Fabrication and flexural strength of porous Si3N4 ceramics with Li2CO3 and Y2O3 as sintering additives

By employing sintering additives of Li2CO3 and Y2O3,porous Si3N4 ceramics are prepared after experiencing the processes of sintering and post-vacuum heat treatment at 1680 and 1550°C,respectively.The experimental results demonstrate the completed phase transformation fromαtoβ-Si3N4 in Si3N4 ceramic samples with a amount of 1.60 wt%Li2CO3(0.65 wt%Li2O)and 0.33 wt%Y2O3 additives.The as-synthesized porous Si3N4 ceramics exhibit high flexural strength((126.7±2.7)MPa)and high open porosity of 50.4%at elevated temperature(1200°C).These results are attributed to the significant role of added Li2CO3 as sintering additive,where the volatilization of intergranular glassy phase occurs during sintering process.Therefore,porous Si3N4 ceramics with desired mechanical property prepared by altering the addition of sintering additives demonstrate their great potential as a promising candidate for high temperature applications.

Flexural strength of zirconia/stainless steel functionally graded materials

Zirconia/stainless steel (ZrO2/SUS316L) functionally graded materials (FGMs) were fabricated by tape casting and laminating. Microstructures of FGMs were observed by optical microscope. Fracture behavior of FGMs in different loading modes and influences of different gradient changes on flexural strength were investigated. The results show that ZrO2/ SUS316L FGMs with graded components at interlayers are obtained after they are sintered in vacuum and pressureless condition at 1 350 ℃. TheⅠ?Ⅱ mixed mode crack creates in composite layer and grows to both sides zigzag while loading on ZrO2 layer. Flexural strengths are 496.4,421.7 and 387.5 MPa when gradient changes are 10%,15% and 20%,but flexural strengths of the corresponding fracture layers are 387.1,334.6 and 282.3 MPa since cracks of FGMs are affected by three-dimensional stress,respectively. The cracks are generated in ZrO2 layer and extend to SUS316L layer while loading is added on SUS316L layer,flexural strength does not change with the graded components and keeps consistent basically.

PREPARATION AND PROPERTIES OF BULK CERAMICS VIA PYROLYSIS OF POLYCARBOSILANE WITH ACTIVE FILLERS II.FLEXURAL STRENGTH AND ANTI-OXIDATIVE PROPERTIES OF ACTIVE FILLER/PCS DERIVED BULK CERAMICS

The flexural strengths and oxidative resistant properties of the ceramics derived from polycarbosilane and active fillers (Ti, TiH 2, TiB 2, Cr, and CrSi 2) were measured and characterized. The introduction of active fillers enhances slightly the flexural strengths, and further densification is required to obtain higher strengths. The oxidative resistant behaviors of the specimens with active fillers are, by means of weight gain in air, poorer compared with those without active fillers.

Influence of the column-to-beam flexural strength ratio on the failure mode of beam-column connections in RC frames

The column-to-beam flexural strength ratio(CBFSR)has been used in many seismic codes to achieve the strong column-weak beam(SCWB)failure mode in reinforced concrete(RC)frames,in which plastic hinges appear earlier in beams than in columns.However,seismic investigations show that the required limit of CBFSR in seismic codes usually cannot achieve the SCWB failure mode under strong earthquakes.This study investigates the failure modes of RC frames with different CBFSRs.Nine typical three-story RC frame models with different CBFSRs are designed in accordance with Chinese seismic codes.The seismic responses and failure modes of the frames are investigated through time-history analyses using 100 ground motion records.The results show that the required limit of the CBFSR that guarantees the SCWB failure mode depends on the beam-column connection type and the seismic intensity,and different types of beam-column connections exhibit different failure modes even though they are designed with the same CBFSR.Recommended CBFSRs are proposed for achieving the designed SCWB failure mode for different types of connections in RC frames under different seismic intensities.These results may provide some reference for further revisions of the SCWB design criterion in Chinese seismic codes.

Modeling and Simulation of Wood and Fly Ash Behaviour as Partial Replacement for Cement on Flexural Strength of Self Compacting Concrete

Flexural strength was monitored and predicted on the application improving concrete strength with wood and fly as partial replacement for cement.The study observed the pressure from the constituent of these locally sourced material that has been observed from the study to influence the flexural strength through the effect from this locally sourced addictives.The study monitors concrete porosity on heterogeneity as it reflect on the flexural strength of self compacting concrete.Other condition considered was the compaction and placement of concrete.These effects were monitored at constant water cement ratio from design mix.The behaviour from this effects on the concrete observed the rate of flexural growth under the influences of these stated conditions.The simulation expressed the reactions of these effects through these parameters monitored to influence the system.Numerical simulations were also applied to the optimum curing age of twenty eight days,while analytical simulation was also applied.This concept is the conventional seven days interval that concrete curing were observed,these are improvement done on the study carried out by experts[16].These locally sourced material were experimentally applied.The simulation predictive values are at the interval of seven days of curing,which was also simulated.The predictive values were compared with the experimental values of the researchers[16],and both values developed best fits correlations.The study is imperative because the system considered the parameters used on experimental and observed other influential variables that were not examined.These were not observed in the experimental procedure.Experts in concrete engineering will definitely find these concept a better option in monitoring flexural strength of self compacting concrete in general.

Influence of Glass Fiber wt% and Silanization on Mechanical Flexural Strength of Reinforced Acrylics

The aim is to evaluate the flexural strength of acrylic resin bars depending on the addiction of glass fibers with or without previous 3-methacryloxypropyl-trimethoxysilane (silane) application. Short fibers (3 mm) were treated and added to an acrylic resin powder, being further mixed with acrylic liquid to create bars (25 × 2 × 2 mm) of 11 experimental groups (N = 10), according to the interaction of experimental factors: weight % of glass fibers: (0.5;1;3;4;6 and 7) and silane application (with silane (S) or without silane (N)). Flexural strength and scanning microscopy evaluation were performed (SEM). Data (MPa) were submitted to ANOVA and Tukey (α = 5%). A significant difference between groups was observed (p = 0.001): S7%(128.85 ± 35.76)a, S6% (119.31 ± 11.97)ab, S4% (116.98 ± 25.23)ab, N4% (107.85 ± 24.88)abc, S1% (96.29 ± 20.65)bc, S0.5% (89.29 ± 7.33)cd, S3% (89.0 ± 11.27)cd, N3% (86.79 ± 17.63)cd, N1% (85.43 ± 16.44)cd, Control (73.29 ± 25.0)de, N0.5% (59.58 ± 19.46)e. For N groups, it was not possible to include more than 4%wt fibers. SEM showed better fiber-resin interaction for S groups, and fractures around fibers on N groups. Previous silane application enables the addiction of greater quantity of glass fibers and better interaction with the acrylic resin resulting in higher flexural strength. Without silane, fibers seem to act as initial crack points due to poor interaction.

Impact of Polymer Coating on the Flexural Strength and Deflection Characteristics of Fiber-Reinforced Concrete Beams

Liquid polymers(LP)have become an important structural material used in the construction industry in the last decade.This paper investigates the via­bility of using commercially available LPs as a coating material to improve the flexural strength of fiber-modified concrete beams.The scope included preparing rectangular prism concrete beams with a concrete mixture includ­ing fly ash and fiber and coating them with four different liquid polymers at a uniform thickness following the curing process while one set of sam­ples was maintained under the same conditions as a control group without coating.In addition,cylindrical samples were prepared to determine the compressive strength of the concrete mixture.Following the curing process in an unconfined open-air laboratory environment for another 28 days,con­crete samples were tested to determine the flexural strength and deflection characteristics under center point loading equipment.The results revealed that all four coating types enhanced both the flexural strength and the av­erage maximum deflection of the beams compared to the control group.While the enhancement in the flexural strength changed approximately between 5%and 36%depending on the coating type,the improvements in average maximum deflections varied between 3.7%and 28.4%.

Effect of Environmental Conditions on Flexural Strength and Fracture Toughness of Particulate Filled Glass-Epoxy Hybrid Composites

Multifunctional hybrid polymer composites were projected as novel solutions to meet the demands in various industrial applications ranging from automotive to aerospace. This investigation focuses on processing, flexural strength and fracture toughness characterization of the glass fabric reinforced epoxy (G-E) composites and graphite/fly ash cenosphere (FAC) modified interface between the epoxy matrix and glass fabric. Hand lay-up followed by compression moulding method was used to fabricate the laminates. Flexural and fracture toughness tests at room temperature, elevated temperature and cryogenic temperature were conducted to assess the flexural strength (FS) and mode-I plane-strain fracture toughness (KIC). The experimental and characterization efforts suggest that both graphite and FAC fillers improve bonding at the interface. The study showed that the graphite is more favorable for enhancing FS and KIC of G-E composites. Graphite filled G-E hybrid composites with significant FS and KIC to that of unfilled and FA filled G-E were successfully achieved by incorporating 10 wt% graphite. The incorporation of fillers resulted in improvement of FS, which increased by 43% and 37.7% for 10Gr+G-E and 10FAC+G-E hybrid composites respectively. All composites show a 26% improvement in KIC at cryogenic temperature and a decrease of 12.5% at elevated temperature. According to the SEM observations, fiber debonding from the matrix is suppressed due to the presence and uniform distribution of graphite. In addition, micro-pores, matrix shearing, active toughening mechanisms induced by graphite, such as crack deflection, layer breakage and delamination of graphite layers contributed to the enhanced KIC of hybrid G-E composites.

Study on carbon matrix composite bipolar plates with balance of conductivity and flexural strength

In order to balance the conductivity and flexural strength of graphite composite bipolar plates,the influence of conductive filler on the properties of graphite composite bipolar plate was comprehensively studied by using phenolic resin as binder,natural flake graphite as conductive substrate and functional carbon materials with different structures as auxiliary filler.The results show that the particle size of conductive substrate has an important influence on the conductivity enhancement of auxiliary filler.The influence of conductive particle size on auxiliary filler electrical conductivity improvement was first investigated in this research.The effects of various auxiliary filler concentrations on improving electrical conductivity and flexural strength were then examined.This research has substantial implications for the balance of electrical conductivity and flexural strength of graphite composite bipolar plates.

Balancing flexural strength and porosity in DLP-3D printing Al_(2)O_(3)cores for hollow turbine blades

High porosity and high strength are usually mutually exclusive in the preparation of ceramic materials.However,high porosity and flexural strength are required for the preparation of complex ceramic cores for hollow turbine blades.In this study,Al_(2)O_(3)cores with high porosity and high flexural strength were successfully prepared using digital light processing(DLP)3 D printing technology.The influence of sintering temperature on the microstructure,pore evolution,and flexural strength of the cores were investigated.With an increase in the sintering temperature,the porosity of the ceramic cores first increased and then decreased,reaching a maximum value of 35%at 1400℃.The flexural strength increased with the increase in sintering temperature,but at 1400℃the incremental enhancement of flexural strength was greatest.Combined with the core service requirements and core performance,this study selected 1400℃(open porosity of 35.1%and flexural strength of 20.3 MPa)as the optimal sintering temperature for the DLP-3 D printed Al_(2)O_(3)core.

Effect of mass transfer channels on flexural strength of C/SiC composites fabricated by femtosecond laser assisted CVI method with optimized laser power

In this study,femtosecond laser assisted-chemical vapor infiltration(LA-CVI)was employed to produce C/SiC composites with 1,3,and 5 rows of mass transfer channels.The effect of laser machining power on the quality of produced holes was investigated.The results showed that the increase in power yielded complete hole structures.The as-obtained C/SiC composites with different mass transfer channels displayed higher densification degrees with flexural strengths reaching 546±15 MPa for row mass transfer channel of 3.The strengthening mechanism of the composites was linked to the increase in densification and formation of"dense band"during LA-CVI process.Multiphysics finite element simulations of the dense band and density gradient of LA-CVI C/SiC composites revealed C/SiC composites with improved densification and lower porosity due to the formation of"dense band"during LA-CVI process.In sum,LA-CVI method is promising for future preparation of ceramic matrix composites with high densities.

Microstructure refinement-homogenization and flexural strength improvement of Al_(2)O_(3) ceramics fabricated by DLP-stereolithography integrated with chemical precipitation coating process

In this study,the chemical precipitation coating(CP)process was creatively integrated with DLP-stereolithography based 3D printing for refining and homogenizing the microstructure of 3D printed Al_(2)O_(3) ceramic.Based on this novel approach,Al_(2)O_(3)powder was coated with a homogeneous layer of amorphous Y2O3,with the coated AI2O3 powder found to make the microstructure of 3D printed Al_(2)O_(3) ceramic more uniform and refined,as compared with the conventional mechanical mixing(MM)of Al_(2)O_(3) and Y_(2)O_(3) powders.The grain size of Al_(2)O_(3) in Sample CP is 64.44%and 51.43%lower than those in the monolithic Al_(2)O_(3) ceramic and Sample MM,respectively.Sample CP has the highest flexural strength of 455.37±32.17 MPa,which is 14.85%and 25.45%higher than those of Samples MM and AL,respectively;also Sample CP has the highest Weibull modulus of 16.88 among the three kinds of samples.Moreover,the fine grained Sample CP has a close thermal conductivity to the coarse grained Sample MM because of the changes in morphology of Y_(3)Al_(5)O_(12) phase from semi-connected(Sample MM)to isolated(Sample CP).Finally,specially designed fin-type Al_(2)O_(3) ceramic heat sinks were successfully fabricated via the novel integrated process,which has been proven to be an effective method for fabricating complex-shaped Al_(2)O_(3) ceramic components with enhanced flexural strength and reliability.

Flexural fatigue strength of steel fibrous concrete containing mixed steel fibres

This paper reports investigation conducted to study the fatigue performance of steel fibre reinforced concrete (SFRC) containing fibres of mixed aspect ratio. An extensive experimental program was conducted in which 90 flexural fatigue tests were carried out at different stress levels on size 500 mm×100 mm×100 mm SFRC specimens respectively containing 1.0%, 1.5% and 2.0% volume fraction of fibres. About 36 static flexural tests were also conducted to determine the static flexural strength prior to fatigue testing. Each volume fraction of fibres incorporated corrugated mixed steel fibres of size 0.6 mm×2.0 mm×25 mm and 0.6 mm×2.0 mm×50 mm in ratio 50:50 by weight. The results are presented both as S-N relationships, with the maximum fatigue stress expressed as a percentage of the strength under static loading, and as relationships between actually applied fatigue stress and number of loading cycles to failure. Two-million-cycle fatigue strengths of SFRC containing different volume fractions of mixed fibres were obtained and compared with plain concrete.

INFLUENCE OF LOADING RATE AND SPECIMEN HEIGHT ON FLEXURAL STRENGTH OF Al_2O_3 AT HIGH TEMPERATURES

In this paper, the influence of loading rate and specimen height on flexural strength of Al2O3 at high temperatures has been studied by three-point bending method. The experimental results show that the flexural strength of Al2O3 decreases with increasing specimen height at room temperature, and it tends to stability when height increases to a certain degree (h=5mm in this paper), while the flexural strength of Al2O3 variates unapparently at high temperature with increasing height. There is a critical loading rate R . c. When loading rate R . is less than R . c, the flexural strength of Al2O3 increases with increasing loading rate and it drops sharply when loading rate is higher than R . c. The sensitivity of flexural strength to the loading rate decreases with elevating temperatures.

The ITZ microstructure,thickness,porosity and its relation with compressive and flexural strength of cement mortar;influence of cement fineness and water/cement ratio

A new insight into the interfacial transition zone(ITZ)in cement mortar specimens(CMSs)that is influenced by cement fineness is reported.The importance of cement fineness in ITZ characterizations such as morphology and thickness is elucidated by backscattered electron images and by consequences to the compressive(Fc)and flexural strength(Ff),and porosity at various water/cement ratios.The findings indicate that by increasing the cement fineness the calcium silicate hydrate formation in the ITZ is favored and that this can refine the pore structures and create a denser and more homogeneous microstructure.By increasing cement fineness by about 25%of,the ITZ thickness of CMSs was reduced by about 30%and Fc was increased by 7%–52%and Ff by 19%–40%.These findings illustrate that the influence of ITZ features on the mechanical strength of CMSs is mostly related to the cement fineness and ITZ microstructure.

Flexural Strength and Weibull Analysis of Bulk Metallic Glasses

The flexural strength reliability of bulk metallic glasses （BMGs） plates is analyzed using Weibull statistics. The Weibull modulus （m） and characteristic strength （σ0） of the Zr48Cu45AI7 BMG are 34 and 2630 MPa, respectively, which are much higher than the values of fine ceramics （m 〈 30, σ0 〈 1600 MPa）. In particular, the m values obtained by flexural strength and compressive strength statistics of the Mg61Cu28Gd11 BMG are 5 and 33, respectively, indicating that the m values of BMGs are test method dependent, and only the m values obtained by flexural strength statistics can be used to make a convincible comparison with those of ceramics.

Comparative study of flexural strength test methods on CAD/CAM Y-TZP dental ceramics

Clinically,fractures are the main cause of computer-aided design and computer-aided manufacturing(CAD/CAM)3 mol%-yttria-stabilized tetragonal zirconia polycrystal(Y-TZP)all-ceramic dental restorations failure because of repetitive occlusal loading.The goal of this work is to study the effect of test methods and specimen’s size on the flexural strength of five ceramic products.Both biaxial flexure test(BI)and uni-axial flexure tests(UNI),including three-point flexure test(3PF)and four-point flexure test(4PF),are used in this study.For all five products,the flexural strength is as follows:BI>3PF>4PF.Furthermore,specimens with smaller size(3PF-s)have higher values than the bigger ones(3PF).The difference between BI and UNI resulted from the edge flaws in ceramic specimens.The relationship between different UNI(including 3PF-s,3PF and 4PF)can be explained according to Weibull statistical fracture theory.BI is recommended to evaluate the flexural strength of CAD/CAM Y-TZP dental ceramics.

Effect of size on biaxial flexural strength for cement-based materials by using a triangular plate method

The effect of size on the biaxial flexural strength(BFS)of Portland cement mortar was investigated by using the recently proposed triangular plate method(TPM).An experimental program was conceived to study the size effect by keeping a constant water-cement ratio of 0.485,cement-sand ratio of 1:2.75,and using unreinforced triangular mortar plates of five different thicknesses and seven different side lengths.The BFS of the produced specimens was tested,and variations of BFS depending on specimen thickness and side length were determined.The results indicated that increases in triangular plate specimen side length and specimen thickness led to a decrease in the BFS of Portland cement mortar.The effect of specimen length increase on BFS was more significant than on the effect of the specimen thickness.The variations in specimens’thickness indicated a deterministic Type I size effect,while the variations in specimens’length showed an energetic-statistical Type I size effect.

Effect of Bio-filler on Hybrid Sisal-Banana-Kenaf-Flax Based Epoxy Composites:A Statistical Correlation on Flexural Strength

This work deals with the investigation of the synergistic effect of bagasse ash with sisal-banana-kenaf-flax fibers reinforced epoxy composite for their flexural behavior.The composites with three combinations of hybrid fibers viz.sisal/kenaf(HSK),banana/kenaf(HBK),and banana/flax(HBF)with bagasse ash(BGA)as filler material are fabricated using vacuum bag assisted resin transfer molding.Experiments were conducted based on L27 orthogonal array to understand the influence of control factor viz.fiber volume,alkali concentration&BGA over output response.A'-ray micro computed tomography analysis was conducted over the developed sample to infer the uniform dispersion of fiber and filler material.The experimental results reveal that the addition of fiber up to 30 vol%depicts better strength and further addition results in a negative impact.Increasing in order of BGA decreases the flexural strength of the developed composites.

Flexural Strength and Load-Deflection Behaviour of Hybrid Thermoset Composites of Wood and Canola Biopolymers

The study aims to incorporate cellulosic canola(Brassica napus L.)biopolymers with wood biomass to increase flexural strength more than wood fraction alone.A facile fabrication process-at ambient temperature-is employed for ease of producing two different sets of bio-composites utilizing unsaturated polyester resin:pristine composite structures of 100%wood and hybrid composite structures of a canola-wood blend.The curing process is accompanied by methyl ethyl ketone peroxide(MEKP).Besides the lightweight feature,the hybrid composite structures exhibit maximum flexural strength up to 59.6 and 89.58 MPa at 2.5 and 5%fibre polymer fraction,outperforming the pristine wood composites(49.25 MPa).Also,the bending behaviours of the composite structures are illustrated by the load-deflection curves and the associated SEM micrographs display their fractured and debonded surface at the cross-section.The novel canola fibre benefits from its inherent hollow architecture,facilitating an excellent strength to weight ratio for the thermoset composites.Interestingly,canola displays a fibre diameter and density of 79.80(±41.31)μm and 1.34(±0.0014)g/cc,contributing effectively towards the flexure performance and high packing density.The breaking tenacity(13.31±4.59 g-force/tex)and tensile strength(174.93±60.29)of canola fibres are comparable to other bast fibres.The synergy among fibre diameters,density and break-ing tenacity creates a good interphase to successfully transfer the external compressive load from the resin matrix to the fibres.Further,the two-parameter Weibull distribution model is applied for predicting the failure and reliability probability of composite specimens against a wide range of compressive loads.Finally,prioritized SWOT factors have been summa-rized associated with the prospects and key challenges of canola biopolymers-an attempt to strategize the planning and decision-making process for a potential business environment.The introduction of canola into the plastic industries would ultimately promote the application of sustainable biopolymers in diverse grounds including the interior panels for aerospace,automotive,and furniture industries.