Search Results (23,452)

Yttria-stabilized zirconia (YSZ) has attracted attention as a ceramic implant material owing to its excellent mechanical strength, biocompatibility, and aesthetic properties. However, YSZ is bioinert and lacks the ability to directly bond with bone. This study aims to enhance the bioactivity of 3D-printed porous YSZ through modified simulated body fluid (m-SBF) pretreatments. The porous YSZ substrates fabricated by fused deposition modeling were first etched with hydrofluoric acid (HF) to increase the surface roughness, followed by immersion in CO₃²⁻, Mg²⁺, and/or Zn²⁺ ion-incorporated m-SBFs. Among the tested solutions, the apatite coating formed in Mg²⁺- and Zn²⁺-containing m-SBF within one day, exhibiting uniform precipitation and a reduced tetragonal-to-monoclinic (t→m) transition. The incorporated Mg²⁺ and Zn²⁺ ions were successfully detected on the apatite coating, with Mg/Ca and Zn/Ca ratios of approximately 4.82% and 3.33%, respectively. Mg²⁺ is known to stimulate osteogenesis, while Zn²⁺ exhibits antibacterial activity. Furthermore, compared with standard SBF under high-temperature and high-pH conditions, the m-SBF induced markedly less t→m phase transition on YSZ substrates, suggesting that m-SBF, as a biomimetic medium for imparting bioactivity, provides a more suitable environment for YSZ substrates. This study demonstrates that HF surface treatment combined with Mg²⁺- and Zn²⁺-containing m-SBF pretreatment effectively imparts bioactivity to 3D-printed YSZ, offering a promising approach for next-generation osteoconductive ceramic implants. Full article

Microwave (MW) sintering offers a promising alternative to conventional heating in powder metallurgy, providing faster processing, lower energy consumption, and improved microstructural control. In the diamond tool industry—where cost-efficiency and competitiveness are critical—MW–hybrid sintering shows strong potential for producing segments designed for cutting and polishing natural stone and construction materials. This study investigates the effects of sintering temperature, dwell time, and green density on the densification and mechanical properties of metal matrix composite (MMC) segments containing diamond particles. MW sintering reduced the optimum sintering temperature by 90–170 °C when compared to conventional free sintering. Under optimal conditions (57% green density, 820 °C, 5 min dwell), segments achieved ~95% densification and mechanical properties comparable to hot-pressed (HP) samples. Although MW–hybrid sintered matrices exhibited slightly lower Young’s modulus (~15%) and Vickers hardness (~20%), their flexural strength and fracture toughness remained comparable to HP counterparts. Overall, MW hybrid sintering provides a cost-effective, energy-efficient, and scalable route for fabricating high-performance diamond tool segments, supporting both economic viability and sustainable, competitive manufacturing. Full article

Background and Objectives: The use of cementless total knee arthroplasty (TKA) is increasing, but established methods for assessing bone quality to prevent early failure remain undefined. Current preoperative assessments using central bone mineral density (BMD) do not accurately reflect peripheral bone quality, and intraoperative evaluation is subjective. This study aimed to establish objective assessment methods by analyzing the correlations between a novel visual grading system, CT Hounsfield units (HU), and actual bone strength. Materials and Methods: This prospective study included 131 patients undergoing posterior-stabilized TKA. We developed a novel visual grading system (Excellent, Good, Fair, Poor) based on femoral cutting surface characteristics. CT HUs were measured preoperatively by an assisting surgeon in the box bone area. Femoral box specimens underwent indentation testing to determine their actual bone strength. Minimum Required Strength (MRS) was defined at 2.5-fold the patient’s body weight, and Estimated Withstanding Strength (EWS) was determined by scaling first failure load using area ratios. Patients were classified as “cementless suitable” (EWS > MRS) or “cemented mandatory” (EWS < MRS). Correlations were assessed using Spearman’s rank correlation for visual grade and Pearson correlation for Hounsfield units. ROC curve analysis determined diagnostic accuracy. Results: Visual grade exhibited an exceptionally robust relationship to bone strength (Spearman ρ = 0.903, p < 0.01), whereas HU showed substantial correlation (Pearson r = 0.660, p < 0.01, R² = 0.435). Visual grading achieved excellent diagnostic accuracy (AUC = 0.974, sensitivity 95.1%, specificity 95.9%) using “Good” grade as cutoff. HU demonstrated AUC of 0.938 with 92.7% sensitivity and 81.6% specificity at a cutoff value of 65.2. Conclusions: Our novel visual grading system and CT HU demonstrated excellent correlations with actual distal femoral bone strength and outstanding diagnostic performance for identifying cementless TKA candidates. Unlike traditional subjective intraoperative assessments such as the “thumb test”, this system provides objective visual criteria directly correlated with actual bone strength. Preoperative HU screening with intraoperative visual grading can help prevent early failure. Full article

Static and dynamic uniaxial tensile responses were investigated to accurately characterize and predict the mechanical properties of PEEK (polyether-ether-ketone) at strain rates ranging from 10⁻³ s⁻¹ to 200 s⁻¹ and temperatures ranging from 23 °C to 110 °C. The tensile responses showed dependences on the strain rate and temperature, and the dependences of the yield strength and elastic modulus on the temperature and strain rate were studied. A modified phenomenological Sherwood–Frost constitutive model considering a wide range of strain rates and temperatures was established to characterize the tensile mechanical response of PEEK material before yielding based on the experimental data. The results indicate that the model can accurately describe the pre-yield behavior of PEEK under different temperature and strain rate conditions, thus reducing the dependency on experimental data for subsequent researchers, thereby providing a theoretical foundation and modeling framework for the design and performance evaluation of CF/PEEK composite structures. Full article

This research examined the mechanical, physical, thermal, and durability properties of plastic-based composites made from MSW, namely ultra-high-temperature (UHT) cartons, plastic bags, aluminum foil, and foil bags under both unweathered and accelerated weathering conditions to evaluate their potential as paving slab materials. Composite samples with varying mixing ratios were fabricated and tested based on an experimental design. Statistical analyses using one-way ANOVA confirmed the significant effects of composition on material performance (p < 0.05). The results demonstrated that the mixing ratio markedly influenced mechanical properties. The composite containing 50 wt% UHT carton and 50 wt% foil bags (U50F50) achieved the highest modulus of rupture (121.20 MPa) and modulus of elasticity (2.98 GPa), as well as compressive strength (28.56 MPa), compressive modulus (2.12 GPa), screw withdrawal resistance (54.25 MPa), and hardness (66.25). Under accelerated weathering, all of the composites showed moderate reductions in strength (10 to 30%) due to plastic degradation and surface cracking. In contrast, the composites containing high paperboard fractions (U80P15A5) exhibited greater WA (3.55%) and TS (3.04%), attributed to the hydrophilic nature of cellulose. The inclusion of foil bags effectively reduced WA and TS by limiting moisture penetration. Density measurements demonstrated a gradual increase (0.99 to 1.05 g/cm³) with higher foil content, while accelerated weathering induced an average 10% density reduction. Abrasion resistance improved in foil-rich composites, with U50F50 showing the lowest weight loss (8.56 to 14.02%), confirming its superior structural integrity under mechanical wear. Thermal analysis indicated low conductivity values (0.136 to 0.189 W/m·K), demonstrating favorable insulation performance compared to conventional paving materials. However, higher foil bag fractions enhanced heat conduction, balancing mechanical strength with thermal functionality. Overall, MSW-derived composites containing 30 to 50 wt% foil bags exhibited optimal mechanical durability, abrasion resistance, and thermal stability, making them promising candidates for sustainable paving slab production with low environmental impact and enhanced service life. Full article

Background: Human adipose-derived mesenchymal stem cells (hADMSCs) are widely used in regenerative medicine due to their ability to proliferate and differentiate. Bone tissue engineering represents an innovative alternative to traditional grafts by combining biomimetic materials, stem cells, and bioactive factors to promote bone regeneration. Gellan gum (GG) is a promising scaffold material owing to its excellent biocompatibility and favorable physicochemical characteristics; however, chemical modifications such as methacrylation are necessary to enhance its mechanical strength and long-term stability. In this in vitro study, osteoprogenitor cells are cultured for 21 days on three 3D-printed GGMA-based scaffolds to evaluate their biological response: (i) neat GGMA, (ii) GGMA functionalized with hydroxyapatite (HAp), and (iii) GGMA functionalized with eumelanin derived from black soldier fly (BSF-Eumelanin). Methods: Cell adhesion, viability, proliferation and osteogenic differentiation are evaluated using MTT assays, histological staining (H&E and Alizarin Red S), alkaline phosphatase (ALP) activity, and gene expression analysis of key osteogenic markers. Results: Our results show that all GGMA-based scaffolds support cell adhesion, growth, and proliferation, while BSF-Eumelanin and HAp notably enhance osteogenic differentiation compared to neat GGMA. Conclusions: These findings highlight the potential of embedding bioactive factors into GGMA scaffolds to improve osteoconductive and osteoinductive performance, offering a promising strategy for bone repair. Full article

Fire hazard presents a critical challenge to the structural reliability of underground modular infrastructure. This study examines the fire resistance performance of prefabricated monolithic utility tunnels featuring longitudinal threaded connections. A series of fire exposure tests was conducted on assembled utility tunnel specimens using different bolt materials and thermal conditions, enabling evaluation of fire behavior, deformation behavior, and residual capacity. The observed thermal properties revealed significant temperature gradients across tunnel sections, with the peak internal–external differential reaching 536.8 °C. Post-fire mechanical degradation was evident in reduced stiffness and ductility, and the residual load-bearing capacity declined by up to 12.28% compared to unexposed specimens. Specimens using high-strength threaded bolts demonstrated superior performance compared to stainless steel bolt specimens, exhibiting a 4.67% higher residual capacity and 13.87% less residual deformation. A sequential thermal–mechanical finite element model was developed and calibrated based on experimental results, offering a reliable simulation framework for investigating fire-induced damage and residual strength in modular utility tunnel systems. These findings provide a quantitative basis for fire safety assessment. Full article

Little research is reported on the properties of Portland cement concrete (PCC) mixtures comprising plastic waste materials. Therefore, this novel study was initiated to evaluate the effects of plastic waste materials on different properties of PCC. Plastic boxes and containers made of polypropylene were cut, grinded, pulverized, and incorporated into PCC mixtures. Sand was partially replaced by plastic waste materials with 0%, 5%, 10%, 15%, and 20% volume ratios. Experiments were conducted using PCC cylinders and prisms to evaluate several unique properties of PCC containing plastic waste. Innovative interactions and contributions of several PCC properties including workability, air content, density, water absorption, mechanical properties, rapid chloride ion penetration, and freeze–thaw deterioration are investigated. The new experimental data indicated that the workability and density of PCC decreased with increasing plastic waste replacement levels. The maximum decreases in workability and density were 23% and 6.2% for the PCC with 20% plastic replacement, respectively. On the other hand, our research has shown that air content and water absorption of PCC increases with increasing plastic waste amount. The maximum increase in air content and water absorption were 78% and 29% for the PCC with 20% plastic waste. This study also shows that the mechanical properties of PCC (e.g., compressive and splitting strengths) after 7 and 28 days of moist curing decreased with increasing plastic waste content. Another new finding is that the rapid chloride permeability of PCC increased and the freeze–thaw durability of PCC decreased with an increase in plastic waste amount. One of the most critical discoveries of this experimental study is that plastic waste increases the durability of PCC, i.e., durability factor of PCC with 20% plastic waste was 9.3% compared to 28.5% for the control PCC without plastic waste materials. Full article

In this study, the joining of Cu/Al tubes was achieved using the magnetic pulse-assisted semi-solid brazing (MPASSB) technique. A coupled finite element method–smoothed particle hydrodynamics (FEM-SPH) model was established to analyze the influence mechanism of solid–liquid interface interaction on pore formation during the brazing forming process. The results indicate that the MPASSB technique can produce Cu/Al tube joints with excellent metallurgical bonding and performance at 390 °C, and no brittle Cu/Al intermetallic compounds (IMCs) are formed in the joints. Additionally, a stronger solid–liquid interface interaction and a higher surface roughness of the tubes lead to easier peeling of the copper matrix from the interface, thereby promoting pore formation. Mechanical property tests show that the shear strength of the joints prepared by this method can reach 63.3 MPa, and the fracture occurs in the brazing seam area adjacent to the copper–side interface. The MPASSB technique is expected to provide a feasible technical approach for the high-quality joining of dissimilar Cu/Al materials. Full article

Increasing traffic volumes, heavier axle loads, and the growing frequency of premature pavement distress pose major challenges for modern road infrastructure. In many regions, asphalt pavements experience early rutting, cracking, and moisture-induced damage, underscoring the need for improved material performance and longer service life. Reinforcing fibres are increasingly used to enhance asphalt mixture properties, with aramid fibres recognised for their superior mechanical and thermal stability. This study evaluates the effect of FlexForce (FF) fibres on the mechanical and fracture behaviour of two dense-graded asphalt concretes, AC 16 surf and AC 16 bin, produced with different binders and fibre dosages (0.02% and 0.04% by mixture weight). Laboratory tests, including indirect tensile strength ratio (ITSR), indirect tensile stiffness modulus (IT-CY), crack propagation resistance, and dynamic modulus measurements, were performed to assess moisture susceptibility, stiffness, and viscoelastic behaviour. The results showed that fibre addition had little effect on compactability and stiffness under standard conditions but improved temperature stability and stiffness at elevated temperatures, particularly when used with polymer-modified binders. Moisture resistance decreased slightly, while fracture performance improved moderately at intermediate temperatures. Overall, low fibre dosages (~0.02%) provided the most balanced performance, indicating that the mechanical benefits of aramid reinforcement depend strongly on binder rheology, temperature, and interfacial compatibility. These findings contribute to optimising fibre dosage and binder selection for aramid-reinforced asphalt layers in practice. Full article

The growing demand for eco-efficient construction materials has driven the development of low-clinker cement systems incorporating recycled mineral additives. Finely ground brick powder represents one of such materials with high pozzolanic potential. This article presents an experimental study on the effect of partially replacing slag cement CEM III and ordinary rapid-hardening cement CEM I with brick powder waste of different chemical compositions and fineness levels (63, 32, and 15 µm) on the physical and mechanical properties of blended cement mortars. Compressive and flexural strengths were determined at 2, 7, and 28 days, along with the strength activity index (SAI). Additionally, the setting times and standard consistency were investigated, with the latter showing a correlation with the workability of fresh mortars. Comprehensive microstructural analysis (TGA, SEM, EDX) confirmed the pozzolanic activity of the brick powder, which was manifested by the formation of C-S-H and C-A-S-H phases. The highest strength characteristics were achieved with a 15% replacement of cement by brick powder with a fineness of 32 μm and an increased SiO₂ content (63.06%). Comparative analysis with fly ash- and silica fume-modified mortars revealed that brick powder exhibits comparable performance, confirming its suitability as an active mineral additive. Full article

Inclusive education represents a central pillar of social sustainability, demanding a nuanced understanding of the factors shaping students’ attitudes toward people with disabilities. Grounded in the social–relational model of disability—which conceptualizes disability as the interaction between individual characteristics and environmental barriers—this study examined the effects of emotionally valenced video stimuli (positive, negative, neutral), gender, and tolerance level on university students’ attitudes, using a randomized quasi-experimental design with repeated measures. The intervention was implemented entirely online to ensure consistency and accessibility. A total of 179 undergraduate students from the National University of Science and Technology Politehnica Bucharest (Romania), aged 20 to 23 years (M = 21.4, SD = 1.6), participated in the study, which lasted approximately two weeks. Participants completed pre- and post-intervention assessments, including the Elementary Tolerance Scale and a 25-item Attitude Scale combining strengths-based descriptors with stereotype-consistent items used diagnostically to detect bias (without endorsing such framings). Results revealed a significant main effect of video type, F(2,176) = 10.07, p < 0.001, with higher post-test scores for the positive condition (M = 93.82) compared to the negative (M = 85.88) and neutral (M = 82.67) conditions. Gender (p = 0.033) and tolerance level (p = 0.034) also emerged as significant moderators. We explicitly reject deficit-oriented terminology, contextualizing its use solely for diagnostic and analytical purposes; wherever possible, affirming, strengths-based, and socially grounded language is prioritized. These findings highlight the value of brief, emotionally tailored interventions for fostering inclusive attitudes in higher education and emphasize the importance of ethically curated, co-designed educational materials and measurement practices grounded in dignity and human rights. Ethical Note (Content Warning): The study adopts a social–relational, human-rights perspective on disability. Deficit-based narratives were analyzed exclusively as subjects of critique and are not endorsed. Descriptions of the “negative” stimulus were deliberately minimized to reduce potential harm and included only for scientific transparency. Negative-valence questionnaire items reflect prevalent stereotypes and were used solely as diagnostic indicators of bias. Future research should prioritize collaborative co-creation with scholars and advocates with disabilities and employ ethically curated, inclusive stimuli. Full article

Ultra-high-performance concrete (UHPC) is recognized for its exceptional strength and durability. However, the adoption of UHPC frequently leads to higher material and environmental costs. Accurate prediction of compressive strength is crucial for optimizing material design and reducing construction costs. In this study, a dataset of 800 samples was compiled from published articles. Four models, including random forest (RF), Gaussian Process Regression (GPR), Gradient Boosting (GB) and Artificial Neural Network (ANN), were applied. Results show that ANN and GPR achieved the best accuracy and stability. GB also performed well with good adaptability. RF captured general trends but produced larger errors in the high-strength range. Feature importance analysis highlighted curing age and cement content as the most influential factors, with a combined contribution above 65%. The water-to-binder ratio also affected strength through matrix densification. Extended evaluation with regression error characteristic (REC) curves and environmental impact index (EII) revealed the balance between performance and environmental impact. Higher compressive strength often required higher energy, CO₂, and resource use. The range of 150–250 MPa showed a better balance between performance and sustainability. This study confirms the robustness of machine learning models for strength prediction and provides guidance for green and low-carbon ultra-high-performance concrete design. Full article

According to existing ecological problems, one of the promising developments is the creation of polyfunctional materials, which can be biodegradable, along with possessing antibacterial activity. The present research proposes biocomposites based on PLA with silver nanoparticles (AgNPs) and natural polysaccharides obtained in a twin-screw extruder. Introduction of polysaccharides to PLA-based biocomposites with/without AgNPs led to significant decrease in the elastic modulus and tensile strength, while the elongation at break remained almost unchanged. Thanks to the presence of natural polysaccharides, there was intensified biodegradation in soil despite the AgNP availability. The maximal mass loss was 29% for the PLA–PEG₁₀₀₀–starch + AgNPs (80:10:10 + 0.5 wt%) biocomposite. Analyses of the systems before and after soil exposure were carried out using DSC and FTIR spectroscopy methods. According to a thermal analysis, it was found that PLA crystalline regions degrade during exposure to soil. The same feature was detected during the spectral analysis. The intensity of the characteristic absorption bands of PLA decreased. Furthermore, it was found that the dark areas on the surface of the materials are of a polysaccharide nature and may be signs of biofouling of the materials by microbial flora. The tests on fungus resistance showed that biocidal additives such as AgNPs in PLA-based biocomposites with polysaccharides did not inhibit the development of mycelial fungi–biodestructors. And the increased amount of chitosan in the films contributed to their more active destruction by the end of the observation period. It was demonstrated that such biocomposites can inhibit bacterial growth. Full article

The fatigue of wood is becoming increasingly important in modern engineering, as the safety of the structure must be guaranteed and the use of materials must be optimized at the same time. Predicting the fatigue behavior of wood remains a challenge for many researchers. Interest and the number of studies in this field have increased, highlighting the need for a comprehensive overview of the current state of knowledge on wood fatigue. In this paper, we focus on the study of the fatigue of wood-based materials to understand the similarities and peculiarities of fatigue behavior compared to other engineering materials and to identify opportunities for new research. We present the influence of physical and mechanical properties on fatigue life and identify similarities in the fatigue behavior of wood, polymeric materials and steel. The basic properties that differentiate the fatigue life of wood from that of other materials are heterogeneity, orthotropy, viscoelasticity, hygroscopicity, mechanosorptivity and the lack of a clear threshold value for fatigue strength. The differences in fatigue life between solid wood and laminated wood are not uniformly defined by researchers. We provide an overview of the measurement methods used to monitor the fatigue state, the models used to predict fatigue life and the simulations of the stress–strain response to cyclic loading. We identify areas where wood is subject to fatigue and determine which areas are most critical under cyclic loading. We make suggestions for further research that would contribute significantly to a better understanding and management of wood fatigue. Due to the wide variety of wood species used in the studies, it is impossible to compare the results. In order to obtain a comprehensive overview of the response of wood to fatigue under different test conditions, the test methods need to be standardized. Full article