Strength Properties Of Materials Research Articles

CONDUCTIVE POLYMER COMPOSITE MATERIALS BASED ON FURAN POLYIMINES FOR BIPOLAR FUEL CELL PLATES

Conductive polymer composite materials for bipolar fuel cell plates with a polymer electrolyte membrane have been successfully prepared using 2,5-diformylfuran synthesized from plant biomass. The composites were prepared using a conductive filler (natural graphite) and polyimines from 2,5-diformylfuran and aromatic and aliphatic diamines (p-phenylenediamine, meta-toluenediamine, and hexamethylenediamine). The effect of polyimine content and its type on the electrically conductive and strength properties of materials has been studied. It is shown that the electrical conductivity of the composite increases with a decrease in the content of the polymer binder, while its mechanical properties change in the reverse order. The best materials were made using polyimine based on 2,5-diformylfuran and meta-toluenediamine (MTDA). The lowest value of interfacial contact resistance (0.01 Ohm·cm2) was shown by composites with 45% vol. binder content, and the highest mechanical strength (compressive and bending 21.8 and 32 MPa, respectively), containing 85% vol. polyimine. Sample MTDA-75 has demonstrated an optimal combination of electrical conductivity and mechanical properties. The interfacial contact resistance of the composite was 0.04 Ohm·cm2, and the strength was 15 and 22.5 MPa for compression and bending, respectively. Thus, composites based on polyimines from 2,5-diformylfuran and various diamines and natural graphite as an electrically conductive filler demonstrate great potential for the production of bipolar fuel cell plates with a polymer electrolyte membrane, and correspond to the strategic direction for the development of materials with minimal carbon footprint. For citation: Kataria Y.V., Klushin V.A., Kashparova V.P., Tokarev D.V., Smirnova N.V. Conductive polymer composite materials based on furan polyimines for bipolar fuel cell plates. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 3. P. 93-99. DOI: 10.6060/ivkkt.20236603.6766.

Application of the Improved POA-RF Model in Predicting the Strength and Energy Absorption Property of a Novel Aseismic Rubber-Concrete Material.

The application of aseismic materials in foundation engineering structures is an inevitable trend and research hotspot of earthquake resistance, especially in tunnel engineering. In this study, the pelican optimization algorithm (POA) is improved using the Latin hypercube sampling (LHS) method and the Chaotic mapping (CM) method to optimize the random forest (RF) model for predicting the aseismic performance of a novel aseismic rubber-concrete material. Seventy uniaxial compression tests and seventy impact tests were conducted to quantify this aseismic material performance, i.e., strength and energy absorption properties and four other artificial intelligence models were generated to compare the predictive performance with the proposed hybrid RF models. The performance evaluation results showed that the LHSPOA-RF model has the best prediction performance among all the models for predicting the strength and energy absorption property of this novel aseismic concrete material in both the training and testing phases (R2: 0.9800 and 0.9108, VAF: 98.0005% and 91.0880%, RMSE: 0.7057 and 1.9128, MAE: 0.4461 and 0.7364; R2: 0.9857 and 0.9065, VAF: 98.5909% and 91.3652%, RMSE: 0.5781 and 1.8814, MAE: 0.4233 and 0.9913). In addition, the sensitive analysis results indicated that the rubber and cement are the most important parameters for predicting the strength and energy absorption properties, respectively. Accordingly, the improved POA-RF model not only is proven as an effective method to predict the strength and energy absorption properties of aseismic materials, but also this hybrid model provides a new idea for assessing other aseismic performances in the field of tunnel engineering.

The Effect of Few-Layer Graphene on the Complex of Hardness, Strength, and Thermo Physical Properties of Polymer Composite Materials Produced by Digital Light Processing (DLP) 3D Printing.

The results of studying the effect of particles of few-layer graphene (FLG) synthesized by self-propagating high-temperature synthesis (SHS) on the complex of strength and thermo physical properties of polymer composite products obtained by digital light processing (DLP) 3D printing are presented. It was discovered to achieve an increase in thermophysical and strength parameters of polymers modified by FLG compared with samples made on the unmodified base resin. This result was achieved due to low defectiveness, namely the absence of Stone-Wales defects in the structure of FLG due to the homogeneous distribution of FLG over the volume of the polymer in the form of highly dispersed aggregates. It was possible to increase hardness by 120%, bending strength by 102%, Charpy impact strength by 205%, and thermal conductivity at 25 °C by 572% at concentrations of few-layer graphene of no more than 2 wt. %.

Correlation between lamina directions and the mechanical characteristics of laminated bamboo composite for ship structure

Abstract With the increased emphasis on the use of recyclable bio-based materials and further understanding of the mechanical properties of laminated bamboo, the development of a new generation of low-cost bamboo-based composites for ship structure has generated a significant interest. Laminated bamboo composites comprising Apus bamboo (Gigantochloa apus) and Waru fiber at different layer orientations were investigated to obtain the mechanical characteristics. The influence of different laminate directions was studied through several methods of mechanical testing, including impact tests using ASTM D256, bending tests using ASTM D7264, and tensile tests using ASTM D3039. Results showed that material strength properties could be improved by using on-axis direction (0°). The bamboo composites with unidirectional (0°) laminate direction exhibited superior mechanical properties to bidirectional laminate directions (45°/−45° and 0°/90°). The addition of Waru fiber improved the mechanical properties of the currently developed material; that is, bending strength increased by about 3.17–14.18% and tensile strength was in the range of 4.88–20.28%. Only those composites with 0° and 0°/90° layer orientations fulfilled the Indonesian Bureau Classification strength threshold.

КЭ моделирование микрогеометрических параметров композитов для оценки их упруго-прочностных свойств

The article presents the results of theoretical, finite-element and experimental determination of the elastic and strength properties of composite materials (CM) based on a metal matrix. The material in question is unidirectional magnesium carbon. Finite element modeling was carried out in linear and nonlinear formulation. The influence of surface defects of carbon fiber on the strength of the composite as a whole is analyzed. The results of the study showed the need to take into account the micro-geometric parameters of the structure and surface defects of reinforcing fibers when determining the strength properties of metal matrix composites. As a result of the research, a new technique for modeling CMs was obtained, which makes it possible to obtain refined mechanical characteristics of composites at the stage of design calculations

Determination of the heat-retaining capacity of layered materials for shoe lining by the method of mathematical planning of the experiment

A layered composite material for shoes was obtained by the adhesive bonding method. The middle layer of the material consists of a non-woven material made from a mixture of camel and sheep wool, the top and bottom layers consist of cotton jersey, and a polymer adhesive is located between the layers. The layers are bonded by thermal duplication at a temperature of 150±5°C for 2.0±0.2 minutes. As an optimization parameter, the heat-retaining capacity of the material was chosen depending on the thickness, surface density and percentage of camel wool. The strength and thermophysical properties of the layered material are determined.

Experimental study on cracking behavior of concrete containing hole defects

Cavity often exists in the mass concrete when insufficient vibration occurs. These defects play an important role in the failure mechanism of concrete. Cracking behavior of surface flaws in concrete is widely investigated, while research on failure mechanism of internal flaws is limited because it is difficult to cut internal flaws in specimens and cannot capture the cracking processes of internal flaws through direct observations. In this study, a novel method for preparing concrete samples with embedded flaws is first proposed by volatilization of camphor. AE and CT techniques are adopted to investigate the internal damage failure behavior of hollowed concrete. Experimental results demonstrate that internal hole defects result in a reduction of strength and deformation properties of concrete materials. The peak strength, crack initiation stress, and deformation properties of hollowed concrete specimen decrease with the cavity diameters. Since hole defects induce high stress concentration which exacerbates crack initiation, AE events of specimen with an internal cavity occurred much earlier than the case of intact specimen. The ultimate failure modes of concretes are dominated by tension failure. For intact specimens, tension cracks mainly happen near to the boundaries of specimens. While for hollowed specimens, tension cracks initiated at the cavity perimeter, which then propagated to the boundaries of specimens.

Study of finite fracture of the micro contact on the friction interface induced by stress waves

Frictional interface commonly exist in nature and kinds of materials. The dynamic behavior of the frictional interface has a profound impact on the macro strength and other properties of materials. This paper mainly studies the influence of finite fracture of the micro contact the interface under stress wave loading theoretically and simulatively. Based on the micro contact fracture mechanism of friction, a two-dimensional interface friction model including a triangular micro bulge is established with linear elastic constitutive relationship and D-P failure criterion. The results show that the interaction of the incoming stress disturbance and the micro bulge will induce the fracture of the bulge, and with the decrease of the inclination angle of the micro-contact, the fracture position of the triangular micro contact gradually moves upward from the root, and a crack propagating towards the matrix occurs in the top corner of the triangle. Moreover, in the micro process of fracture, a three wave profile centered on the fracture surface: longitudinal wave, transverse wave and interface wave, will be generated A new interesting phenomenon is that at the moment of loading, a micro stress disturbance is produced synchronously from the interface and propagates to the substrate in the form of longitudinal wave. More comparative examples and analysis show that the mechanism of this disturbance is related to the overall gravity micro adjustment acting on the interface. This work connects fracture and wave, and reveals the finite fracture of micro contact of the friction interface and wave effect, which is expected to provide an effective way for earthquake prediction, so as to advance the earthquake prediction time.

Analysis of the limiting states of cylindrical elastic-plastic shells under tension and combined loading by internal pressure and tension

The elastic-plastic deformation, limiting states and supercritical behavior of cylindrical shells under tension and combined loading by internal pressure and tension to failure are studied theoretically and experimentally. This problem is characterized by the occurrence of large strains, shape changes and, as a result, an inhomogeneous stress-strain state. In the numerical solution of such problems, the problem arises of constructing true stress-strain curves of materials. In this regard, to study the deformation and strength properties of materials, it is important to use an experimental-computational approach, which makes it possible to take into account the non-uniaxiality and inhomogeneous of the stress-strain state without accepting simplifying hypotheses. The paper presents a new efficient algorithm for constructing a true stress-strain curve, which is based on the procedure of nonlinear extrapolation of the curve. Such an algorithm, in the process of direct numerical solution of the problem, consistently constructs a stress-strain curve without using repeated direct calculations, which significantly (at times) increases its efficiency. Based on the experimental-computational approach, the true stress-strain curves for solid rods and shells made of 10KhSND and 10G2FBYu steels were determined under tension and combined loading by internal pressure and tension to failure. The failure of shells under tension occurs at lower (at times) values of true strain than solid rods. Significant differences in true stresses and strains at the moment of failure are due to different localization of deformation of solid rods and shells after the loss of stability of plastic deformation in tension. It is shown numerically and experimentally that after loss of stability of plastic deformation according to Considerer in tension, the cylindrical shell contains two forms of loss of stability until the moment of failure. The first form of loss of stability, as in solid rods, is characterized by localization of deformations along the diameter of the sample in the form of a neck, and the second form is characterized by localization of deformations along the thickness of the sample, which determines the final stage of failure. Under the action of internal pressure on the shell, the first form of loss of stability of plastic deformation degenerates with the formation of a neck inside the shell, and only the form of loss of stability is observed, caused by the localization of deformations along the thickness of the shell.

EVALUATION OF THE THERMAL AND MOISTURE AGING INFLUENCE IN AGGRESSIVE ENVIRONMENTS ON THE CHANGE IN THE OF THE MECHANICAL BEHAVIOR OF FIBERGLASS BY A SHORT BEAM BENDING TESTS BASED ON ACOUSTIC EMISSION TECHNIQUE

The work is aimed at experimental research and description of the mechanical behavior and degradation of the fibrous structural composite material strength properties during thermal and moisture aging in aggressive (operational) environments of different duration and temperatures. The object of the study was STEF structural fiberglass. STEF is a laminated fiberglass reinforced plastic obtained by hot pressing of glass fabric impregnated with a thermosetting binder based on combined epoxy and phenol-formaldehyde resins. After preliminary aging under various temperature-time conditions, fiberglass samples were tested at normal temperature for interlayer shear. To study the defect initiation and propagation during the deformation of fiberglass after preliminary aging under various temperature-time conditions and environments, the acoustic emission method is used in this work, which makes it possible to study the deformation stage structure and track the processes associated with the formation of defects in the structure of the fibrous composite. Influence of various media, such as industrial water, sea water and machine oil, at different durations (15, 30, 45 days) and temperatures (22°, 60° и 90 °С) on the processes of composite destruction and the implementation of various mechanisms damage accumulation during quasi-static interlaminar shear tests were obtained and analyzed. The paper presents the test results obtained by the acoustic emission signals processing. The data illustrating the stages of damage accumulation are presented and described, and the main mechanisms of damage to the composite structure under loading are analyzed. The results of a study of the microstructure of samples obtained using a stereomicroscope before and after thermal and moisture aging in aggressive media are described.

Mechanical Strength and Thermal Properties of Cement Concrete Containing Waste Materials as Substitutes for Fine Aggregate.

The increasing volume of waste and the requirements of sustainable development are the reasons for the research on new waste management concepts. The research results presented in this paper show the effect of recycled aggregate on the selected properties of cement concrete. The aggregates obtained from three types of wastes are tested: recycled concrete paving, crushed ceramic bricks, and burnt sewage sludges. The recycled aggregates replaced 25% and 50% of the volume of the fine aggregate. The tested aggregates worsen the concrete mixes' consistency and decrease, to some extent, the compressive strength of the concrete. However, the tensile splitting strength of the concrete with recycled aggregates is similar to that of the reference concrete. Using recycled aggregates worsens the tightness of the concrete, which manifests itself by increasing water penetration depth. The thermal properties of concrete are slightly affected by the type and content of the recycled aggregate. Considering the expected improvement in recycled aggregate processing, they can be an alternative to natural aggregates. Using recycled aggregates in cement concrete requires extensive studies to search for ways to increase their possible content without worsening concrete performance.

Study of the limiting parameters of deep drawing of sheet blanks made of heat-resistant copper alloys

This article studies the mechanism of thin-walled workpiece deep drawing in the mould with a conical die and determines the forming limit state that occurs at the time of the bottom detachment in the radius part of the punch when stresses in the meridional direction reach their maximum value. This condition is determined by a decrease in the workpiece edge size at the stage of slow material hardening and a decrease in the workpiece flange area that are main factors hindering the process. This condition makes it possible to establish a criterion used to determine the limiting drawing ratio (ratio of the diameter of the workpiece to the diameter of the part), namely: equality of meridional stresses in the punch radius rounding area and the material tensile strength. The paper establishes the effect of the workpiece material strength properties, friction and die taper on the limiting drawing ratio. A change in the plastic and strength properties of the BrKh08 heat-resistant copper alloy (tensile strength, yield strength) does not affect the material hardening constant values and practically does not affect the limiting drawing ratio. The paper uses a comprehensive research method including theoretical analysis and modeling in the ANSYS/LS-DYNA software with input data for the 1.35 mm thick workpiece 100 mm in diameter made of BrKh08. The article presents computer simulation stages indicating main process parameters such as the workpiece material model, mechanical properties, type of elements, kinematic loads, conditions of contact interaction between elements, etc. Process simulation results confirmed theoretical conclusions necessary for the process implementation without part defects.

Printability, Thermal and Compressive Strength Properties of Cementitious Materials: A Comparative Study with Silica Fume and Limestone

Over the past decade, 3D printing in the construction industry has received worldwide attention and developed rapidly. The research and development of cement and concrete products has also become quite well-established over the years, while other sustainable materials receive considerably lower attention in comparison. This study aims to investigate the influence of the two most commonly used sustainable cementitious materials i.e., silica fume and limestone powder, on printability, thermal and mechanical properties of fly ash-Portland cement blends. Ternary blends containing Portland cement, fly ash and silica fume or limestone powder are prepared, whereas phase change material (PCM) is introduced to improve the thermal behavior. Based on the rheological properties and concurrent 3D concrete printing, improved buildability of the modified mixtures is linked to their static yield stress. Anisotropic mechanical properties are observed for 3D printed specimens, while cast specimens exhibit a maximum 41% higher compressive strength due to better material compaction. It is clear from the results that addition of silica fume and limestone powder ranged from 5% to 10%, reducing the anisotropic mechanical properties (maximum 71% and 68% reduction in anisotropic factor, respectively) in the printed specimens. The PCM addition ranged from 5% to 10% and improved thermal performance of the mixtures, as measured by a decrease in thermal conductivity (9% and 13%) and an increase in volumetric heat capacity (9% and 10%), respectively. However, the PCM-containing mixtures show around 29% reduction in compressive strength, compared to the control specimen, which necessitates new material design considering matrix strengthening methods.

Utilizing nano-SiO2 for modifying the microstructure, strength and transport properties of sustainable cementitious materials with waste concrete powder

Using waste concrete powder as an alternative binder in green cementitious materials contributes to reduce the number of construction and demolition waste, and developing an effective method to modify the performance of waste concrete powder blended cementitious materials is necessary. The influences of nano-SiO2 at 0–3% dosage on cementitious materials containing waste concrete powder as partial cement replacement (0–50%), under a ratio of 1:2 for both water-to-binder and binder-to-sand, were investigated in this study with the aspects of micro-structure and macro-performance. The results illustrated that mixing waste concrete powder negatively impacted the hydration reaction and micro-structure of cement paste; however, the mix of nano-SiO2 promoted the secondary hydration reaction and refined pore diameter of waste concrete powder mixed paste. Mixing nano-SiO2 raised the drying shrinkage but reduced the water loss of paste including waste concrete powder. The replacement of cement by waste concrete powder caused the reduction in compressive strength of paste. But at a fixed substitution level of waste concrete powder in paste, the compressive strength rose with the increment of nano-SiO2 content up to 3%. The transport properties rose as waste concrete powder was incorporated in mortar, but the mix of nano-SiO2 significantly reduced the transport properties of waste concrete powder incorporated mortar. Particularly, the effects of nano-SiO2 addition on the decrease in water absorption became more distinct as high content of waste concrete powder was blended. Optimizing the content of waste concrete powder and nano-SiO2 can obtain green cementitious materials owning good strength and low transport properties.

Preparation and characterization of vacuum insulation panels with hybrid composite core materials of bamboo and glass fiber

Thermal insulation materials of vacuum insulation panels (VIPs) are manufactured utilizing an efficient and cost-effective hybrid multi-level network composite core material made from natural and sustainable bamboo fiber (BF) as a raw material and glass fiber (GF) as a reinforcing agent. The morphological, textural structural, gas permeability, and tensile strength properties of the core materials, as well as the thermal insulation performance of VIP, are examined. The results showed that both the bamboo and glass fibers are uniformly dispersed in the core material and achieved a three-dimensional (3D) network structure. The inclusion of glass fiber may significantly alter the core material's structure, resulting in a considerable decrease in the thermal conductivity of VIP. VIP constructed entirely of bamboo fiber BGF0 has relatively high thermal conductivities of 12.62 mW/(m·K), which can be reduced to 4.81 mW/(m·K) while maintaining excellent aging performance by using hybrid composite core material BGF50.

PHYSICAL-TECHNICAL PROPERTIES OF VERMICULITE MINERAL DETERMINED BASED ON EXPERIMENTS AND ANALYTICAL PHYSICAL MODELING. Part 2

In order to develop technologies and technological equipment for processing vermiculite concentrates and conglomerates including sungulite-vermiculite raw materials, it is necessary to define strength, optical and aerodynamic properties of the above-mentioned materials. This paper gives new topical and classified information about these properties obtained by experiments and analytical physical modelling. The results gained by the author of the present paper and other authors supplement existing data about physical properties and constants of vermiculite as building and refractory material with new topical information.

Flexural strength of Epoxy resin and Bagasse fiber reinforced composite materials

In this research, we are going to take out to investigate flexural strength and tensile strength properties of composite material with the using of epoxy resin and bagasse fibre in the powder form. These composites are bonded using epoxy resin and hardener mixed in appropriate volume. This composite was prepared with using bagasse fibre in powder form and the bagasse fibre powder used with different ratio in each material which are prepared and we found the high strength at the using 5gm bagasse fibre powder in both of Tensile and Flexural strength. Here for preparing specimen using Hand layup method. It can be use in more way because rare future of the environmentally friendly, waste utilization, good strength, bio-degradability and alternative for plastic.

Use of automatic tensile testing machines for assessing the strength properties of packaging materials for baked confectionery products

The authors conducted this study to assess the influence of the strength properties of packaging materials for baked confectionery products on the tensile strength, fracture strength, and elongation level. The purpose of this study was to evaluate the mechanical properties (impact strength, fracture strength, and distance to fracture). The paper presents a brief overview of modern methods of functional and operational properties control for polymer packaging materials used for food products and describes their features. The objects of the study were samples of packaging for gingerbread purchased from trade organizations. It has been shown that quality control of polymer packaging materials for food is key in determining the possibility of their intended use. The test results allow evaluating the possibilities and limitations, optimizing the technological process, and obtaining high-quality packaging. In conclusion, the authors give recommendations to gingerbread manufacturers to increase the competitiveness of the product and meet consumer demand.

Comparison of the strength and structural properties of the specimens made of EOS PH1 stainless steel of additive manufacturing and 30KhGSA hardened steel of traditional production

Nowadays, promising and dynamically developing additive manufacturing of complex parts for small-scale production actively succeeds traditional technologies in many industries including aircraft engineering. A method of selective laser fusing also finds effective application along with a well-known methods of additive manufacturing like selective laser sintering, laser metal deposition, plasma-jet hard-facing and electron beam melting etc. The results of comparing the structural, mechanical and tensile strength properties of materials used for manufacturing complex-shaped products by additive and traditional methods revealed the advantage of additive manufacturing which is the basis for their introduction into industry. The goal of the study is a comparative study of the microstructure, mechanical characteristics, fatigue life and fatigue fracture of the specimens made of EOS PH1 stainless steel produced by additive manufacturing and 30KhGSA hardened steel specimens obtained by a traditional technology. Fatigue resistance tests of the specimens were carried out in conditions of uniaxial longitudinal stretching. The microstructural features of the microsections of the cross sections of the samples were studied using stereomicroscope and scanning electron microscopy. Fractographic study of the macro- and micro fracture patterns of the specimens was carried out to identify the structural features of the fractures, fracture nuclei and their correlation with the microstructural imperfections. It is shown that selective laser melting technology used for manufacturing EOS PH1 stainless steel specimens, provides production of the specimens with a rather high tensile strength characteristics comparable to the characteristics of 30KhGSA hardened steel specimens. Therefore, EOS PH1 stainless steel has a great potential as a material for manufacturing parts and products that have high requirements for the strength, hardness and fatigue life.

Lateritic Soil Improvement Using Lime and MOFIC

This study investigates the effects of mucilage from Opuntia ficus-indica cladode (MOFIC), a bio-modifier, on Lime-stabilized Lateritic soil's durability and index features. Specifically, this research assessed the alterations to the Atterberg limits, compaction characteristics, California bearing ratio (CBR), index values and the unconfined compressive strength (UCS) properties of the soil samples and the stabilised samples through laboratory experiments. Lime + MOFIC was added to the soil at 0%, 2%, 4%, 8%, 12% and 16% wt (%) of soil. The result confirms alteration in the index and strength characteristics of the soil upon the addition of MOFIC to the Lime-treated Lateritic soil. The geotechnical characteristics of the soil improved from a subgrade soil to a subbase material upon the addition of 2% of LIME + MOFIC; with the presence of Lime + MOFIC at 2–4%, the bearing capacity of the soil improved from a subgrade material to a subbase material according to the Nigerian General Specification. The highest CBR value in Lime-stabilised was 56%, while the CBR value of Lime + MOFIC-stabilised soil was 70%. This represents a 20% increment in CBR. The presence of polysaccharides in MOFIC enhanced the soil binding attributes of the Lime and hence accelerated the strength properties of the soil. The promotion of green construction and reduction in environmental impacts of using Lime motivates the use of MOFIC in the study. Based on the result of the experimental research, MOFIC is thereby recommended as an eco-friendly alternative for enhancing engineering properties of pavements interlayers. The addition of MOFIC improved the index and strength properties of pavement interlayer material in road construction.