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 materia...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%.展开更多
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 acti...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.展开更多
To counter the strength problem of drill string in well of large curvature and small diameter, well axis was taken as datum mis. Based on description of deflection of well an's and on analysis of three dimensional...To counter the strength problem of drill string in well of large curvature and small diameter, well axis was taken as datum mis. Based on description of deflection of well an's and on analysis of three dimensional forces of a small section of drill string, equilibrium differential equations of large deflection drill string were established. The internal forces were found by Longe-Kutta method. The stresses were found by using them and the strength prerequisite was established. Stresses of drill string in lateral horizontal well H767 were computed. The results are in agreement with those of finite element model and soft-rope rigidified model. But the method is simpler for computation than finite element model and is more perfect than soft-rope rigidified model. Curvature of the well is too large and there is stress concentration so that the fraction accident of drill string occurs.展开更多
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 ...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.展开更多
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 so...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.展开更多
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) we...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.展开更多
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, flexur...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 (K<sub>IC</sub>). 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.展开更多
This study compares the effect of treated pineapple leaves fibres (T-PALF) with sodium hydroxide solution and untreated fibres (N-PALF) on the compressive and flexural strength of earth bricks stabilized with 3% and 5...This study compares the effect of treated pineapple leaves fibres (T-PALF) with sodium hydroxide solution and untreated fibres (N-PALF) on the compressive and flexural strength of earth bricks stabilized with 3% and 5% cement. The fibre content ranged from 0% to 5% in steps of 1% by weight. The compressive strength tests were made at 7, 14, 21 and 28 days of curing;the flexural strength test were conducted at 28th day only. The results show that the T-PALF had a higher compressive strength when comparing to the N-PALF. The highest compressive strength of the bricks was obtained at 28 days of curing. The compressive strength at 28 days of stabilized brick at 3% and 5% of cement reinforced with T-PALF were 4.01 and 4.81 MPa, respectively, while the one reinforced with N-PALF was 3.19 and 4.63 MPa, respectively. The results further show that the highest flexural strength of both stabilized bricks at 3% and 5% of cement reinforced with T-PALF and N-PALF was obtained with the bricks stabilized with 5% of cement reinforced with T-PALF. This results show that bricks stabilized with 5% cement and reinforced with 3% of treated fibres content are good for construction of load bearing walls. It was observed;a significant improvement of the reinforced blocks under flexure than under compression.展开更多
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 di...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.展开更多
Objectives: The effect of ceramics construction (press- able, machinable) and corrosion on flexural strength and micro-hardness was studied. Materials & Methods: Two types of ceramics were tested: IPS e-max Press ...Objectives: The effect of ceramics construction (press- able, machinable) and corrosion on flexural strength and micro-hardness was studied. Materials & Methods: Two types of ceramics were tested: IPS e-max Press and IPS e-max CAD. Forty samples were constructed and divided into 2 groups according to the type of ceramics. Each group was then subdivided into 2 subgroups. Subgroups 1 were not subjected to corrosion while subgroups 2 were subjected to corro-sion test. Finally each subgroup was divided into 2 classes according to the type of test: biaxial flexural strength, micro-hardness. Results: There was a sig-nificant difference between the two tested ceramics as regard weight loss as IPS e-max CAD recorded less weight loss than IPS e-max Press. As regard the flex-ural strength, IPS e-max CAD recorded significant higher strength than IPS e-max Press. Corroded sam- ples recorded significant lower flexural strength than non-corroded samples for the two tested ceramics. As regard the Vickers micro-hardness test, the results showed significant difference between the two tested ceramics. IPS e-max CAD recorded higher mi-cro-hardness values than IPS e-max Press. The results also showed that the corroded samples recorded no significant micro-hardness values than non- corroded samples for the two tested ceramics. Conclusions: IPS e-max CAD recorded less weight loss weight loss after being subjected to corrosion test than IPS e-max Press. The method of fabrication affected the flexural strength µ-hardness of ceramic as machinable ceramic (e-max CAD) recorded significant higher data than pressable ceramic (e-mas Press). Corrosion decreased the flexural strength of both tested ceramics but had no effect on micro- hardness.展开更多
The main objective of this experimental study is to investigate the behavior of Recycled Reactive Powder Concrete (RRPC) developed from finely dispersed local waste raw materials. In this study, RRPC was developed by ...The main objective of this experimental study is to investigate the behavior of Recycled Reactive Powder Concrete (RRPC) developed from finely dispersed local waste raw materials. In this study, RRPC was developed by utilizing local wastes (finely dispersed waste glass powder, waste fly ash and waste ceramic powder) together with Portland cement, fine sand, admixture, steel fibers and water through full replacement of silica fume as well as quartz powder for sustainable construction practice. In this study, all raw materials for making RRPC were analyzed for X-Ray Fluorescence analysis. For sustainability of local construction works, this study employed standard curing method at ambient temperatures instead of steam curing at higher temperatures. Moreover, hand mixing was used throughout the study. To evaluate the structural performances of the developed RRPC mixes, compressive and flexural strengths of RRPC were investigated experimentally and compared with the control mix. The experimental results indicated that replacing the silica fume fully by finely dispersed local waste glass powder (GP) and fly ash (FA) is a promising approach for local structural construction applications. Accordingly, a mean compressive strength of 62.9 MPa and flexural strength of 8.8 MPa were developed using 50% GP-50% FA at 28thdays standard curing. In this study, 17.56% larger compressive strength and 30.6% flexural strength improvements were observed as compared to the control mix.展开更多
Purpose: The mechanical strength of polymethyl methacrylate (PMMA) remains far from ideal for maintaining the longevity of denture. The purpose of this study was to evaluate the effect of Zirconium oxide (ZrO2) nanofi...Purpose: The mechanical strength of polymethyl methacrylate (PMMA) remains far from ideal for maintaining the longevity of denture. The purpose of this study was to evaluate the effect of Zirconium oxide (ZrO2) nanofillers powder with different concentration (1.5%, 3%, 5% and 7%) on the flexural strength, fracture toughness, and hardness of heat-polymerized acrylic resin. Materials and methods: Zirconium oxide powders with different concentrations (1.5%, 3%, 5% and 7%) were incorporated into heat-cure acrylic resin (PMMA) and processed with optimal condition (2.5:1 Powder/monomer ratio, conventional packing method and water bath curing for 2 hours at 95。C) to fabricate test specimens of PMMA of dimensions (50 × 30 × 30 mm) for the flexural strength, fracture toughness, and (50 × 30 × 30 mm) were fabricated for measuring hardness. PMMA without additives was prepared as a test control. Three types of mechanical tests;flexural strength, fracture toughness and hardness were carried out on the samples. The recorded values of flexural strength in (MPa), fracture toughness in (MPa.m1/2), and hardness (VHN) were collected, tabulated and statistically analyzed. One way analysis of variance (ANOVA) and Tukey’s tests were used for testing the significance between the means of tested groups which are statistically significant when the P value ≤ 0.05. Results: Addition of Zirconium oxide nanofillers to PMMA significantly increased the flexural strength, fracture toughness and hardness. Conclusion: These results indicate that Zirconium oxide nanofillers added to PMMA has a potential as a reliable denture base material with increased flexural strength, fracture toughness, and hardness. According to the results of the present study, the best mechanical properties were achieved by adding 7%wt ZrO2 concentration.展开更多
This critical review presents a parametric approach to the evaluation of flexural strength of advanced ceramic or glass like cylindrical rods at ambient temperature.The parameters governing the measurement and evaluat...This critical review presents a parametric approach to the evaluation of flexural strength of advanced ceramic or glass like cylindrical rods at ambient temperature.The parameters governing the measurement and evaluation of flexure strengths of glasses and ceramics are detailed with references.The scope for improvement in the existing ASTM STM C-1684 standard is described with a logical rationale and the parameters that need to be addressed are listed and explained.展开更多
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 u...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.展开更多
Attempts are being made to utilize Reinforced Baked Clay (RBC) as a substitute of Reinforced Cement Concrete (RCC) for construction of low cost houses in plains of Pakistan. Since baked clay is considered to be more b...Attempts are being made to utilize Reinforced Baked Clay (RBC) as a substitute of Reinforced Cement Concrete (RCC) for construction of low cost houses in plains of Pakistan. Since baked clay is considered to be more brittle as compared to concrete. Therefore, it is necessary to investigate how deflection and crack width of RBC beams subjected to impact loading are governed by amount of reinforcement. This paper presents the behaviour of RBC beams under drop weight impact loading. The beams were reinforced with two steel bars, one in compression zone and the other in tension zone. In group A beams, the diameter of steel bars was 12.7 mm, while the beams of group B were reinforced with steel bars of 15.8 mm diameter. The RBC beams were subjected to repeated impacts of a hammer of mass 21 kg falling from a height of 1000 mm. The results show that 1) three times reduction in deflection, and 2) 2.5 times decrease in crack width, were achieved in RBC beams by increasing the area of steel to 50%. In addition to this, all the RBC beams failed within nine blows of the hammer, irrespective of area of reinforcement.展开更多
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 employ...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.展开更多
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 t...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.展开更多
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 stren...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.展开更多
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 ...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.展开更多
文摘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%.
文摘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.
文摘To counter the strength problem of drill string in well of large curvature and small diameter, well axis was taken as datum mis. Based on description of deflection of well an's and on analysis of three dimensional forces of a small section of drill string, equilibrium differential equations of large deflection drill string were established. The internal forces were found by Longe-Kutta method. The stresses were found by using them and the strength prerequisite was established. Stresses of drill string in lateral horizontal well H767 were computed. The results are in agreement with those of finite element model and soft-rope rigidified model. But the method is simpler for computation than finite element model and is more perfect than soft-rope rigidified model. Curvature of the well is too large and there is stress concentration so that the fraction accident of drill string occurs.
基金National Key R&D Program of China under Grant No.2017YFC1500601National Natural Science Foundation of China under Grant Nos.51678541 and 51708523Scientific Research Fund of the Institute of Engineering Mechanics,China Earthquake Administration under Grant No.2016A01。
文摘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.
文摘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.
基金The authors thank NAP/MEPA-Esalq-USP for support,assistance and availability of the laboratory and microscopy equipment which enabled the development of this research.
文摘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.
文摘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 (K<sub>IC</sub>). 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.
文摘This study compares the effect of treated pineapple leaves fibres (T-PALF) with sodium hydroxide solution and untreated fibres (N-PALF) on the compressive and flexural strength of earth bricks stabilized with 3% and 5% cement. The fibre content ranged from 0% to 5% in steps of 1% by weight. The compressive strength tests were made at 7, 14, 21 and 28 days of curing;the flexural strength test were conducted at 28th day only. The results show that the T-PALF had a higher compressive strength when comparing to the N-PALF. The highest compressive strength of the bricks was obtained at 28 days of curing. The compressive strength at 28 days of stabilized brick at 3% and 5% of cement reinforced with T-PALF were 4.01 and 4.81 MPa, respectively, while the one reinforced with N-PALF was 3.19 and 4.63 MPa, respectively. The results further show that the highest flexural strength of both stabilized bricks at 3% and 5% of cement reinforced with T-PALF and N-PALF was obtained with the bricks stabilized with 5% of cement reinforced with T-PALF. This results show that bricks stabilized with 5% cement and reinforced with 3% of treated fibres content are good for construction of load bearing walls. It was observed;a significant improvement of the reinforced blocks under flexure than under compression.
基金Project (2007K06-13) supported by the Science and Technique Research and Development Program of Shaanxi Province, China
文摘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.
文摘Objectives: The effect of ceramics construction (press- able, machinable) and corrosion on flexural strength and micro-hardness was studied. Materials & Methods: Two types of ceramics were tested: IPS e-max Press and IPS e-max CAD. Forty samples were constructed and divided into 2 groups according to the type of ceramics. Each group was then subdivided into 2 subgroups. Subgroups 1 were not subjected to corrosion while subgroups 2 were subjected to corro-sion test. Finally each subgroup was divided into 2 classes according to the type of test: biaxial flexural strength, micro-hardness. Results: There was a sig-nificant difference between the two tested ceramics as regard weight loss as IPS e-max CAD recorded less weight loss than IPS e-max Press. As regard the flex-ural strength, IPS e-max CAD recorded significant higher strength than IPS e-max Press. Corroded sam- ples recorded significant lower flexural strength than non-corroded samples for the two tested ceramics. As regard the Vickers micro-hardness test, the results showed significant difference between the two tested ceramics. IPS e-max CAD recorded higher mi-cro-hardness values than IPS e-max Press. The results also showed that the corroded samples recorded no significant micro-hardness values than non- corroded samples for the two tested ceramics. Conclusions: IPS e-max CAD recorded less weight loss weight loss after being subjected to corrosion test than IPS e-max Press. The method of fabrication affected the flexural strength µ-hardness of ceramic as machinable ceramic (e-max CAD) recorded significant higher data than pressable ceramic (e-mas Press). Corrosion decreased the flexural strength of both tested ceramics but had no effect on micro- hardness.
文摘The main objective of this experimental study is to investigate the behavior of Recycled Reactive Powder Concrete (RRPC) developed from finely dispersed local waste raw materials. In this study, RRPC was developed by utilizing local wastes (finely dispersed waste glass powder, waste fly ash and waste ceramic powder) together with Portland cement, fine sand, admixture, steel fibers and water through full replacement of silica fume as well as quartz powder for sustainable construction practice. In this study, all raw materials for making RRPC were analyzed for X-Ray Fluorescence analysis. For sustainability of local construction works, this study employed standard curing method at ambient temperatures instead of steam curing at higher temperatures. Moreover, hand mixing was used throughout the study. To evaluate the structural performances of the developed RRPC mixes, compressive and flexural strengths of RRPC were investigated experimentally and compared with the control mix. The experimental results indicated that replacing the silica fume fully by finely dispersed local waste glass powder (GP) and fly ash (FA) is a promising approach for local structural construction applications. Accordingly, a mean compressive strength of 62.9 MPa and flexural strength of 8.8 MPa were developed using 50% GP-50% FA at 28thdays standard curing. In this study, 17.56% larger compressive strength and 30.6% flexural strength improvements were observed as compared to the control mix.
文摘Purpose: The mechanical strength of polymethyl methacrylate (PMMA) remains far from ideal for maintaining the longevity of denture. The purpose of this study was to evaluate the effect of Zirconium oxide (ZrO2) nanofillers powder with different concentration (1.5%, 3%, 5% and 7%) on the flexural strength, fracture toughness, and hardness of heat-polymerized acrylic resin. Materials and methods: Zirconium oxide powders with different concentrations (1.5%, 3%, 5% and 7%) were incorporated into heat-cure acrylic resin (PMMA) and processed with optimal condition (2.5:1 Powder/monomer ratio, conventional packing method and water bath curing for 2 hours at 95。C) to fabricate test specimens of PMMA of dimensions (50 × 30 × 30 mm) for the flexural strength, fracture toughness, and (50 × 30 × 30 mm) were fabricated for measuring hardness. PMMA without additives was prepared as a test control. Three types of mechanical tests;flexural strength, fracture toughness and hardness were carried out on the samples. The recorded values of flexural strength in (MPa), fracture toughness in (MPa.m1/2), and hardness (VHN) were collected, tabulated and statistically analyzed. One way analysis of variance (ANOVA) and Tukey’s tests were used for testing the significance between the means of tested groups which are statistically significant when the P value ≤ 0.05. Results: Addition of Zirconium oxide nanofillers to PMMA significantly increased the flexural strength, fracture toughness and hardness. Conclusion: These results indicate that Zirconium oxide nanofillers added to PMMA has a potential as a reliable denture base material with increased flexural strength, fracture toughness, and hardness. According to the results of the present study, the best mechanical properties were achieved by adding 7%wt ZrO2 concentration.
文摘This critical review presents a parametric approach to the evaluation of flexural strength of advanced ceramic or glass like cylindrical rods at ambient temperature.The parameters governing the measurement and evaluation of flexure strengths of glasses and ceramics are detailed with references.The scope for improvement in the existing ASTM STM C-1684 standard is described with a logical rationale and the parameters that need to be addressed are listed and explained.
基金the financial supports from the National Key R&D Program of China(Nos.2020YFB1505904 and 2018YFB1502502-04)。
文摘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.
文摘Attempts are being made to utilize Reinforced Baked Clay (RBC) as a substitute of Reinforced Cement Concrete (RCC) for construction of low cost houses in plains of Pakistan. Since baked clay is considered to be more brittle as compared to concrete. Therefore, it is necessary to investigate how deflection and crack width of RBC beams subjected to impact loading are governed by amount of reinforcement. This paper presents the behaviour of RBC beams under drop weight impact loading. The beams were reinforced with two steel bars, one in compression zone and the other in tension zone. In group A beams, the diameter of steel bars was 12.7 mm, while the beams of group B were reinforced with steel bars of 15.8 mm diameter. The RBC beams were subjected to repeated impacts of a hammer of mass 21 kg falling from a height of 1000 mm. The results show that 1) three times reduction in deflection, and 2) 2.5 times decrease in crack width, were achieved in RBC beams by increasing the area of steel to 50%. In addition to this, all the RBC beams failed within nine blows of the hammer, irrespective of area of reinforcement.
基金supported by MITACS Canada,Composites Innovation Centre(CIC Engineering,Canada)the University of Manitoba Graduate Fellowship.
文摘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.
基金financially supported by the Funding from the National Key R&D Program of China(No.2018YFB1106600)the Fundamental Research Funds for Central Universities(WK5290000002)。
文摘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.
文摘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.
基金support from the National Natural Science Foundation of China(Nos.51972269 and 51672217)the Fundamental Research Funds for the Central Universities(No.3102019ghxm014)the Creative Research Foundation of the Science and Technology on Thermostructural Composite Materials Laboratory(No.JCKYS2020607001)。
文摘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.