Search

The fabrication of complex shaped Si3N4 parts by conventional methods is challenging due to its high hardness and mechanical strength. Additive manufacturing (AM) appeared as a competitive way to attain three-dimensional complexity at lower costs. However, most of AM technologies still present limitations in producing high dense ceramics, mainly due to several difficulties in developing proper feedstock. This work presents the fabrication of dense silicon nitride-based ceramics by using an extrusion based additive manufacturing technique (direct ink writing, also known as robocasting) and cold isostatic pressing (CIP) as a post processing step. Silicon-nitride aqueous based inks containing different amounts of solids loading (36, 38 and 39 vol%) and proper rheological characteristics for the printing process were studied. The use of CIP (200 MPa) is suggested to reduce or even eliminate defects and porosity and consequently, to improve mechanical performance of the final parts. Relative density, microhardness and flexural strength increased as solids loading in the inks increased and were further improved when CIP pressing was used. Parts produced by robocasting with an ink containing 39 vol% and cold isostatic pressed at 200 MPa exhibited an average relative density around 99%, 1475 HV2 microhardness value and 650 MPa flexural strength, values similar to those of silicon nitride ceramics fabricated by conventional processing. published

The flexural performance of a spliced composite slim beam with a slotted web (SCSB-SW) was assessed and prediction formulae of flexural capacity and initial stiffness for the beam were deduced. Through a four-point bending test, the flexural performance of the SCSB-SW was preliminary studied. The experimental results indicated that the section of the SCSB-SW conformed to the plane section assumption in the elastic stage. The beam failed in a ductile failure mode while there was no obvious relative slip between the steel beam and concrete slab in the failure stage. Finite-element models were developed and validated using the test results. A parametric analysis revealed that even if the cross-sectional dimensions and the position of the neutral axis in the beam are changed, the results predicted by the formulae still matched the numerical results well. The material strength, the thickness of the bottom flange of the steel beam and the concrete slab dimensions were found to play key roles in the flexural capacity of the beam, whereas the compressive strength grade of the concrete, the depth of the steel beam web and the dimensions of the concrete flange have significant effects on the initial stiffness of the beam.

Monolithic zirconia and hybrid ceramic restorations have been widely used in the last decade for both anterior and posterior dental restorations. However, their use lacks sufficient scientific evidence in most cases, as the expeditious manufacturing of these versatile ceramic materials exceeds the limits of in vitro and/or in vivo validation. This study aimed to evaluate and compare the mechanical properties (flexural strength, fracture toughness, Vickers hardness, and brittleness index) of three CAD-CAM monolithic multilayer zirconia ceramics (GNX—Ceramill Zolid® Gen-X, ZCP—IPS e.max® ZirCAD, and UPC—Upcera® Esthetic Explore Prime) and one CAD-CAM monolithic multilayer polymer-infiltrated hybrid ceramic (ENM—Vita® Enamic) with a CAD-CAM monolithic lithium disilicate ceramic as a control (EMX —IPS e.max® CAD). A total of 160 discs (GNX = 32, ZCP = 32, UPC = 32, ENM = 32, and EMX = 32) were cut, polished, and fully sintered (except for the ENM). Half of the samples for each group were subjected to hydrothermal aging. Descriptive analysis and ANOVA tests were used to compare the groups. The zirconia groups showed significantly higher mechanical properties than the EMX group for both the non-aged and aged samples (p < 0.05). The ENM group showed the lowest brittleness index, while EMX showed the highest. The mechanical properties of monolithic multilayer zirconia ceramics were generally better than those of monolithic multilayer polymer-infiltrated hybrid ceramic and lithium disilicate ceramic. All groups showed, to some extent, a change in their mechanical properties after aging, with the ENM being the most affected.

Translucent zirconias have been developed with better esthetics than high-strength zirconias by reducing opacity. However, studies on their translucency and strength are sparse.The purpose of this in vitro study was to compare the relationship between translucency and biaxial flexural strength of recently developed high-translucency zirconia, high-strength zirconia, and lithium disilicate ceramics.Disks (n=12) were fabricated for 5 ceramic materials: high-strength zirconia (BruxZir 16 shaded), translucent zirconia (BruxZir Anterior shaded, Katana UTML, Katana STML), and lithium disilicate (IPS e.max, Press HT, and LT). A standard tessellation language (STL) file was designed, and the specimen milled, finished, and glazed according to manufacturer's instructions for each material. The translucency parameter was calculated against black and white backgrounds and white and stump shade with ND4 background by using a spectrophotometer. Biaxial flexural strength was calculated by using the 3-ball test. The load was applied at a crosshead speed of 0.5 mm/min with a 49-N load cell until failure occurred. Translucency parameter and biaxial flexural strength data were analyzed with 1-way analysis of variance (ANOVA). A Tukey honest significant difference multiple comparison test was used to determine significant differences (α=.05).The IPS e.max HT was more translucent against both backgrounds (32.85 for black/white and 15.34 for white/stump), while BruxZir 16 was the least translucent (19.78 for B/W and 8.83 for W/S). All groups tested differed in translucency (P.001) except for BruxZir Anterior and Katana STML, which were not significantly different (P=.052). For biaxial flexural strength, BruxZir 16 had the highest strength (995.44 MPa) and e.max HT, the lowest (186.75 MPa). No significant differences were found between BruxZir anterior and Katana STML, Katana UTML and IPS e.max LT, or IPS e.max LT and IPS e.max HT (P.05). Translucency parameter values using both backgrounds were strongly correlated (r=0.99). However, biaxial flexural strength values were inversely related to translucency parameter values when using black/white and white/stump shade but with high correlation (r=-0.777 and -0.756 respectively).Lithium disilicate was the most translucent and yet the weakest material, whereas high-strength zirconia was the most opaque ceramic and the strongest. Katana UTML had the highest translucency but was weakest among translucent and high-strength zirconia materials. Overall, translucency was negatively correlated with biaxial flexural strength.

Two damage regimes—“brittle” and “ductile”—have been identified in the literature on ceramic grinding, machining, grit blasting, and wear. In the brittle regime, the damage mechanism is essentially crack formation, while in the ductile region, it is quasiplasticity. Onset of the brittle mode poses the greater threat to strength, so it becomes important to understand the mechanics of ductile–brittle thresholds in these materials. Controlled microcontact tests with a sharp indenter are employed to establish such thresholds for a suite of contemporary computer-aided design/computer-aided manufacturing dental ceramics. Plots of flexural strength S versus indentation load P show a steep decline beyond the threshold, consistent with well-established contact mechanics relations. Threshold dimensions occur on a scale of order 1 µm and contact load of order 1 N, values pertinent to practical grit finishing protocols. The ductile side of ceramic shaping is accessed by reducing grit sizes, applied loads, and depths of cut below critical levels. It is advocated that critical conditions for ductile shaping may be most readily quantified on analogous S( P) plots, but with appropriate machining variable (grit size, depths of cut, infeed rate) replacing load P. Working in the ductile region offers the promise of compelling time and cost economies in prosthesis fabrication and preparation.

This paper describes a statistical and mathematical approach to optimize the mechanical properties of a wood plastic composite with Polyethylene Terephthalate (PET) as polymeric matrix. Wood plastic composite are materials that consist of a primary continuous polymer phase, where a secondary filler dispersed phase is embedded, the filler generally is wood fibers or sawdust. The slack variable approach in mixture experiments, consist in selecting a component of the mixture as slack variable, to subsequently design and analyze the experiment in terms of the remaining components. With the experimental design information three slack variable model were fit. Using response surface graphs, we show how different compositions modify the mechanical properties of wood plastic composite. Besides, by the desirability function, the optimal formulation of the compound that simultaneously maximizing the mechanical properties of wood plastic composite, was obtained. Finally, the components proportions that provides the best tensile, flexural and compression strength are presented.

The mechanical properties of two commercial epoxides have been investigated in both unfilled and filled with varying the weight fraction of Nano Aluminum powder and Nano Aluminum with Nano Titanium powder. The values of Young’s modulus, modulus of rigidity, yield stress, tensile strength, flexural strength have been studied at room temperature to identify the specific influence of Aluminum powder (the particle size for Aluminum powder is less than or equal to 50 nm (d ≤ 50). The weight fraction has different values (equals to 10%, 20% and 30%), and Nano Aluminum with Nano Titanium powder for Aluminum powder, the particle size (d) is less than or equal to 50 nm (d ≤ 50). The weight fraction has different values (equals to 10%, 20% and 30%). Also for Titanium powder, the particle size is less than or equal to 50 nm (d ≤ 50), and the weight fraction is 1% for each different weight fractions of Aluminum powder to epoxy resin. The experimental results obtained from laboratory have been analyzed in order to achieve the best result. It is concluded that Young’s modulus and modulus of rigidity increase when the weight fraction for Nano Aluminum powder and Nano Aluminum with Nano Titanium powder increase.

Nowadays, renewable source materials play a significant part in creating lightweight structural materials. In this work, Azadirachta indica (Neem Gum) was taken as natural filler material in epoxy matrix with different volume fraction. The hand lay-up method was used. The mechanical properties such as tensile, flexural and impact tests were found for five different specimens. The effect of natural filler on the mechanical properties was observed and found that 40% addition of neem powder produces better mechanical strength in tensile, flexural and impact strength.

A typical conversion process of a complete-arch immediate loading protocol entails preparing holes in a complete denture for connection to interim copings, which reduces the strength of the prosthesis. The excellent mechanical properties of milled polymethyl methacrylate (PMMA) disks may provide interim prostheses with improved strength.The purpose of this in vitro study was to measure the flexural strength and failure load of simulated acrylic resin immediate implant-supported interim prostheses fabricated by conventional processing and computer-aided manufacturing.A master patient model was created with an acrylic resin base and 2 BioHorizons Internal 4.5-mm-diameter implants placed with a 21.5-mm span and multiunit abutments (MUA) tightened to place. Two groups with different prosthodontic designs were used: one represented the standard fixed prosthesis with support at each end (noncantilever, NC), and the other group represented the cantilever portion of the prosthesis (cantilever, C). Two connection designs of prosthesis blocks to MUA abutments were evaluated: one with typical holes in the prosthesis for capturing interim copings and one with a low-profile coping. For the heat-processed PMMA groups (HP/NC and HP/C), wax patterns were milled, and heat-polymerized denture base PMMA prostheses were processed. The milled PMMA groups (M/NC and M/C) were milled from a tooth-shaded PMMA disk for the prosthesis blocks. The milled low-profile groups (Mlp/NC and Mlp/C) had identical dimensions except that connection to the low-profile coping was designed with a cement space and a narrow diameter screw access hole and was milled from a PMMA disk. The failure load (N) of the cantilever prostheses was recorded, and for NC groups, the 3-point flexural strength formula (MPa) was calculated. The Weibull modulus, characteristic strength, and summary statistics were computed, and the groups were statistically analyzed with ANOVA and the post hoc Tukey test (α=.05).The mean flexural strengths (MPa) were HP/NC=91.35 ±18.92; M/NC=143.94 ±36.79; Mlp/NC=117.06 ±13.86. Significant differences were found among groups (P.001). Mean failure loads (N) and Weibull modulus (WM) of cantilever prosthesis strengths were for HP/C=512.66, WM=5.597; M/C=695.06, WM=4.875; Mlp/C=254.97, WM=1.797 (P.001).Implant fixed interim structures milled from high-density PMMA blanks had a 35% higher flexural strength for both the standard prostheses and the cantilever prostheses than heat-processed denture base PMMA. The low-profile coping design was stronger than the heat-processed material, and the failure point was relocated from the lateral walls to the cervical margin area.

This present research and explores the properties of concrete's structural and durability High-density polyethylene granules (HDPE) are partly replaced by the coarse aggregate. Five separate concrete mixtures of grade M30 have been built to partially replace the coarse aggregate from 1% to 5%. The properties of strength and durability such as compressive strength, split tensile test, flexural test and durability test such as rapid chloride permeability test, acid test, alkaline test, sulphate test assault. In the acids, the samples will equate with control concrete after 190 days for durability test cubes. The experiment is conducted to evaluate how much the acid attacks on the concrete. The loads are determined by an average of 3 for the compressive strength, split tensile, flexural test.

Nowadays, environmental sustainability is the responsible of engineering community for which the usage of waste or recycling is essential towards ecological sustainability, for which green materials are considered widely in all sectors. Because of the significance of characteristic filler supported composites in the advancement of lightweight materials, this research exploration centers around utilizing biodegradable garbage such as used tea dust powder reduces the impact of environmental pollution. In this study, effect of organic residue, tea dust is effectively recycled/utilized for fabricating polymer composite to find its suitability in engineering applications. Epoxy polymer is considered as matrix material and different volume fractions of used tea dust powders (10, 20, 30, 40, 50, and 60 vol%) are used as reinforcement. Hand-layup approach is adopted for fabricating the polymer composite and the samples are tested for their mechanical properties viz., impact, flexural and tensile strength. Based on the mechanical strength the best combination is found to be 40% vol. in epoxy matrix; higher addition than 40% reduces the strength due to lower bonding between the powders and matrix.

Whether it's concrete technology, design approaches, or the creation of novel materials, there's always a time delay between laboratory innovations and their practical implementations in the construction sector. However, practical application of steel fibre reinforced concrete is much ahead in the field of research and development. The purpose of this research was to examine the flexural behaviour of high-performance fibre reinforced concrete (HPFRC) in particular. HPFRC mix has been designed to obtain a concrete grade of M60. The modified IS technique is used to create the mix design. Dosage of superplasticizer was adjusted for each mix with incremental fibre content. Steel fibre used in the study comprised of crimpled fibre having 0.4 mm diameter and aspect ratio of 69.09. The hooked end fibre bearing 0.62 mm and aspect ratio of 69.09 is also used. The volume of the fraction of steel fibre namely 0.25 %, 0.5 %, 0.75 %, 1 %, 1.25 % and 1.5 % used in this experimental investigation. Results indicate that introduction of steel fibre significantly improved not only the crack behaviour but also increased the flexural strength significantly. Addition of steel fibre to HPFRC imparted significant increase in Young’s Modulus. Strength studies were conducted by means of Young’s Modulus for 28 days respectively for M 60 concrete. The goal of this study is to determine the role of fibres in post-cracking and fracture behaviour of concrete, as well as the stress–strain behaviour of cracked concrete specimen.

Present days natural fibers have transformed the matter of research field among various fields of study to inculcate it in the manufacture of composites instead of the production of composites using areca and sisal polymer-based composite. This is due to respective advantages related to natural fibers like eco-friendly, low cost, convenience in copiousness, and biodegradability. Stacks of work have been carried out in the production of natural fiber-reinforced polymer composites, using natural fibers like areca and sisal polymer-based composite and their mechanical properties have been studied. Here is an attempt made on the literature survey of areca and sisal fibre built polymer composites where different properties of areca and sisal fibers, its adulthood level, surface treatment effect on properties of fibers, composite formation with different matrices, its mechanical properties have been highlighted.

This review reports the outcome of an research experimental on flexural behaviour of partially strengthened reinforced concrete beams along with Engineered Cementitious Composite (ECC). 6 beams were moulded and examined in total. Three beams were tested to determine the influence of plastic hinge length, whereas two beams were examined to determine the effect of large layers of ECC in the tension zone. The remaining beam acted as control beam. Along with beam specimens, cylinders and cubes were tested to evaluate the mechanical characteristics of both ECC and concrete. All the beams are strengthened using ECC plastic hinges and layers. And they could withstand maximum load than the regulate beams. Load capacities of reinforced concrete (RC) beams strengthened with ECC plastic hinges were 2.85 – 6.34 times more than those of the corresponding control beams. Similarly, RC beams having load capacities 5.71–8.45 times with ECC layers were even better. In general, ECC application increased the ductility of Reinforced concrete beams.

Concrete will be the very flexible material. Because of continuous and persistent demands made on concrete to assemble the several problematic necessities, extensive examination work is being carried out in region of concrete method. The engineers have frequently pushing restrictions to expand its presentation with support of supplementary cementitious materials and innovative chemical admixtures such as steel slag, fly ash, and silica fume and so on. Nanomaterial concrete is advanced one the composition of nanomaterial concrete it has following water, coarse aggregate, cement nano silica grain of the size of 10 nm-140 nm and fine aggregate. The nano materials like nano alumina, nano titanium oxide, nano silica, and carbon nano tubes, so on, which are currently utilized in concrete to change its strength assets. The “nano materials” have functions or properties diverse from same materials of bigger size. The “nano materials” have a bigger value of ratio among volume and surface region than other same particles in larger size, creating the “nano-materials” much reactive. The “nano silica” will react with C3S and C2S in cement &generate CSH-2 that will create a solid &strong connection of gel. In current survey, properties of strength like split tensile, compressive, and flexural strength of M50 and M40 grades of concrete with utilization of nano silica (1%, 1.5%, 2%, 2.5%) and micro silica (5%, 7.5%, 10%, 15%) as incomplete replacement of cement were deliberated. It was establish from evaluation survey that concrete composites with better properties could be generated utilizing nano silica, micro silica, and mixture of nanosilica and micro silica.

The purpose of this study was to determine the strength of hollow concrete block masonry walls, beams, and columns, and compare their values with brick masonry walls and ordinary reinforced concrete beams and columns. The specimens for the hollow concrete block and brick masonry walls were prepared and tested for compressive and flexural strengths as well as horizontal and diagonal shear strengths. Moreover, two hollow concrete blocks and two ordinary reinforced concrete beams were designed to experience flexural and shear failure and loaded under a two-point bending load. Meanwhile, a hollow concrete block and an ordinary reinforced concrete column were also constructed and subjected to centric axial loads until they collapsed. The results showed the hollow concrete block masonry walls have greater strength than those made with bricks while both flexural and shear capacity as well as the flexural ductility of reinforced hollow concrete block beams were higher than ordinary reinforced concrete beams. Meanwhile, the centric compressive axial strength of the reinforced hollow concrete block column was smaller due to the inefficient bond it has with the infilled concrete which leads to their separation under the compressive axial load.

The objectives of this study were to evaluate the mechanical properties of lithium disilicate components produced by additive manufacturing (AM) and to assess the effect of build orientation on the resistance to fracture.Oversized bars were printed with a glass-filled photoactive resin using a digital light processing technique. After sintering and post-processing, flexure and chevron notch fracture toughness bars were obtained in three principal orientations (0°, 45°, and 90°) with respect to the build direction. Mechanical properties were obtained according to the relevant ASTM standards. The hardness, indentation fracture resistance, and elastic modulus were measured for each orientation, and a Weibull analysis was conducted with the flexure responses. Fractography of the fracture surfaces was performed to identify the failure origins.The 0° orientation exhibited characteristic strength, Weibull modulus, and elastic modulus of 313 MPa, 4.42, and 168 ± 3 GPa, respectively, which are comparable to lithium disilicate materials from traditional processes. However, build orientation contributed significantly to the flexure strength, elastic modulus, and Weibull modulus; the characteristic strengths for the 45° and 90° build orientations were 86 MPa and 177 MPa, respectively. The primary contribution to the orientation dependence was the number of residual build layer-related flaws from incomplete union between printed layers. Of note, hardness and the fracture toughness were not dependent on build orientation.AM of lithium disilicate materials can achieve the mechanical properties of materials produced by traditionally processing. Thus, while further process development is warranted, the outlook for dentistry is promising.

Statement of problem Whether procedures performed before the cementation of computer-aided design and computer-aided manufacturing (CAD-CAM) glass-ceramic restorations, including milling, fitting adjustment, and hydrofluoric acid etching introduce defects on the ceramic surface that affect the mechanical and surface properties is unclear. Purpose A systematic review and meta-analysis were conducted to assess the effect of milling, fitting adjustments, and hydrofluoric acid etching (HF) on the flexural strength and roughness (Ra) of CAD-CAM glass-ceramics. Material and methods Literature searches were performed up to June 2020 in the PubMed/MEDLINE, Web of Science, and Scopus databases, with no publication year or language limits. The focused question was “Do milling, fitting adjustments, and hydrofluoric acid etching affect the flexural strength and roughness of CAD-CAM glass-ceramics?” For the meta-analysis, flexural strength and Ra data on milling, fitting adjustment, and HF etching versus control (polishing) were analyzed globally. A subgroup analysis assessed the effect of etching parameters (HF concentration and time) on the flexural strength and roughness of CAD-CAM glass-ceramics with different microstructures. Comparisons were performed with random-effect models at 5% significance. Results Fourteen studies from 2764 potentially relevant records were included in the qualitative syntheses, and 12 in the meta-analysis. Milling and fitting adjustments increased roughness and reduced the flexural strength of CAD-CAM glass-ceramics. The effect of HF etching was dependent on the glass-ceramic microstructure, HF concentration, and etching time. For feldspathic- and leucite-reinforced ceramics, HF 5% applied for between 30 and 120 seconds increased roughness without affecting flexural strength. For lithium disilicate glass-ceramics, HF concentrations greater than 4.9% used for 20 seconds or more reduced the strength without affecting the surface roughness. Conclusions The flexural strength of CAD-CAM glass-ceramic is reduced by grinding procedures such as milling and fitting adjustment. Ceramic microstructure, HF concentration, and etching time determined the effect of hydrofluoric acid etching on the flexural strength and surface roughness of glass-ceramic materials.

Statement of problem The development of polymethyl methacrylate (PMMA) computer-aided design and computer-aided manufacturing (CAD-CAM) resin blocks with reported improved mechanical properties has simplified complete denture production. However, whether the objective of improved mechanical properties has been achieved compared with conventional heat-polymerized PMMA is not yet clear. Purpose The purpose of this systematic review and meta-analysis was to evaluate the mechanical properties of denture base resins manufactured by conventional heat-polymerization and by CAD-CAM in terms of flexural strength, flexural modulus, and surface roughness. Material and methods Electronic databases (PubMed/MEDLINE, Scopus, Web of Science) were independently searched by 2 researchers for relevant studies published up to November 2020. The population, intervention, comparison, and outcome (PICO) question was, “Does the conventionally manufactured, heat-polymerized PMMA resin, as a denture base, demonstrate the same mechanical properties as the CAD-CAM resin block?” In addition, a meta-analysis was based on the inverse variance method. Flexural strength, flexural modulus, and surface roughness were analyzed through the continuous outcome evaluated by mean difference and standard deviation, with 95% confidence intervals. To evaluated heterogeneity, the I2 value (≤25%=low, ≥50%=moderate and ≥75%=high) and the P value were considered. P Results Thirteen in vitro studies were included in the analysis. A total of 507 specimens were evaluated, 222 conventional and 285 CAD-CAM. In terms of flexural strength, the data showed no significant difference when conventional heat-polymerized PMMA was compared with CAD-CAM PMMA resins (P=.06; mean difference=18.28; 95% confidence interval:-0.42 to 36.97). In terms of flexural modulus, there was a significant difference for the CAD-CAM PMMA group (P=.01; mean difference=589.22; 95% confidence interval: 117.95 to 1060.48). In terms of surface roughness, a significant difference was observed between the groups (P=.02; mean difference=-0.53; 95% confidence interval: -0.97 to -0.09) with the conventional heat-polymerized PMMA resin having higher surface roughness values. Conclusions The mechanical properties of CAD-CAM PMMA resins were generally improved when compared with heat-polymerized polymethyl methacrylate resin.

SUMMARY This study investigated the effect of different intermediary layer materials under class II mesio-occluso-distal (MOD) resin composite restorations on volumetric cuspal deflection, gap formation, and fracture strength. In total, 32 sound human maxillary premolars were used. After large, standardized Class II MOD cavities were prepared, a universal adhesive (Clearfil Universal Bond Quick, Kuraray) was applied. The premolars were randomly allocated into four groups according to different intermediary layer materials (n=8): Group Z250 (control)/micro-hybrid composite (Filtek Z250, 3M ESPE); Group EST/low-viscosity bulk-fill resin composite (Estelite Bulk Fill Flow, Tokuyama Dental Corp) + micro-hybrid composite; Group NOV/nanofiber-reinforced low-viscosity composite (NovaPro Flow, Nanova) + micro-hybrid composite; and Group RIB/polyethylene fiber [Ribbond, Ribbond Inc] + micro-hybrid composite. Distilled water was used for storage for 24 hours. Using microcomputed tomography (micro-CT), the teeth were scanned immediately after cavity preparation (T0), then 24 hours after restorative procedures (T1). Volumetric cuspal deflection in cubic millimeters (mm3) was analyzed on the palatal and buccal regions of each restoration individually at T0 and T1 scans. Gap formation (mm3) was evaluated to quantify the volume of black spaces at the tooth-resin interface on the T1 scan. After these scans, using a universal testing machine, the teeth were subjected to a fracture strength test (0.5 millimeters/minute [mm/min]). The fracture surfaces were analyzed with a stereomicroscope. The data were analyzed using the Kruskal-Wallis, one-way analysis of variance (ANOVA), and Dunn’s tests (p< 0.05). No significant differences in volumetric cuspal deflection and fracture strength were detected for all tested groups (p>0.05). Group RIB exhibited significantly higher gap formation values in comparison with all other groups (p

This paper presents the bending characteristics of sawdust-crete laminated composite slab. The materials used in the laboratory experiments include: Ordinary Portland Cement, river sand, gravel, sawdust, plywood, nails, reinforcement bars, stirrups and water. Manual mixing method was adopted and all sawdust-crete ingredients were batched by weight. A total of 48 slabs of size 1200mm x 1000mm x 100mm, 1200mm x 1000mm x 125mm, 1200mm x 1000mm x 150mm and 1200mm x 100mm x 175mm were cast for flexural strength from the mix ratios 0.75:1:2:2 and 0.75:1:3:3. Out of the 48 slabs cast, 32 were produced from sawdust-crete laminated composite (with 12.5mm and 20mm as the thickness of plywood for the laminate), 8 were produced from normal concrete ingredients (coarse aggregates, fine aggregates, cement and water) with 10mm rebar and mix ratio of 0.45:1:2:4. The remaining 8 slabs were made from plain sawdust-crete with mix ratio of 0.75:1:3:3. During the experiment, the maximum deflection for the slab was observed to occur at the slab with size 1200mm x 1000mm x 100mm no matter the core content used to produce the slab while the minimum deflection occurs at the size 1200mm x 1000mm x 175mm. The deflection of slab decreases with increase in slab thickness while flexural strength increases with increase in slab thickness. The flexural strength results of slab were compared by percentage difference and the results shows that there is significant difference between the two sets of slabs. Also, by comparing the results of plain sawdust-crete slab to that of sawdust-crete laminated composite slab, the result show that laminates with plywood increases flexural strength up to 68.4%. Conclusively, laminated sawdust-crete can be used for slabs that is not carrying too much load like residential houses.

The design of astonishing combinations of benzoxazine resins with various fillers is nowadays of great interest for high quality products, especially in ballistic armors. The objective of this study is to investigate a new hybrid material prepared as multi-layered composite plate by hand lay-up technique. Different composites were manufactured from Kevlar fabrics reinforced polybenzoxazine, which was filled with silane treated microcrystalline cellulose (MCC Si) at various amounts in the interlayers. The developed materials were tested for their flexural, dynamic mechanical and ballistic performance. The aim was to highlight the effect of adding different amounts of MCC Si on the behavior of the different plates. Compared to the baseline, the dynamic mechanical and bending tests revealed an obvious decrease of the glass transition of 21 °C and a notable increase in storage modulus and flexural strength of about 180 %and17%, respectively, upon adding 1% MMC Si as filler. Similarly, the ballistic test exhibited an enhancement in kinetic energy absorption for which the composite supplemented with 1% MCC Si had the maximal energy absorption of 166.60 J. These results indicated that the developed panels, with interesting mechanical and ballistic features, are suitable to be employed as raw materials to produce body armor.

Purpose To determine and compare the mechanical properties of 3D-printed yttriastabilized zirconia to milled isostatic pressed yttria-stabilized zirconia, with the following hypotheses: (1) The flexural strength of 3D-printed yttria-stabilized zirconia is comparable to milled yttria-stabilized isostatic pressed zirconia; and (2) thermocycling and chewing simulation do not affect the flexural strength of 3D-printed yttria-stabilized zirconia. Materials and methods A total of 30 bars of an experimental 3D-printed 3 mol% yttriastabilized zirconia (LithaCon 3Y 230, Lithoz) and 10 bars of milled isostatic pressed zirconia (Prettau Zirconia, Zirkonzahn) were utilized. The printed zirconia bars were divided into three groups (n = 10 bars per group): (1) untreated (control); (2) thermocycled; and (3) tested after chewing simulation. A flexural strength test was performed on all samples using a three-point bend test in an Instron Universal testing machine. One-way analysis of variance on ranks was used to compare milled to printed zirconia. The effects of thermocycling and load cycling on 3D-printed zirconia were also determined. Results The flexural strength values for milled and printed zirconia were 936.3 ± 255.0 MPa and 855.4 ± 112.6 MPa, respectively. There was no statistically significant difference in flexural strength between the milled and printed zirconia (P = .178). No statistically significant differences were observed between the control 3D-printed zirconia group and the thermocycled (888.4 ± 59.3 MPa) or load-cycled printed zirconia (789.6 ± 133.8 MPa; P = .119). Conclusion Printed 3 mol% yttria-stabilized zirconia has comparable flexural strength to milled yttria-stabilized isostatic pressed zirconia. The thermocycling and chewing simulation used in this study did not significantly alter the flexural strength of the printed 3 mol% yttria-stabilized zirconia. These results indicate a promising role for 3D printing in the fabrication of zirconia restorations. Additional studies are needed to explore the full potential of this technology.

High-performance ballistic fibers, such as aramid fiber and ultra-high-molecular-weight polyethylene (UHMWPE), are commonly used in anti-ballistic structures due to their low density, high tensile strength and high specific modulus. However, their low modulus in the thickness direction and insufficient shear strength limits their application in certain ballistic structure. In contrast, carbon fiber reinforced epoxy resin matrix composites (CFRP) have the characteristics of high modulus in the thickness direction and high shear resistance. However, carbon fibers are rarely used and applied for protection purposes. A hybridization with aramid fiber reinforced epoxy resin matrix composites (AFRP) and CFRP has the potential to improve the stiffness and the ballistic property of the typical ballistic fiber composites. The hybrid effects on the flexural property and ballistic performance of the hybrid CFRP/AFRP laminates were investigated. Through conducting mechanical property tests and ballistic tests, two sets of reliable simulation parameters for AFRP and CFRP were established using LS-DYNA software, respectively. The experimental results suggested that by increasing the content of CFRP that the flexural properties of hybrid CFRP/AFRP laminates were enhanced. The ballistic tests’ results and the simulation illustrated that the specific energy absorption by the perforation method of CFRP achieved 77.7% of AFRP. When CFRP was on the striking face, the shear resistance of the laminates and the resistance force to the projectiles was promoted at the initial penetration stage. The proportion of fiber tensile failures in the AFRP layers was also enhanced with the addition of CFRP during the penetration process. These improvements resulted in the ballistic performance of hybrid CFRP/AFRP laminates was better than AFRP when the CFRP content was 20 wt% and 30 wt%.

Made available in DSpace on 2022-04-29T08:45:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Indiana University Delta Statement of problem: Whether a computer-aided design and computer-aided manufacture (CAD-CAM) fabricated high-translucency lithium disilicate veneer on a lithium disilicate substructure would increase the strength of the restoration compared with a traditional feldspathic porcelain veneer is unclear. Purpose: The purpose of this in vitro study was to evaluate the effect of different lithium disilicate veneer application methods on a lithium disilicate substructure on their biaxial flexural stress (BFS). Material and methods: Lithium disilicate disks were fabricated so that when combined with the veneering disks, they had a dimension of 12×1.2 mm. Experimental groups were as follows (n=15): resin-bonded lithium disilicate veneer, lithium disilicate veneer adhesively cemented to lithium disilicate; sintered lithium disilicate veneer, lithium disilicate veneer sintered to lithium disilicate; sintered feldspathic veneer, feldspathic porcelain applied to lithium disilicate; and monolithic lithium disilicate, the control group. Weibull distribution survival analysis was used to compare the differences in the resistance to fracture after fatigue. The total number of cycles was analyzed by using 1-way ANOVA (α=.05). A finite element analysis (FEA) was also performed. The maximum principal stress (MPS) was used as the failure criterion. Results: The sintered feldspathic veneer group had significantly lower fatigue resistance than sintered lithium disilicate veneer or resin-bonded lithium disilicate veneer (P

The as-solution-treated Sm2Co17-type magnets exhibiting a single 1:7H phase with different average grain sizes (D) are designed. Anisotropy of bending strength (Rbb) and compressive strength (Rmc) of the magnets was investigated. Moreover, the Rbb increases from 86 to 173 MPa with D decreasing from ∼52 to ∼18 μm for group c//h samples. The Hall-Petch correlation was employed to reveal the effect of grain size on mechanical properties of the magnets, giving deep understand the mechanical anisotropy characteristics. The relatively high Hall-Petch coefficient KRbb (0.79 MPa·m1/2) gives rise to the largest Rbb (173MPa) for group c//h samples. The mechanical anisotropy of the samples is well explained based on crystal structure and grain size features (grain boundaries). Grain refinement is an effective way to enhance the mechanical properties of Sm2Co17-type sintered magnets.

This study aimed to develop and characterize an ion-releasing experimental fiber-reinforced flowable composite (Bio-SFRC) and dentin treatment solution made of poly(acrylic acid) (PAA) with a high molecular weight. In addition we also evaluated the interface structure and mineralization potential between the Bio-SFRC and dentin.Some mechanical properties (flexural properties and fracture toughness) of Bio-SFRC in comparison with commercial inert (G-aenial Flo X) and ion-releasing materials (ACTIVA-BioActive Base/Liner and Fuji II LC) were assessed (n = 8/group). Calcium-release at different time-points was measured during the first six weeks by using a calcium-ion selective electrode. Surface analysis of composites after being stored in simulated body fluid (SBF) was investigated by using SEM/EDS. Dentin disks (n = 50) were prepared from extracted sound teeth and demineralization was simulated by acid etching. SEM/EDS was used to evaluate the microstructure of dentin on the top surface and at interface with composites after being stored in SBF.Bio-SFRC showed higher fracture toughness (1.6 MPa mDeveloping such reinforced ion-releasing flowable composite and PAA solution might offer the potential for mineralization at the interface and inside the organic matrix of demineralized dentin.

In this study, it is aimed to determine the effect of steel and macro synthetic fibers used in different ratios and types on the physical and mechanical properties of concrete. For this purpose; Macro synthetic fiber was used at 0.25%, 0.30% and 0.35% by volum4, steel fiber at 0.50%, 0.75% and 1.00% by volume. Chemical additives and marble powder were used in fixed proportions. In the study, the water / cement ratio was taken as 0.54 constant according to the fiber concrete TS 802 mixture. In this research, beams of 10 × 10 × 40 cm and 15 cm cube samples were produced for fresh and hardened concrete properties. The effect of fiber type and ratio was investigated by performing physical and mechanical tests on the produced samples. As a result of the study, as the fiber ratio of fiber mixes in fresh concrete increased, workability and unit volume weights decreased. As a result, as the fiber ratio in fresh concrete increases, the fiber ratio has negatively affected the workability and the unit volume weights decreased. In hardened concrete; In hardened concrete; As the fiber ratio increased, the initial crack stress and bending stress increased. The highest mechanical and physical properties were given by 1.00% steel fiber and 0.35% macro synthetic fiber concretes., Yapılan bu çalışmada farklı oran ve tiplerde kullanılan çelik ve makro sentetik liflerin betonun fiziksel ve mekanik özelliklerine etkisinin belirlenmesi amaçlanmıştır. Bu amaçla; Makro sentetik lif hacimce %0.25, %0.30 ve %0.35 oranında, çelik lif hacimce % 0.50, % 0.75 ve % 1.00 oranında kullanılmıştır. Çalışmada lifli betonların karışım hesabı TS 802’ esas alınarak yapılmış ve su/çimento oranı 0.54 sabit alınmıştır. Bu araştırmada taze ve sertleşmiş beton özellikleri için 10 × 10 × 40 cm boyutlarında kiriş ve 15 cm’lik küp numuneler üretilmiştir. Üretilen numuneleri üzerinde fiziksel ve mekanik deneyler yapılarak lif tipi ve oranını etkisi araştırılmıştır. Çalışma sonucunda taze betonda lifli karışımlar da lif oranı artıkça, işlenebilirlik ve birim hacim ağırlıklarını da azalmıştır. Sonuç olarak taze betonda lifli karışımlar da lif oranı artıkça, işlenebilirliği olumsuz olarak etkilerken birim hacim ağırlıklarını da düşürmüştür. Sertleşmiş betonda ise; Lif oranı arttıkça ilk çatlak gerilmesi ve eğilme gerilmesi arttırmıştır. En yüksek mekanik ve fiziksel özellikleri %1.00 çelik lifli, %0.35 makro sentetik lifli betonlar vermiştir.

Micro-cracks are inherently present in concrete, leads to debilitation of structures. Methods used for managing micro-cracks have a certain degree of toxicity and also possesses certain drawbacks that made them not completely efficient. Bacterial technique when used in fresh concretes results in calcite precipitation in voids and consequently improves the strength and lowers permeability of concrete. Bio- cement is the combination of Bacillus pasteurii 5% and nutrients Urea, Calcium Lactate 95%. In this study by adding 0.5, 1, 1.5 and 2% Bio- cement by weight of cement and observed compressive strength, flexural strength values after 7 and 28 days of curing for M25 grade of concrete.

Dentures should have proper fluoride release and physical properties. We evaluated how surface prereacted glass ionomer (S-PRG) nanofillers influenced fluoride release, flexural strength, and surface characteristics of polymethylmethacrylate (PMMA) resin.PMMA resin disc (n = 14) and rectangular (n = 5) specimens containing 0, 20 wt% microparticles, and 20 wt% nanoparticles of S-PRG were prepared. Six-disc specimens were examined for surface roughness; eight-disc specimens were immersed in 5 ml of deionized water for 24 h before analyzing the fluoride levels on days 1-3, 12, and 15. They were recharged with 1000 ppm fluoride solution for 24 h and stored in deionized water for five cycles. Fluoride release was examined. The flexural strength of the rectangular specimens was determined using a three-point bending test. Data were analyzed by two-way repeated-measures ANOVA.S-PRG nanofiller had the highest fluoride exchange rate and did not significantly change the surface roughness compared with the microparticle and control groups; however, the nanofillers agglomerated and reduced the flexural strength to below 65 MPa.Incorporating 20 wt% nanofillers into resin enhanced the fluoride exchange property greater than microfillers at the same content, but diminished the mechanical properties of the resin.Incorporating 20 wt% S-PRG nanofillers in resin denture base can improve the fluoride releasing property without affecting the surface roughness.

In this paper, the manufacturing of macro-porous tubular ceramic supports for membranes is described. The novel supports are fabricated from natural diatomite and alumina raw materials using the extrusion method. The structure was analyzed by X-ray diffraction (XRD) and mercury porosimetry techniques; the presence of possible defects was investigated by scanning electron microscopy (SEM). The permeability has been measured from water flux in standard experiments. Experimental results show that the open porosity, the average pore size (APS), the pore size distribution, the strength, and the permeability of sintered supports, have been found to depend, mainly on the concentration of alumina (Al2O3) additive. Supports prepared with the addition of 10 wt.% of alumina and sintered at 1200 °C, can be considered as the most optimized; they have a porosity ratio of about 46%, an APS is around 7.7 μm, a flexural strength value of about 28 MPa, and water permeability of around 15 m3 h−1 m−2 bar−1. Such materials could be of great interest in the supports fabrication for membrane application, for instance, water filtration.

Shear and flexural failure are commonly known as the highest catastrophic failure mode as it never gives any earlier notice before the collapse. The most common shape in the structure of beams and girders is T-section. Therefore it will be more necessary to investigate the condition of these structures. In this research, the flexural behaviour of RC T-beams is investigated experimentally and analytically strengthened with Basalt Fiber Reinforced Polymer (BFRP). A symmetrical one-point static loading system is applied on RC T-beams superficially bonded with 45° degree, and 90° wrapping up to failure. The effects of both wrapping patterns of BFRP on RC T-beams were investigated for ultimate load carrying capacity, deflection, strain, and failure modes. The experimental results demonstrate that superficially bonded BFRP can enhance the flexural capacity and reduce the deflection of the beam significantly. Further, the results show that the most effective wrapping pattern was a 45° degree than 90°wrapping and without wrapping. Then the RC T- beam was modeled by using ABAQUS to validate the present experimental and analytical results. After a series of comparative studies, the analytical results fairly admit with the experimental results. In the end, this study surmised showing different cracking patterns and yield points of the beam with and without strengthening. It is hoped that the results of this study will be of considerable help for the strengthening of T- beams and structures.

La2Sn2O7/SnO2 powder was synthesized by chemical co-precipitation method, and Ag-La2Sn2O7/SnO2 composites were prepared by hot-pressing sintering. The electrical resistivity, density, Brinell hardness and flexural strength of Ag-La2Sn2O7/SnO2 composites were measured. Moreover, the effect of La2Sn2O7 content on the arc erosion behavior of Ag-La2Sn2O7/SnO2 composites at 7 kV voltage was studied. With the increase of La2Sn2O7 content, the arc duration and arc energy decrease, and the breakdown strength increases. The surface morphology of Ag-La2Sn2O7/SnO2 composites after arc erosion was investigated using scanning electron microscopy and three-dimensional laser confocal scanning microscopy. With the increase of La2Sn2O7 content, the smaller the erosion damage, the better the anti-arc erosion performance. However, too much La2Sn2O7 results in the decrease of Ag-La2Sn2O7/SnO2 properties and severe arc erosion. X-ray photoelectron spectroscopy was used to determine the composition of the erosion region. The effect of La2Sn2O7 on wettability between Ag and SnO2 was investigated, and the erosion mechanism of Ag-La2Sn2O7/SnO2 composites was discussed systematically. This study can provide a reference for the application of Ag matrix electrical contact materials in high-voltage electrical appliances.

The housing problem in Tunisia has become more acute due to the high cost of construction materials, thus constituting a source of concern for the population. To resolve the crisis, upgrading abundant local materials has become a necessity. This paper aimed to assess the potential use of Jebel Menchar's geomaterial to develop compressed earth brick (CEB). Laboratory tests were performed to determine the physical, chemical and mineralogical properties. Series of destructive and non-destructive tests were carried out to characterize the properties of bricks based on their composition in terms of compressive strength, flexural strength, water absorption and ultrasonic testing. The results indicated that all of the bricks studied exhibited a compressive strength greater than 2.3 Mpa during the 28-day experiments, thus suggesting a high potential ability to reduce building material problems, while also providing the brick industry a useful and inexpensive new raw material with less CO2 emissions.

The present study evaluated the effect of different rinsing postprocessing solutions on surface characteristics, flexural strength, and cytotoxicity of an additive manufactured polymer for orthodontic appliances. These solutions have been deemed an alternative to the standard isopropanol which is a flammable liquid, known to have toxic effects.Tested specimens were manufactured using direct light processing of an orthodontic appliance polymer (FREEPRINT® splint 2.0, Detax) and post-processed with different post-rinsing solutions, including isopropanol (IPA), ethanol (EtOH), EASY 3D Cleaner (EYC), Yellow Magic7 (YM7), and RESINAWAY (RAY), respectively. All groups were post-cured following the manufacturer's instructions. Surface topography and roughness (Ra and Rv) were evaluated. In addition, flexural strength was measured by a three-point bending test. An extract test was performed to evaluate cytotoxicity. The data were analyzed by the Kruskal-Wallis test with Dunn's multiple comparisons test (p 0.05).Various post-rinsing solutions did not significantly affect the roughness values (Ra and Rv). Specimens post-processed with EtOH (98.1 ± 12.4 MPa) and EYC (101.1 ± 6.3 MPa) exhibited significantly lower flexural strength compared to the groups of IPA (110.7 ± 5.3 MPa), RAY (112.1 ± 5.6 MPa) and YM7 (117.3 ± 5.9 MPa), respectively. Finally, there were no cytotoxic effects of parts cleaned with different post-rinsing solutions.Considering the use of 3D-printed orthodontic appliance materials, different rinsing postprocessing procedures did not affect surface characteristics. However, the flexural strength was significantly influenced, which could be attributed to the chemical ingredients of the post-rinsing solutions. Various post-rinsing treatments had no alternation concerning cytocompatibility.

To evaluate the effect of post-curing times on the color change, flexural strength (FS), modulus (FM) and microhardness at different depths of four 3D printed resins.A characterization of the light emitted by 3D-resin post-curing unit (Wash and Cure 2.0, Anycubic) was performed. The tested 3D printed resins were Cosmos Temp3D (COS), SmartPrint BioTemp (SM) Resilab3D Temp (RES) and Prizma3D BioProv (PRI) were evaluated under five different post-curing conditions (no post-curing or 5-, 10-, 15, and 20 min of post-curing). For color change analysis, 10 mm diameter x 1 mm thick discs (n = 7) were printed, and the luminosity, color and translucency were measured before post-curing as control, and repeatedly after 5 min cycles of post-curing until a total of 20 min was reached for ΔEThe post-curing time significantly influenced the ΔEA fine adjustment of the post-curing time is crucial to produce adequate mechanical properties in 3D-printed restorative resins, while minimizing the color alterations on the restorations. For the evaluated resins, 5-10 min of post-curing will result in adequate mechanical properties, without affecting the acceptability in the color of the material. However, the results are material-dependent, and evaluation of each specific resin is advised.

Concrete-filled double-skin tubular beams consist of two tubes, placed eccentrically or concentrically, with the hollow space between the two tubes filled with concrete. This type of construction can thus combine the properties of steel and concrete to provide the advantage of increased strength, ductility, stiffness and economy of the section. This paper reports on a study into the flexural properties of beams made of square hollow section steel for the both inner and outer tube, connected with steel strips. In total, 12 specimens were tested under monotonic and cyclic loading. The effects of the concrete infill, the eccentricity of the inner tube, the provision of minimum steel reinforcement and slip control due to the attachment of steel strips at the end of the beams were studied. Beams with an eccentric inner tube showed better flexural response and were also more economical due to the reduced concrete volume; their load-carrying capacity under cyclic loading was less than that under monotonic loading. Compared with beams without longitudinal reinforcement, the beams with longitudinal reinforcement showed improved flexural strength when subjected to cyclic loading.

PURPOSE To assess the influence of substructure and dimension on the fracture strength of ceramic discs made from both lithium disilicate ceramic and zirconia. MATERIALS AND METHODS A total of 128 intact maxillary third molars were collected, and standardized enamel and dentin discs were fabricated. Lithium disilicate ceramic (IPS e.max CAD, Ivoclar Vivadent; n = 64) and zirconia (Katana, Kuraray; n = 64) discs with 0.5-mm (n = 32 IPS and n = 32 Katana) and 1-mm (n = 32 IPS and n = 32 Katana) thickness were produced, and each group was divided into two subgroups (n = 16 each) that were luted to the enamel or dentin discs using Panavia V5 (Kuraray). Half of the specimens in each subgroup were aged (chewing simulation and thermocycling), and all specimens were loaded until fracture in a universal testing machine (Z010, Zwick/Roell). Differences between Katana and IPS with respect to enamel and dentin as substructure and the thickness of the ceramic were analyzed by use of a nonparametric test (Mann-Whitney U test). RESULTS In un-aged specimens, fracture loads were not significantly (P > .05) different between zirconia and IPS specimens for 1- or 0.5-mm thickness. However, fracture loads were significantly higher (P < .001) in specimens supported by enamel, independent of the ceramic material. In aged specimens, the fracture loads of all specimens were significantly (P < .01) higher when supported by enamel; however, in the 0.5-mm groups, zirconia achieved significantly higher breaking loads than IPS when luted to dentin. CONCLUSION When 0.5-mm ceramic discs were luted to dentin, zirconia outperformed IPS with respect to breaking loads.

PURPOSE: To evaluate the biaxial flexural strength of different porcelain-to-zirconia thickness ratios and bonding strategies of a stress-free bilayer CAD/CAM ceramic system. MATERIALS AND METHODS: A total of 60 zirconia discs (diameter: 15 mm; thickness: 0.3 or 0.5 mm; n = 30 for each thickness) were divided into six groups (n = 10 each) according to porcelain-to-zirconia ratio and bonding strategy: VM/Zr (control): zirconia discs veneered with a feldspathic ceramic (VM 9, Vita) in 0.9-mm and 0.7-mm thicknesses using a conventional hand-layering technique; VB/Zr-SBU: zirconia discs airborne particle–abraded with 50-μm Al(2)O(3) particles followed by an MDP primer application (Single Bond Universal, 3M) and bonded to the porcelain with a resin cement (Panavia F 2.0, Kuraray); and VB/Zr-RC: zirconia discs airborne particle–abraded with 30-μm silica-coated Al(2)O(3) particles and silanized and bonded to the porcelain with the same resin cement. Before cementation, the VB (Vitablocs II) discs were etched with 5% hydrofluoric acid (60 seconds), followed by silane application. The bilayers (thickness = 1.2 mm) were loaded with 750 g while light curing the resin cement. Two porcelain-to-zirconia thickness ratios were evaluated: 0.9: 0.3 mm and 0.7: 0.5 mm. All groups were subjected to 106 mechanical cycles, followed by a biaxial flexural test. Data (MPa) were subjected to two-way analysis of variance (ANOVA), Tukey test (5%), and Weibull analyses. RESULTS: Two-way ANOVA revealed that the factor porcelain-to-zirconia ratio (P = .0556) was not significant; however, the bonding strategy factor was statistically significant. Among the 0.5-mm zirconia groups, the VB/Zr-SBU group presented higher flexural strength (s) than the VM/Zr or VB/Zr-RC groups. Similar results were also found for the 0.3-mm zirconia groups, in which the VB/Zr-SBU group also presented higher strength than the others, which were similar in comparison (Tukey). The Weibull modulus was similar among the groups; however, the characteristic strength was significantly different (P = .000). CONCLUSION: The zirconia bonding strategy with 50-μm Al(2)O(3) airborne-particle abrasion, followed by a primer application, increases the flexural strength of a stress-free bilayer CAD/CAM ceramic system.

Studies investigating the mechanical stability of lithium disilicate-strengthened aluminosilicate glass-ceramic that do not require sintering after milling compared with other computer-aided design and computer-aided manufacturing (CAD-CAM) materials are lacking.The purpose of this in vitro study was to investigate the flexural strength of CAD-CAM zirconia, lithium disilicate, and lithium disilicate-strengthened aluminosilicate glass-ceramics with and without fatigue conditions.Specimens (N=90, n=15) (12×4×3 mm) from the following CAD-CAM materials were prepared and polished: lithium disilicate glass-ceramic (IPS e.max CAD); lithium disilicate-strengthened aluminosilicate glass-ceramic (N!ce); and zirconium dioxide ceramic (IPS e.max ZirCAD). All specimens were divided into 2 subgroups: immediate testing without aging and simulation of aging by using a mastication simulator for 1 200 000 cycles (5 °C-55 °C). Thereafter, flexural strength testing was performed by using a universal testing machine (1 mm/min) on nonaged and aged specimens. The data were evaluated by using nonparametric 2-way ANOVA and Wilcoxon rank post hoc tests (α=.05).Both the material type and aging significantly affected the results (P.001). The interaction was not significant (P.05). Under nonaged conditions, zirconium dioxide ceramic (1136 ±162 MPa) showed significantly higher mean ±standard deviation flexural strength (P.001) than lithium disilicate (304 ±34 MPa) and lithium disilicate-strengthened aluminosilicate glass-ceramic (202 ±17 MPa). The glass-ceramic groups were also significantly different from each other (P.001). After aging, zirconium dioxide (1087.9 ±185.3 MPa) also presented significantly higher mean ±standard deviation flexural strength (P.001) than lithium disilicate (259 ±62 MPa) and lithium disilicate-strengthened aluminosilicate glass-ceramic (172 ±11 MPa) (P.001). Aging significantly decreased the flexural strength of lithium disilicate (14.6%) (P=.03) and lithium disilicate-strengthened aluminosilicate glass-ceramic (14.5%) (P=.01) but had minimal effect on the zirconium dioxide ceramic (4.3%) (P=.29).Among the tested CAD-CAM materials, the mechanical performance of lithium disilicate-strengthened aluminosilicate glass-ceramic was comparable with that of lithium disilicate and considerably lower than that of zirconia. Aging decreased the flexural strength of both lithium disilicate and lithium disilicate-strengthened aluminosilicate glass-ceramic.

Statement of problem The use of reduced platform sets (implants and abutments) can help to control crestal bone loss around implants, which is essential for optimizing esthetics and biomechanical behavior. However, the information available on the fracture resistance of implants with a reduced platform is sparse. Purpose The purpose of this in vitro study was to analyze the maximum fracture strength value of implants with different platform designs during quasistatic fatigue, followed by a simulation of different bone levels of cervical insertion. Material and methods One hundred and twenty sets of dental implants and abutments with different diameters and platform designs were tested. All implants had an internal hexagon connection and conical macrogeometry. Four groups (n=30) were studied: O4.0-mm implants with a regular matched platform (rMatch group), O4.0-mm implants with a regular switched platform (PSwitch group), O5.0-mm implants with a wide matched platform (wMatch group), and O5.0-mm implants with a wide switched platform (wSwitch group). Three conditions simulating different levels of bone position around the cervical portion of the implants were proposed: insertion at the implant shoulder level=0 mm (L0), level=3 mm of insertion loss (L3), and level=5 mm of insertion loss (L5). All sets of all groups and proposed insertion level were subjected to a fracture strength test at 30 degrees in relation to the axis of the sets in a universal testing machine. Results Regardless of the insertion levels tested, the switched platform implants (rSwitch and wSwitch groups) showed similar mean fracture strength values (P>.05), while the implants of matched platforms (rMatch and wMatch groups) showed different fracture strength values for all insertion levels tested (P Conclusions The fracture strength values of the switched platform implants were lower at all insertion levels tested. However, for all insertion levels tested, the implants with a switched platform presented less deformation, whereas, in the matched platform implants, there was significant deformation of the implant structure.

This research assessed the suitability Atili seed shell as partial replacement of conventional coarse aggregates in no-fines concrete. The results show that the workability of no fines concrete improves as the percentage replacement coarse aggregate with Atili seed shell increases. The compressive strengths of all the samples fall within acceptable range of compressive strength of no-fines concrete.The percentage of water absorbed by the concrete reduced as the percentage replacement coarse aggregate with Atili seed shell increases.&nbsp

White Marble has beenused as a material since from the past. The marble dust which is the residue of marble is very harmful and it needs good disposal efforts. Marble dust is a waste product formed during the production of marble about 25% of the original marble mass is lost in the form of dust. The highlights incorporated in this paper is that how we can use marble dust as a replacement agent. Use of marble dust as a replacement for fine aggregate in concrete is investigated. Marble has replaced fine aggregate at content levels of 0, 4, 8, 12, and 16 in concrete. Five different series of concrete mixtures were designed to investigate the various properties on Marble dust concrete. Gradual reduction in compressive strength was observed with the increase in the percentage of Marble dust. It also concludes that up to 4% of Marble slurry can be added into concrete mixes without considerable reduction in strength of concrete. Percentage of water absorption decreases as the % of marble aggregate increases. The objective of the study was to study the effect of partial replacement of fine aggregates with rubber aggregates on different percentages of Marble Dust aggregates to M25 mix. Utilization of Marble dust aggregates, which is a waste product, in concrete construction is economically viable and environmentally effective. The present work is based on the effect of addition of marble dust in Portland cement concrete.

Currently, the introducing of basalt and natural fibers into different geopolymer swift growth of geopolymers. Despite of geopolymers have good properties such as fire resistance, flame resistance, higher compressive strength and higher durability, they suffer from low tensile strength and flexural strength. Different types of fibers were used to increase flexural strength, tensile strength, fracture toughness and ductility of geopolymers. The current article goals to brief the available earlier studies focused on the effect of basalt fibers and different natural fibers on the properties of geopolymers.

A strengthening technique using prefabricated stone plates reinforced with carbon-fibre-reinforced-polymer bars is proposed to improve the flexural performance and maintain the original appearance of exposed stone beams. The effectiveness of the technique was experimentally evaluated using three stone beam specimens, considering the reinforcement ratio as the main parameter. For comparison, two specimens strengthened with near-surface-mounted (NSM) polymer bars and one bare stone specimen were also tested. The test results showed that the prefabricated plates shifted the failure mode of the stone beams from brittle fracture to more ductile behaviour manner accompanied by multiple flexural cracks. A significant increase in load-carrying and deformation capacities was observed and the flexural strength tended to increase with an increase in the polymer reinforcement ratio. No end-slip in the polymer bars was observed, indicating good bond characteristics between the prefabricated plates and the stone beams and effective composite action. Compared with specimens with NSM polymer bars, the specimens strengthened with prefabricated polymer-reinforced plates showed similar load-carrying capacity. A simplified theoretical model for predicting the flexural strength of strengthened stone beams was developed and assessed.

The aim of this study was to compare the mechanical properties of three-dimensionally (3D)-printed and conventional surgical plates used for the repair of maxillary or mandibular defects under the same experimental conditions, and to provide experimental evidence for the future application and clinical trial of 3D-printed individualized surgical plates. For the experimental group, two groups of surgical plates with thicknesses of 2.0 mm and 2.5 mm were designed and 3D-printed by electron beam melting, using Ti-6Al-4V as raw material. Conventional commercially available surgical plates with the same thickness were adopted as the control group. A Vickers hardness tester and universal testing machine were used to measure the mechanical properties of the plates (hardness, bending strength, tensile strength, and yield strength). The mechanical properties of 3D-printed surgical plates were significantly better than those of conventional surgical plates of the same thickness (P 0.001). Comparing the surgical plates of different thickness, the 2.5 mm-thick plates had the highest bending strength in the experimental group (P 0.001) and the best hardness (P 0.001), bending strength (P = 0.001), tensile strength (P = 0.001), and yield strength (P = 0.001) in the control group. No statistical difference was found between the two kinds of plates in the experimental group in terms of hardness (P = 0.060), tensile strength (P = 0.096), and yield strength (P = 0.496). The 3D-printed surgical plates have better mechanical properties than the conventional ones.

This paper reports the test results for eight high-strength concrete square pile caps. The main variables are the area of flexural steel bars and the configuration patterns of flexural steel bars. The test results show that the ultimate load on the pile cap increases as the total area of the flexural steel bars increases. The load–displacement curves are not significantly affected by an increase in the total area of the flexural steel bars. For a specific area of flexural steel bar, the ultimate load on the pile caps in a bunched square reinforcement pattern is no greater than that for pile caps in a grid reinforcement pattern. Pile caps in a bunched square reinforcement pattern exhibit no significant mechanical advantage over pile caps in a grid reinforcement pattern. Square pile caps in a grid reinforcement pattern perform better because this pattern is more conducive to concrete casting than a bunched square reinforcement pattern. The softened strut-and-tie model more accurately predicts the ultimate load for pile caps than the ACI sectional method for various shear span-to-depth ratios and compressive strengths of concrete. The ACI sectional method overestimates the flexural strength of the square pile cap.

We sought to compare the bond strength of resin cement on moist dentin to that on dry dentin, and determine the relationship between the bond strength and flexural strength of resin cement. The water content of the moist and dry dentins was estimated using infrared spectroscopy. Four adhesive and three self-adhesive resin cements were used. At three times of immediately, after one-day storage, and after 20,000 thermocycles (TC 20k), the shear bond strengths were measured. For all resin cements, both the shear bond strength and the flexural strength were the lowest immediately after setting; however, after one day of water storage or TC 20k, these resin cements had the highest values. Regardless of the condition of the dentin surface upon shear bond strength, the flexural strength of each resin cement was correlated with the shear bond strength of the dentin surface.

Improvement in individual mechanical properties of carbon steels, such as strength or ductility, can no longer keep up with the increasingly demanding service environment. Therefore, it is of practical significance to improve two or more mechanical properties accurately and efficiently. In this work, five machine learning algorithms are first employed to establish prediction models for different mechanical properties (tensile strength, fracture strength, Charpy absorbed energy, hardness, fatigue strength, and elongation) based on the collected carbon steels data. Then, a set of mutually exclusive properties (tensile strength and elongation) and the key descriptors of the corresponding properties are identified by feature engineering, and the importance of the key materials descriptors is analyzed. The prediction models based on key descriptors for tensile strength and elongation also demonstrate good accuracy. All the key descriptors are considered as input features for the comprehensive performance (CP) calculated from the product of tensile strength and elongation. Finally, we develop a machine learning prediction model for CP and successfully apply the efficient global optimization algorithm to optimize two mutually exclusive mechanical properties. This work provides a new multi-objective optimization strategy that is expected to be used for the development of new steels with excellent comprehensive performance.