Search Results (3,184)

Functionally graded materials (FGMs) effectively alleviate residual stress induced by physical property mismatch at dissimilar material interfaces through a graded transition in composition or structure. Among these, the matching of the coefficient of thermal expansion (CTE) is a core indicator for ensuring the service reliability of the joint. Traditional composition design relies on empirical trial-and-error, which makes it difficult to efficiently identify the optimal path in a high-dimensional composition space. This study proposes a data-driven, machine learning-assisted composition design method. Based on a high-precision dataset covering 15 elements and 747 CTE data points, six typical regression models were systematically evaluated. The results show that the random forest (RF) model achieves the best performance, with a coefficient of determination (R²) of 0.929 and a root mean square error (RMSE) of 0.658 on the test set. Using the SHapley Additive exPlanations (SHAP) method, the lattice constant (c), Young’s modulus (YM), and temperature (T) were identified as the key physical descriptors governing the thermal expansion behavior. Experimental validation shows that the CTE prediction deviation of the model for the high-performance Fe-based alloy Norem02 in the range of 20–300 °C is only 0.89%. Based on this framework, the composition of the 316L/Norem02 transition layer was successfully designed in this study. This effectively reduced the interfacial thermal expansion mismatch. Consequently, it provides a reliable theoretical basis for the rational design of dissimilar material interfaces under extreme service conditions. Full article

The increasing use of low-density polyethylene (LDPE) has prompted growing interest in its application as a replacement for conventional aggregates in concrete. This study investigated the effects of replacing sand with 10%, 20%, and 30% LDPE granules in concrete. Compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, slump, and density tests were performed. The results showed a gradual decrease in compressive strength (from 26.91 MPa in the reference mix to 16.56 MPa with 30% LDPE), tensile strength (from 2.46 MPa to 1.84 MPa), and flexural strength (from 3.37 MPa to 2.59 MPa). Decreases were also observed in modulus of elasticity, slump, and density values. However, LDPE-substituted concretes increased their axial and lateral strain capacities, showing improvement in ductility and deformation ability. Experimental results demonstrated a delicate balance between mechanical strength and sustainability benefits. It was demonstrated that low rates of LDPE substitution could balance performance with environmental advantages. The experimental results presented in this study were combined with previous research to create a dataset. Based on this dataset, exponential models predicting the properties of LDPE-substituted concrete and mortar were proposed. The proposed exponential models outperformed existing linear models in prediction accuracy, yielding coefficient of determination (R²) values up to 0.981 and significantly reduced mean absolute percentage error (MAPE) values, ranging from 1% to 17% depending on the dataset. Full article

The effective utilization of recycled concrete powder remains a key challenge for sustainable construction. In this study, carbonated recycled concrete powder (CRCP) was applied to replace cement at levels of 4–16% in Portland cement–fly ash (OPC-FA) systems, and its effects on fresh properties, hydration behavior, shrinkage, pore structure, and mechanical performance were systematically investigated. The incorporation of CRCP reduced flowability and accelerated setting, while slightly advancing and enhancing the main hydration peak at 4–8% replacement, accompanied by higher CH at early ages and increased C–S–H formation at later stages. More significantly, the addition of CRCP substantially decreased both autogenous and drying shrinkage, achieving reductions in the ranges of 6.0–21.4% and 3.2–24.1%, respectively. This improvement is primarily attributed to the elevated internal relative humidity and the lowered capillary pressure within the system. In addition, the mechanical properties exhibited a clear optimum with the addition of 8% CRCP, where the 28 d compressive strength and flexural strengths increased by 16.3% and 4.0%, respectively. Further analysis indicates that this improvement is associated with a higher fraction of high-modulus regions and an increase in average elastic modulus from 23.89 GPa to 27.42 GPa, reflecting a denser microstructure. These results demonstrate that CRCP can effectively regulate hydration and microstructure, providing a feasible approach for improving dimensional stability and mechanical performance while enabling the value-added utilization of recycled concrete powder. Full article

This study proposes a novel synergistic design strategy to enhance the oxidation resistance of FeNiCuAl-based high-entropy alloys by integrating multi-element alloying (Cr-Co-Mn), trace Y modification, and laser-cladding-induced nanocrystallization. While the Base Alloy exhibited a mass gain of approximately 15 mg/cm² after oxidation at 900 °C for 120 h, the addition of Cr_2.5Co_2.5Mn_2.5 promoted the formation of a multilayered oxide scale (outer MnCr₂O₄/inner Al₂O₃), reducing the parabolic oxidation rate constant to 1.7 × 10⁻⁵ mg²·cm⁻⁴·s⁻¹. The originality of this work lies in the coupling of compositional and microstructural engineering; further addition of 0.5 at.% Y decreased this constant to 1.7 × 10⁻⁶ mg²·cm⁻⁴·s⁻¹—a three-order-of-magnitude reduction relative to the Base Alloy, while increasing the apparent oxidation activation energy to ~350 kJ/mol. After 100 thermal cycles at 1000 °C, the designed alloy showed a mass change of only 0.05 ± 0.02 mg/cm², with its critical load and interfacial fracture energy reaching 78 N and 14.8 J/m², respectively. Furthermore, the alloy retained a hardness of 310 HV, an elastic modulus of 135 GPa, and a tensile strength of 240 MPa at elevated temperature. These results demonstrate that the synergistic integration of chemical and structural optimization provides a new paradigm for designing low-cost, high-performance FeNiCuAl-based protective coatings. Full article

Bone scaffolds are porous artificial structures that replace damaged bone tissue and promote bone regeneration. In clinical settings, bone cement is used to provide initial fixation stability between the bone scaffold and surrounding bone tissue. To analyze the performance of bone scaffolds more accurately, the cement mantle should be considered. This study considers the cement mantle between the bone scaffold and surrounding bone tissue and the structural behavior according to variations in the elastic modulus of the cement mantle and the pore size of the bone scaffold. The results showed that the cement mantle energy ratio increased with increasing pore size, particularly in the femoral head and intertrochanteric region. In the femoral head with a pore size of 1.50 mm, increasing the cement mantle elastic modulus from 7 to 24 GPa reduced the mean strain energy within the bone scaffold from 3.79 μJ to 2.51 μJ, corresponding to a decrease of approximately 33.8%. These findings suggest that as cement mantle stiffness increases, external loads may not be sufficiently transferred to the bone scaffold interior, and the proportion of the load borne by the cement mantle may increase. In the femoral neck, the cement mantle energy ratio also increased with increasing pore size; however, the magnitude of this change was more limited than that in the other regions of interest. These findings highlight the mechanical importance of the cement mantle and suggest that both cement stiffness and scaffold pore size should be jointly considered to ensure appropriate load sharing for bone regeneration. Full article

This paper develops an analytical treatment of vibro-acoustic wave propagation in a cylindrical waveguide containing two clamped elastic membranes and a central flexible-shell segment. The acoustic field obeys the time-harmonic Helmholtz equation, the shell motion is described by Donnell–Mushtari thin-shell theory under axisymmetric loading, and the membrane response is governed by classical membrane theory and incorporated through a tailored Galerkin scheme. The resulting coupled fluid–structure boundary-value problem is solved by the Mode-Matching Method: the acoustic potentials are expanded in orthogonal radial eigenfunctions within each subregion, and continuity of pressure, normal velocity, and structural displacement are enforced at every interface. The mirror symmetry of the configuration is exploited by an exact decomposition into symmetric and anti-symmetric sub-problems, each of which reduces to a truncated linear algebraic system of dimension $4N+4$ for the unknown modal amplitudes. Acoustic power-balance identities provide a quantitative consistency check on the numerical implementation and diagnose convergence with respect to the truncation order; structural damping is accommodated through complex-modulus substitutions for the shell and the membrane tension without altering the algebraic structure of the system. The numerical results demonstrate that the dual-membrane configuration delivers transmission-loss values exceeding $25\mathrm{dB}$ across the low-frequency band relevant to HVAC and automotive applications, with a representative plateau near $13\mathrm{dB}$ at the reference geometry, through resonance-driven modal coupling between the acoustic field and the compliant interfaces. Parametric studies identify the excitation frequency, the inner-membrane radius, the shell radius, and the chamber length as effective design parameters for tuning the attenuation. The formulation furnishes a unified and computationally efficient analytical tool for predicting and optimising noise attenuation in flexibly coupled cylindrical duct systems. Full article

The development of electronic substrates from locally available materials is critical for sustainable lunar infrastructure. This work investigates the synthesis, processing, and characterization of cyanate ester–lunar regolith simulant (CE-LRS) composites designed specifically for the extreme lunar environment. LRS were evaluated as functional fillers at loadings up to 55 wt.% with CE binder selected for its thermal stability (T_g > 230 °C), vacuum compatibility, and known radiation resistance from prior literature. A vacuum-assisted curing procedure was developed that utilizes the lunar environment as a processing advantage, reducing porosity from approximately 7% to less than 1% as quantified by X-ray micro-computed tomography. Dynamic mechanical analysis revealed that increased filler loading and vacuum processing enhanced the storage modulus and T_g through constraining polymer chain mobility at the filler-binder interface, confirming effective stress transfer and interfacial adhesion. Scanning electron microscopy also verified intimate polymer–filler wetting. Waveguide measurements in the microwave frequency range demonstrated that the composites remain non-magnetic while exhibiting moderately increased permittivity and low dielectric loss, meeting the requirements for radio-frequency substrate applications. Through material selection and process design that embraces, rather than ignores, lunar environmental constraints, this work establishes the CE-LRS composites that represent a viable pathway for the in situ fabrication of structural electronics on the Moon. Full article

The growing demand for sustainable and economically efficient road maintenance solutions has driven the development of materials that reduce the use of natural aggregates and promote waste valorization. In this context, this study evaluates the use of reclaimed asphalt pavement (RAP) and greywacke aggregates derived from Panasqueira mining by-products as partial or total substitutes for granite aggregates in cold asphalt mixtures intended for rapid pothole repair. Reference mixtures and recycled mixtures were produced with controlled proportions of RAP and greywacke, using cationic bituminous emulsion and hydrated lime, as well as an additional mixture composed only of RAP with a fluxing cold binder. Three commercial mixtures, identified as CCM1, CCM2, and CCM3, were also evaluated. Performance was analyzed through Cantabro particle loss, Marshall stability and flow, indirect tensile stiffness modulus, and water sensitivity (ITSR). The results show that greywacke provides a robust granular skeleton, while RAP content and binder type influence stiffness, cohesion, and moisture resistance. Overall, the combination of RAP and greywacke proved to be technically viable and, in several cases, superior to the commercial mixtures studied. Full article

Titanium matrix composites (TMCs) are increasingly vital in aerospace for their high specific strength and wear resistance, with compositional gradient design serving as a key strategy to mitigate thermophysical mismatches between ceramic and metal phases. This study utilized laser-directed energy deposition with concurrent wire-powder feeding (LDED-WP) to fabricate TiC/Ti6Al4V gradient composites, employing a laser power of 2700 W, wire feed rates of 110–150 cm/min, and calibrated powder feed rates ranging from 50.22 to 497.13 g/h. Along the build direction, the TiC content was progressively increased from 10 wt.% to 60 wt.%. Investigations into microstructural evolution revealed that the reinforcement morphology transitions from chain-like eutectic TiC to dendritic primary TiC, while the lamellarα-Ti width refines significantly from 4.07 ± 1.15 μm to 0.45 ± 0.29 μm. EBSD analysis confirmed that higher TiC concentrations weaken the characteristic <001> solidification texture, reducing intensity from 11.24 to 7.64. Furthermore, KAM analysis highlighted that thermal expansion and elastic modulus mismatches trigger substantial geometrically necessary dislocation (GND) accumulation at interfaces. Consequently, Vickers hardness improved by 164% along the gradient, peaking at 950 HV. Although the composite achieved an ultimate tensile strength of 630 MPa, the elongation was limited to 2.4% due to crack nucleation in TiC-rich regions and interfacial instability. Full article

Tropical lignocellulosic residues are increasingly relevant feedstocks for lignin-containing nanocellulose composites, but their performance cannot be predicted from botanical origin or bulk lignin percentage alone. This review defines the interface as the geometrical boundary between phases and the interphase as the finite, compositionally graded region in which lignin distribution, nanocellulose morphology, adsorbed water, and the surrounding matrix jointly govern stress transfer and mass transport. Using an evidence-weighted framework, the literature is organized into the following categories: residual-lignin nanofibrils, redeposited-lignin systems, lignin nanoparticle assemblies, compatibilized thermoplastic hybrids, and all-lignocellulosic sheets. Representative quantitative observations show that controlled residual lignin can the increase water contact angle from approximately 35 degrees to 78 degrees and reduce oxygen permeability by up to 200-fold in nanopapers, while selected PLA/LCNF systems show tensile-strength and modulus increases of 37% and 61%, respectively; however, high or poorly distributed lignin can suppress fibrillation, lower viscosity, weaken gel networks, and reduce reproducibility. The most defensible near-term product windows are packaging layers, grease/oil barrier papers, coatings, paper-like multilayers, and selected porous media. Thermoplastic matrices remain process-sensitive, and biomedical, additive-manufacturing, nano-reactor, and energy-material claims require stronger validation of the extractables, rheology, humidity history, TEA/LCA metrics, and end-of-life behavior. This review, therefore, provides a critical, application-backward roadmap for tropical biorefineries in which interfacial function, wet handling, drying energy, and process integration are assessed together rather than treated as independent variables. The abbreviations used in the abstract are defined as follows: CNFs, cellulose nanofibrils; CNC, cellulose nanocrystals; LCNF, lignin-containing cellulose nanofibrils; LCNCs, lignin-containing cellulose nanocrystals; PLA, poly(lactic acid); PHB, polyhydroxybutyrate; PHAs, polyhydroxyalkanoates; PVA, poly(vinyl alcohol); DESs, deep eutectic solvents; TEA, techno-economic analysis; LCA, life-cycle assessment; ML, machine learning. Full article

To improve the functional performance and digestibility of casein-rich ingredients, this study investigated the effects of trisodium citrate (TC) chelation and spray drying on the functional properties and in vitro digestibility of micellar casein isolate (MCI). TC chelation improved the foaming, emulsifying, gelling, and digestive properties of casein to different extents. Compared with MCI, trisodium citrate-chelated casein (TCC) exhibited significantly enhanced foaming capacity; specifically, the foaming capacities of TCC-40 and TCC-60 increased to 58.0% and 60.0%, respectively. TC reduced particle size, leading to increased foam volume, whereas foam stability decreased at higher chelation levels. In terms of emulsifying properties, TCC-10 exhibited optimal performance, with most emulsion droplet diameters distributed within 1–5 μm. TC chelation induced a significant negative shift in zeta potential (p < 0.05), suggesting improved emulsion stability. Gelation behavior was linked with concentration, showing TCC-40 induced the shortest gelation time (3.98 min) and the highest storage modulus. TC significantly enhanced casein digestibility in both adult and elderly in vitro digestion models, with digestion efficiency in the elderly model approaching that of the adult model. Confocal laser scanning microscopy (CLSM) pictures indicated that calcium chelation reduced gastric floc compactness, facilitating enzymatic access and improving protein hydrolysis efficiency. The study reveals the advantage of calcium chelation on the functional properties and digestibility of casein-based powder. Full article

Extending the service life of structural components through sustainable replacement is a key strategy for reducing material consumption and environmental impact in the cycling industry. This study evaluates the potential substitution of bicycle frame components, combining fused deposition modeling (FDM) with externally applied fiber tape reinforcement. Preliminary experimental validation was conducted on coupon specimens to assess the mechanical and environmental viability of the proposed material system. Two thermoplastic substrates, a bio-based green co-polyester (GreenTEC PRO, GT) and polycarbonate (PC), were printed at three orientations and reinforced with unidirectional carbon fiber (CF) or flax fiber (Flax) tapes. The results show that fiber position was the dominant factor governing both ultimate flexural strength (UFS) and elastic modulus (EF), accounting for over 74% and 81% of total variability, respectively. Carbon fiber reinforcement increased mean UFS from 60.6 MPa to 142.9 MPa, with peak values of 236.4 MPa, while flax fiber provided a statistically significant intermediate reinforcement, reaching up to 108.9 MPa. The bio-based GT substrate performed comparably to PC across all configurations, demonstrating that sustainability goals need not compromise structural performance. Bilateral fiber placement and 90° printing orientation consistently yielded the best mechanical response. These findings support the hybrid FDM/prepreg approach as a viable, tooling-free, and environmentally conscious strategy for the replacement of bicycle frame components. Full article

Unconventional oil and gas reservoirs naturally have low porosity and low permeability, which necessitate reservoir stimulation during production to achieve commercial exploitation. Therefore, to improve reservoir stimulation effectiveness, this study established a thermal–hydraulic–mechanical coupled numerical model suitable for hydraulic fracturing experiment scales based on rock mechanics, elasticity mechanics, damage mechanics, and flow mechanics theories, combined with maximum principal stress and Mohr–Coulomb damage criteria. The model was numerically solved within a finite element framework and used to simulate the reservoir hydraulic fracturing process. The results indicate that the propagation behavior of hydraulic fractures is controlled by reservoir rock mechanical properties, geostresses, reservoir temperatures, fracturing fluid viscosities, and injection rates. Among these, the increase in principal stress difference, reservoir temperature, fracturing fluid viscosity and injection rate promotes the propagation of hydraulic fractures along the direction of the maximum horizontal principal stress, whereas an increase in the rock’s elastic modulus reduces the propagation length of the hydraulic fractures. During fracturing, the fracturing fluid fractures the reservoir rock, significantly improving its porosity and permeability. This not only enhances the mobilization of unconventional oil and gas resources but also provides effective flow pathways for their migration, thereby ensuring the commercial viability of unconventional oil and gas resource extraction. Additionally, selecting a fracturing process that matches the geological characteristics of the study area during fracturing design is a prerequisite for improving the reservoir stimulation effect. The results of this study provide a reference for fracturing design and optimization. Full article

Hydraulic fracturing is critical for unconventional oil and gas development, yet perforation-induced initial damage impairs the integrity of the casing–cement sheath–formation assembly, causing fracturing fluid channeling and reduced stimulation efficiency. A stress-seepage coupling numerical model was established to simulate interface fracture initiation, propagation, and sealing failure, quantifying axial and circumferential channeling evolution at the cement–formation interface. Key parameters (casing eccentricity, cement elastic modulus, injection rate, and minimum horizontal in situ stress) were systematically analyzed. Results show fluid preferentially migrates through perforation-weakened zones, with channeling initiating via axial debonding, then circumferential propagation, and finally dominant axial extension. Casing eccentricity exacerbates channeling, while higher cement elastic modulus or in situ stress mitigates it significantly; injection rate affects channeling length but not fracture initiation/propagation pressures. This study provides theoretical and practical guidance for fracturing channeling risk control. Full article

Background/Objectives: The development of high-performance biocompatible polymers such as zirconium-reinforced polyether ether ketone (BioHPP^®) has expanded the range of materials available for implant-supported prostheses, traditionally limited to metal alloys and zirconia. Due to its favorable mechanical properties and elastic modulus similar to cortical bone, BioHPP^® has been proposed as a potential alternative in implant prosthodontics. This systematic review aimed to analyze the biomechanical behavior of zirconium-reinforced PEEK and assess its advantages and limitations in implant prosthetic applications. Methods: A systematic review was conducted in accordance with PRISMA 2020 guidelines, including studies published between 2011 and 2025 that evaluated the performance of BioHPP in implant prosthetic applications. Results: The search strategy identified 34 studies that met the inclusion criteria. The included studies evaluated mechanical properties such as fracture resistance, elastic modulus, stress distribution, and peri-implant tissue response. Zirconium-reinforced PEEK demonstrated fracture resistance values reaching up to 1623.31 N and an elastic modulus of approximately 4 GPa, comparable to cortical bone. Several studies also reported favorable stress distribution patterns and reduced mechanical complications when compared with conventional metallic materials. Conclusions: Zirconium-reinforced PEEK exhibits promising biomechanical characteristics for use in implant-supported prostheses, particularly due to its fracture resistance and bone-like elastic modulus. However, the available evidence is predominantly based on in vitro and finite element studies. Long-term clinical trials are required to confirm its clinical performance and establish definitive recommendations for routine use. Full article