Study of the fracture features of layered ceramics in its microvolumes by indentation methods

2020 ◽  
Vol 2020 (01) ◽  
pp. 98-113
Author(s):  
O. Grigoriev ◽  
◽  
L. Melakh ◽  
T. Mosina ◽  
N. Brodnikovsky ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Crack Resistance ◽  
Thermal Stresses ◽  
Ceramic Composites ◽  
Strength Properties ◽  
Composites Manufacturing ◽  
Young’S Moduli ◽  
Layered Ceramics ◽  
Indentation Methods ◽  
Elastic Characteristics

Technology and modes of ZrB2―SiC layered ceramic composites manufacturing have been developed. The structures, elastic characteristics and strength properties of the materials under investigation have been studied. Effect of internal stress fields on fracture processes in the indentation area and mechanical properties of the ceramics in its microvolumes has been investigated both in layers and at their interfaces. Using values of contact tensile strength along different directions in layers of the composites, effective residual thermal stresses have been calculated (≈180 MPa). The obtained data on contact tensile strength and effective crack resistance, taking into consideration the contributions of residual stresses to their values, have been used for estimations of contact strength and crack resistance of the layer materials themselves. The fracture toughness measured by the three-point bending method is 3,3—3,7 MPa · m1/2. Analysis of the data obtained indicates that the spark notch provides a greater sharpness of the crack tip and better conditions for measuring K1c, while processing with a blade picks up a sharp thermal crack in the notch tip. The elastic properties of the multilayer system (SiC—15% ZrB2) + (SiC—30% ZrB2) were studied using ultrasonic research methods. The values of the velocities of sound and elastic characteristics are sufficiently large and close to those expected from the models of the composite, which does not contain noticeable porosity and microcracks in the layers themselves and in the region of their boundaries. For directions along and across the plane of the layers, the values of Young's moduli differ by about 6%. For the directions of propagation of an ultrasonic wave along and across the layers, anisotropy of ultrasonic velocities of ~5% and elastic moduli of ~10—12% is observed, which may be due to the texture that develops in the structure of the layers during hot pressing. Keywords: layered ceramics, indentation, strength properties, thermal stresses.

Increased dryness after pressing and wet web strength by utilizing foam application technology

TAPPI Journal ◽  
2016 ◽  
Vol 15 (11) ◽  
pp. 731-738 ◽  
Author(s):  
KARITA KINNUNEN-RAUDASKOSKI ◽  
KRISTIAN SALMINEN ◽  
JANI LEHMONEN ◽  
TUOMO HJELT
Keyword(s):  
Tensile Strength ◽  
Guar Gum ◽  
Paper Industry ◽  
Reference Sample ◽  
Strength Properties ◽  
Cellulose Microfibrils ◽  
Application Technology ◽  
Ethylene Vinyl Alcohol ◽  
Wet Pressing ◽  
Web Strength

Production cost savings by lowering basis weight has been a trend in papermaking. The strategy has been to decrease the amount of softwood kraft pulp and increase use of fillers and recycled fibers. These changes have a tendency to lower strength properties of both the wet and dry web. To compensate for the strength loss in the paper, a greater quantity of strength additives is often required, either dosed at the wet end or applied to the wet web by spray. In this pilot-scale study, it was shown how strength additives can be effectively applied with foam-based application technology. The technology can simultaneously increase dryness after wet pressing and enhance dry and wet web strength properties. Foam application of polyvinyl alcohol (PVA), ethylene vinyl alcohol (EVOH), carboxymethyl cellulose (CMC), guar gum, starch, and cellulose microfibrils (CMF) increased web dryness after wet pressing up to 5.2%-units compared to the reference sample. The enhanced dewatering with starch, guar gum, and CMF was detected with a bulk increase. Additionally, a significant increase in z-directional tensile strength of dry web and and in-plane tensile strength properties of wet web was obtained. Based on the results, foam application technology can be a very useful technology for several applications in the paper industry.

scholarly journals Evaluation of the Impact of Organic Fillers on Selected Properties of Organosilicon Polymer

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1103
Author(s):  
Sara Sarraj ◽  
Małgorzata Szymiczek ◽  
Tomasz Machoczek ◽  
Maciej Mrówka
Keyword(s):  
Tensile Strength ◽  
Natural Fiber ◽  
Accelerated Aging ◽  
Strength Properties ◽  
Visual Observation ◽  
Walnut Shell ◽  
Pistachio Shell ◽  
Thermoplastic Matrix ◽  
Static Tensile ◽  
The Impact

Eco-friendly composites are proposed to substitute commonly available polymers. Currently, wood–plastic composites and natural fiber-reinforced composites are gaining growing recognition in the industry, being mostly on the thermoplastic matrix. However, little data are available about the possibility of producing biocomposites on a silicone matrix. This study focused on assessing selected organic fillers’ impact (ground coffee waste (GCW), walnut shell (WS), brewers’ spent grains (BSG), pistachio shell (PS), and chestnut (CH)) on the physicochemical and mechanical properties of silicone-based materials. Density, hardness, rebound resilience, and static tensile strength of the obtained composites were tested, as well as the effect of accelerated aging under artificial seawater conditions. The results revealed changes in the material’s properties (minimal density changes, hardness variation, overall decreasing resilience, and decreased tensile strength properties). The aging test revealed certain bioactivities of the obtained composites. The degree of material degradation was assessed on the basis of the strength characteristics and visual observation. The investigation carried out indicated the impact of the filler’s type, chemical composition, and grain size on the obtained materials’ properties and shed light on the possibility of acquiring ecological silicone-based materials.

scholarly journals Absorption and Strength Properties of Short Carbon Fiber Reinforced Mortar Composite

Buildings ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 300
Author(s):  
Md. Safiuddin ◽  
George Abdel-Sayed ◽  
Nataliya Hearn
Keyword(s):  
Tensile Strength ◽  
Carbon Fiber ◽  
Water Absorption ◽  
Carbon Fibers ◽  
Strength Properties ◽  
Fiber Content ◽  
Test Results ◽  
Air Content ◽  
Entrapped Air ◽  
Short Carbon

This paper presents the water absorption and strength properties of short carbon fiber reinforced mortar (CFRM) composite. Four CFRM composites with 1%, 2%, 3%, and 4% short pitch-based carbon fibers were produced in this study. Normal Portland cement mortar (NCPM) was also prepared for use as the control mortar. The freshly mixed mortar composites were tested for workability, wet density, and entrapped air content. In addition, the hardened mortar composites were examined for compressive strength, splitting tensile strength, flexural strength, and water absorption at the ages of 7 and 28 days. The effects of different carbon fiber contents on the tested properties were observed. Test results showed that the incorporation of carbon fibers decreased the workability and wet density, but increased the entrapped air content in mortar composite. Most interestingly, the compressive strength of CFRM composite increased up to 3% carbon fiber content and then it declined significantly for 4% fiber content, depending on the workability and compaction of the mortar. In contrast, the splitting tensile strength and flexural strength of the CFRM composite increased for all fiber contents due to the greater cracking resistance and improved bond strength of the carbon fibers in the mortar. The presence of short pitch-based carbon fibers significantly strengthened the mortar by bridging the microcracks, resisting the propagation of these minute cracks, and impeding the growth of macrocracks. Furthermore, the water absorption of CFRM composite decreased up to 3% carbon fiber content and then it increased substantially for 4% fiber content, depending on the entrapped air content of the mortar. The overall test results suggest that the mortar with 3% carbon fibers is the optimum CFRM composite based on the tested properties.

scholarly journals Influence of Alumina Nanofibers Sintered by the Spark Plasma Method on Nickel Mechanical Properties

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 548 ◽  
Author(s):  
Leonid Agureev ◽  
Valeriy Kostikov ◽  
Zhanna Eremeeva ◽  
Svetlana Savushkina ◽  
Boris Ivanov ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Elastic Modulus ◽  
Strength Properties ◽  
Alumina Nanoparticles ◽  
Metal Powders ◽  
Wide Range ◽  
The Matrix ◽  
Spark Plasma ◽  
Average Size

The article presents the study of alumina nanoparticles’ (nanofibers) concentration effect on the strength properties of pure nickel. The samples were obtained by spark plasma sintering of previously mechanically activated metal powders. The dependence of the grain size and the relative density of compacts on the number of nanofibers was investigated. It was found that with an increase in the concentration of nanofibers, the average size of the matrix particles decreased. The effects of the nanoparticle concentration (0.01–0.1 wt.%) on the elastic modulus and tensile strength were determined for materials at 25 °C, 400 °C, and 750 °C. It was shown that with an increase in the concentration of nanofibers, a 10–40% increase in the elastic modulus and ultimate tensile strength occurred. A comparison of the mechanical properties of nickel in a wide range of temperatures, obtained in this work with materials made by various technologies, is carried out. A description of nanofibers’ mechanisms of influence on the structure and mechanical properties of nickel is given. The possible impact of impurity phases on the properties of nickel is estimated. The tendency of changes in the mechanical properties of nickel, depending on the concentration of nanofibers, is shown.

Study on Particleboard made from Nipa palm (Nypa fruticans) stem wood and Rajkoroi (Albizia richardiana) wood

2018 ◽  
Vol 25 (1) ◽  
pp. 15-18
Author(s):  
Md. Mahabubur Rahaman ◽  
◽  
Khurshid Akhter ◽  
S. Hossain ◽  
Md. Rakibul Islam ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Dimensional Stability ◽  
Bending Strength ◽  
Strength Properties ◽  
Wood Chips ◽  
Standard Specification ◽  
Stem Wood ◽  
Nypa Fruticans ◽  
Albizia Richardiana ◽  
Nipa Palm

The study was conducted to find out the suitability of making particleboard using nipa palm (Nypa fruticans) stem wood and rajkoroi (Albizia richardiana) wood chips. Particleboards were fabricated at six different ratios of nipa palm stem and rajkoroi wood chips such as 100:0, 75:25, 50:50, 25:75, 10:90 and 0:100. Characteristics of particleboards such as modulus of rupture, internal bond strength, water absorption, thickness swelling and moisture content were measured. Results shows that particleboards made from 100% rajkoroi wood chips have the highest static bending properties and highest tensile strength properties of other particleboards but 100% nipa palm stem wood chips have the lowest static bending and lowest tensile strength properties of other particleboards. 10% nipa palm stem wood chips particleboard have the highest bending strength and tensile strength is better than 100% nipa palm stem wood chips and other mixing chips of particleboards. Mechanical, water resistance and dimensional stability properties were tested according to Indian standard specification. Tensile strength passed the British and German standard specification and nearest to Bureau of Indian Standard, bending strength was found nearest to Indian Standard but lower than German and British Standard specification. Strength property of rajkoroi wood chips particleboard is higher than nipa palm steam wood chips particleboard but dimensional stability is lower than nipa palm steam wood chips particleboard.

scholarly journals Influence of Bitumen Type and Asphalt Mixture Composition on Low-Temperature Strength Properties According to Various Test Methods

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2118 ◽  
Author(s):  
Marek Pszczola ◽  
Cezary Szydlowski
Keyword(s):  
Tensile Strength ◽  
Low Temperature ◽  
Cooling Rate ◽  
Strength Properties ◽  
Test Methods ◽  
Asphalt Mixtures ◽  
Bending Test ◽  
Mixture Composition ◽  
Tension Stress ◽  
Strength Reserve

In regions with low-temperatures, action transverse cracks can appear in asphalt pavements as a result of thermal stresses that exceed the fracture strength of materials used in asphalt layers. To better understand thermal cracking phenomenon, strength properties of different asphalt mixtures were investigated. Four test methods were used to assess the influence of bitumen type and mixture composition on tensile strength properties of asphalt mixtures: tensile strength was measured using the thermal stress restrained specimen test (TSRST) and the uniaxial tension stress test (UTST), flexural strength was measured using the bending beam test (BBT), and fracture toughness was measured using the semi-circular bending test (SCB). The strength reserve behavior of tested asphalt mixtures was assessed as well. The influence of cooling rate on the strength reserve was investigated and correlations between results from different test methods were also analyzed and discussed. It was observed that the type of bitumen was a factor of crucial importance to low-temperature properties of the tested asphalt concretes. This conclusion was valid for all test methods that were used. It was also observed that the level of cooling rate influenced the strength reserve and, in consequence, resistance to low-temperature cracking. It was concluded that reasonably good correlations were observed between strength results for the UTST, BBT, and SCB test methods.

scholarly journals STUDY OF THE EFFECT OF TiB2 PARTICLES ON THE STRUCTURE, DEFORMATION BEHAVIOR, AND PROPERTIES OF THE ALUMINUM ALLOY 1550

2020 ◽  
pp. 102-116
Author(s):  
Aleksandr B. VOROZHTSOV ◽  
◽  
Vladimir V. PLATOV ◽  
Aleksandr A. KOZULIN ◽  
Anton P. KHRUSTALEV ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Yield Strength ◽  
Relative Elongation ◽  
Rolling Direction ◽  
Strength Properties ◽  
Rolled Sheet ◽  
Master Alloys ◽  
Cast Alloys ◽  
Tib2 Particles

In this work, the special master alloys containing aluminum and TiB2 powder with bimodal particle size distribution in three mixture compositions are prepared. The master alloys are infused into the melts using an external ultrasound source. The castings with particles had smaller grain sizes than the initial castings without particles. It is found that the hardness, yield strength, and ultimate tensile strength reach higher values with an increase in the relative elongation of the cast alloys with added particles. A warm rolling mode is employed for the studied alloys to obtain sheet blanks. It is shown that the staged shrinkage of the billets up to deformation of 80 % with periodic heating up to 300 °C allows one to obtain defect-free sheet products. The structure of the rolled sheet-alloys is characterized by the plate-shaped grains elongated along the rolling direction with pockets of submicron-sized grains in between. The strength properties of the studied rolled alloys exceeded those of the cast alloys. In the case of the rolled alloys, an increase in the yield strength, ultimate tensile strength, and ductility is revealed for the alloys with particles as compared to the ones with no particles added.

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