Search Results (1,775)

Nanocomposites consisting of titanium carbonitride nanoparticles (TiCN) and epoxy resin were fabricated and studied as the filler content was varied. Nanocomposites’ structural investigation was conducted via X-ray Diffraction technique (XRD), while their morphology was examined by employing Scanning Electron Microscopy (SEM). Viscoelastic mechanical properties were assessed by Dynamic Mechanical Thermal Analysis (DMTA). Results revealed the reinforcing ability of TiCN nanoparticles. The dielectric characterization of the nanocomposites was carried out using Broadband Dielectric Spectroscopy (BDS) over a wide frequency and temperature range. Dielectric spectroscopy revealed two relaxation processes related to the polymer matrix: the α-relaxation, associated with the glass-to-rubber transition, and the β-relaxation, associated with the rearrangement of side polar groups. In addition, in the low-frequency–high-temperature region, interfacial polarization (IP) was observed. IP is related to the presence of nanoparticles and to the accumulation of unbound charges at the system’s interface and includes contributions from a dipolar process and charge migration (conductivity). Alternating current conductivity generally increases with filler content, though it is also affected by frequency and temperature. Conductivity could influence Electrode Polarization (EP), which often masks the dipolar process of IP. A simple method for removing the EP effect is formulated and tested. Full article

In this study, fully bio-based oligomers of butylene succinate (OBS) with different molecular weights (low: L-OBS, medium: M-OBS and high: H-OBS) were incorporated into poly(butylene succinate) (PBS) by melt mixing at varying loadings of 5–15 wt%. Then, PBS/OBS films were obtained by thermo-compression and characterized to assess their suitability for sustainable food packaging. Thus, OBS were homogeneously incorporated into PBS matrix and modulated the thermal, mechanical, and barrier properties of the PBS. L-OBS (Mn = 1150 g·mol⁻¹) plasticized the amorphous PBS, depending on its concentration, more effectively than M-OBS (Mn: 8700 g·mol⁻¹) and H-OBS (Mn: 18,650 g·mol⁻¹), as deduced from the thermo-mechanical analysis. In every case, OBS enhanced crystallinity, mainly L-OBS, which reduced the film strength and increased water vapor permeability, depending on its concentration. In contrast, H-OBS improved mechanical strength, stiffness, and barrier performance. In all cases, X-ray diffraction confirmed the preservation of the PBS’s monoclinic crystalline structure but slightly shifted the diffraction angle depending on the ratio of the end-chain groups in the blend, thus reflecting the contribution of OBS in the crystalline lattice. Finally, oligomer incorporation resulted in an overall migration increase in different food simulants, impairing their application in packaging. Full article

Our investigation into Hibiscus rosa-sinensis fibers (HRFs) for composite applications involved a multi-step process, primarily fiber extraction through water retting and subsequent surface modification by using sodium hydroxide (NaOH) and trimethoxy methyl silane (TMMS). Through the compression molding technique, untreated HRF-reinforced poly-lactic acid (PLA) composites (UHRFCs), NaOH-treated HRF-reinforced PLA composites (NHRFCs), and TMMS-treated HRF-reinforced PLA composites (THRFCs) were fabricated. The experiments were conducted, and the findings revealed a substantial increase in properties of both NHRFCs and THRFCs compared to UHRFCs. Notably, these enhancements encompassed tensile strength (13.66% and 19.39%), tensile modulus (13.41% and 20.70%), flexural strength (15.98% and 23.17%), flexural modulus (17.13% and 26.58%), impact strength (15.62% and 33.07%), Shore-D hardness (4.19% and 5.00%), storage modulus (9.88% and 13.07%), loss modulus (7.52% and 17.36%), dielectric constant at 6.5 Hz (13.22% and 23.96%), and significant improvements in the acoustic resonance frequency at 1897 Hz (79.50% and 81%). Peak thermal degradation temperatures of these composites are 420.62 ± 3.43 °C, 439.51 ± 3.54 °C, and 469.07 ± 3.11 °C, respectively, and biodegradability results showing accelerated degradation within 30 days. These findings highlight the substantial effectiveness of treatments in enhancing diverse properties, underscoring the potential applicability of these composites in various industrial sectors requiring superior performance and sustainable materials. Full article

Vanadium borate (V₃BO₆) has recently been synthesized and identified as a promising material for use in energy storage applications, particularly as a potential anode for lithium-ion batteries. However, despite previous studies highlighting its electrochemical performance, a comprehensive understanding of its intrinsic mechanical, thermal, and vibrational properties remains limited. The compound crystallizes in an orthorhombic phase with the Pnma (No. 62) space group. To explore its intrinsic physical characteristics, full geometry optimization of the unit cell and atomic positions was performed using density functional theory (DFT) within the CASTEP framework. The Perdew–Burke–Ernzerhof (PBE) functional under the generalized gradient approximation (GGA) was used to model exchange–correlation effects. A plane-wave cut-off of 408 eV and a 6 × 6 × 13 Monkhorst–Pack grid were employed to ensure numerical convergence. The optimized lattice constants (a = 9.9025 Å, b = 8.4751 Å and c = 4.5354 Å) are highly consistent with experimental data, which confirms the reliability of the computational approach adopted. The elastic behaviour was further investigated using the first-principles strain-energy method, yielding nine independent elastic constants consistent with orthorhombic symmetry. The calculated bulk and shear moduli, along with the anisotropy parameters, suggest that V₃BO₆ has a favourable balance of mechanical robustness and moderate ductility. A Vickers hardness of 10.95 GPa and a B/G ratio of approximately 1.93 corroborate these findings. Additional parameters, such as Poisson’s ratio, Debye temperature and average sound velocities, were derived to gain deeper insight into the material’s thermomechanical performance. These results provide a solid theoretical foundation for understanding the mechanical stability and potential anode suitability of V₃BO₆ in lithium-ion battery systems. Full article

This study addresses the poor compatibility between resin and reinforcement and the weak interfacial bonding in poly(ether ether ketone) (PEEK)-based composites by preparing several macromolecular silane coupling agents. Three types of coupling agents with different structures were synthesized using hydroxyl-terminated PEEK oligomers, and their structures were confirmed by FT-IR, NMR, and XPS analyses. The molecular weights were determined by GPC, and TG analysis showed that all three coupling agents exhibited good thermal stability. Glass fibers and carbon fibers were surface-modified with these coupling agents. SEM and EDS analyses revealed uniform coatings on the fiber surfaces, accompanied by increases in the characteristic elements of the coupling agents. Mechanical tests showed that the tensile and flexural strengths of the treated composites were higher than those of the untreated ones. DSC and TG results indicated significant improvements in crystallinity and thermal properties. These enhancements are attributed to improved fiber–matrix compatibility and interfacial bonding. Overall, this work establishes a structure-tailored macromolecular silane coupling strategy, providing new insights into structure–property relationships and offering an effective approach to enhance the performance of PEEK-based composites. Full article

MXenes are an emerging class of two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides with a unique combination of mechanical, electrical, and thermal properties. While MXenes have been extensively studied in electrochemical and materials science contexts, their mechanical behavior and engineering relevance remain comparatively underexplored. This paper provides a mechanically focused synthesis of MXene research, connecting structure, synthesis, processing, mechanical properties, and functional performance to engineering applications. Emphasis is placed on the tunability of tensile, elastic, shear, and thermomechanical properties through controlled variation of composition, surface terminations, and defects. Comparisons with graphene are used to clarify performance trade-offs and application-specific advantages. Key challenges, including environmental stability, moisture sensitivity, durability, scalability, cost, and integration with conventional engineering materials, are critically examined alongside current mitigation strategies. Applications in structural composites, mechanical reinforcement, energy storage, electromechanical systems, and MXene-based sensors and actuators are discussed to demonstrate practical relevance. By framing MXenes as engineerable materials rather than isolated nanomaterials, this work serves as a technical reference and entry point for mechanical engineers and interdisciplinary researchers seeking to design and deploy MXenes in advanced engineering systems. Full article

In response to the growing demand for sustainable manufacturing, 3D printing using recycled polyethylene terephthalate (rPET) offers a novel waste-to-value conversion method. Although the application of rPET in additive manufacturing has attracted significant attention from both the academic and industrial sectors, substantial challenges impede its further development, notably the high processing shrinkage and poor mechanical properties of the final product. This study focuses on developing recycled PET-based composites with favorable processing, thermal, and mechanical properties. Regranulates were produced via twin-screw extrusion using PET flakes, multifunctional chain extenders, and short glass fibers (GFs). The rPET-GF composites were characterized in terms of their processing, thermal, thermomechanical, and mechanical properties. Epoxy-functional chain extender modification effectively increased the molecular weight and improved the processability, whereas GF reinforcement enhanced the tensile properties of both injection-molded and FDM-manufactured parts. A primary advantage of the rPET systems developed in this study is their delayed crystallization kinetics. These findings highlight the significant potential of the composites developed herein for extrusion-based additive manufacturing (MEX-AM), as delayed crystallization facilitates enhanced interfacial adhesion, lower volumetric shrinkage, and superior dimensional stability. Full article

The global transition to renewable energy underscores the urgent need for safe, efficient, and cost-effective storage solutions for green hydrogen and green ammonia. This review critically examines their fundamental characteristics and unique behaviours, emphasising storage, handling, and integration engineering challenges. To identify the influential studies, knowledge gaps and future trends in the research area, a systematic Scopus-based bibliometric and data analysis is conducted. A novel approach is adopted to identify the better green energy storage option between green hydrogen storage and green ammonia storage, combining a risk-mitigation assessment framework, strengths, weaknesses, opportunities, threats (SWOT) analysis, and a multicriteria taxonomy based on the properties and behaviour of hydrogen and ammonia. This study also analysed and reviewed the performance of the hydrogen and ammonia storage system across technical, thermomechanical, safety/risk and economic dimensions. This review further addresses the limitations in technological bottlenecks, unresolved safety concerns and current simulation approaches to evaluate the performance of green hydrogen and green ammonia. The identified limitations open doors to future research priorities in this research area, including the techno-economic viability, standardisation, and modelling accuracy of hydrogen and ammonia storage systems. The evaluation presented by this study allows for precise identification of suitable energy storage based upon various operational and economic contexts. Full article

In this study, a biodegradable composite based on PLA reinforced with banana rachis fiber—derived from agricultural waste and forming the structural core of banana bunches—is developed. The fibers are evaluated with and without thermomechanical processing to enhance the properties of parts produced through material extrusion additive manufacturing (MEX), a technology with a screw feeding system. A preliminary study of the additive manufacturing process is conducted to ensure adequate processability of the matrix during the process. In addition, different composite formulations (0, 5, 10 and 15 wt.% fiber) are analyzed through morphological, thermal (TGA and DSC), rheological, and mechanical characterization, complemented by SEM analysis. This comprehensive characterization revealed that the incorporation of WTP fibers served to reinforce the PLA matrix for the tensile modulus, from 2273.54 ± 123.66 MPa to 2612.51 ± 95.16 MPa with 15% of WTP fiber. A similar trend was observed for the flexural modulus, which increased from 2456 ± 61.16 MPa in the neat PLA to 3189.68 ± 52.24 MPa for the PLA-15% WTP composite. The results demonstrate the feasibility of the process and the production of parts with acceptable quality under appropriate manufacturing conditions. Full article

Epoxy encapsulation is widely used in dry-type transformer windings to improve insulation performance and mechanical robustness. However, significant thermo-mechanical residual stresses can be introduced during curing and cooling due to material property mismatch, leading to cracking and reliability concerns. This study aims to quantitatively analyze the evolution of thermal-mismatch-related residual stress in epoxy-encapsulated windings and to develop a reliability-oriented improved curing process. A representative encapsulated winding structure and a conventional industrial curing schedule are first modeled, and the evolution of the epoxy degree of cure is calculated based on curing kinetics. The obtained cure history is then coupled with a transient thermo-mechanical finite-element model that incorporates cure-dependent material properties to evaluate the residual stress distribution. The simulation results indicate pronounced stress concentration in specific regions of the encapsulation, which corresponds well with typical cracking locations observed in practice, demonstrating the validity of the proposed approach. Based on this model, several modified curing temperature profiles are further investigated to clarify the effects of temperature levels and dwell times on the development of residual stress. Finally, a reliability-oriented curing process improvement is identified, which effectively reduces stress concentration and mitigates cracking while maintaining adequate curing reliability. Full article

The increasing prevalence of cardiovascular diseases highlights the need to develop vascular grafts that match the mechanics of native vascular tissue and offer functional adaptability. This study reports the development and systematic optimization of a shape-memory polyurethane acrylate (PUA)-based photocurable resin for digital light processing (DLP)-based four-dimensional printing (4DP) applications. Resin formulations were designed by controlling hard/soft segment ratios, reactive diluent content, and crosslink density to position the glass transition temperature (T_g) within the physiological range (25–40 °C). Thermomechanical characterization was performed via dynamic mechanical analysis (DMA) and tensile testing, while a full-factorial Design of Experiments (DoE) approach was applied to optimize DLP process parameters—namely layer thickness, exposure time, and post-curing time. The developed resin formulation yielded a T_g of 38 °C as determined by DMA. Following process optimization, regression models showed high statistical fit (R² > 99%), and experimental validation under optimal conditions (layer thickness: 82.83 µm, exposure time: 11 s, post-curing: 2 min) resulted in an elongation at break of 64.0 ± 3.4%, a Young’s modulus of 10.9 ± 0.1 MPa, and a tensile strength of 6.2 ± 0.3 MPa. The optimized system exhibited thermally triggerable shape memory behavior at near-body temperature, with mechanical properties consistent with natural arterial tissue benchmarks. These findings demonstrate a promising material design strategy for DLP-based 4D-printed vascular structures. Full article

Aluminum alloys, particularly those in the Al-Cu and Al-Mg-Si series, are extensively employed in aerospace, automotive, and structural applications owing to their favorable strength-to-weight ratio. However, optimizing their mechanical and surface properties to meet advanced performance requirements remains a critical challenge. Over the past three decades, extensive research has explored thermochemical treatments, precipitation hardening, and thermomechanical processing, yet most studies have examined these methods in isolation. This review systematically analyzes the influence of each treatment route on microstructural evolution, precipitation behavior, and mechanical performance, with emphasis on grain refinement, precipitation kinetics, surface hardening, and fatigue resistance. Particular attention is given to severe plastic deformation, advanced surface modification techniques, and aging behavior under different conditions. The review also highlights gaps in the current literature, including limited integration of hybrid treatment cycles, insufficient understanding of coupled diffusion-precipitation mechanisms, a lack of high-temperature performance data, and minimal industrial-scale validation. Future research directions are proposed to develop optimized hybrid processing strategies, predictive computational models, and scalable treatment cycles. This consolidated review provides a comprehensive foundation for advancing aluminum alloy design, aiming to achieve tailored surface-to-core property gradients suitable for next-generation aerospace and automotive applications. Full article

High-entropy perovskite oxides attract considerable attention due to their outstanding properties and extensive applications. In this work, the lattice distortion and the mechanical, thermal and electronic structure properties of high-entropy (Ca_0.2Sr_0.2Ba_0.2La_0.2Pb_0.2)TiO₃ (CSBLPT) are investigated through first-principles calculations. The results suggest that the influence of O atoms on lattice distortion is predominant, and the effect of overall A-site atoms plays a distinctly greater role than that of the B-site atoms. The mechanical results show that the high-entropy CSBLPT has a lower Young’s modulus and higher fracture toughness than ternary SrTiO₃. The Debye temperature also indirectly indicates that the thermal expansion coefficient of the studied high-entropy perovskite is greater than that of SrTiO₃. As for thermal conductivity, the obtained result of CSBLPT is also appreciably lower than that of SrTiO₃, and the lowest thermal conductivity is along the [100] direction. The Fermi level of high-entropy CSBLPT is transferred to the conduction band, exhibiting a degenerate n-type semiconductor behavior with metallic-like characteristics, and the Bader charge values are also related to the local lattice distortion, which may cause differences in thermomechanical properties between high-entropy CSBLPT and SrTiO₃. Above all, high-entropy CSBLPT is a preferable TBC material with excellent performance under working conditions compared to SrTiO₃. Full article

X-band copper resonating cavities are key components of future pulsed GHz normal-conductive multi-TeV accelerators. High electric field gradients are required for emerging applications; however, as gradients increase, components’ lifetime decreases, primarily due to radiofrequency (RF) breakdown. Coating technologies are being investigated in several laboratories to improve RF structure, performance and lifetime. To this end, we investigated the feasibility of fabricating nanometer-periodic Cu/Mo metallic multilayers on three-dimensional (3D) aluminum mandrels designed to replicate X-band copper resonating cavities. These nanometer-period multilayers are proposed to mitigate surface degradation due to electric breakdown at high accelerating gradients by stabilizing inner cavity surfaces against dislocation evolution and roughening caused by thermo-mechanical fatigue. High-Power Impulse Magnetron Sputtering (HiPIMS) in a bias-controlled dual closed-field magnetron configuration was employed to deposit alternating Mo and Cu nano-layers onto the 3D geometries. Given the complexity of HiPIMS technology, plasma pulse evolution was studied by combining time-resolved optical emission spectroscopy with electrical measurements of the pulse discharge. The influence of the process parameters, particularly the applied DC bias, on film growth was studied using non-destructive microprobe α-particle elastic backscattering spectrometry (µEBS) and scanning transmission electron microscopy (STEM). STEM and µEBS analyses confirmed that Mo layers with thicknesses of approximately 5–35 nm were successfully deposited repeatedly on thicker Cu layers (30–150 nm), preserving individual layer properties with minimal interdiffusion and alloying. The layers were deposited inside trenches with an aspect ratio of 5:1 representative of X-band irises. This technology, coupled with the replica process, could be applied to highly engineered nanostructured coatings for X-band cavity treatment in compact particle accelerator prototypes, as it may improve electrical breakdown lifetime under high accelerating fields, at least for degradation processes driven by the high mobility of copper dislocations. Full article

Heat-assisted metal spinning comprises incremental forming routes, conventional spinning, shear spinning and flow forming, performed at elevated temperature to increase formability. This review consolidates the main advances of the last fifteen years. It outlines spinning mechanics and the rationale for heating (higher ductility, lower forming forces and microstructure control), then compares global and local heating strategies (furnace, flame, induction, laser and hot-gas convection) in terms of temperature uniformity, industrial practicality, energy efficiency and cost. Key process parameters (spindle speed, feed rate and thickness reduction) are discussed with respect to defect formation, and representative windows for defect mitigation are reported. Progress in modeling is reviewed, including coupled thermo-mechanical finite element simulations, damage/formability prediction and emerging data-driven optimization. The review also summarizes microstructural evolution under heat-assisted conditions, phase transformation, dynamic recrystallisation and grain growth, and its impact on final properties. Across more than 100 studies, evidence shows that robust thermal management can roughly double achievable deformation before failure and enables property tailoring in difficult-to-form alloys (Ni-based alloys, high-strength steels, Al, Mg and Ti). Remaining challenges include reliable in situ temperature measurement/control and improved predictive fidelity of simulations. Future opportunities include digital twins, real-time sensing and adaptive, machine-learning-assisted control. Full article