Transverse Bending Strength Research Articles

Reinforced Epoxy Binder Modified with Borpolymer.

Polymer binders based on epoxy resins have unique properties that contribute to their use in many composite industries. The potential of using epoxy binders is due to their high elasticity and strength characteristics, thermal and chemical resistance, and resistance to climatic aging. This is the reason for the existing practical interest in modifying the composition of epoxy binders and understanding the strengthening mechanisms in order to form reinforced composite materials with a required set of properties based on them. This article presents the results of a study of the process of dissolving the modifying additive of polymethylene-p-triphenyl ether of boric acid in the components of an epoxyanhydride binder applicable to the production of fibrous composite materials. The temperature and time conditions for the dissolution of polymethylene-p-triphenyl ether of boric acid in anhydride-type isomethyltetrahydrophthalic anhydride hardeners are presented. It has been established that the complete dissolution of the borpolymer-modifying additive in iso-MTHPA occurs at a temperature of 55 ± 2 °C for 20 h. The effect of the modifying additive of polymethylene-p-triphenyl ether of boric acid on the strength properties and structure of the epoxyanhydride binder has been studied. Increases in transverse bending strength up to 190 MPa, elastic modulus up to 3200 MPa, tensile strength up to 0.8 MPa, and impact strength (Charpy) up to 5.1 kJ/m2 are observed when the content of the borpolymer-modifying additive in the composition of the epoxy binder is 0.50 mass. %.

About the experience of using hardmetals in the production of roller cone bits at Volgaburmash JSC

Since 2017, Volgaburmash JSC (Samara, Russia) tested purchased 90%WC–10%Co carbide powder mixtures and finished carbide drill bits from various manufacturers. The work was carried out in order to check the possibility of using purchased products as raw materials at the plant to reduce the production cycle for the manufacture of carbide inserts for roller cone bits. This intercommodity substitution (outsourcing) is carried out with the aim of potential cone bit cost reduction and production process acceleration so that the plant can operate in the heavily competitive environment of foreign and domestic markets. The article focuses on the analysis and detailed comparison of the micro- and macrostructure, physical, mechanical, chemical and processing properties of purchased hard-alloy mixtures and sintered inserts of various manufacturers including Volgaburmash JSC. All properties of materials under study were determined in accordance with the VBM JSC company standard STP 582-17. Much attention is paid to comparing crack resistance or Palmqvist fracture toughness values of the alloy and analysis of microstructure images and fracture propagation pattern after using scanning electron microscopy tests. In addition, consideration is given to such important hard alloy properties as hardness and transverse bending strength. Based on the results of the conducted research, conclusions are presented on the expediency of using purchased hard-alloy materials at the Volgaburmash JSC metallurgical shop in comparison with internally manufactured materials.

Влияние химического состава матрицы на структуру и свойства монолитных СВС-композитов

Introduction. The development of new wear-resistant materials obtained by the method of self-propagating high-temperature synthesis (SHS) is an urgent problem in materials science. The SHS method is most widely used in the field of creating new powder materials. Much less attention has been paid to the production of monolithic non-porous composites. For monolithic composites, it is very important to identify the role of the metal matrix and phase transformations in the process of secondary structure formation after the completion of the synthesis process when the obtained material is cooled. The aim of this work was to carry out a comparative analysis of the structure and properties of SHS composites of the Fe-Ti-C-B, Fe-Ni-Ti-C-B, Fe-Ni-Cr-Ti-C-B, and Cu-TiC-B systems. Materials and research methods. Composites were obtained from powder mixtures consisting of thermoreactive components Ti, C, and B, as well as matrix Fe, Fe-Ni, Fe-Ni-Cr, and Cu. The initial powders were thoroughly mixed, loaded into a steel tube container, and the powder mixture was preliminary compacted. Then, the workpieces were heated in an electric furnace to the temperature of the onset of autoignition. After completion of the SHS, the workpieces were deformed with a force of 250 MPa in a hydraulic press at a temperature not lower than 1000 ° C. Samples were cut from the obtained sandwich plates for microstructural studies, density determination, hardness measurements, transverse bending tests and abrasive wear resistance tests. Results and discussion. All investigated composites were characterized by an uneven distribution of strengthening particles TiC and TiB2 over the volume. The use of the Fe-Ni matrix led to the formation of regions with the γ-Fe + Fe2B eutectic structure in the composite and an additional strengthening phase Ni3Ti. The use of Fe-Ni-Cr metal-matrix components led to the formation of two solid solutions in the matrix - austenite and ferrite, and Cr23C6 particles were formed along the boundaries of austenite grains. The maximum transverse bending strength was shown by SHS composites of the Fe-Ti-C-B and Cu-Ti-C-B systems with a matrix of FCC solid solutions. All composites had a hardness of 66 -72 HRC and showed the same abrasion resistance.

Effect of graphene oxide surface treatment on the interfacial adhesion and the tensile performance of flax epoxy composites

The high stiffness and damping properties of flax fibres promote the integration of biocomposites in structural applications. However, the strength of flax/epoxy composites is still limited compared to glass/epoxy composites. Graphene oxide (GO) has proved to be a promising building block for nanocomposites due to its high toughness, stiffness and tunable interfacial interactions with polymers. This study aims to understand the potential of GO-based surface treatment of flax fibres to modify the interfacial adhesion and tensile performance of flax fibre/epoxy composites. GO-modification improves the interfacial shear strength of elementary flax fibre/epoxy by 43%. The interfacial improvement is also established by the 40% higher transverse bending strength compared to untreated flax/epoxy composites. The tensile moduli of GO-modified flax/epoxy composites are on average 2 GPa higher than for untreated flax fibre/epoxy composites in all strain ranges. The quasi-static longitudinal tensile strength of unidirectional composites is not affected by GO-modification.

Internal structure influence on the impact strength and dynamic fracture toughness of hybrid polymer matrix composites with integrated elastomer interlayers

The strength and impact resistance of hybrid polymer matrix composites (HPMCs) made of PMCs and elastomer layers (ELs) are significantly influenced by internal structure and manufacturing technology. The paper proposes integration of two ELs, evenly spaced in relation to neutral axis, in three cross-section configurations. Elastomer layers (Kraibon, Kraiburg Company) were integrated between the layers of carbon epoxy prepreg (EP121-C20-45). Corresponding pure PMCs without two ELs were used as reference material. Description of dynamic response of the HPMCs under low velocity impact is the aim of the paper.3-point bending (3-PB) tests were performed for the HPMCs using the drop tower Instron Ceast 9350 to assess transverse impact bending strength for out-of-plane loading and dynamic fracture toughness KId for in-plane loading. The maximum forces required to initiate fracture processes and the total absorbed energy up to the samples failure were estimated.Application of integrated ELs in HPMCs significantly changed their dynamic material characteristics at low velocity impact, i.e. led to the increase of the absorbed energy about 41% for transverse impact bending and about 168% for in-plane loading in comparison to the PMC.

Fabrication and characterization of NbC-CoCrFeNiMn high-entropy alloy cermets

NbC based cermets with CoCrFeNiMn high-entropy alloys (HEAs) binders were fabricated by powder metallurgy. The effects of sintering temperatures on the microstructure and mechanical properties of NbC-HEAs cermets were systematically examined. The results show that the relative densities of NbC-HEAs sintered at different temperatures were about 90%. The XRD shows that a brittle M23C6 (M = Cr, Co, Fe, Ni) phase was detected in the cermets. The average particle size of NbC increased with increasing the sintering temperature. The coarsening of NbC particles caused the decrease of hardness and transverse bending strength (TRS) of the cermets. The highest TRS (497 MPa) was obtained for the cermet sintered at 1400 °C. The calculated activation energy was 696.6 kJ/mol, which was much higher than those in single element binders. Large cracks were observed for the cermets sintered at high temperatures, which suggested grain coarsening could reduce the toughness of cermets.

Study of the crack resistance and fracture mechanism of steel-aluminum composite material

Steel-aluminum composite materials are widely used in technology due to perfect wedding of their weight efficiency and high mechanical properties. This is the reason for their wide application in the aerospace industry for manufacturing case-type parts of rockets, fuel tanks and elements of aviation armor. The goal of the study is analysis of the crack resistance and the mechanism of fracture of aluminum-steel composite material (20 vol.%) with a density of 2.85 g/cm 3. The matrix component of the material was obtained using a finely dispersed aluminum powder PAP-2. The reinforcing component was made of steel meshes woven from austenitic steel cable (08Kh17N13M2). The transverse bending strength of the obtained material (550 – 600 MPa) was calculated from the maximum load corresponding to the first jump (onset) of the crack nucleating in the matrix. The crack resistance of the composite material at the stage of fracture initiation (estimated using K 1 c parameter) varied from 15 to 30 MPa · m 1/2 . The crack resistance of the composite at the stage of fracture development was described using the specific effective fracture work γ F ranged from 2 × 10 4 to 8 × 10 4 J/m 2 . The latter parameter exceeds by the order of magnitude the value γ F determined for steel St3, aluminum alloy D16T, and titanium alloy VT-5. The high value of γ F (which is an advantage of the obtained composite) is attributed to high-energy-consuming mechanism of the material fracture provided by the increased energy consumption for the destruction of the bridges between the matrix aluminum layers by cutting them off with a cable resulting from the shear stresses, for overcoming the friction forces when pulling cable out of the matrix, and for shifting layered packets formed by diffusion-bonded aluminum scaly particles inside the matrix. The properties of the obtained steel-aluminum composite provide the expediency of using the material for lightweight structural elements operated under mechanical loading.

Flooding has more adverse effects on the stem structure and yield of spring maize (Zea mays L.) than waterlogging in Northeast China

Abstract Lodging is a major element restricting the yield and quality of spring maize (Zea mays L.). A 2-year field experiment was implemented to explore the effects of flooding and waterlogging stress on the vascular bundle structure, mechanical properties of the stem and yield of two spring maize hybrids, Demeiya1 (DMY1) and Keyu16 (KY16), in Northeast China. Flooding and waterlogging treatments were conducted for different durations (3, 6, and 9 days for flooding and 5, 10, and 15 days for waterlogging) at the seedling (V3), jointing (V6), and tasseling (VT) stages. The results showed that plant height, ear height, stem diameter, stem length, rind penetration strength and transverse bending strength of the third base internode, cortical thickness, number of vascular bundles and stem bleeding intensity all significantly decreased with increasing duration of flooding or waterlogging. These changes led to a decline in the lodging ability of stems and ultimately caused a reduction in yield in both spring maize hybrids. Both maize varieties were most vulnerable to flooding and waterlogging stress at the V3 stage, followed by the V6 and VT stages, and the longer the flooding or waterlogging duration, the more significant the effects of flooding or waterlogging stress on the stem characteristics and grain yield of both spring maize hybrids.

Mechanical enhancement of UHMWPE fibers by coating with carbon nanoparticles

Fiber-reinforced plastic (FRP) is composed of reinforced fibers and matrix resin, and has high specific strength and low-density materials. Because of the orientation of the fibers within them, FRPs are prone to buckling damage when under compression along the axial direction of the fiber, especially flexible organic ones. The compressive performance of FRP is largely dependent on fiber properties. the buckling load of FRP will increase with the increasing of fiber’s. In this study, we developed a way to improve the compressive and bending strength of ultra-high molecular weight polyethylene (UHMWPE) fibers. Carbon nanotubes (CNTs) and vapor-grown carbon fibers (VGCFs) were coated on the surface of UHMWPE fibers by pyrrole vapor deposition. The transverse compressive strength and bending strength of single UHMWPE fibers were determined by microcompression and single fiber bending measurements, respectively. The experiment result showed that coating UHMWPE fibers with CNTs and VGCFs increased both their transverse compressive strength and bending strength. It is excepted that the improved fiber would applied in FRP for better compressive performance.

Morphological aspects and mechanical properties of single bamboo fibers and flexural characterization of bamboo/ epoxy composites

A novel mechanical extraction process was developed to obtain long bamboo fibers to be used as reinforcement in structural composites. A single-fiber tensile test at four different span lengths for fibers of the bamboo species Guadua angustifolia was performed. Strength values of 800 MPa and Young’s modulus of 43 GPa were obtained. Unidirectional bamboo fiber/epoxy composites (BFC) were produced with untreated and alkali-treated fibers to evaluate the effectiveness of the new reinforcing material. Flexural tests were performed with two fiber orientations (longitudinal and transverse). The longitudinal flexural strength is higher when untreated fibers are used while the treatment benefits the longitudinal flexural stiffness of the composite. Transverse strength increases at lower alkali concentrations, but the transverse three-point bending strength of untreated bamboo in epoxy is already quite high at around 33 MPa. The results illustrate that these bamboo fibers present a natural and renewable option to reinforce composites in several applications where glass fiber and traditional natural fibers are used nowadays.

Deposition of Protective Coatings on Tungsten-Free Hard Alloys

The process of deposition of coatings of titanium carbide, vanadium carbide, and chromium carbide on the surface of the tungsten-free hard alloys TN20, KNT16, and KKhN15 is investigated. The structure and phase composition of specially created layers are explored and the microhardness measured (11.5-24.5 GPa). The optimal temperature-time conditions for deposition of carbide coatings is determined. The ultimate transverse bending strength of hard alloys with and without coatings is determined. From the results of industrial tests, a two- to five-fold increase in the durability of plates in cutting was noted.

The effect of the addition of poly(methyl methacrylate) fibres on some properties of high strength heat-cured acrylic resin denture base material.

The self-reinforcement of acrylic resin with butadiene styrene surface treated poly(methyl methacrylate) fibres has been reported to have the potential to substantially improve the transverse bend strength of conventional heat-cured acrylic resin. The aim of this study was to investigate the effect of the addition of butadiene styrene surface treated poly(methyl methacrylate) fibres in cross-ply arrangement to high impact acrylic resin on the transverse and impact strength. Specimens were prepared as specified in the International Standard Organization and British Standards for the Testing of Denture Base Resins (ISO 1567, 1988; BS 2487, 1989) and the British Standard Specification for Orthodontic resins (BS 6747, 1987) for transverse bend and impact testing. The impact strength was measured using a Zwick pendulum impact tester and the transverse bend strength measured using a Lloyds Instruments testing machine. The results showed that the impact strength was not improved with the addition of fibres, high impact acrylic resin with fibres (LF) 11.1 kJ m-2 and high impact acrylic resin (L) (12.5 kJ m-2). The modulus of rupture was decreased with the addition of fibres (57.8 MPa) for (LF) compared with (60.4 MPa) for (L). The modulus of elasticity was also reduced with the addition of fibres (1834.9 MPa) (LF) and 2086.2 MPa (L) as was the peak load (LF) (50.8 N) and (L) (55.8 N). It was concluded that the addition of surface treated poly(methyl methacrylate) fibres in cross-ply arrangement to high strength acrylic resin did not produce an improvement in the impact or transverse strength and cannot be recommended as a method of reinforcement.

An investigation into the transverse and impact strength of "high strength" denture base acrylic resins.

A range of materials, often marketed as high strength resins is available. These materials are often expensive options to conventional heat-cured acrylic resin. The aim of this study was to investigate transverse and impact strength of five "high strength" acrylic resin denture base materials. A conventional heat-cured acrylic resin was used as a control. Specimens were prepared as specified in the International Standard Organization (ISO 1567: 1988) and British standards for the Testing of Denture Base Resins (BS 2487: 1989) and the British Standard Specification for Orthodontic resins (BS 6747: 1987) for transverse bend and impact testing. The impact strength was measured using a Zwick pendulum impact tester and the transverse bend strength measured using a Lloyds Instruments testing machine. The results showed that Metrocryl Hi, Luctitone 199 and N.D.S. Hi all had an impact strength which was significantly higher than the control. For the modulus of rupture, there was a significant difference between Sledgehammer and the other groups. There was no significant difference between the other groups and the control. For the modulus of elasticity, Sledgehammer produced the highest value followed by the control. The remaining four materials had a modulus of elasticity less than the control.

Impregnation Behaviors in Composite Processing

Abstract In the first part of this paper, impregnation was positioned in terms of consolidation in composite processing and theoretical model for impregnation behaviors was presented. Impregnation behaviors were classified using the parameters contained in the model. Calculation for some simple cases was conducted. In the second part, impregnation behaviors of two material groups were experimentally estimated by on-line measurement of tool gap displacement during compression molding for making UD composites. First material group is composed of 4 kinds of thermoplastic composite materials. The other is thermoplastic film stacking with opened and unopened reinforcing fiber tows. Microscopic observation on the cross-section of parts fabricated at various molding time and measurement of transverse bending strength of these parts were also conducted. Based on the theoretical model proposed in the first part and these experimental data, impregnation behaviors of these materials were systematically discussed. The results suggest basic technological ways for attaining good impregnation in thermoplastic composites.

TLP M4

Abstract TLP M4 is a powder metallurgy produced high-speed tool steel with a combination of wear resistance, high impact toughness, and transverse bend strength. This datasheet provides information on composition, physical properties, and hardness as well as fracture toughness. It also includes information on high temperature performance and wear resistance as well as heat treating. Filing Code: TS-586. Producer or source: Timken Latrobe Steel.

Structural Features and Properties of Alloy 84% WC ― 16% Co, Obtained by Hot Pressing in the Solid and Liquid Phases. Part 2. Influence of the Temperature at which the Specimens are Made on Their Physicomechanical Properties

We have studied the changes that occur in the resistivity, the transverse bending strength, and the fracture toughness (cracking resistance) of a hard alloy obtained by hot pressing at about 500 MPa and sintering over a wide range of temperatures (950-1450°C) as well as the how those parameters are affected by solid-phase and liquid-phase annealing. The porosity dependence of the resistivity is shown not to be single-valued. Other factors affect the resistivity, e.g., the degree of particle interaction and the state of the structural components, which vary with the porosity. The resistivity curve for hot-pressed specimens has an inflection in the region of 1200°C. The resistivity increases at a faster rate at lower temperatures. In the temperature range studied the porosity dependence of the transverse bending strength and the fracture toughness is linear: σb = σ0 b(1 − 3.53Θ) and K 1c = K 0 1c (1 − 3.44Θ). Prolonged solid-phase annealing of hot-pressed specimens improves their mechanical properties owing to a decrease in porosity.

The mechanical properties of unidirectional thermoplastic composites manufactured by a micro-braiding technique

‘Micro-braided yarn' has been proposed as a means of overcoming the difficulty of manufacturing long-fiber-reinforced thermoplastic composites. Micro-braided yarn is a processing material system that may be used for complex-shaped composites such as textile structural composites. In this study, unidirectional glass-fiber/PA6-Nylon composites manufactured from micro-braided yarns were molded in order to investigate the effect of the micro-braiding structure and processing conditions on impregnation and mechanical properties. The void content was determined in order to examine the quality of impregnation and this was found to decrease with increasing holding time when the pressure was applied to the preform. Axial and transverse bending tests were carried out. The axial-bending strength was well correlated with the void content. However, the transverse bending strength was affected by both the void content and the dispersion of the glass-fiber bundles.

開繊された強化繊維束の樹脂含浸挙動

The technology for opening tow was applied to the opening of reinforcing fiber tow for thermoplastic composites. The effect of its opening on the impregnation behaviors of matrix resin was inveatigated in comparison with those for unopened tow through experiments and theoretical calculations. On-line measurement of void volume change during compression molding for carbou fiber/nylon 6 composite was carried out. Micro-scopic observation on the cross-section of parts fabricated at several molding time and measurement of transverse bending strength of these parts were also conducted. Based on the theoretical model presented previously, the void volume changes for several molding conditions were simulated under a certain assumptive void pressure-change. All these results show consistently that the tow opening makes the impregnation of matrix resin into the reinforcing fiber much easier.

The influence of impregnation condition on reinforced ethylene-vinyl-acetate elastomer composite

Experiments were conducted to investigate the effect of impregnation conditions on glass fiber-reinforced ethylene–vinyl–acetate elastomer. Both the matrix elastomer resin and reinforcing glass fiber were premixed and compression-molded using a specially constructed mold. The mold prevents the flowing out of the matrix resin during fabrication. The impregnation time was varied between 5 and 25 min. The level of impregnation was measured through the optical micrographs of the cross section, estimation of void contents using the ignition method, and transverse bending strength. The morphology of the fractured surface was studied using scanning electron microscopy (SEM). The results showed that the longer the impregnation time, the lower the void contents. Both the bending modulus and strength increased with increasing impregnation time. The SEM micrograph shows little adhesion between the matrix and the reinforcing glass fiber. © 1996 John Wiley & Sons, Inc.

Effect of geometrical structural parameters on the strength properties of hard alloys based on titanium carbide

Experimental data on the strength properties of titanium carbide hard alloys prepared under different sintering conditions were obtained. The relationship of properties to the geometrical structural parameters is elucidated. It was established that the transverse bend strength increases with decrease in the degree of contact of the carbide grains.