Search Results (781)

Triply periodic minimal surface (TPMS) lattices are an emerging class of cellular architectures whose smooth, mathematically defined surfaces enable highly tailorable mechanical performance. This study quantifies the compressive elastic response of three sheet-based TPMS topologies, i.e., Diamond, Gyroid, and Lidinoid, through finite element (FE) analysis and experimental validation. For each topology, the effective Young’s modulus was computed by single-cell finite element analysis under uniaxial compression boundary conditions on a 2 mm unit cell across five wall thicknesses (0.35, 0.45, 0.65, 0.95, and 1.30 mm), corresponding to relative densities from approximately 25% to 95%. Experimentally, cylindrical specimens of 316L stainless steel at 70% relative density were fabricated by laser powder bed fusion (LPBF) and tested in uniaxial compression with a strain rate of 10⁻³ s⁻¹ per ISO 13314:2011 (i.e., 0.02 mm/s). The Diamond topology exhibited the highest effective modulus across the full density range, followed by Lidinoid and Gyroid. FE predictions agreed with experimental moduli within 4.7% for Diamond (100.2 GPa vs. 95.5 ± 3.9 GPa), 0.04% for Gyroid (79.8 GPa vs. 79.8 ± 0.88 GPa), and 1.5% for Lidinoid (85.6 GPa vs. 86.9 ± 3.5 GPa). Moreover, the Gibson–Ashby exponents determined span the range from stretching- to bending-dominated deformation with n = 1.69 for Diamond, 1.74 for Lidinoid, and 2.08 for Gyroid. Single-cell FE analysis accurately captured the effective elastic response of LPBF 316L stainless steel TPMS lattices examined. Full article

The present study investigates the combined influence of manufacturing route and material configuration on the mechanical, elastic, viscoelastic, and impact behavior of Kevlar–carbon hybrid laminates. Three eight-ply laminate configurations (V1, V2, and V3) were manufactured through distinct technological routes: fully prepreg-based hot pressing, Kevlar-prepreg/dry-carbon hand lay-up followed by vacuum curing, and multi-stage hybrid consolidation combining repeated hot pressing with subsequent vacuum curing. The experimental characterization included tensile tests according to ASTM D3039, compression tests according to ASTM D695, determination of Young’s modulus from extensometer measurements and Poisson’s ratio using strain-gauge instrumentation, dynamic mechanical analysis (DMA), and low-velocity impact tests under controlled energy conditions. The novelty of this work consists in the integrated process–configuration–property comparison of these Kevlar–carbon hybrid routes within the same experimental framework, rather than in a generic demonstration that manufacturing affects composite laminates. The V1 laminate exhibited the highest strength-related performance, reaching an average tensile strength of 335.88 MPa and a compressive strength of 165.85 MPa, and it also showed the highest DMA storage modulus at 30 °C, E’ = 53.42 GPa. The V2 laminate presented lower tensile performance but the most pronounced damping response, with the highest tanδ peak value. The Young’s modulus determined from the extensometer measurements was 29.26 ± 1.45 GPa for V1, 26.10 ± 0.22 GPa for V2, and 29.52 ± 1.27 GPa for V3, indicating comparable longitudinal stiffness for the V1 and V3 laminates. The results indicate that the measured behavior is governed by the combined effects of reinforcement form, matrix/resin arrangement, consolidation route, and laminate architecture. Direct quantification of laminate compaction, fiber volume fraction, and void content was outside the scope of the present experimental campaign and is identified as a necessary step for future validation. Full article

Silicon carbide (SiC) is a key material for next-generation miniaturized devices and MEMS operating in harsh environments. This paper presents a comprehensive investigation of anisotropic damping mechanisms in heteroepitaxial 3C-SiC double-clamped beam resonators for MEMS applications. Unlike conventional isotropic loss-factor models, which assign a single scalar damping coefficient to all deformation directions, the proposed framework employs a full 6 × 6 loss-factor tensor expressed in Voigt notation, implemented within the COMSOL Multiphysics finite element environment. The tensor formulation enables the direction-dependent description of energy dissipation, capturing the coupling between shear and normal strain modes that arises from the (111) crystallographic orientation and from the heteroepitaxial defect structure of 3C-SiC grown on silicon substrates. The effects of film thickness, effective Young’s modulus, and residual stress on elastic modulus, resonance frequency, and Q-factor are systematically analyzed across five wafers (w1–w5, thickness range 293–890 nm). Experimentally calibrated anisotropic loss-factor matrices are extracted via least-squares fitting to measured Q-factors, and their Frobenius norms are found to correlate negatively with resonance frequency. The anisotropic model reduces Q-factor prediction errors to below 1% for all wafers, significantly outperforming the isotropic approach, particularly for films thicker than 600 nm. These results demonstrate that an accurate treatment of directional dissipation is essential for the design of high-Q resonators and high-sensitivity strain sensors targeted at geophysical monitoring applications. Full article

The glass transition temperature (Tg) is a pivotal design parameter for polymer performance across diverse applications, yet its rapid prediction within expansive chemical spaces remains a challenge. We present a machine learning (ML) framework for the high-throughput prediction of Tg in binary copolymers, trained on experimental datasets encompassing both homopolymers and copolymers. We evaluate various ML architectures, including graph-based algorithms, to effectively capture non-linear composition–property relationships. The optimized model achieves high predictive accuracy with an RMSE of ~14K and an R² of ~0.98. Crucially, the framework accounts for the chemical diversity of monomeric units by integrating structural descriptors with molar composition ratios, enabling the model to capture complex dependencies of thermal stability on chemical structure and composition. We validate the model’s robustness using physics-based molecular dynamics (MD) simulations. To showcase the platform’s scalability, we generated a library of approximately 148,000 binary copolymer compositions and predicted their Tg, facilitating the rapid mapping of vast design spaces. This extensive virtual library enables the identification of optimal monomer pairings that would be experimentally inaccessible through traditional trial-and-error methods. Through these large-scale exploration studies, we demonstrate the ability to design copolymers for targeted applications, including a specific case study on elastomeric systems. This integrated approach, combining experimental data, ML modeling, and physics-based validation, offers a transformative path for the accelerated discovery and multi-property optimization of functional copolymers. Full article

Although hydrogen embrittlement mechanisms focus predominantly on the plastic deformation regime, the fundamental effect of interstitial hydrogen on the elastic regime remains elusive. The elastic behavior due to hydrogen is critical because lattice alterations drive microstructural instabilities and macro-failure. This work aims to determine the hydrogen-affected single-crystal elastic constants and anisotropy of 304L stainless steel and link them to dislocation-mediated embrittlement mechanisms. Using in situ neutron diffraction and the Kröner model, this study derived, for the first time, the single-crystal elastic constants ($C_{\mathrm{i}\mathrm{j}}$) of 304L austenitic stainless steel. Hydrogen charging expanded the lattice constant by ~0.7% (from 3.558 $\mathrm{\AA }$ to 3.583 $\mathrm{\AA }$) and selectively increased $C_{11}$ and $C_{12}$ while leaving $C_{44}$ nearly unchanged. Consequently, while bulk polycrystalline Young’s and shear moduli remained invariant, Zener’s anisotropy and Poisson’s ratios increased. Hydrogen reduced the shear modulus of the {111}<110> slip system by ~8.3% and the Peierls–Nabarro stress by approximately 38%. The experimental derivation of single-crystal elastic moduli proved that lattice-scale modifications selectively enhanced volumetric stiffness while lowering the slip-direction shear modulus. Coupled with hydrogen-induced lattice expansion, these findings validate the theoretical volumetric and modulus components of the hydrogen-enhanced localized plasticity mechanism, thereby elucidating its fundamental origin. Full article

Shape-memory polymers (SMPs) are gaining significant attention for their ability to recover predefined shapes via external stimuli. Among thermally activated systems, biodegradable blends of polylactic acid (PLA) and polycaprolactone (PCL) are particularly promising for biomedical devices and soft actuators. This study develops a thermo-mechanical theoretical model to investigate the shape-memory behavior of a PLA/PCL composite blend under controlled thermal cycling. The framework integrates transient heat transfer, temperature-dependent elasticity, and viscoelastic dynamics to predict temperature evolution, deformation, and internal stress. The thermal response is computed via Newton’s law of convection, while the mechanical transition is described by a sigmoidal temperature- and crystallinity-dependent Young’s modulus. Beam bending theory is employed to evaluate the spatial distribution of strain and stress. A parametric sensitivity analysis was performed to evaluate the influence of different parameters, including the crystallinity grade, convective heat transfer coefficient, glass transition temperature, and viscoelastic recovery constant. The theoretical study accurately reproduces the shape-memory cycle, quantifying performance through fixation and recovery ratios. This model provides a robust tool for the rational design and optimization of biodegradable smart polymer structures. Full article

The demand for sustainable, high-performance biomaterials has driven intense research towards natural polysaccharide hydrogels. Accordingly, this study aimed to synthesize novel starch-based hydrogel materials, considering their inherent hydrogel-forming capabilities together with diverse potential applications (e.g., pharmaceuticals, medicine, and the cleaning application for the artifacts). To obtain hydrogels with enhanced mechanical and physico-chemical properties, starch was combined with other polymeric species (i.e., alginate, polyvinyl alcohol, and polyvinylpyrrolidone), and a gelling process was induced by using calcium cations or borate anions. Two distinct hydrogels (named S-Ca and S-SB, respectively) were prepared and characterized by a range of instrumental and experimental techniques. The assessed properties included water and solvent resistance, equilibrium water content, water-releasing capacity, morphology and microstructural features with their composition by SEM-EDS analysis, and mechanical properties (tensile strength, elasticity, Young’s modulus, and hardness). The results indicated that the investigated hydrogels exhibited suitable properties for a variety of applications, including surface cleaning processes in the field of cultural heritage conservation. For instance, they showed equilibrium water content (between 80 and 90%) comparable with other hydrogels commonly used as cleaning tools (e.g., agar and p(HEMA)/PVP) and quite low water-releasing capacity (between 10 and 17 mgcm⁻²). Moreover, the S-SB hydrogel displayed distinctly better tensile strength and elongation at break than hydrogel prepared in the presence of Ca²⁺ (S-Ca). Notably, S-SB experienced considerable elasticity improvement after freezing–thawing cycles, as indicated by a decrease in tensile strength (from 275 to 102 kPa) and an increase in elongation at break (from 121 to 275%). However, it should be noted that the hydrogel selection depends on the requirements of the target application, as different processes demand materials with distinct characteristics. Hence, both S-Ca and S-SB hydrogels were tested as cleaning tools for the removal of artificially aged acrylic coating (i.e., Paraloid B-72) from the surface of marble and wood specimens, respectively. The tests provided positive results, as aged coating was satisfactorily removed by applying the hydrogels loaded with a nanostructured emulsion (NSE). These novel starch-based hydrogels demonstrate significant potential as high-performance alternatives to conventional hydrogel systems currently used in conservation science as well as in other industrial applications. Full article

Magnesium–rich environments are frequently encountered in cementitious systems, including the use of high–Mg raw materials in clinker production, cement–clay interfaces relevant to nuclear waste disposal, and exposure of cement–based materials to seawater, where progressive decalcification can substantially alter the structure and durability of calcium aluminosilicate hydrate (C–A–S–H) phases. In this study, density functional theory (DFT) calculations were employed to investigate the combined effects of interlayer and intralayer partial decalcification, Mg²⁺ substitution, and reinforcement with epoxy– and hydroxyl–functionalized reduced graphene oxide (rGO) on the structural stability and elastic properties of alkali charge–balanced C–A–S–H under dry and hydrated conditions. Adsorption–energy calculations reveal thermodynamically favorable interactions between functionalized rGO and silicate hydrate species in the presence of Mg²⁺, with hydroxyl/rGO promoting stronger interfacial stabilization and epoxy/rGO preserving greater graphene lattice integrity. The results demonstrate that Mg²⁺ substitution together with rGO intercalation generally enhances the mechanical response of partially decalcified structures through structural densification and interfacial cohesion. Relative to dry systems, hydration further improves elastic performance, increasing Young’s modulus and bulk modulus by 1–11% and 4–19%, respectively, for interlayer decalcified nanocomposites, while intralayer configurations exhibit stronger but model–dependent enhancements of up to ≈22% and ≈33%. Compared with untreated systems, rGO–treated nan–composites exhibit enhanced stiffness, with Young’s modulus and bulk modulus increasing by up to ≈22% and ≈15%, respectively. Overall, these findings provide atomistic insights into stabilization mechanisms in partially decalcified alkali charge–balanced C–A–S–H systems and identify Mg²⁺–rGO incorporation as a promising strategy for mitigating decalcification–induced degradation in durable low–carbon cementitious nanocomposites. Full article

Carbon nanotube (CNT)-reinforced composites are promising advanced materials due to their exceptional mechanical properties. This paper presents a comprehensive investigation of the mechanical behavior of CNT/epoxy composites through theoretical modeling and experimental validation. An equivalent cylindrical fiber model was developed to transform CNTs into effective reinforcement phases, enabling the application of classical composite mechanics. Three reinforcement configurations were analyzed: two unidirectional short fiber models (aligned and staggered) and a three-dimensional four-directional braided long-fiber model. The effects of geometric parameters, including the diameter-to-thickness ratio (D/t) and fiber aspect ratio, on the effective elastic moduli were systematically evaluated. Static and dynamic compression experiments were conducted using an MTS 810 testing system and a Split Hopkinson Pressure Bar (SHPB) to examine the influence of loading rate, vacuum treatment, and reinforcement type (CNT, SiC, and hybrid SiC/CNT) on composite strength. The results indicated that 3 wt% CNT reinforcement increases the Young’s modulus by 30% under static loading and enhanced the dynamic compressive strength under impact loading. The vacuum degassing process significantly affected composite quality, with insufficient vacuum leading to strength degradation due to void formation. Theoretical predictions using Mori–Tanaka and dilute methods showed good agreement with experimental results at low reinforcement volume fractions. Scanning electron microscopy revealed uniform CNT dispersion and provided insights into failure mechanisms, including CNT pull-out and breakage. This work contributes to the understanding of structure–property relationships in CNT-reinforced polymer composites and provides guidelines for achieving their optimal design. Full article

Uranium dioxide (UO₂) is the standard fuel in light water reactors, but improving its mechanical performance is essential for achieving higher burnups. This study employs first-principles density functional theory with the DFT + U approach to investigate the effect of molybdenum (Mo) substitution on the elastic properties of UO₂. Supercell models with Mo concentrations from 3.125 to 9.375 at.% are constructed, and elastic constants are calculated using the stress–strain method, complemented by Bader charge and charge density analyses. The results reveal a non-monotonic concentration-dependent behavior: at 3.125 at.% Mo, the shear and Young’s moduli increase by ~16% and ~14%, respectively, indicating significant stiffening; at higher concentrations (6.25 and 9.375 at.%), both moduli decrease, leading to softening of UO₂ lattice. Bader charge analysis shows that Mo loses only 0.13 electrons (vs. 2.56 for U) and the Mo–O bond is much shorter than the U–O bond; this is evidence of covalent bonding between Mo and O atoms that acts as local strengthening centers at low doping. The softening at higher concentrations is attributed to increased lattice distortion and enhanced bond delocalization, supported by changes in Cauchy pressure, Debye temperature, and Vickers hardness. The calculated elastic modulus and hardness of pure UO₂ are in good agreement with previously reported experimental data. For Mo-doped UO₂ systems, this work establishes a quantitative composition–property relationship, providing a theoretical reference for future experimental investigations. Full article

Y₂SiO₅ (YSO) and Lu₂SiO₅ (LSO) are orthosilicates used in photonic and scintillation applications. Isovalent substitution on the rare-earth sublattice in YSO–LSO solid solutions enables systematic tuning of lattice parameters and elastic properties without changing the underlying monoclinic structural framework. A systematic ab initio study of structural, elastic, and vibrational properties of Ce-free YSO–LSO solid solutions is performed within density functional theory using a localized Gaussian-type orbital basis. Nine compositions spanning the full range from YSO to LSO with a Lu content step of 12.5% are investigated. A total of 76 symmetry-independent Y/Lu substitution patterns are explicitly constructed. For each configuration, full geometry optimization and calculation of second-order elastic constants are carried out using the stress–strain approach. Bulk, shear, and Young’s moduli, as well as Poisson’s ratio, are obtained using the Voigt, Reuss, and Hill averaging schemes. Sound velocities and Debye temperatures are derived from the Hill-averaged elastic moduli and density. The unit-cell volumes decrease smoothly with increasing Lu content and follow Vegard’s law, indicating uniform lattice contraction. The Hill-averaged bulk modulus increases from 92 GPa (YSO) to 115 GPa (LSO), the Young’s modulus rises from 151 to 180 GPa, and a strong directional anisotropy (ratio ∼2) is preserved across the entire series. The Debye temperature decreases monotonically from 518 K to 439 K, indicating that the increase in mass density outweighs the stiffening-induced tendency toward higher sound velocities. These results provide quantitative guidance for composition selection and stress management in LYSO-based crystal detectors. Full article

This study examines the complex interplay between dynamic response and mineralogical microstructures across various geological formations, particularly differentiating between mineralized and metamorphic rocks. Utilizing a comprehensive vibration-based approach, in conjunction with petrographic analysis and ultrasonic wave propagation, the study clarifies the significant impact of microstructural features, such as disseminated sulfides and foliated planes, on the complex’s global dynamic behavior. This study investigates six representative rock samples from mineralized and metamorphic geological zones using integrated petrographic analysis, ultrasonic wave velocity testing, density and physical property measurements, and free-vibration dynamic analysis. The results show that the composition and mechanical properties differ significantly. Mineralized rocks contain a high proportion of sulfide minerals, reaching approximately 75% in some samples, and exhibit significantly higher densities, with the APZ sample reaching 3950 kg/m³. In contrast, metamorphic rocks have an average density of 2700 kg/m³. This difference in composition leads to different dynamic responses. Mineralized zones have dynamic elastic moduli that are much higher than those of metamorphic rocks, with Young’s Modulus reaching up to 134.17 GPa and shear moduli ranging from 49.78 GPa to 56.14 GPa, which is about 50% higher than metamorphic rocks (28.9 GPa to 30.5 GPa). However, macro-mechanical deflection tests show that highly foliated metamorphic rocks (like PFT) exhibit the largest deflection of 0.52 mm, while demineralized rocks (like CP) exhibit the smallest deflection of 0.26 mm. Dynamic vibration analysis shows that microstructural “flaws” significantly affect energy dissipation. For example, the Transitional Phase Zone (TPZ) in mineralized rocks has the highest damping ratio (1.67%) and the lowest natural frequency (270 Hz) in its suite. This is different from the more rigid Advanced Pyritization Zone (APZ), which has a damping ratio of 1.1% and a frequency of 395 Hz. These new correlations provide a more accurate basis for the non-destructive assessment of structural stability in mineralized settings, highlighting that local micro-stiffness does not necessarily indicate macroscopic dynamic rigidity. Full article

Post-fire evaluation of reinforced concrete (RC) columns in existing buildings demands reliable non-destructive methods capable of quantifying stiffness loss, identifying damage patterns, and supporting decisions on repair or replacement. This study develops and validates a dynamic NDT methodology that integrates Experimental Modal Analysis (EMA) and sonic testing (ST) based on elastic wave propagation to characterise the mechanical condition of fire-damaged RC columns. The procedure combines global dynamic indicators (natural frequencies and mode shapes) with local measurements of the dynamic Young’s modulus along the column height. A numerical finite element (FE) model is employed to validate the sensitivity and consistency of the proposed dynamic indicators under controlled degradation scenarios. After validation, the methodology is applied to two real fire events affecting basement columns in residential buildings. In the first case, several columns exhibit significant stiffness reductions, with pronounced modulus losses in the most exposed regions, leading to the recommendation of comprehensive strengthening measures. In the second case, results show minimal variations in most elements, allowing targeted intervention on a single moderately affected column. The study demonstrates that the combined EMA–ST approach provides a robust and cost-efficient basis for diagnosing fire-exposed RC columns and for guiding post-fire structural decision-making in practice. Full article

Static wetting is a widely adopted method for determining surface and interface tensions of materials. In this study, the effects of elasticity and thickness are analytically investigated using a spherical cap model, for an incompressible elastic thin layer bonded to a rigid substrate. The asymptotic solutions are derived based on the principle of stationary total potential energy. Explicit formulas are provided to link the droplet shape to the surface/interface energies, the thickness and the Young’s modulus of the layer. Furthermore, the model is refined with the aid of numerical results of spherical indentation. The refined model shows reasonable agreement with existing experimental data of contact angles for various layer thicknesses with a maximum deviation of 5°, whereas the deviation yielded by the classical Young’s equation exceeds 15°. Furthermore, the predicted Young’s modulus based on the explicit formulas is 3.2 kPa, close to 3 kPa obtained from macro bulk rheometry experiments. These agreements demonstrate that the present model has the potential to capture the effects of thickness and elasticity, thereby improving the prediction accuracy of surface energies, and provide an alternative method to characterize the Young’s modulus of the layer based on measurements of contact angles across various contact radii. Full article

This study investigates the elastic anisotropy and thermodynamic properties of the L1₂-type ScAl₃ phase under extreme conditions (0–1500 K and 0–50 GPa) using first-principles calculations. The elastic constants were determined using a precise stress–strain method, with polycrystalline moduli derived via the Voigt–Reuss–Hill (VRH) approximation. A systematic analysis was conducted to characterize the elastic anisotropy of Young’s modulus, shear modulus, and Poisson’s ratio. Results demonstrate that ScAl₃ is mechanically stable and exhibits near-perfect elastic isotropy (A^U = 0.0001). Thermodynamic analysis via the quasi-harmonic Debye–Grüneisen model reveals that the phase maintains its structural integrity and significant heat resistance up to 1500 K, despite thermal softening. These findings provide theoretical insights into the physical nature of ScAl₃ intermetallics and offer quantitative guidance for the design and thermal treatment of Sc-reinforced aluminum alloys in high-temperature aerospace applications due to their superior combination of strength and toughness. Full article