Search Results (141)

Banana fibres (BFs), derived from the pseudo-stems of Musa acuminata, represent a widely available agricultural residue with strong potential as an eco-friendly reinforcement in composite materials—particularly in bio-based epoxy or thermoplastic systems used in automotive interiors, packaging, and lightweight construction. However, their inherent variability presents challenges for consistent and reliable mechanical characterisation. This study investigates the effect of wood ash treatment, an eco-friendly alternative to conventional alkaline processing, on the tensile strength of single BFs. Fibres were treated in aqueous wood ash solutions at two pH levels (12.4 and 13.5) and soaking durations of 3 h and 24 h, and then tested according to ASTM C1557. At least 50 valid tensile tests per series were performed, and the results were analysed using a two-parameter Weibull distribution to quantify characteristic strength and variability, complemented by reliability analysis to assess survival probability. Untreated fibres exhibited low characteristic strength (396.6 MPa) and a Weibull modulus of 1.79, confirming significant scatter. Treated fibres showed marked improvements: the highest characteristic strength was achieved at pH 13.5 for 3 h (552.8 MPa, m = 3.17), while the greatest uniformity was observed at pH 13.5 for 24 h (m = 4.62). Reliability curves confirmed superior performance of treated fibres, with 75% survival strengths up to 373 MPa compared to 198 MPa for untreated. These findings demonstrate that wood ash treatment enhances both the strength and reliability of BFs for sustainable composite applications. Full article

To evaluate the frost resistance of basalt fiber-reinforced concrete (BFRC) and predict its service life, this study conducted 225 quick freeze–thaw (F-T) cycle tests. Specifically, it systematically investigated how basalt fiber (BF) volume content (0.1%, 0.2%, 0.3%) and the incorporation method (single-doped 18 mm, mixed-doped 6 mm/12 mm/18 mm) affect concrete frost resistance. Meanwhile, a two-parameter Weibull distribution model was established to quantitatively predict the service life of BFRC. The results showed that BF significantly improved the frost resistance of concrete: the reference group without BF had a relative dynamic elastic modulus (RDEM) of less than 60% after 25 F-T cycles, while the group with 0.3% volume content of single-doped 18 mm BF still maintained structural integrity after 225 F-T cycles, with a frost resistance grade exceeding F225. Furthermore, within the scope of this study, the frost resistance effect of single-doped 18 mm BF was better than that of mixed-doped BF, and the frost resistance of concrete gradually improved with the increase in BF volume content. In high-altitude cold regions (e.g., Songpan County, Sichuan Province) with 85 annual F-T cycles, the predicted service life of BFRC with 0.3% single-doped BF reached 49 years, which was approximately 25 times that of the reference group (2 years). This study delivers a systematic comparison of the frost resistance between single-doped long and mixed-doped BF, along with a targeted life prediction model for high-altitude cold regions (85 annual F-T cycles, annual temperatures below 6 °C), which collectively offer a theoretical and technical basis for BFRC durability design in freeze–thaw environments. Full article

The aim of this study is to evaluate the mechanical properties and long-term stability of 3D-printable resins for permanent fixed dental prostheses (FDPs), focusing on whether material performance is influenced by 3D-printer type or by differences in resin formulations. Specimens (N = 621) were printed. CAD/CAM blocks (BRILLIANT Crios) served as control. Flexural strength (FS) with elastic modulus (E_calc), Weibull modulus (m), Martens’ hardness (HM), indentation modulus (EIT), elastic modulus (E_RFDA), shear modulus (G_RFDA), and Poisson’s Ratio (ν) were measured initially, after water storage (24 h, 37 °C), and after thermocycling (5–55 °C, 10,000×). SEM analysis assessed microstructure. Data were analyzed using Kolmogorov–Smirnov, ANOVA with Scheffe post hoc, Kruskal–Wallis with Mann–Whitney U, and Weibull statistics with maximum likelihood (α = 0.05). A ceramic crown printed with Midas showed higher FS, HM, and EIT values after thermocycling than with Pro55s, and higher E_calc scores across all aging regimes. A Varseo Smile Crown Plus printed with VarseoXS and AsigaMax showed a higher FS value than TrixPrint2, while AsigaMax achieved the highest initial E_calc and E_RFDA values, and VarseoXS did so after thermocycling. HM, EIT, and G_RFDA were higher for TrixPrint2 and AsigaMax printed specimens, while ν varied by system and aging. 3Delta Crown, printed with AsigaMax, showed the highest FS, E_calc, HM, EIT, and m values after aging. VarseoSmile triniQ and Bridgetec showed the highest E_RFDA and G_RFDA values depending on aging, and Varseo Smile Crown Plus exhibited higher ν initially and post-aging. Printer system and resin formulation significantly influence the mechanical and aging behaviors of 3D-printed FDP materials, underscoring the importance of informed material and printer selection to ensure long-term clinical success. Full article

Laminated bamboo (LB) represents a promising sustainable construction material, inheriting bamboo’s high strength, lightweight properties, and good ductility. However, the dimensional stability of mechanical performance—specifically size effects—remains a critical design challenge requiring systematic investigation. This study investigates the compression behavior of LB with tests of four specimen groups spanning volumes from 62,500 to 4,000,000 mm³ (25 × 25 × 100 mm to 100 × 100 × 400 mm). The research objectives encompass (i) characterizing compression behavior and failure mechanisms across different specimen scales, (ii) quantifying geometric and volumetric size effects on mechanical properties, (iii) evaluating theoretical frameworks for size effect prediction, (iv) developing progressive modeling approaches incorporating material heterogeneity, and (v) establishing design parameters for practical applications. Results demonstrate modest proportional size effects (1.60% strength reduction, 8.62% modulus reduction for 4× proportional scaling) but significant geometric optimization benefits, with cubic specimens achieving 15.78% higher strength and 25.11% greater modulus than equivalent-volume prismatic specimens. All specimens exhibited interfacial delamination failure with size-dependent crack propagation patterns. Theoretical analysis incorporates Weibull statistics, Bažant’s fracture mechanics, and Carpinteri’s fractal theory, with fracture energy modeling performing optimally. Three progressive modeling approaches achieve prediction accuracies ranging from 1.17% to 0.37% errors, with density-coupled modeling providing superior performance despite minimal density variations (COV = 9.27%). The research establishes size effect factors (0.86 for strength, 0.78 for modulus) and critical dimensions (125.64–126.14 mm), addressing critical gaps in LB size-dependent behavior. These parameters enable the development of reliable design methodologies for large-scale sustainable construction. Full article

Damaged material invariably exhibits a lower resonance frequency than undamaged material due to its reduced stiffness. Under fatigue loading, damage accumulates until failure, so changes in resonance frequency can be utilised as a variable to predict fatigue life. Conventional fatigue life prediction methods have a low success rate, prompting the exploration of alternative approaches. We have presented a novel method for predicting the fatigue life of spruce wood based on changes in resonance frequency during fatigue, using a representative specimen (i.e., one out of five specimens tested, with four used for static strength reference). We conducted a low-cycle fatigue test and monitored the resonance frequency alongside the dynamic and static modulus of elasticity. All three types of data were employed to predict fatigue life using between 40% and 100% of the measurement data. Of the two fatigue life prediction methods investigated, the Weibull cycle density distribution using resonance frequency measurements proved most appropriate. The error decreases monotonically with the amount of resonance frequency measurement data used for fatigue life prediction, reaching its lowest value of 1% when the full resonance frequency dataset is used. The proposed fatigue life prediction method should be further validated with a larger sample size, as fatigue is inherently a statistical phenomenon. Full article

In high geothermal tunnels (>28 °C), curing temperature critically affects early-age concrete mechanics and durability. Uniaxial compression tests under six curing conditions, combined with CT scanning and machine learning-based crack analysis, were used to evaluate the impacts of curing age, temperature, and fiber content. The test results indicate that concrete exhibits optimal development of mechanical properties under ambient temperature conditions. Specifically, the elastic modulus increased by 33.85% with age in the room-temperature group (RT), by 23.35% in the fiber group (F), and decreased by 26.75% in the varying-temperature group (VT). A Weibull statistical damage-based constitutive model aligned strongly with the experimental data (R² > 0.99). Fractal analysis of CT-derived cracks revealed clear fractal characteristics in the log(Nr)–log(r) curves, demonstrating internal damage mechanisms under different thermal histories. Full article

Solar fuels production requires developing redox active materials with porous structures able to withstand thermochemical cycles with enhanced thermal stability under concentrated solar irradiation conditions. The mechanical performance of 3D-printed, macroporous black zirconia gyroid structures, coated with redox-active ceria, was assessed for their suitability in solar thermochemical cycles for CO₂ and H₂O splitting. Experiments were conducted using a 1.5 kW solar furnace to supply the high-temperature concentrated heat to a windowed reaction chamber to carry out thermal redox cycling under realistic on-sun conditions. The ceria coating on ceramic structures improved the thermal stability and redox efficiency while minimizing the quantity of the redox material involved. Crushing strength measurements showed that samples not directly exposed to the concentrated solar flux retained their mechanical performance after thermal cycling (~10 MPa), while those near the concentrated solar beam focus exhibited significant degradation due to thermal stresses and the formation of Ce_xZr_1−xO₂ solid solutions (~1.5 MPa). A Weibull modulus of 8.5 was estimated, marking the first report of such a parameter for fused filament fabrication (FFF)-manufactured black zirconia with gyroid architecture. Failure occurred via a damage accumulation mechanism at both micro- and macro-scales. These findings support the viability of ceria-coated cellular ceramics for scalable solar fuel production and highlight the need for optimized reactor designs. Full article

This study investigates the effect of boron carbide (B₄C) ceramic reinforcement on the microstructural, mechanical, electrical, and electrochemical properties of CoCrMo, Ti, and 17-4 PH alloys produced via powder metallurgy for potential biomedical applications. A systematic experimental design was employed, incorporating varying B₄C contents into each matrix through mechanical alloying, cold pressing, and vacuum sintering. The microstructural integrity and dispersion of B₄C were examined using scanning electron microscopy. The performance of the materials was evaluated using several methods, including Vickers hardness, pin-on-disk wear testing, ultrasonic elastic modulus measurements, electrical conductivity, and electrochemical assessments (potentiodynamic polarization and EIS). This study’s findings demonstrated that B₄C significantly enhanced the hardness and wear resistance of all alloys, especially Ti- and CoCrMo-based systems. However, an inverse correlation was observed between B₄C content and corrosion resistance, especially in 17-4 PH matrices. Ti-5B₄C was identified as the most balanced composition, exhibiting high wear resistance, low corrosion rate and elastic modulus values approaching those of human bone. Weibull analysis validated the consistency and reliability of key performance metrics. The results show that adding B₄C can change the properties of biomedical alloys, offering engineering advantages for B₄C-reinforced biomedical implants. Ti-B₄C composites exhibit considerable potential for application in advanced implant technologies. Full article

Bamboo scrimber (BS) has been emerging as a promising construction material prepared from natural bamboo due to its high mechanical strength. However, the variability of the properties of bamboo scrimber is large, which limits the reliability assessment of bamboo scrimber in engineering applications. In this study, the variability of mechanical properties and dimensional stability of bamboo scrimber prepared by units pretreated at different temperatures (denoted as BS-150 and BS-200 for 150 °C and 200 °C, respectively) were compared and probabilistically analyzed using normal, lognormal, and Weibull distribution models. The results showed that BS-200 had a significantly lower thickness swelling rate (TSR), modulus of rupture (MOR) and shear strength (SS), with the modulus of elasticity (MOE) remaining essentially unchanged compared to BS-150. Probabilistic analysis revealed that the MOR, MOE, and TSR of BS-150 followed a lognormally distribution, and the shear strength was normally distributed. In contrast, the MOR, MOE, SS, and TSR of BS-200 all exhibited lognormal distributions. Meanwhile, the variability in TSR and SS for BS-200 was significantly reduced. The results provide a data base for the engineering application of bamboo scrimber and a new research idea for the evaluation of properties of forest biomass-based materials based on probabilistic analysis. Full article

The aim of this study was to develop an experimental self-etch dental adhesive (SE) by synthesizing graphene oxide–functionalized zirconia (GO-ZrO₂) and hydroxyapatite–functionalized zinc (HA-Zn) as inorganic powders together with bis-GMA _(0–2) (bisphenol A-glycidyl methacrylate) oligomers as main components of the organic matrix. The adhesive was compared to the current gold standard adhesive Clearfill SE Bond 2 (CSE) using cytotoxicity assays, shear bond strength (SBS) tests, and resin–dentin interface analyses. Cytotoxicity assays with human gingival fibroblasts (HGF-1) revealed reduced cell viability at early time points but indicated favourable biocompatibility and potential cell proliferation at later stages. SBS values for the experimental adhesive were comparable to CSE after 24 h of storage while aging did not significantly affect its bond strength. However, SBS exhibited more consistent resin tag formation and higher Weibull modulus values post-aging. A scanning electron microscopy (SEM) analysis highlighted differences in resin tag formation, suggesting the experimental adhesive relies more on chemical bonding than micromechanical interaction. The experimental adhesive demonstrated promising potential clinical properties and bond durability due to the integration of GO-ZrO₂ and HA-Zn fillers into the adhesive. Full article

In this work, the metal salts were introduced into the resin-solvent gel system to leverage their ortho-substitution effect, thereby accelerating the polymerization-induced phase separation process. Subsequent in-situ carbonization resulted in the preparation of porous carbon materials with three-dimensional interconnected pores. By precisely tuning the parameters of the resin-solvent-metal ion system, control over the pore structure of the porous carbon was achieved, with a porosity range of 16.5% to 66.5% and a pore diameter range of 8 to 248 nm. The addition of metallic salts can simply and effectively increase the pore structure after carbonization, making the infiltration of molten silicon easier. This is beneficial to the joining process of silicon carbide ceramics. Based on these findings, a high-reliability joining technique for large-sized (135 mm × 205 mm) silicon carbide ceramics was developed. The resulting interlayer was dense and defect-free, exhibiting a joining strength of 309 ± 33 MPa and a Weibull modulus of 10.67. These results highlight the critical role of structured porous media in advancing the field of large-sized ceramic joining. Full article

As a primary construction material, concrete plays a vital role in the development of infrastructure, including bridges, highways, and large-scale buildings. In Northeast China, the structural integrity of concrete faces severe challenges due to freeze–thaw cycles and substantial diurnal temperature variations. This study involved a thorough examination of concrete’s performance under varying numbers of temperature differential cycling (60 to 300) and freeze–thaw cycles (75 to 300). The results showed that both freeze–thaw and temperature differential cycling led to increasing mass loss with the number of cycles. Peak mass losses reached 3.1% and 1.2% under freeze–thaw and temperature differential cycles, respectively, while the combined action resulted in a maximum mass loss of 4.1%. The variation trends in dynamic elastic modulus and compressive strength differed depending on the environmental conditions. Under identical freeze–thaw cycling, both properties exhibited an initial increase followed by a decrease with increasing temperature differential cycles. After 120 temperature differential cycles, the dynamic modulus and compressive strength increased by 4.7–6.2% and 7.5–10.9%, respectively. These values returned to near their initial levels after 180 cycles and further decreased to reductions of 17.0–22.6% and 15.3–29.4% by the 300th cycle. In contrast, under constant temperature differential cycles, dynamic modulus and compressive strength showed a continuous decline with increasing freeze–thaw cycles, reaching maximum reductions of 5.0–11.5% and 18.1–31.8%, respectively. Notably, the combined effect of temperature differential and freeze–thaw cycles was significantly greater than the sum of their individual effects. Compared to the superposition of separate effects, the combined action amplified the losses in dynamic modulus and compressive strength by factors of up to 3.7 and 1.8, respectively. Additionally, the fatigue life of concrete subjected to combined temperature differential and freeze–thaw cycles followed a two-parameter Weibull distribution. Analysis of the S-N_f curves revealed that the coupled environmental effects significantly accelerated the deterioration of fatigue performance. Full article

To investigate the effects of different strain rates and fracture densities on the mechanical behavior of coal, CT scanning was employed to quantify fracture content in coal specimens. Uniaxial compression tests were conducted to analyze the mechanical characteristics of coal, followed by the establishment of a statistical damage constitutive model for fractured coal. The results demonstrate: (1) The compressive strength of coal specimens shows a positive correlation with increasing strain rate, while the elastic modulus exhibits an initial decrease followed by an upward trend. Compressive strength displays a negative correlation with fracture density. Under a strain rate of 0.001 s⁻¹, the elastic modulus decreases significantly with increasing fracture density, whereas this trend becomes less pronounced at higher strain rates. Notably, compressive strength demonstrates greater sensitivity to fracture density variations. (2) Within the dynamic strain rate range of 0.001 s⁻¹~0.05 s⁻¹, the fractal dimension of fragmented coal particles ranges from 1.0 to 1.3. Both the average mass of ejected fragments and the mean fractal dimension of fractured particles increase progressively with strain rate elevation, indicating enhanced non-uniformity in particle size distribution. (3) Significant correlations exist between Weibull distribution parameters (F₀, m) and strain rate/fracture density. A critical threshold emerges at 0.01 s⁻¹ strain rate, where F₀ and m exhibit opposite variation trends before and after this threshold. Similarly, a fracture density threshold between 0.3%~0.45% is identified, with F₀ and m demonstrating contrasting evolution patterns below 0.3% and above 0.45% fracture density under increasing strain rates. (4) Based on the established relationships between Weibull parameters (F₀, m), strain rate, and fracture density, the dynamic statistical damage constitutive model for coal was modified. A systematic methodology for determining parameters in the revised model was subsequently proposed. Full article

Using desert sand (DS) to pour concrete is a feasible idea to solve the shortage of river sand. However, the frost resistance of desert sand concrete (DSC) is a key problem that must be solved for applying DSC in practical engineering. Therefore, this study on the performance and reliability analysis of DSC under a freeze–thaw cycle (FTC) was carried out. The DSC specimens were subjected to the FTC test with desert sand replacement ratios (DSRRs) of 0%, 20%, 40%, 60%, 80%, and 100%. Then, the appearance, mass, relative dynamic elastic modulus (RDEM), and compressive strength of DSC were analyzed and discussed. Moreover, the damage mechanism of DSC was discussed via microstructural analysis. The results indicated that as the FTCs increased, the mass loss rate of concrete increased, while the RDEM and compressive strength decreased. Among the samples, DSC-40 showed the best resistance to the FTC. After 250 cycles, the changes in mass, RDEM, and compressive strength of DSC-40 were 2.73%, 15.19%, and 27.2% lower than those of DSC0. Finally, the DSC reliability model was established by using the Weibull probability distribution method. Among all groups, DSC-40 showed the best reliability, and the failure life was 287 FTCs, which was approximately 1.55-times longer than DSC0. This model could provide a theoretical basis for the durability evaluation and life prediction of DSC structures in cold regions. Full article

Lithium disilicates are widely used in restorative dentistry due to their aesthetics, strength, and durability. Increased strength can be achieved by increasing crystal fraction, but this modification also reduces translucency. Recently developed lithium disilicates like Amber Mill claim to offer customizable translucency via firing protocols without changes in flexural strength. This study evaluated whether Amber Mill’s firing protocols produce significant differences in translucency without changing flexural strength. Forty specimens (n = 10) were assessed for translucency using Contrast Ratio (CR) and Translucency Parameter (TP) tests under four firing protocols designed to obtain high translucency (HT), medium translucency (MT), low translucency (LT), and medium opacity (MO). Using the three-point bending test, sixty specimens (n = 15) were tested for flexural strength with the same four firing protocols. The Weibull modulus and characteristic strength were also calculated, and SEM observation was performed. The CR and TP tests revealed statistically significant translucency differences only between MO and LT/MT/HT. Flexural strength ranked as MO > LT > MT > HT, with significant differences observed between MO vs. MT/HT and LT vs. HT. The findings indicate that the recommended firing protocols for the same shaded blocks resulted in limited differences in translucency. Additionally, higher translucencies were associated with reduced flexural strength, highlighting a trade-off between aesthetic and mechanical properties for Amber Mill. Full article