental and manufacturing variations. Health monitoring can reduce these safety factors by continuously assessing the condition of the joint. While intrinsic and extrinsic sensing approaches exist, they are often based on periodic inspection or manual sensor integration, which limits their suitability for continuous in-service monitoring. This study investigates a novel sensor placement using additively manufactured strain sensors deposited by jet dispensing across the adhesive gap. Tensile lap-shear specimens were fabricated using CFRP (carbon-fiber-reinforced plastic) laminate, an epoxy adhesive, and silver-ink strain sensors placed internally within the joint and externally across the adhesive gap. Mechanical testing revealed that externally printed sensors produced an average resistance change of 65.3% near the failure stress of the adhesive joint, an order of magnitude higher than sensors embedded within the adhesive layer with 6.6% average resistance change. However, the average coefficient of variation increased as well, from 7.6% for internal to 32.6% for external. This sensor response exceeds reported environmentally induced variations in printed sensors and thus represents a promising candidate for condition monitoring. Further work is required to demonstrate actual damage detection capabilities and assess long-term stability under environmental and cyclic loading conditions. Full article

Pultrusion is an efficient continuous manufacturing process for fiber-reinforced polymer (FRP) composites, but conventional open-bath impregnation has limitations such as resin exposure, quality variation, and resin loss. To overcome these limitations, closed-injection pultrusion (CIP) and short-pot-life resin systems have recently been introduced. However, the effects of processing variables on the quality and properties of composites manufactured using such resin systems have not been fully clarified. In this study, the effects of resin viscosity and pulling speed on the quality and mechanical properties of carbon FRP (CFRP) and glass FRP (GFRP) composites manufactured by CIP were investigated. CFRP and GFRP composites were fabricated at resin temperatures of 30 and 40 °C and pulling speeds of 300, 400, and 500 mm/min. The manufactured composites were evaluated in terms of void content, microstructure, hardness, and tensile properties. The results showed that increasing pulling speed increased void content and promoted macrovoids and locally poor impregnation, whereas the influence of resin temperature was relatively limited. Hardness, tensile strength, and elastic modulus decreased as pulling speed increased. These results demonstrate that CFRP and GFRP composites can be successfully manufactured by CIP using short-pot-life resin systems, and that precise control of resin viscosity and pulling speed is essential for achieving high quality and mechanical performance. Full article

Rice (Oryza sativa L.) straw-return can improve soil carbon (C) sequestration, but its adoption in intensive rice systems is limited by short fallow periods (<30 days), which likely lead to incomplete straw decomposition and increase methane emissions under continuous flooding (CF). Brittle rice straw, characterized by lower recalcitrant fiber content and rapid decomposition, may overcome this constraint; however, its environmental performance under alternate wetting and drying (AWD) remains unclear, such as broader C allocation. This 150-day microcosm study evaluated the interaction of straw type (brittle vs. non-brittle) and water management (CF vs. AWD) on greenhouse gas (GHG) emissions, dissolved C production, soil C storage, and aggregate formation in two contrasting paddy soils (sandy loam vs. silty clay loam). Compared with non-brittle straw, brittle straw returns reduced net GHG emissions by approximately 28.4% under CF and 39.6% under AWD. The combination of brittle straw with AWD produced the lowest net GHG emissions (0.61 kg CO₂-eq m⁻²), indicating that intermittent oxygen input effectively mitigated the early decomposition-related emission risk. Brittle straw also increased the concentrations of dissolved inorganic C by 14.2% and nitrate by 64.3% under AWD, suggesting enhanced mineralization and potential inorganic C stabilization. Regardless of straw type, straw return improved soil C stocks by 27.3% in sandy loam and 29.6% in silty clay loam, while also promoting macroaggregate formation. Overall, this study demonstrated that coupling brittle rice straw with AWD can reduce GHG emissions while maintaining soil C benefits, offering a promising residue management strategy for intensive rice cultivation. Full article

Addressing issues such as corrosion and the eccentric wear of metal tubing strings, low heating efficiency, and high operation and maintenance costs of lifting systems in heavy-oil extraction, core equipment comprising carbon-fiber-reinforced PEEK (Polyetheretherketone) multi-layer composite continuous tubing has been developed. This equipment integrates an embedded cable-laying system and an intelligent regulation module, establishing a rodless oil-extraction technology system suitable for heavy-oil reservoirs. This article systematically describes the process structure, preparation principle, core characteristics, and key parameters of this composite continuous tubing. By deriving an equivalent thermal-resistance model for the multi-layer structure and an unsteady-state heat-transfer equation, precise regulation of the wellbore temperature field is achieved. Combined with field tests at Well A in Jinghe Oilfield, the tubing’s effectiveness in reducing viscosity, increasing production, saving energy, and extending the operational cycle in heavy-oil extraction is verified. The results show that the carbon-fiber-reinforced PEEK composite continuous tubing possesses characteristics such as high strength, strong corrosion resistance, low friction, and high thermal insulation. When paired with a viscosity–temperature coupling regulation algorithm, the heating efficiency is improved by 40% compared to traditional electric heating rods. The efficiency ranges from 37% to 43% when the formation thermal conductivity fluctuates by ±20%. Field applications have achieved a 230% increase in daily oil production, a 30% reduction in system energy consumption, and an extension of the hot washing cycle to over 180 days. The development of this tubing breaks through the technical bottleneck of traditional metal tubing, providing a new material solution for the efficient and intelligent development of heavy-oil extraction, and has broad promotional value. Full article

The rapid growth of global air traffic places the aviation industry under dual pressure: meeting increasing demand for aircraft while substantially reducing life-cycle environmental impacts. As advancements in aerodynamics, propulsion, and the adoption of lightweight composite materials continue to reduce operational fuel burn, the relative significance of manufacturing and End-of-Life phases is expected to increase. This study develops a low-fidelity aerostructural optimization framework for high aspect ratio wings that integrates life-cycle considerations into early-stage material selection. Using aluminum and carbon fiber reinforced polymers (CFRP) as reference materials, the framework quantifies trade-offs in mass savings, fuel burn, and CO₂ equivalent emissions across production, operations, and disposal phases. Results show that while CFRP offers substantial benefits in structural efficiency and operational emissions, aluminum performs more favorably in End-of-Life scenarios due to its high recyclability. The study further evaluates the potential of Sustainable Aviation Fuel (SAF) blending as a complementary decarbonization lever, revealing that moderate SAF adoption can offset part of the operational advantage of CFRP. Overall, this work demonstrates the importance of coupling material choice with life-cycle assessment in aerostructural design and outlines a pathway toward multi-objective optimization frameworks that balance performance with environmental sustainability. Full article

Rotary-percussive drilling is extensively used for efficient hard rock breakage, and the performance of impregnated diamond bits (IDBs) is primarily governed by matrix characteristics and diamond parameters. However, under impact conditions, diamonds do not behave as static cutting elements. Instead, they undergo a continuous cycle of microfracture (creating fresh sharp edges), intact retention (maintaining stability), and matrix wear-induced exposure (renewal). This work reveals this impact-driven dynamic balance mechanism. Fe-based matrix IDBs with different carbon fiber contents (regulating matrix hardness) and diamond parameters (concentration, particle size) were fabricated to study the effects of relevant parameters on bit wear and drilling performance under rotary-percussive drilling conditions. Within the experimental scope, it was found that carbon fiber can reduce the torque during drilling. The optimal balance of the three phases occurs at a matrix hardness of 95.8 HRB, where the combined proportion of micro-fracture and whole diamonds reaches 69.9% and emerging diamonds 12.9%, yielding the highest wear performance index α = 0.236. With increasing diamond concentration, the rate of penetration (ROP) and diamond exposure height decreased and the proportion of blunt diamond increased; the best balance is at an 80% concentration (α = 0.213). When the diamond mesh size increases, the ROP decreases rapidly, the torque first decreases and then increases, the proportion of whole diamonds first increases and then decreases, and the proportion of pull-out diamonds first decreases and then increases. The optimal mesh size is #50/60 (α = 0.241). This study not only provides parameter optimization, but also offers a mechanical understanding of how impact controls diamond self-sharpening and renewal, providing a new foundation for designing IDBs for impact rotary drilling. Full article

Because the environmental pollution arising from microplastics and carbon emissions continues to intensify, biodegradable alginate fibers have become green candidates to relieve the environmental crisis. However, the facile fabrication of alginate fibers with excellent mechanical strength and specific functionalities remains challenging. This study incorporates titanium dioxide (TiO₂) nanoparticles into pre-crosslinked sodium alginate (SA) spinning solutions to fabricate multifunctional alginate composite fibers by a one-step wet-spinning strategy. Due to the pre-crosslinking of calcium ions (Ca²⁺), the spinning solution shows favorable rheological performance for wet spinning, ensuring the continuous fabrication of the fibers. By optimizing the TiO₂ content, SA/TiO₂ composite fibers exhibit oriented and uniform morphology, as well as enhanced mechanical performance (breaking stress of 400 MPa and Young’s modulus of 17.2 GPa). The incorporation of TiO₂ also endows the fibers with excellent formaldehyde degradation and quick self-extinguished capacity, expanding their applications in formaldehyde-removal and flame-retardant textiles. Full article

Fabric-reinforced cementitious matrix (FRCM) composites are strengthening systems composed of a technical textile embedded in a cementitious or lime-based matrix and are increasingly used for strengthening existing masonry and concrete structures due to their compatibility with traditional substrates. The mechanical behavior of FRCM composites is controlled by the combined contribution of the textile reinforcement, the matrix, and the interface developed between them, with the textile–matrix interface playing a critical role in stress transfer, crack development, and post-cracking response. Since this interface is primarily defined by the coating applied to the textile, coating configuration represents a key parameter influencing both the mechanical and durability performance of the composite. In this study, carbon textile–reinforced FRCM systems incorporating a lime-based matrix and different coating strategies, including single-layer SBR coatings and multilayer SBR–epoxy coatings, were experimentally investigated. Tensile tests were conducted on unconditioned specimens as well as after exposure to water and alkaline environments to assess the evolution of tensile behavior and damage mechanisms under durability-related conditioning. The results indicated that the influence of coating configuration is slightly detectable in the pre-cracking elastic stage but becomes significant in the post-cracking stages, where load transfer and damage evolution are predominantly governed by the textile–matrix interface. Scanning electron microscopy (SEM) observations supported the mechanical findings by revealing distinct differences in coating, interfacial continuity, and fiber–matrix bonding, particularly after environmental exposure. Overall, the multilayer coating configuration, consisting of the factory SBR-coated carbon textile further modified with epoxy, resulted in higher maximum tensile strength (reaching up to 1958 MPa compared with 1531–1780 MPa for the single SBR-coated configuration), greater strain capacity (ε_max up to 0.01244 mm/mm compared with 0.00925–0.01066 mm/mm), and higher energy absorption under prolonged water and alkaline conditioning up to 3000 h. In quantitative terms, the multilayer SBR–epoxy coating improved the maximum tensile stress by approximately 10–15% and the total energy absorption capacity by 25–35%, depending on the conditioning regime. These findings demonstrate the effectiveness of multilayer coating architecture in improving long-term tensile retention, interfacial stress transfer, and post-cracking deformation capacity of lime-based carbon FRCM systems. Full article

Developing sustainable and fire-resistant infrastructure is a critical technological, economic, and environmental challenge for modern construction stakeholders. Traditional cementitious composites experience severe microstructural degradation under extreme temperatures and their high carbon footprint exacerbates global environmental concerns. While the individual high-temperature behaviors of supplementary cementitious materials and fibers have been widely studied, the long-term synergistic mechanisms of high-volume fly ash combined with steel fibers under extreme thermal shock remain critically underinvestigated. To address this urgent need and bridge this scientific gap, hybrid mortars incorporating high-volume fly ash (FA) and steel fibers (SF) were tested under prolonged curing (150 days) and extreme heat (up to 600 °C). In terms of engineering and construction effects, the optimal CFA50-F hybrid composite delivered the highest residual compressive and flexural capacities (retaining nearly 60% of its late-age compressive strength at 32.00 MPa), preserved acoustic continuity (restricting UPV loss to 41.4%), and severely restricted high-temperature capillary permeability (limiting the water absorption increase to 49.7%) compared to traditional plain matrices. Scientifically, this superior resistance is governed by a two-step protective mechanism. High-volume FA chemically stabilizes the matrix by consuming vulnerable portlandite and preventing the formation of expansive calcium oxide. Simultaneously, ultra-fine FA particles physically densify the interfacial transition zones, securely anchoring the steel fibers and preventing premature high-temperature pull-out, while enabling the fibers to bridge thermally induced macro-cracks successfully. Environmentally and economically, an annualized service-life Life Cycle Assessment (LCA) revealed that substituting 50% of the cement with FA completely subsidizes the production-stage carbon penalty of the metallic reinforcement. By extending the operational lifespan to 40 years, the CFA50-F composite achieves a net 27% reduction in annualized global warming potential, providing a highly sustainable and cost-effective material solution. Full article