Search Results (9,000)

Hydrogels have emerged as a crucial category of polymeric materials in materials science due to their three-dimensional network structure and remarkable capacity for water absorption and retention. However, conventional single-function hydrogels do not satisfy the increasing demands of advanced applications in biomedicine and environmental engineering. This paper focuses on the design, preparation, and performance characterization of nanofiber-reinforced polyacrylamide hydrogels to overcome this limitation. A bilayer structure, consisting of tensile layers and actuator layers based on a polyacrylamide/sodium alginate (PAM/SA) matrix integrated with functional materials, was developed. Nanocellulose (CNF) was incorporated to regulate mechanical properties by adjusting its content ratio with PAM, while poly-N-isopropylacrylamide (PNIPAM) and multi-walled carbon nanotubes (MWCNTs) were added to confer photothermal responsiveness. The deformation of the hydrogel was induced by temperature changes resulting from infrared illumination. The results indicate that the CNF-reinforced hydrogels exhibit enhanced mechanical strength—with the tensile strength reaching 17 kPa (89% higher than pure PAM) and fracture strain approaching 900% when the CNF content is 0.44 wt.% and PAM/SA mass ratio is 4:1—and they display reversible thermosensitive responses (reaching 60 °C within 100 s under near-infrared irradiation) following the incorporation of carbon nanotubes. This paper presents a novel strategy for the development of multifunctional hydrogel-based actuated systems, expanding the application potential of hydrogels in human motion tracking and drug delivery. Full article

Architected polymer composites use spatially organized phases to achieve targeted property combinations. Shape forming elements (SFEs) are modular coextrusion die inserts that impose internal architectures by reshaping multiple melt streams. This study evaluates three SFE designs (Jacks, I-Beam, and Barn Door) that position a liquid crystalline polymer (LCP) and an amorphous polyamide (APA) in distinct core–shell configurations. Polymer clay prototyping and ANSYS Polyflow simulations were used to screen flow behavior, followed by extrusion at two puller speeds and characterization via optical microscopy and tensile testing. Microscopy revealed that abrupt area transitions and viscosity contrast disrupt encapsulation and distort designed features. Regression analysis showed that LCP content governs stiffness and strength, while higher puller speed enhances reinforcement through molecular orientation. Cross sectional geometries were quantified using interfacial perimeter, moments of inertia, and polar dispersion ratios, and correlated to tensile performance. Increased interfacial length reduced modulus, strength, and ductility. Modulus improved with LCP orientation and confinement, strength increased when LCP was placed at vertical extremities, and elongation was maximized by horizontally distributing LCP within a thick APA shell. These results demonstrate that SFEs enable tunable tradeoffs between stiffness, strength, and ductility. Full article

This paper provides a comprehensive review on the effects of plant fibers on cement-based materials, focusing on the enhancement of mechanical properties and durability. Plant fibers, as a sustainable and renewable resource, are increasingly recognized for their potential in improving the performance of cement-based composites. The review begins with an exploration of fiber composition and structure, followed by a detailed discussion of interfacial modification strategies that enhance the bond between plant fibers and cement matrices. Key mechanisms such as fiber dispersion, bridging, and internal curing are examined to explain how plant fibers impact hydration, pore structure, and mechanical properties like compressive strength, flexural strength, splitting tensile strength, and impact toughness. The paper also reviews the role of plant fibers in enhancing the durability of cement-based materials, particularly in terms of resistance to alkali degradation, acid attack, freeze–thaw cycles, chloride ion penetration, and self-healing behavior. The findings suggest that plant fibers offer a dual benefit by improving both the mechanical and durability performance of cement-based materials. The paper concludes with recommendations for future research directions, emphasizing the need for better understanding the interactions between plant fibers and cement matrices to optimize the long-term performance of plant fiber-reinforced cementitious composites. Full article

Selective laser melting (SLM) offers a promising route for fabricating high-performance Cu–Sn alloys; however, the extremely transient thermal behavior of the molten pool and its influence on microstructural evolution and mechanical properties remain insufficiently understood. In this study, a finite element model based on ABAQUS was developed to simulate the transient temperature field and molten pool dynamics of Cu–10Sn alloy during the SLM process. By systematically varying the volumetric energy density (VED), the interplay among molten pool geometry, thermal characteristics, microstructure, and mechanical performance was investigated through a combination of numerical simulation and experimental investigation. The results reveal that increasing VED significantly enlarges the molten pool dimensions, elevates the peak temperature, and intensifies the maximum heating and cooling rates, thereby altering solidification conditions. At a VED of 208.33 J/mm³, the molten pool reached its maximum dimensions, with a length of 230 μm, a width of 161 μm, and a depth of 85 μm, resulting in the highest relative density within the investigated range (98.33%). Under this processing condition, the Cu–10 wt.% Sn (Cu–10Sn) alloy exhibited microhardness values of 190 HV near the solidified areas of melt pool interior and 208.4 HV near the solidified areas of melt pool boundary, accompanied by an ultimate tensile strength of 494 MPa. These findings elucidate the critical role of molten pool thermal behavior in governing microstructural refinement and mechanical properties of SLM-fabricated Cu–10Sn alloys and provide a mechanistic basis for understanding the effect of process parameters. Full article

The aim of the study was to modify polylactide with zinc oxide nanoparticles (ZnO), raspberry leaf extract (E), and a combined ZnO/extract system (EZnO) in order to prepare novel packaging materials via a solvent-free method, namely cast extrusion. Physicochemical properties: Morphology (GPC, SEM, FTIR), mechanical (tensile tests, puncture), barrier (WVTR, OTR, UV-Vis) and water contact angle for PLA-based films with two thickness ranges were investigated. Additionally, antimicrobial (antibacterial, antifungal and antiviral) tests were performed. GPC results revealed that the presence of the extract counteracted biopolyester degradation during hot melt processing. The best mechanical properties (TS ca. 50 MPa, EB ca. 18%) were obtained for PLA modified with raspberry leaf extract (PLA/E). EZnO addition led to the highest increase in oxygen (with 25%) and water vapor (up to ca. 28%) barrier properties. The material with EZnO addition was also found to be the only one to demonstrate antibacterial effectiveness, although the activity was insignificant. However, the incorporation of EZnO into the biopolymer matrix enhanced its antiviral properties, resulting in the complete inactivation of Φ6 bacteriophage particles used as a surrogate of SARS-CoV-2 virus. Full article

In this research, a novel polyarylene ether nitrile (PEN) coating material was fabricated through a facile stepwise polymerization method, which provides metallic substrates used in the oil industry with remarkable corrosion protection performance. A variety of characterization techniques were employed to evaluate the comprehensive properties of the PEN coating materials against a commercially established high-temperature-resistant epoxy coating. Based on the TGA curves, the PEN3 coating exhibited a T_5% value of 521 °C, which was 44.72% higher than that of the epoxy coating. According to the tensile experiment, the PEN coatings demonstrated improved mechanical performance, achieving tensile strength and breaking elongation values of 89.37 MPa and 7.14% (PEN3), respectively, while the epoxy achieved values of 18.67 MPa and 0.32%, respectively. EIS tests revealed that all the PEN coatings exhibited superior corrosion resistance compared to the epoxy coating. Among them, the PEN3 coating remained intact without failure and showed the highest impedance value (5.665 × 10⁷ Ω·cm²), which was two orders of magnitude higher than epoxy. Our research confirmed that the PEN coating material provided enhanced corrosion resistance, thermal stability and mechanical properties, positioning it as an alternative option to replace epoxy coating in prolonging the service life of steel piping in oil field applications. Full article

Producing high-conductivity aluminum conductors for power transmission involves 23 trace elements and multiple interconnected thermo-mechanical stages. The ultra-low alloying levels required to preserve high electrical conductivity create a narrow compositional window and highly imbalanced distributions, which hinder traditional data-driven learning. Here, we developed a physics-guided machine-learning framework based on 4458 valid industrial production records to predict tensile strength and electrical resistivity. In addition to raw composition and process parameters, we introduce ratio descriptors (e.g., Fe/Si and Al/Si) and propose a physics-informed metric termed the Equivalent Solute–Heat Index (ESHI) to couple key solute chemistry (Si, Fe, B) with normalized thermal-history intensity. Fe and Si primarily influence resistivity through impurity/solute scattering, while B mainly affects microstructural uniformity via grain refinement. Incorporating ESHI as an augmented signal into the best-performing XGB surrogate markedly improves generalizability, increasing the tensile strength R² from 0.75 to ~0.92. SHAP analysis reveals that ESHI dominates the decision logic by modulating both targets with metallurgically interpretable mechanisms: solute-controlled scattering and thermal history-traced second-phase evolution that stabilizes the microstructure. NSGA-III was further employed to map the Pareto front and identify composition–process combinations that optimize the strength–conductivity trade-off, enabling improved mechanical reliability while minimizing resistive losses in practical power-transmission applications. Experimental validation on industrial wires confirms this reliability. Full article

Intralayer hybridisation provides a powerful strategy for tailoring the stiffness–strength–ductility balance of fibre-reinforced composites through architecture control. This study investigates the flexural behaviour of carbon/glass intralayer hybrid composites with varying carbon-to-glass (C:G) ratios and degrees of dispersion using a finite element modelling framework supported by experimental validation against published flexural test data. Four hybrid ratios (C:G = 2:1, 1:1, 1:2, and 1:4) and multiple dispersion levels were examined under three-point bending to quantify the effects of intralayer architecture on flexural strength, modulus, and strain to failure. The results show that carbon-rich hybrids retain high flexural stiffness and strength while achieving substantial improvements in failure strain and damage tolerance compared with pure carbon laminates. In these systems, flexural strength is strongly influenced by dispersion, with moderate-to-high dispersion improving strain compatibility, delaying tensile-side carbon fibre fracture, and enhancing strength. In contrast, glass-dominated hybrids exhibit flexural behaviour that is largely insensitive to dispersion, with strength and modulus following near rule-of-mixtures trends and failure governed by progressive glass fibre and matrix damage. Across all hybrid ratios, flexural modulus is controlled primarily by fibre volume fraction, whereas flexural strength and failure strain depend sensitively on intralayer architecture when carbon fibres remain the dominant load-bearing phase. These findings clarify the respective roles of hybrid ratio and dispersion in governing flexural performance and extend recent studies by demonstrating a systematic transition from dispersion-dominated to ratio-dominated behaviour as glass content increases. The results provide mechanistic insight and practical design guidance for optimising intralayer hybrid composites for lightweight, damage-tolerant structural applications. Full article

Ball-end copy-milling is widely used for finishing complex components, yet its influence on surface integrity is generally overlooked and remains insufficiently addressed. Milling often generates tensile residual stresses at the machined surface, which are detrimental to fatigue performance and commonly require costly postprocessing, particularly in fatigue-critical parts such as turbine blades. In this context, the present study evaluates the capability of Prestress-Assisted Machining under uniform bending loads to improve the surface integrity of ball-end copy-milled Aluminium 5083 workpieces. Experimental tests were conducted on slender specimens with different thicknesses and curvature radii while maintaining constant cutting conditions. After machining and unclamping, surface residual stresses were measured by X-ray diffraction, and the effects of prestressing on geometry, cutting forces and surface roughness were also assessed. The results demonstrate that this method markedly increases compressive residual stresses in the prestressing direction, from approximately 30 MPa to about 180 MPa, and that this variation can be accurately described by subtracting the elastic prestressing stress from the residual stresses obtained without external loads applied. Moreover, no relevant adverse effects were observed in cutting forces or roughness, and corrected toolpaths allowed a uniform slot depth. These findings identify bending-based Prestress-Assisted Machining as an effective and predictable strategy for improving surface integrity in ball-end copy-milling and extend its applicability beyond previously reported pocket and slot milling operations. Full article

In this study, scanning electron microscopy (SEM) analysis is used to reveal the real microstructure of C75S steel and to compare grain morphology and deformation features with numerical predictions. A micro-scale finite element model of C75S steel is developed to investigate its tensile response in order to understand how steel actually deforms and fails at the microstructure level. Subsequently, the validated microstructural model is employed to simulate the cutting process using the finite element method, focusing on stress concentration and damage initiation at the grain and interface zones. The results demonstrate that microstructural modelling provides improved insight into deformation and fracture mechanisms compared to homogenised approaches, highlighting the critical role of cementite distribution and interfacial behaviour during tensile loading and micro-scale cutting. The cementite particle sizes in C75S steel range from approximately 0.5 to 2.0 µm, with circularity values between 0.7 and 0.95 and a volume fraction of about 10–12%. The proposed framework offers a robust basis for predicting the cutting performance of high-carbon steels. Full article

This study investigates the effect of chemical modification of xylite—a fraction derived from Polish lignite—using succinic anhydride (SA) on the morphology and mechanical performance of isotactic polypropylene (iPP) composites. Xylite was incorporated at loadings of 1, 10, and 25 wt% and in two particle size ranges (40–63 µm and 63–125 µm), with and without SA (0.5 and 2 wt%). The composites were characterized by wide-angle X-ray scattering (WAXS), Fourier-transform infrared spectroscopy (FTIR), and tensile testing to evaluate crystallinity (Xc), β-phase content (kβ), and mechanical properties. Unmodified xylite reduced crystallinity (Xc down to ~37%) and significantly decreased ductility, with elongation at break strongly negatively correlated with filler content (r ≈ −0.68), indicating poor dispersion and weak interfacial adhesion. In contrast, SA addition (0.5–2 wt%) partially restored crystallinity (up to ~48%) and increased stiffness (Young’s modulus up to 2120 MPa), while altering β-phase content. FTIR analysis indicated reduced intermolecular hydrogen bonding between xylite surface hydroxyl groups in the presence of SA, consistent with interfacial chemical interactions, likely via esterification. The β-phase content showed a moderate positive correlation with xylite loading (r = +0.43) and a negative correlation with elongation at break (r = −0.46), suggesting that excessive β-phase formation may reduce toughness. Larger particles (63–125 µm) provided slightly improved elongation at break and stiffness. Overall, SA acts as both a compatibilizer and a morphology-directing agent, enabling precise control of the stiffness–ductility balance and crystalline structure in iPP/xylite composites. These results establish chemically modified lignite-derived fillers as a viable strategy for engineering cost-efficient polyolefin materials with tunable structure–property relationships, offering strong potential for scalable industrial implementation. Full article

To investigate the inevitable aging of composite insulators under the coupled effects of electrical, thermal, ice, and fog stresses, as well as to explore their aging mechanisms and residual strength prediction methods, this study collected operational insulator samples from four environmental regions: Tibet, Yunnan, Hunan Xuefeng Mountain, and Anhui/Chongqing. Mechanical properties, including tensile strength, elongation at break, and shear resistance, were tested. The results indicate that the degradation of mechanical performance in composite insulation components can be attributed to the synergistic interaction of operational environments and material characteristics, with the aging behavior of high-temperature vulcanized (HTV) silicone rubber exhibiting significant non-linearity. Based on existing research, molecular dynamics simulations were employed to construct microstructural models at different aging stages, and it was verified that main chain scission, reduced system density, and changes in the elemental chemical environment during aging are closely related to the degradation of material mechanical properties. Based on hyper-elastic constitutive theory and fracture mechanics, a quantitative method for assessing the comprehensive aging degree was proposed, with “service years” and “operational altitude” as the core dimensions. A negative exponential model was established to describe the strength degradation of silicone rubber materials. This model enables the non-destructive estimation of the residual mechanical strength of in-service insulators in complex regions without power interruption, providing a decision-making framework for grid operation and maintenance. Full article

The mechanical performance of concrete cutoff walls in deep overburden is decisive for dam safety. Current coarse mesh models struggle to accurately simulate their response under complex conditions. In this paper, a refined numerical model is established specifically for a concrete cutoff wall in deep overburden. The deformation and stress characteristics and mesh sensitivity of the cutoff wall are systematically investigated. A quantitative index of overstress area ratio is introduced innovatively, and the effects of cutoff wall mesh size along the thickness direction, dam height, and overburden parameters on the deformation and stress characteristics of the cutoff wall are explored in detail. The results show that the stress characteristics of the cutoff wall requires a fine mesh model with an element thickness ≤ 1/4 of the cutoff wall. The change in dam height and overburden parameters mainly affects the stress magnitude of the cutoff wall but does not change its tensile stress distribution pattern. The variable-size mesh generation achieves collaborative optimization of accuracy and efficiency, and the calculation amount is significantly reduced by about 16%, with error below 5%. This study presents an efficient method and can provide technical support for the safety evaluation of concrete cutoff walls in deep overburden. Full article

Alkali-activated concrete can reduce reliance on Portland cement by valorizing industrial by-products. This study evaluates slag-based alkali-activated concretes incorporating natural diatomaceous earth (M2, M3) and residual diatomaceous earth from industrial filtration (V6–V7), benchmarked against an OPC reference. The experimental program measures compressive, tensile and flexural strengths and elastic modulus, and examines steel–concrete bond behavior through bond stress–slip response at multiple slip levels. Member-level performance is assessed using reinforced beams tested under four-point bending, and cracking is compared in the constant-moment region using crack number and average spacing derived from post-test observations. Results show that diatom-based alkali-activated mixtures can achieve mechanical performance comparable to OPC concrete, with clear dependence on diatom source and mixture design. Bond response is markedly mixture-dependent and cannot be inferred from compressive strength alone. All beams exhibited flexural behavior suitable for structural applications, with the RV6 mixture providing the most favorable overall response among the tested members. These findings support the feasibility of residual diatomaceous earth as a viable component in structural alkali-activated concretes. Full article

Polyurea elastomers are widely used in industry thanks to their exceptional mechanical properties. However, cold-pour systems typically require extended ambient curing times to achieve optimal performance. This study investigates whether accelerated thermal curing can replicate or exceed the mechanical properties obtained through the standard ambient cure protocol. Specimens were prepared by hand-mixing and then cured at temperatures of 50 $°\mathrm{C}$ and 70 $°\mathrm{C}$ for 1 h, 3 h and 6 $\mathrm{h}$. Selected specimens were then aged at room temperature for up to 7 d. Uniaxial tensile tests were conducted, with strain measured via a video-tracking technique. Porosity analysis was performed using cross-section micrographs. The results show that a 6 $\mathrm{h}$ cure at 50 $°\mathrm{C}$ yields mechanical properties comparable to those obtained through the standard ambient cure, while a 6 $\mathrm{h}$ cure at 70 $°\mathrm{C}$ significantly surpasses them. Post-cure aging was found to be particularly effective for specimens with a thickness of 1.5 $\mathrm{m}$$\mathrm{m}$, achieving a tensile strength of 4.7 $\mathrm{M}$$\mathrm{Pa}$ after 7 d, exceeding that declared by the manufacturer. Full article