Maximum Bending Strength Research Articles

Effects of glass fiber size and content on microstructures and properties of KNO3-based water-soluble salt core for high pressure die casting

The water-soluble salt core with higher bending strength and toughness is necessary to withstand the high pressure needed to manufacture some complex parts by high pressure die casting (HPDC). In this paper, the effects of glass fiber size and content on microstructures and properties of KNO3-based (KNO3-30 mol%KCl) water-soluble salt core were systematically studied. The results showed that increasing the glass fiber content greatly improved the bending strength and impact toughness of the KNO3-based salt core, decreased the water solubility rate and increased the humidity resistance. In addition, increasing the glass fiber size sharply enhanced the impact toughness of the KNO3-based salt core, while decreasing the bending strength, water solubility rate and humidity resistance. The maximum bending strength and impact toughness of the reinforced KNO3-based salt core with the glass fiber were, respectively, 41.32 ± 0.38 MPa and 2.146 ± 0.108 kJ/m2, which were 55.9% and 315.1% higher than those of the unreinforced KNO3-based salt core, respectively. The microstructures show that the glass fibers were evenly distributed in the KNO3-based salt core, which significantly refined the KCl primary phases, especially for the 12.5-μm glass fiber. Meanwhile, many fiber pull-out holes were observed in the KNO3-based salt cores with 75-μm and 25-μm glass fiber. The grain refinement, fiber pull-out and crack deflection were the main mechanism for improving the strength and toughness of the KNO3-based salt core.

Variations in structure and properties of vitrified bonds and vitrified diamond composites prepared by sol-gel and melting methods at different sintering temperature

Differences in structure and properties of Na2O–Al2O3–B2O3–SiO2 vitrified bonds and vitrified diamond composites prepared by sol-gel and melting methods were methodically discussed. Results showed that the vitrified bond prepared by sol-gel method contained more [AlO4] tetrahedron and owned higher bending strength, with the maximum value reaching 137 MPa, 31.73% higher than that prepared by melting method (104 MPa). As the sintered temperature rose, coefficient of thermal expansion of the vitrified bond prepared by sol-gel method increased first and then decreased, acquiring a maximum value of 5.75 × 10−6 °C −1 at 720 °C, which was still much lower than the minimum value of vitrified bond prepared by melting method (7.02 × 10−6 °C −1). The vitrified diamond composite prepared by sol-gel method possessed lower sintering shrinkage than that prepared by melting method, and could be applicable to the production of grinding tools with high dimensional accuracy. What's more, the maximum bending strength of vitrified diamond composites obtained by sol-gel method was 106 MPa, 24.7% higher than that of vitrified diamond composites prepared by melting method (85 MPa).

Mechanical Properties of Cu-B/Diamond Composites Prepared by Gas Pressure Infiltration

Diamond particles reinforced boron-alloyed Cu matrix (Cu-xB/diamond, x = 0.1, 0.2, 0.3, 0.4, 0.5, and 1.0 wt.%) composites were prepared by gas pressure infiltration. The size of the diamond particles was ~ 230 μm and the diamond volume fraction in the composites was ~ 66%. The interfacial carbide evolution plays an important role in improving the interfacial bonding and enhancing the mechanical properties of the Cu-B/diamond composites. The tensile, compressive and bending strengths firstly increase and then decrease with increasing boron content, giving a maximum tensile strength of 204 MPa, a maximum compressive strength of 608 MPa, and a maximum bending strength of 513 MPa at 0.5 wt.% B addition. The monotonic uniaxial tensile stress–strain curves of the Cu-B/diamond composites were predicted by using the Mori–Tanaka, generalized self-consistent, and Torquato identical hard spheres approximation models. The results suggest that alloying B to Cu matrix is an effective route to strengthening Cu/diamond composites.

Porous Al2O3 ceramics with spontaneously formed pores and enhanced strength prepared by indirect selective laser sintering combined with reaction bonding

Complex-shaped porous Al2O3 ceramics with spontaneously formed pores and enhanced strength were prepared by indirect selective laser sintering (SLS) combined with reaction bonding (RB) using Al2O3, Al and epoxy resin E12 mixed powders as raw materials. The influence of the Al amount (0–32.5 wt%) on microstructure, dimensional change, porosity, pore size distribution and bending strength of sintered bulks were investigated. The phase transition, pore structure evolution and strength enhancement mechanisms of porous ceramics with Al addition were analyzed. Owing to distinctive characteristics of Al oxidation in the RB process, including volume expansion during oxidation, spontaneously formed pores and improved bonding force, the change rate in dimension was reduced, the porosity was maintained and bending strength was enhanced, compared with the case of adding only organic binders. The sintered bulks with the Al addition of 22.5 wt% had a dimensional change of <0.99%, porosity of 54.5 ± 0.2% and maximum bending strength of 10.8 ± 0.6 MPa, which was 6.8 times as that of samples with no Al addition. The findings illustrate that understanding pore structure evolution and strength enhancement mechanisms will help design high-performance porous Al2O3 ceramics prepared by powder-based additive manufacturing.

Mechanical and morphological characterization of basalt/Cissus quadrangularis hybrid fiber reinforced polylactic acid composites

In today's scenario, most of the research works are carried out on the replacement of synthetic fibers using eco-friendly materials called natural fibers. Although there are many research findings in connection with natural fibers, in this work, a new combination of natural fiber having high biomedical potential is reinforced in the polymer composite. Three different weight fractions of polylactic acid, basalt, and Cissus quadrangularis fibers were melt mixed using twin-screw extruder named as PBCQ 1, PBCQ 2, and PBCQ 3. The mechanical, physical, and thermomechanical properties were studied by testing tensile, flexural, impact, hardness, water absorption, Fourier-transform infrared spectroscopy, and dynamic mechanical analysis of the injection-molded biomedical composite specimens prepared as per ASTM standards. It was noticed that the PBCQ 2 composite has the maximum elongation strength, bending strength, shear strength, and shore D hardness compared to other composites taken in this study. Water absorption of PBCQ 1 and PBCQ 2 composites are relatively less than PBCQ 3. The scanning electron microscopy micrograph of PBCQ composites shows tight bonding between the matrix and fibers. The adhesion of matrix and fibers was confirmed by Fourier-transform infrared spectroscopy graph, which indicates the stretching of molecular structure for the occurrence of O–H, C=O, and C–H links. The dynamic mechanical analysis curve of the PBCQ 2 composite indicates high storage modulus and less loss modulus compared to PBCQ 1 and PBCQ 3 due to the low weight percentage of basalt fiber in these composites.

Microstructure Evolution and Mechanical Properties of Melt Spun Skutterudite-based Thermoelectric Materials.

The rapid solidification of melt spinning has been widely used in the fabrication of high-performance skutterudite thermoelectric materials. However, the microstructure formation mechanism of the spun ribbon and its effects on the mechanical properties are still unclear. Here, we report the microstructure evolution and mechanical properties of La–Fe–Co–Sb skutterudite alloys fabricated by both long-term annealing and melt-spinning, followed by sintering approaches. It was found that the skutterudite phase nucleated directly from the under-cooled melt and grew into submicron dendrites during the melt-spinning process. Upon heating, the spun ribbons started to form nanoscale La-rich and La-poor skutterudite phases through spinodal decomposition at temperatures as low as 473 K. The coexistence of the micron-scale grain size, the submicron-scale dendrite segregation and the nanoscale spinodal decomposition leads to high thermoelectric performance and mechanical strength. The maximum three-point bending strength of the melt spinning sample was about 195 MPa, which was 70% higher than that of the annealed sample.

Microstructural evolution and mechanical characterization of Nb-interlayer-inserted Ti–6Al–4V/Si3N4 joints brazed with AuNiTi filler

The interfacial microstructure evolution and mechanical behavior of Ti–6Al–4V/Si3N4 joints with insertion of a 2 mm-thick Nb interlayer were studied by brazing with Au96.5Ni3Ti0.5 (mass%) alloy as a heat- and corrosion-resistant filler. When the joints were brazed at 1323 K with holding times of 0, 5, and 10 min, multilayered Au4Ti, Au2Ti, AuTi, AuTi3, and Au2Nb3 intermetallic compounds were formed at the Ti–6Al–4V/Nb interface, whereas two distinct regions consisting of Au2Nb3 layer and Au–Ni solid solution were predominantly developed at the Nb/Si3N4 interface. Joints brazed with a 0 min holding time fractured, with initiation at the reaction-layer/Si3N4 interface and propagation into the Si3N4 with a concave morphology because of large residual stress; the joints exhibited a maximum average room-temperature bending strength of 53 MPa.

The effect of immersion with time and water variations on bending strength of malapoga wood (Toona Ciliata M. Roem)

Bending strength is a parameter used in wood structure planning. The purpose of this study was to determine the effect of time and water of immersion on increasing bending strength. The main ingredient of this research is malapoga wood (Toona Ciliata M. Roem) which was previously preserved by immersion with brackish water, sea water and river for 2,4,6 and 8 weeks. Bending strength specimen and testing procedure refer to ASTM D14. A cross section of the test specimen is then subjected to a macro photograph to determine its failure mechanism. The test results show that Immersion using river water gives a greater bending strength value followed by using brackish water and sea water. The maximum bending strength of the river water is 26. 64 MPa at the time of immersion 4 weeks later followed by brackish water at 25. 86 MPa while the maximum bending strength value of seawater occurs in immersion for 6 weeks which is 24. 52 MPa. The immersion time causes the malapoga wood to become denser due to all the cavities in the malapoga wood filled with material contained in brackish water, sea and river so that the fibers of malapoga wood close up, dry out and crystallize inside the malapoga wood cavity which causes the bending strength of malapoga to increase.

Bending resistance of PVA fiber reinforced cementitious composites containing nano-SiO2

AbstractIn this study, the effects of polyvinyl alcohol (PVA) fiber content and nano-SiO2 (NS) on bending resistance of cementitious composites were investigated including bending strength and toughness. PVA fiber contents from 0.6% to 1.5% were added in the composites. The NS contents was 0% and 2% by mass. The water to binder ratio (w/b) was 0.38 for all composites. The specimens were cured for 28 days under 20∘C and relative humidity of 95% before bending test. The results show that the bending strength was improved with PVA fiber content increasing and the maximum bending strength was obtained at PVA fiber content of 1.5%. Although PVA fiber increased bending resistance regardless of NS addition, the optimal content was 1.2%. When the fiber content was less than 1.2%, the bending resistance of cementitious composites increased with fiber content. However, the toughness began to decrease as PVA fiber content increased from 1.2 % to 1.5%.2% NS addition decreased both bending strength and toughness due to the fact that NS was prone to self-desiccation and flock together, resulting in micro crack and strength loss.

The effect of transition metal oxides on the sintering and properties of ceramics in the ZrO2-Al2O3 system

The paper presents the results of the investigation of the transition metals oxides – cobalt and iron additives influence on the sintering and properties of the ceramic material based on ZrO2- Al2O3 system with 10 wt.% Al2O3. It is shown that the addition of the oxides resulted in the significant increase of the sintered ceramic materials ZrO2-10%Al2O3 strength and decrease of sintering temperature. The maximum bending strength was more than 800 MPa (sintered at 1450 °C) and porosity was less than 1%.

Effect of TiO2 content on the microstructure and mechanical and wear properties of yttria-stabilized zirconia ceramics prepared by pressureless sintering

A yttria-stabilized zirconia ceramic is prepared by pressureless sintering at 1350 °C, and the effects of TiO2 additive (0–10.0 wt%) on the microstructure, phase composition, and mechanical properties of the ceramic are investigated. The ceramic with no added TiO2 consists mainly of a monoclinic phase with a few tetragonal phases. With increasing TiO2 content, more t-ZrO2 phases are stabilized to room temperature, and a new phase, ZrTiO4, forms when the content of the TiO2 excess reaches 5 wt%. TiO2 facilitates the elimination of pores in the YSZ ceramics and increases the densification of the YSZ ceramics. The relative density increases from 91.5% (TiO2 0 wt%) to 96.2% (TiO2 10 wt%). Performance test results show a maximum bending strength of 312.56 MPa when the TiO2 content of reaches 10 wt%. The micro-hardness and wear resistance of the YSZ ceramics first increases then decreases as the TiO2 content increases, and the maximum micro-hardness and best wear resistance occur when the TiO2 is added at 5 wt%; the maximum micro-hardness and the minimum volume wear rate is 1792.5 HV and 2.06 × 10−4 mm3 N−1 × m, respectively. The wear mechanism of the ceramic is mainly plastic deformation and microcracking, and the fracture mechanism is mainly intergranular fracture. These results show that TiO2 is an effective sintering additive that promotes more t-ZrO2 phases stabilized at room temperature, with acceptable mechanical and wear resistance properties.

Mechanical Properties Of Tensile And Bending Strength Analysis In Biocomposite [SAGOO/PMMA] Material

Biocomposite material is a common material used in biomedical application. One of medical problems related to bone restoration which caused by accidents and injuries resulted in fracture bone parts. Biocomposite (Sagoo/PMMA) is being developed as a solution to solve that particular problem. In current research, tensile and flexural strength of sagoo/PMMA is tested and examined. There are correlation between value of tensile strength, value of bending strength, and curing time, with maximum tensile strength and bending strength were achieved by curing the specimen for 12 hours, with the maximum value of tensile strength is 3,337 MPa, and the maximum flexural is 2,653 MPa. The minimum tensile strength was achieved by curing the specimen for 6 hours with minimum value of tensile strength is 1,502 MPa, while the minimum flexural was acquired at curing time for 24 hours with minimum of bending strength is 0,536 MPa

Bending and shear performance of Australian Radiata pine cross-laminated timber

Cross Laminated Timber (CLT) is increasingly being used in commercial and residential construction in Australia due to its inherent strength and sustainability credentials. Until recently, infrastructure building projects using CLT have been reliant on imported products from overseas manufacturers. There is now a viable Australian grown and fabricated CLT product from Radiata pine. This paper summarises the experimental results on the mechanical behaviour of Australian Radiata pine CLT panels in out-of-plane bending and shear. Three-layer 105 mm thick panels and five-layer 145 mm panels with three different spans were tested. The results demonstrate strong correlations to existing theoretical models and were used to validate the finite element model (FEM) developed in this research.The experimental results showed that the average bending stiffness of the CLT panels were marginally greater than theoretical values. The maximum bending strength for Radiata pine exceeded the characteristic strength of 14.0 MPa for grade XLG1 external laminas, with three-layer CLT samples averaging 28.7 MPa and five-layer CLT samples averaging 26.8 MPa. The maximum observed shear stresses ranged from 1.55 MPa to 2.18 MPa, which also exceeded the rolling shear characteristic strength of 1.2 MPa for the feedstock. The results also highlighted that the shear strength decreases with an increasing thickness of the CLT panel.

Synthesis and mechanical properties of mullite ceramics with coal gangue and wastes refractory as raw materials

AbstractWith coal gangue and high alumina refractory solid wastes as raw materials, needle‐like mullite powder, with an average diameter of about 1 μm, was synthesized at 1300°C by using the conventional solid‐state reaction method. Mullite ceramics were derived from the inexpensive needle‐like powder. Phase composition was examined by using X‐ray diffraction (XRD), while morphologies of the ceramics were observed by using scanning electron microscopy. The content and distribution of elements in the sintered samples were characterized with energy dispersive spectrometer and X‐ray fluorescence spectroscopy. Mechanical properties of the mullite ceramics were studied by using the three‐point bending method. The aspect ratio of the needle‐like mullite particles was up to 6. The mullite sample sintered at 1500°C for 3 hours had a density of 2.515 g·cm−3, which was slightly lower than the theoretical density. Maximum fracture toughness and bending strength of the mullite ceramics were 1.82 MPa·m1/2 and 71.76 MPa, respectively. This study realizes the resource utilization of gangue and high alumina refractory solid wastes, and the prepared mullite ceramics have good application prospect.

Influence of Cr2O3 on the viscosity and crystallization behavior of glass ceramics based on blast furnace slag

CaO–MgO–Al2O3–SiO2 glass-ceramics with various Cr2O3 contents are successfully prepared from blast furnace slag as the main raw material using a conventional melting method. The influence of Cr2O3 addition on the viscosity, crystallization kinetics, structure, and properties of the obtained materials are systematically determined by viscometry, differential scanning calorimetry, Fourier-transform infrared spectroscopy, X-ray powder diffraction, thermal-field-emission environmental scanning electron microscopy, and corrosion-resistance property tests. The results showed that the obtained glass-ceramics is composed of dendritic diopside (main crystalline phase) and bulk spinel (second crystalline phase). With increasing amount of Cr2O3, the viscosity of the slag glass melt increases. In addition, the samples exhibit crystallization activation energies in the range 378–454 kJ/mol, with slight fluctuations. Moreover, the crystallization index increases from 0.84 to 2.80. The obtained glass-ceramics exhibit a maximum density, bending strength, and acid and alkali resistances of 2.97 g/cm3, 196.69 MPa, 97.61%, and 98.04% respectively, demonstrating their wide application potential for various industrial applications.

Functionally Graded W-Cu Materials Prepared from Cu-Coated W Powders by Microwave Sintering

Three-layered W-Cu (W-10Cu/W-20Cu/W-30Cu, weight percentage) functionally graded materials were fabricated by laminate pressing of Cu-coated W composite powders with different Cu contents (10-30 wt.% Cu) and W particle sizes in the powders and microwave sintering of the powder compacts. The microstructure and the physical and mechanical properties of the graded materials were investigated. The experimental results show that the relative density of the graded W-Cu samples sintered at 1250 °C for 20 min is above 97%. Cu has a gradient layer distribution in the thickness direction, and there is good combination between the layers in the graded samples. Furthermore, the graded W-Cu materials exhibit good physical and mechanical properties. The sintered samples have thermal conductivities above 210 W m K−1, and the maximum bending strength and hardness reach 1004 MPa and 346 HV, respectively. The present results show that functionally graded W-Cu materials with high density, gradient Cu and W distribution, and good properties can be successfully prepared by laminate pressing and microwave sintering.

Fabrication and machining performance of ceramic cutting tool based on the Al2O3-ZrO2-Cr2O3 compositions

This study presents the cutting tool development of zirconia toughened alumina (ZTA) with chromia addition. The process used for its development is solid-state, in which the powders of Alumina (Al2O3), Zirconia (ZrO2) and Chromia (Cr2O3) were processed by a ball mill, compacted under a Cold Isostatic Press (CIP) and sintered at a constant temperature of 1400°C with 9h soaking time. The initial study investigated the effect of Polyethylene glycol (PEG) as a binder, CIP and hardness of Al2O3-ZrO2 mixtures. The percentage composition between Al2O3 and ZrO2 was varied to choose the best for the highest mechanical performances determined by the density, porosity and properties analysis. The cutting tool that possessed the highest hardness and bending strength was selected the Al2O3-ZrO2 mixture was mixed 0.6wt% Cr2O3 for machining trials within the cutting speed of 200–350m/min and constant feed rate and depth of cut of 0.150mm/rev and 0.5mm, respectively. The results of the ZTA mixed with Cr2O3 and combined with the ratio 80-20-0.6wt% showed that the addition of 0.6wt% PEG and a CIP pressure at 300MPa and 60s dwell time resulted maximum hardness and bending strength of 71.03 HRc and 856.02MPa, respectively. The fabricated cutting tool was capable to reach 225s tool life when machining AISI 1045 at a lower cutting speed of 200m/min and higher feed rate of 0.150mm/rev.

Enhanced mechanical and electromagnetic properties of polymer composite with 2.5D novel carbon/quartz fiber core-spun yarn woven fabric

A set of radar absorbent carbon/quartz fiber hybrid core-spun yarns (9B, 12B17A, and 12B25A) with different braided structure (round and flat) and braiding angle (17° and 25°) were designed, and then the mechanical and electromagnetic properties of the corresponding 2.5D core-spun yarn/epoxy composites (9BC, 12B17AC, and 12B25AC) were investigated in this study. The results showed that the composite made by round core-spun yarns with large braiding angle (12B25AC) had the highest mechanical properties and the best radar absorbing properties in the three types of 2.5D core-spun yarn/epoxy composites. The effective absorption bandwidth (reflection loss &lt; −10 dB), maximum reflection loss value, tensile strength, and bending strength of the 12B25AC was 3.9 GHz (14.1–18 GHz), −17.2 dB at 16.7 GHz, 428.43 MPa, and 545.10 MPa, respectively. Therefore, the 2.5D reinforced composite by the round core-spun yarns with large braiding angle offers a unique architectural method to attain both outstanding radar absorption and mechanical performances.

The fabrication of Al2O3–Al FGM by SPS under different sintering temperatures: Microstructural evaluation and bending behavior

The present study aimed to evaluate the microstructural and bending behavior of five-layers FGM structures fabricated by spark plasma sintering under different sintering temperatures. For this purpose, FGM samples containing four layers of Al2O3–Al ceramic matrix alongside an alumina layer were sintered under 40 MPa pressure and three different sintering temperatures 1050, 1400 and 1450 °C. The optimum microstructure with less micro-voids and aluminum islands was observed in the sample with maximum relative density of 90.7%, which sintered at 1450 °C. For the sample sintered at 1050 °C, the amount of porosity reached about 36%, which caused the lowest bending strength of 55 MPa and the maximum bending strain of (6.35%). Indeed, the flexural strength which depends on relative density, controlled by sintering temperature. For instance, the maximum bending strength of ~358 MPa associated with minor elongation (~3.7%) was obtained in sample sintered at the highest temperature. Also, the bending strength results were accorded with the fracture analysis. While the fracture surface of sample sintered at lowest temperature comprised of cracked particles and remarkable voids, the fracture surface analysis of specimens sintered at 1400 °C and 1450 °C illustrated transgranular and intergranular fracture. For the latter samples, the contribution of each fracture mechanism was governed by sintering temperature and chemical composition of layers. Considerably, sintering at 1400 °C prevents grain growth and extends weak boundary, which tends to intergranular fracture. In addition to temperature, the presence of aluminum reduced the strengthen ceramic/ceramic bonds, and consequently, motivated intergranular fracture in layers having further metal constituent.

Design and mechanical properties of Mo-10Si-7B alloys doped with lanthanum oxide by a hot pressing process

Mo-10Si-7B alloys doped with different mass fractions (0.3, 0.6, 0.9, and 1.2 wt%) of lanthanum oxide (La2O3) were prepared by liquid-liquid doping, mechanical alloying, and hot pressing. The obtained alloys have shown a fine-grained structure comprising of α-Mo, Mo5SiB2, and Mo3Si phases. The microstructures of the Mo-10Si-7B alloys revealed that their grains became finer with an increase in the content of La2O3. The maximum bending strength of Mo-10Si-7B alloys (1.48 GPa) was obtained upon doping with 0.9 wt% La2O3. The fracture toughness of the corresponding alloys was ∼15.58 MPa·m1/2, indicating that La2O3 through liquid-liquid doping significantly improved the bending strength and fracture toughness of doped alloys compared to un-doped alloys. Also, the densities of the obtained alloys were relatively high, mainly due to hot pressing, which reduces the porosity, micro-cracks, and other defects.