• Advances in concrete construction
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• v.8 no.3
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• pp.207-215
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• 2019

Application of nanotechnology can be used to tailor made cementitious composites owing to small dimension and physical behaviour of resulting hydration products. Because of high aspect ratio and extremely high strength, carbon nanotubes (CNTs) are perfect reinforcing materials. Hence, there is a great prospect to use CNTs in developing new generation cementitious materials. In the present paper, a parametric study has been conducted on cementitious composites reinforced by two types of multi walled carbon nanotubes (MWCNTs) designated as Type I CNT (10-20 nm outer dia.) and Type II CNT (30-50 nm outer dia.) with various concentrations ranging from 0.1% to 0.5% by weight of cement. To evaluate important properties such as flexural strength, strain to failure, elastic modulus and modulus of toughness of the CNT admixed specimens at different curing periods, flexural bending tests were performed. Results show that composites with Type II CNTs gave more strength as compared to Type I CNTs. The highest increase in strength (flexural and compressive) is of the order of 22% and 33%, respectively, compared to control samples. Modulus of toughness at 28 days showed highest improvement of 265% for Type II 0.3% CNT composites. It is obvious that an optimum percentage of CNT could exists for composites to achieve suitable reinforcement behaviour and desired strength properties. Based on the parametric study, a tentative optimum CNT concentration (0.3% by weight of cement) has been proposed. Scanning electron microscope image shows perfect crack bridging mechanism; several of the CNTs were shown to act as crack arrestors across fine cracks along with some CNTs breakage.

• The Journal of Advanced Prosthodontics
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• v.15 no.2
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• pp.80-92
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• 2023

PURPOSE. This study incorporated the nanomaterial, nanostructured silver vanadate decorated with silver nanoparticles (AgVO₃), into heat-cured resin (HT) at concentrations of 2.5%, 5%, and 10% and compared the adhesion of multispecies biofilms, surface characteristics, and mechanical properties with conventional heat-cured (HT 0%) and printed resins. MATERIALS AND METHODS. AgVO₃ was incorporated in mass into HT powder. A denture base resin was used to obtain printed samples. Adhesion of a multispecies biofilm of Candida albicans, Candida glabrata, and Streptococcus mutans was evaluated by colony-forming units per milliliter (CFU/mL) and metabolic activity. Wettability, roughness, and scanning electron microscopy (SEM) were used to assess the physical characteristics of the surface. The mechanical properties of flexural strength and elastic modulus were tested. RESULTS. HT 10%-AgVO₃ showed efficacy against S. mutans; however, it favored C. albicans CFU/mL (P < .05). The printed resin showed a higher metabolically active biofilm than HT 0% (P < .05). There was no difference in wettability or roughness between groups (P > .05). Irregularities on the printed resin surface and pores in HT 5%-AgVO₃ were observed by SEM. HT 0% showed the highest flexural strength, and the resins incorporated with AgVO₃ had the highest elastic modulus (P < .05). CONCLUSION. The incorporation of 10% AgVO₃ into heat-cured resin provided antimicrobial activity against S. mutans in a multispecies biofilm did not affect the roughness or wettability but reduced flexural strength and increased elastic modulus. Printed resin showed higher irregularity, an active biofilm, and lower flexural strength and elastic modulus than heat-cured resin.

• Steel and Composite Structures
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• v.17 no.3
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• pp.215-236
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• 2014

The flexural behaviour of steel beams significantly affects the structural performance of the steel frame structures. In particular, the flexural overstrength (namely the ratio between the maximum bending moment and the plastic bending strength) that steel beams may experience is the key parameter affecting the seismic design of non-dissipative members in moment resisting frames. The aim of this study is to present a new formulation of flexural overstrength factor for steel beams by means of artificial neural network (NN). To achieve this purpose, a total of 141 experimental data samples from available literature have been collected in order to cover different cross-sectional typologies, namely I-H sections, rectangular and square hollow sections (RHS-SHS). Thus, two different data sets for I-H and RHS-SHS steel beams were formed. Nine critical prediction parameters were selected for the former while eight parameters were considered for the latter. These input variables used for the development of the prediction models are representative of the geometric properties of the sections, the mechanical properties of the material and the shear length of the steel beams. The prediction performance of the proposed NN model was also compared with the results obtained using an existing formulation derived from the gene expression modeling. The analysis of the results indicated that the proposed formulation provided a more reliable and accurate prediction capability of beam overstrength.

• Journal of Technologic Dentistry
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• v.37 no.3
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• pp.107-113
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• 2015

Purpose: This study provided the basic data for selecting the zirconia blocks by comparing the mechanical properties of the all ceramic crown between the domestic, import, translucent and shade blocks that were used in clinically. Methods: Currently, the most commercial block of five types(one import and two domestic block which is the translucent and shade) were used. It were elucidated by means of three point bending test, hardness test, FE-SEM observations and EDX analysis. The results were analyzed using a one-way ANOVA and Scheffe post hoc test for significant findings. Results: For flexural strength, LT specimen was the highest as 733.1 MPa, followed by JT specimen(712.0 MPa), ZT specimen(646.0 MPa), LS specimen(553.1 MPa), JS specimen(429.0 MPa). One-way ANOVA showed statistically significant difference between groups for flexural strength(p<0.05). For hardness, ZT specimen was the highest as 1556.5 Hv, followed by JT specimen(1540.3 Hv), LT specimen(1512.3 Hv), JS specimen(1472.0 Hv), LS specimen(1353.3 Hv). One-way ANOVA showed statistically significant difference between groups for hardness(p<0.05). Conclusion: Domestic block was higher than import block for flexural strength, and translucent block was higher than shade block for flexural strength. However, all blocks showed clinically acceptable range. There was no significant difference in hardness between domestic and import blocks. And significant difference was observed in translucent and shade blocks.

• The Journal of Advanced Prosthodontics
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• v.11 no.4
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• pp.202-208
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• 2019

PURPOSE. Fabrication of zirconia restorations with ideal mechanical properties in a short period is a great challenge for clinicians. The purpose of the study was to investigate the effect of heating rate on the mechanical and microstructural properties of monolithic zirconia. MATERIALS AND METHODS. Forty monolithic zirconia specimens were prepared from presintered monolithic zirconia blanks. All specimens were then assigned to 4 groups according to heating rate as Control, Group $15^{\circ}C$, Group $20^{\circ}C$, and Group $40^{\circ}C$. All groups were sintered according to heating rates with the sintering temperature of $1500^{\circ}C$, a holding time of 90 minutes and natural cooling. The phase composition was examined by XRD analysis, three-point bending test was conducted to examine the flexural strength, and Weibull analysis was conducted to determine weibull modulus and characteristic strength. Average grain sizes were determined by SEM analysis. One-way ANOVA test was performed at a significance level of 0.05. RESULTS. Only tetragonal phase characteristic peaks were determined on the surface of analyzed specimens. Differences among the average grain sizes of the groups were not statistically significant. The results of the three-point bending test revealed no significant differences among the flexural strength of the groups (P>.05). Weibull modulus of groups was ranging from 3.50 to 4.74. The highest and the lowest characteristic strength values were obtained in Group $20^{\circ}C$ and Control Group, respectively. CONCLUSION. Heating rate has no significant effect on the flexural strength of monolithic zirconia. Monolithic zirconia restorations can be produced in shorter sintering periods without affecting the flexural strength by modifying the heating rate.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6A
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• pp.1033-1039
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• 2006

The purpose of this study are to evaluated bond, flexural properties and control of plastic shrinkage cracking of crimped type synthetic fiber with amplitude 6 mm and height 1.8 mm reinforced cement based composites. Bond and flexural test were conducted in accordance with the JCI-SF 8 and JCI SF-4 standard, respectively. The plastic shrinkage cracking test was conducted for evaluating the effect of fiber in reducing shrinkage cracking in cement based composites. Test results indicated that the crimped typel synthetic fibers performed significantly better than the straight type fiber in terms of interface toughness and pullout load and the crimped type synthetic fibers improved the flexural toughness of concrete. Also, the increasing the crimped type synthetic fiber volume fraction from 0.00% to 1.00% improved the plastic shrinkage cracking resistance. Specially, the effect of control of plastic shrinkage cracking is excellent at the more than 0.5% fibre volume fraction.

• Composites Research
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• v.26 no.4
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• pp.213-217
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• 2013

The focus in the present work is to study the agro-waste corn husk bio-filler as reinforcement for polypropylene. These materials have been created by extrusion and injection molding. The effect of filler content by 10, 20, 30 and 40 wt. % and mesh sizes of 50~100, 100 and 300 on the mechanical properties was studied. For the un-notched specimens, the results of flexural strength showed a declining trend with increase the filler loading and the results of impact strength showed an increasing trend with increase the mesh size. In contrast, enhanced flexural modulus was observed with increasing filler loading and size.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2002.11a
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• pp.77-86
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• 2002

In this study we intended to investigate properties of cement mortar with recycled PET fiber, PE fiber, and PP fiber such as slump flow, compressive strength, tensile strength, and flexural strength. As results of experiment, several properties of specimen with recycled PET fiber were little low comparing those of specimen with PE fiber and PP fiber. But if we see from point of economy and recycle of industrial wastes, it has enough reason to be used. Compressive strength of specimen with recycled PET fiber at 56 days was about 10% higher, but tensile strength and flexural strength were lower than that of no-fiber.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.10
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• pp.1330-1337
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• 2018

In this study, 40, 50, 60, and 70 wt% filler dispersed samples were prepared for the current GIS Spacer or environmentally friendly GIS. In the AC electrical breakdown, EMSC and EMAC decreased with increasing filler content, and EMSC showed better breakdown strength than EMAC. The mechanical properties such as tensile strength and flexural strength of EMSC and EMAC were also increased with increasing filler content. In addition, EMSC results in better mechanical properties than EMAC. The reason for this is considered to be one in which the influence of the interface is important.

• KCI Concrete Journal
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• v.14 no.4
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• pp.161-169
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• 2002

The mechanical properties of fiber reinforced porous concrete for use as a planting material were investigated in this study. Changes in physical and mechanical properties, subsequent to the addition of carbon fiber and silica fume, were studied. The effects of recycled aggregate were also evaluated. The applicability as planting work concrete material was also assessed. The results showed that there were no remarkable changes in the void and strength characteristics following the increase in proportion of recycled aggregate. Also, the mixture with 10% silica fume was found to be the most effective for strength enforcement. The highest flexural strength was obtained when the carbon fiber was added with $3\%$. It was also noticed that PAN-derived carbon fiber was superior to Pitch-derived ones in view of strength. The evaluation of its usage for vegetation showed that the growth of plants was directly affected by the existence of covering soil, in case of having the similar size of aggregate and void.