Search Results (67)

The demand for lower-impact materials in mobility has increased interest in the lightweight composite structures for electric vehicles (EVs). This study presents an extended and revised dataset for biaxial non-crimp fabric (NCF) composite laminates intended for two-wheeled EV chassis applications, building on earlier published results by repeating all mechanical tests and recalculations and by adding a full stress–strain analysis, a repeatability assessment across multiple specimens, and a digital image correlation (DIC)-based strain evaluation. Three material families, represented by four laminate conditions, were investigated: carbon/epoxy composites post-cured for 4 h and 10 h, glass-fiber composites, and linen (flax) composites. The tensile and flexural behaviors were characterized according to ISO 527-4 and ISO 14125, respectively, while a GOM ARAMIS optical system was used to obtain the axial strain, transverse strain, and Poisson’s ratio. Carbon laminates showed the highest performance, with the 10 h post-cure condition reaching 1126 MPa tensile strength, up to 60 GPa Young’s modulus, 696 MPa flexural strength, and 43 GPa flexural modulus. Glass laminates provided intermediate properties, whereas flax laminates showed lower strength but higher compliance and deformation capacity. The obtained results show that the biaxial NCF composites studied in this work offer weight-saving potential for micro-mobility chassis and provide a standard-based benchmark for future durability and life-cycle studies. Full article

This paper innovatively employs an epoxy-free composite layer with basalt fiber-reinforced polymer (BFRP) and engineered cementitious composite (ECC) to reinforce the two-way concrete slab structure. Five strengthened slabs and one reference slab were tested under biaxial bending moments with four-side simply supported conditions. The thickness of ECC (15, 25, 35 mm) and BFRP grid (1, 2, 3 mm) were selected as two main variables in the test program. The experimental results showed that the cracking and ultimate load of the strengthened slabs were substantially improved. Notably, the cracking pattern was shifted from diagonally concentrated cracks to discontinuous short cracks, with no apparent debonding of the composite layer. As the thickness of the BFRP grid and ECC increases, both the flexural capacity and stiffness improve, with decrease in the maximum deflection and effective utilization rate of steel reinforcement and BFRP grid at mid-span. Furthermore, a theoretical model considering different positional distribution of yield line was proposed to predict the bearing capacity of the strengthened slabs, with the calculated values aligned well with the experimental results. This research highlights the FRP–ECC composite as a robust reinforcement method for two-way slabs, and offers a good design-oriented reference basis in the field. Full article

Inter-module connections are the critical load-transfer components in modular steel buildings (MSBs), whose mechanical behavior directly governs the overall safety and seismic performance of the entire structural system. To address the unresolved issue that the influence of complex loading conditions, especially the coupling effect of biaxial bending, on the load-transfer mechanism and degradation law of bayonet-type self-locking and unlockable connections remains poorly understood, two groups of full-scale quasi-static tests were conducted in this study. Specimen S1 (0°) was designed for the in-plane compression–bending–shear loading condition, while Specimen S2 (45°) was designed for the spatial compression–biaxial bending–shear loading condition. The test results demonstrate that both groups of specimens exhibit typical three-stage mechanical characteristics. The average initial stiffness of Specimen S1 (0°) is 5.47 kN/mm, while that of Specimen S2 (45°) is 6.08 kN/mm. The average ultimate load of S1 (0°) reaches 162.8 kN, and that of S2 (45°) is 164.85 kN. The average ductility coefficient of S1 (0°) and S2 (45°) is 2.79 and 2.14, respectively. Comparative analysis indicates that Specimen S1 (0°) presents superior energy dissipation capacity and ductility, while Specimen S2 (45°) has higher initial stiffness accompanied by faster stiffness degradation in the late loading stage. A high-fidelity refined FE model of the bayonet-type self-locking and unlockable connection was established. The FE analysis results are in good agreement with the test results, with the relative error of the positive flexural bearing capacity controlled within 5%. On this basis, parametric FE analysis was carried out to explore the influence of axial compression ratio on the mechanical performance of the connection. Furthermore, theoretical calculation formulas for the ultimate flexural bearing capacity of the connection under in-plane compression–bending–shear loading and spatial compression–biaxial bending–shear loading were proposed respectively. The calculated results are compared with the test data, with all relative errors within 10%, which verifies that the proposed formulas have favorable prediction accuracy for the ultimate flexural bearing capacity of the connection under both aforementioned complex loading conditions. Full article

The mechanical recycling of mono-material biaxially oriented polypropylene (BOPP) packaging films produces recycled polypropylene (rPP) with degraded properties, limiting its use in higher-performance applications. This study investigates rPP reinforcement with 6–12 µm microcellulose fibres (MCFs, 2–10 pbw) and microcellulose-derived biochar (BC, 5–20 pbw), characterized by DSC, TGA/DTG, MVR/MFR, temperature-dependent rheology, mechanical testing and water contact angle (WCA) measurements. Both fillers acted as heterogeneous nucleating agents, shifting crystallization by up to 4 °C and increasing crystallinity by 2–4%. MCF introduced an additional low-temperature degradation step, whereas BC increased onset and peak degradation temperatures by up to 20 °C and increased char yield. Low MCF loadings increased MVR/MFR by 20–25% and reduced melt viscosity, while BC decreased flow indices by up to 50% and stiffened the melt. Tensile and flexural moduli increased by 15–25% with MCF and 40–50% with BC, with a stiffness–toughness trade-off at the highest BC contents. MCF reduced the water contact angle to 63.0° at 10 pbw, while BC increased it to 108.1° at 20 pbw, indicating opposite effects on surface wettability. Converting a single cellulosic feedstock into fibrous or carbonised fillers enables bio-based upgrading of rPP, in line with circular economy principles. Full article

Three-dimensional (3D) printing is increasingly used for the fabrication of definitive crowns; however, whether specific post-curing hardware is mandatory for clinical success remains a practical concern. This study provided a practical comparison evaluating the effect of two post-curing units on the biaxial flexural strength (BFS), Weibull modulus (m), Martens hardness (HM), indentation modulus (EIT), water sorption (WSP), and water solubility (WSL) of 3D-printed resins for permanent crowns, compared with a conventional resin composite. A total of 200 specimens were fabricated from two 3D-printed resins (Permanent Crown™ and CrownTec™) and a conventional resin composite (Filtek Universal Restorative™) used as a control. The 3D-printed specimens were post-cured using either a Formcure or an Otoflash G171 unit. WSP and WSL were measured after 90 days of water ageing, while BFS, HM, and EIT were evaluated after 24 h of storage using standardised methods. All materials exhibited WSP and WSL values within ISO limits, with the control group showing significantly higher values and superior mechanical properties. Among the 3D-printed resins, post-curing significantly affected only HM and EIT for Permanent Crown™ resin, with no significant differences in BFS. Overall, the tested 3D-printed resins demonstrated high processing stability across different curing protocols, suggesting that clinical performance remains consistent regardless of the post-curing unit used. Full article

Multilayer zirconias have recently been introduced as dental biomaterials to combine improved translucency with sufficient mechanical reliability by implementing yttria-driven gradients in phase composition. Such materials can be considered functionally graded ceramics, where local phase stabilization influences strength and crack resistance. However, manufacturer-specific gradient profiles and their structure–property relationships remain insufficiently characterized. This study investigated two commercially available multilayer zirconias with distinct gradient concepts: IPS e.max^® ZirCAD Prime (continuous gradient) and KATANA™ Zirconia YML (stepwise gradient). Ten equidistant sections along the blank height were analyzed using quantitative X-ray diffraction and Rietveld refinement to quantify zirconia phase fractions and estimate local Y₂O₃ content. Mechanical behavior was evaluated by biaxial flexural strength testing (ball-on-three-balls method) and fracture toughness testing using the chevron-notched beam technique. Both materials exhibited pronounced yttria- and phase-dependent gradients consistent with their reported layer designs. Regions with increased yttria content showed higher t″ fractions and reduced fracture toughness and strength, whereas deeper regions displayed increased mechanical performance associated with higher fractions of transformable tetragonal phase. These findings emphasize that multilayer zirconias exhibit spatially dependent mechanical properties, which should be considered in biomaterial selection and restoration design, particularly when balancing aesthetic demands and fracture resistance. Full article

This study evaluated the influence of various surface treatments on the bonding performance and mechanical behavior of zirconia, with particular emphasis on the effect of laser surface texturing (LST) compared with conventional 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) and airborne particle abrasion (APA) methods. Two zirconia compositions, 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) and 5 mol% partially stabilized zirconia (5Y-PSZ), were subjected to four surface treatment protocols: as-milled, 10-MDP, APA, and LST (n = 12). Shear bond strength (SBS) to titanium and biaxial flexural strength (BFS) of zirconia were measured. Surface morphology, failure mode, and phase composition were analyzed using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Data were analyzed with two-way ANOVA and Tukey’s post hoc test (α = 0.05), and the reliability of flexural strength was assessed using Weibull analysis. Surface treatment significantly affected SBS (p < 0.05). The LST groups exhibited the highest SBS values and a higher proportion of mixed failures, whereas other groups predominantly showed adhesive failures. However, LST-treated specimens, particularly 5Y-PSZ, showed reduced BFS. XRD confirmed phase stability, although localized microstructural changes were observed after LST. LST enhanced the zirconia–titanium interfacial bond strength and promoted mixed failure modes; however, this improvement was accompanied by a reduction in flexural strength, particularly in 5Y-PSZ. Full article

This study analyzes the mechanical behavior of a quasi-isotropic biaxial glass fiber–vinyl ester composite in a multiaxial stress condition and the effect of the orientation of the fibers. A ply structure was created through the process of vacuum infusion using six layers of biaxial fabric that were oriented to 15°. Tensile samples were isolated at 0, 15, 30, 45 and 90 degrees relative to the warp direction. It was found that strength and stiffness strongly depend on orientation, with maximum tensile strengths of 157.2 MPa at 90° and 125 MPa at 0°, and minimum tensile strengths 59.6 MPa at 15°, showing fiber and shear failures, respectively. MAT_124 underwent finite element analysis in LS-DYNA, and the results were excellent, with a difference of less than 1.5%. Three-point bending and Charpy impact tests indicated that flexural properties were lower at 15° and 90°, whereas off-axis orientations were generally better at impact energy absorption, although at 45°, binding sites were few and far between. The results have important implications for the design of laminates subjected to complicated loads. Full article

This study aimed to assess how different resin matrix formulations affect the fatigue resistance of resin dental composites. Model dental composites were formulated using six distinct monomer mixtures: two Bis-GMA (bisphenol A-glycidyl methacrylate):TEGDMA (triethylene glycol dimethacrylate) (60:40 and 80:20 mole%), two UDMA (urethane dimethacrylate):TEGDMA (60:40 and 80:20 mole%), one Bis-GMA:UDMA:TEGDMA (35:35:30 mole%), and one Fit852:UDMA:TEGDMA (35:35:30 mole%). Cyclic fatigue resistance (CFR) of the resin composites was measured in a biaxial test mode using staircase analysis. Additional evaluations included biaxial flexural strength (BFS), degree of conversion (DC), water sorption (WS), and viscoelastic properties of the unfilled resins, such as the storage modulus (E′), loss modulus (E″), tan δ (E″/E′), and stiffness (k′). Data were subjected to one-way ANOVA with Tukey post hoc analyses. Pearson correlation and stepwise regression analyses were conducted to examine the relationships among variables. The UT6040 model composite exhibited the highest CFR (82.61 ± 8.83 MPa), significantly outperforming other formulations. Tan δ of the resin matrix showed the strongest correlation with CFR (r = 0.974), and was also shown to be the most influential predictor for the CFR of the particulate composites. The composition of the resin matrix has a significant impact on the CFR of dental composites. Among the properties evaluated, the viscoelastic parameter tan δ emerged as a strong and reliable predictor of CFR, emphasizing the importance of targeting viscoelastic behavior in the design of dental composite formulations. Full article

The aim was to optimize a series of aluminosilicate glasses for the synthesis of leucite glass-ceramics (GC) for dental applications. Appen predictive models were used to design a series of aluminosilicate glasses to control optical, thermal and mechanical properties. Glasses were produced using melt quenching methods, annealed and processed into powders and further heat-treated and milled to produce GC powders. Glasses/GCs were characterized using dilatometry, HTXRD, SEM and ²⁷Al MAS-NMR and GCs tested using biaxial flexural strength (BFS) for comparison to commercial leucite GC products. The results indicated good prediction to experimental measurement correlations (for coefficient of thermal expansion, refractive index and density) and provided evidence of leucite GCs’ optimization compared to commercial products. This included significant BFS and Weibull m increases, improved microstructural control and designed translucency, meeting the demands for strong, esthetic and durable single-tooth restorations. The simple predictive approach, combined with complementary characterization techniques, allowed structure–property relations of aluminosilicate glasses/glass-ceramics to be understood, and may find similar applications in other glass systems beyond dentistry. Full article

The aim of translucency-enhancing liquids (TEL) is to locally influence the phase composition of zirconia in order to increase its translucency. This study aimed to determine the influence of TEL on 3Y- and 4Y-TZP zirconia concerning roughness, hardness, wear, flexural strength, dynamic stability and fracture force of fixed dental prostheses after thermal cycling and mechanical loading. Two zirconia materials (4Y-TZP; 3Y-TZP-LA, n = 8 per material and test) were investigated with and without prior application of TEL. Two-body wear tests were performed in a pneumatic pin-on-block design (50 N, 120,000 cycles, 1.6 Hz) with steatite balls (r = 1.5 mm) as antagonists. Mean and maximum vertical loss as well as roughness (Ra, Rz) were measured with a 3D laser-scanning microscope (KJ 3D, Keyence, J). Antagonist wear was determined as percent area of the projected antagonist area. Martens hardness (HM; ISO 14577-1) and biaxial flexural strength (BFS; ISO 6872) were investigated. The flexural fatigue limit BFSdyn was determined under cyclic loading in a staircase approach with a piston-on-three-ball-test. Thermal cycling and mechanical loading (TCML: 2 × 3000 × 5 °C/55 °C, 2 min/cycle, H₂O dist., 1.2 × 10⁶ force á 50 N) was performed on four-unit fixed dental prostheses (FDPs) (n = 8 per group) and the fracture force after TCML was determined. Statistics: ANOVA, Bonferroni test, Kaplan–Meier survival, Pearson correlation; α = 0.05. TEL application significantly influences roughness, hardness, biaxial flexural strength, dynamic performance, as well as fracture force after TCML in 3Y-TZP. For 4Y-TZP, a distinct influence of TEL was only identified for BFS. The application of TEL on 3Y- or 4Y-TZP did not affect wear. TEL application has a strong effect on the mechanical properties of 3Y-TZP and minor effects on 4Y-TZP. All effects of the TEL application are of a magnitude that is unlikely to restrict clinical application. Full article

(1) Background: The work aims to determine different chemical and mechanical properties with and without BPA dental resin–matrix composites under the same curing and testing conditions. (2) Methods: Disc-shaped specimens were prepared from six resin–matrix composites used in dentistry, three with BPA (BE-Brilliant EverGlow^TM, ED-IPS Empress Direct, FS-Filtek^TM Supreme XTE) and three without (AF-Admira Fusion, BF-Enamel Plus HRi Bio Function Enamel, N/C). Specimens were photoactivated using an LED light-curing unit. The chemical and mechanical properties were analysed. (3) Results: The FS group exhibited the most significant water sorption (31.17 µg/mm³), while the BF showed the lowest (12.23 µg/mm³). Regarding the diffusion coefficient, the result recorded for the group AF is faster-absorbing water, and the group NC is slower. In both test methods (biaxial flexural strength and compressive strength), the resistance to flexural loading of the AF group was significantly lower than all other resin composites evaluated. (4) Conclusions: According to all the parameters studied, we verified that the BF presents the best chemical–mechanical behaviour. Resins free of BPA may not influence chemical–mechanical performance. However, the inorganic matrix has more influence on mechanical properties than the organic matrix. Full article

This study investigated the feasibility and effectiveness of a commercial top-down stereolithography (SLA)-based system for the additive manufacturing of zirconia dental prostheses. Yttria-stabilized zirconia–resin slurries were prepared, and zirconia objects were fabricated using a top-down SLA system. Thermogravimetric–differential thermal analysis was used to examine the resin, while X-ray fluorescence spectroscopy and X-ray diffraction were used to analyze the printed samples. The microstructures of additively manufactured and subtractively manufactured zirconia were compared using field emission scanning electron microscopy (FE-SEM) before and after sintering. Biaxial flexural strength tests were also conducted to evaluate mechanical properties. The green bodies obtained via additive manufacturing exhibited uniform layering with strong interlayer adhesion. After sintering, the structures were dense with minimal porosity. However, compared to subtractively manufactured zirconia, the additively manufactured specimens showed slightly higher porosity and lower biaxial flexural strength. The results demonstrate the potential of SLA-based additive manufacturing for dental zirconia applications while also highlighting its current mechanical limitations. The study also showed that using a blade to evenly spread viscous slurry layers in a top-down SLA system can effectively reduce oxygen inhibition at the surface and relieve internal stresses during the layer-by-layer printing process, offering a promising direction for clinical adaptation. Full article

This study examined the degree of monomer conversion (DC) and mechanical properties of experimental orthodontic adhesives containing monocalcium phosphate monohydrate (MCPM), Sr-bioactive glass (Sr-BAG) nanoparticles, and andrographolide. Experimental adhesives were prepared with a 4:1 powder-to-liquid ratio, containing methacrylate monomers with varying formulations of glass fillers and additives. DC was measured using ATR-FTIR (n = 5) with and without bracket placement under two curing protocols: conventional LED (1200 mW/cm², 20 s) and high-intensity LED (3200 mW/cm², 3 s). The biaxial flexural strength and modulus were tested after 4-week water immersion (n = 8). Transbond XT was used as the commercial comparison. Transbond XT exhibited higher DC (33–38%) than the experimental materials. Conventional LED curing produced higher DC than high-intensity LED, while bracket placement reduced DC by approximately 10% in the experimental materials but minimally affected Transbond XT. Transbond XT demonstrated a superior biaxial flexural strength (188 MPa) compared to the experimental adhesives (106–166 MPa, p < 0.05). However, the experimental formulations with low additive concentrations showed a comparable biaxial flexural modulus (5.0–5.5 GPa) to Transbond XT (5.6 GPa) (p > 0.05). Although the experimental adhesives exhibited lower DC and strength than the commercial product, their values still met the ISO standards, suggesting their potential clinical viability despite their modified compositions. Full article

The objective of this study was to evaluate the biaxial flexural strength of zirconia-reinforced lithium silicate (ZLS, eMax CAD, Ivoclar Vivadent) and lithium disilicate (LDS, Suprinity, VITA)) discs after abrasion with a diamond tip, before or after crystallization of the ceramic. Discs of 1.2 × 15 mm dimensions were fabricated. The samples were separated into two groups: AC—abrasion with a diamond tip before material crystallization, and CA—material crystallization and subsequent abrasion with a diamond tip (n = 15). The initial roughness was measured before abrasion/crystallization, and final measurement was performed after abrasion/crystallization/polishing. The abraded surface was placed downward during the biaxial flexural strength test, and the data were recorded. The final roughness was significantly higher compared to the initial roughness in all groups. The ZLS-AC and LDS-AC groups (both materials with abrasion prior to material crystallization) showed higher biaxial flexural strength values than groups that underwent abrasion before crystallization. This study concluded that the clinical adjustment performed by abrasion with the diamond tip of glass ceramics lithium disilicate and zirconia-reinforced lithium silicate carried out prior to crystallization favored the resistance of the ceramics. Full article