Strength Properties Of Materials Research Articles

Strength Properties of Composite Board Materials Based on Ligno-Cellulose Fiber, Modified by Steam Explosion Treatment

The article presents the results of using activated lingo-cellulosic material, obtained by the method of steam explosion treatment, as the basis for the production of composite pressed boards without a binder. The influence of steam explosion treatment modes on the physical and chemical properties of the wood pulp product and the strength properties of the resulting board materials is considered.

Discussion of “Reclaimed Lignin-Stabilized Silty Soil: Undrained Shear Strength, Atterberg Limits, and Microstructure Characteristics” by Tao Zhang, Guojun Cai, and Songyu Liu

The discussers read with interest the recent paper by Zhang et al. (2018), which reports on the investigation of the effects of 0–12% lignin additive on some index and shear strength properties of a silty soil material. The use of the fall-cone device to study undrained shear strength variation with moisture content is pleasing to see and shows how the approach is useful for this purpose: namely the study of undrained strength variation. We wish to make the following comments regarding some of the underlying assumptions in the paper by way of offering some other explanations and interpretations for the results obtained.

ИССЛЕДОВАНИЕ АДГЕЗИОННЫХ И ТЕПЛОЗАЩИТНЫХ СВОЙСТВ РЕЗИН НА ОСНОВЕ ЭТИЛЕН-ПРОПИЛЕН-ДИЕНОВЫХ С АРИМИДНЫМ НАПОЛНИТЕЛЕМ

Reinforced materials of the "fabric filler-vulcanized rubber" type may be successfully operated under the condition of the specified adhesive strength at the interface of the "substrate-polymer (rubber) "contact. The article presents theoretical infor-mation about ethylene propylene (EDM) and ethylene-propylene-diene (EPDM) synthetic rubbers, known internationally under the brand name EPDM-monomer, arimide fiber and laboratory research methods. The advantages of using EDM and EPDM in the manufacture of heat-protection coatings are; high heat resistance, low density, good compatibility with fillers (mineral and synthetic), compatibility with epoxy and phenol-formaldehyde resins, belong to coking materials. The article also provides the results of experiments and analysis of the data obtained, namely, the adhesive strength and thermal effect of rubbers based on EPDM with an arimide filler of a non-woven structure. The object of the research was modified heat-protective materials based on EPDM, and the subject of the research was selected rubber compounds based on EPDM and synthetic arimide fiber. To as-sess the physicochemical and thermophysical properties, a derivatographic analysis was performed, which includes TGA and DTA, two vulcanized rubber-woven samples from rubbers of grades 51-1615, 51-2110 together with arimide fiber. For the first time, results were obtained using ethylene-propylene-diene rubbers, including modification with a phenol-formaldehyde resin, which gives a higher erosion resistance when exposed to high-speed heat flow. Analysis of the results of experimental studies has shown that the use of arimide fiber can provide higher strength and thermophysical properties of heat-protective materials. In general, the results obtained may be of practical significance for the development of new-generation products.

An examination of initial structural degradation in tubular braided composites through region-by-region strain analysis

The objective of this study was to characterize the early structural degradation behavior of tubular braided composites (TBCs) under quasi-static tension through direct quantification of the surface strains developed in their yarn-reinforced and unreinforced (resin-rich) material regions. Kevlar-epoxy TBCs with varying braid angles and numbers of yarns were analyzed through quasi-static testing and stereo digital image correlation (DIC) analysis to understand how the yarn-reinforced and resin-rich regions deformed under tensile loads up to the initiation of structural degradation within the braid structure. Structural weakening was confirmed to initiate in the unreinforced, resin-rich regions of the TBC specimens by way of a normal tensile failure mode, as the strains developed within these regions were the first to deviate from a linear-elastic growth trend and also exceed the expected strain to failure of their constituent material. Through two-way full-factorial ANOVA analysis with a 95% confidence interval, the stress required to initiate degradation within these regions was found to depend significantly upon both the quantity and angular orientation of the preform yarns, the former to a markedly lower extent. The maximum strain accumulated in the resin-rich regions upon their degradation was found to not statistically depend on either of these parameters, affirming that it is purely defined by the strength properties of the constituent neat resin material. To provide conservative and repeatable estimates of the stress to failure in TBC structures, it is recommended that this quantity be estimated from both the global stress-strain data of the entire specimen and the local stress-strain data measured exclusively within its resin-rich regions, with the lower of the two taken. Through these means, the relationship between a TBC’s preform geometry and its stress to failure may be optimally modeled using a polynomial regression trend.

The use of inhibited layers to improve mechanical properties of thermoset composite materials

The present paper discusses the research data on strength properties of polymer composite materials using fiberglass reinforced plastic (FRP) as an example. During the process of fiberglass reinforced plastic curing with the use of hot molding, a thermal gradient inevitably appears throughout the material thickness. This phenomenon results in uneven curing of prepreg layers. Internal stress consequently occurs in the material. It is proposed to control the kinetics of binder curing throughout the material thickness by introducing an inhibitor into the various prepreg layers. Multichannel dielectric analysis was used to study the curing kinetics of fiberglass reinforced plastic. It has been found that the time spread for gelation is 8.6 min in the 15-layer sample. The study of strength properties of the obtained samples demonstrates an increase in flexural strength of PCM-modified samples by 12.7% – 17.7% and a reduction in their anisotropy.

Experimental study on aluminium based sandwich composite with polypropylene foam sheet

Sandwich structures have been widely employed to build lightweight components having good mechanical properties and energy absorbing capacity. Aluminum-foam sandwich structures have been increasingly used in a wide range of applications. This work aims in improving the strength and mechanical properties of aluminum materials by the inclusion of polypropylene foam sheets. This paper studies the various characteristics of the Aluminum/PP/Aluminum sandwich composite which is made by compressive moulding. Tensile test, bending test and microhardness tests were carried out to investigate the characteristics of the sandwich composite. Thermal analysis of sandwich composite is carried out and is compared with aluminium panel

Characterization of Borrow Material for Embankment Fill and Capping Layer Based on Their Index and Strength: Case Study on Arbarakate to Gelemso road, W/Harerghe, Ethiopia

The Arba Rekete-Gelemso gravel Road section is affected by the presence of expansive soil, this soil has shrinking and swelling behavior due moisture fluctuation. The main objective of this research work is to investigate the Characterization of Borrow materials for embankment fill and capping layer based on their index and strength properties for Road Construction of the proposed route. In order to achieve the objectives, field investigation and nine (9) samples were also collected from the identified borrow area and laboratory test analysis were performed such as, Atterberg limits, compaction, CBR and percentage of swell tests. ERA‘s and AASHTO’s standard technical specifications have been used to interpret the data by integrating the field with laboratory test results. The subgrade soil of route, having liquid limit value greater than 60% and plastic index value greater than 30% and CBR value less than 5%, at Chainage km 0+000-4+000, 5+900-8+000, 9+400-12+900, 13+500-14+000, 15+000-16+000, 17+100-17+600, 18+500-20+500, 21+500-34+900, and 35+200-47+000 unsuitable. The index and strength properties of the borrow materials fulfill the requirement for embankment fill and subgrade improvements. Finally, all unsuitable subgrade soil along the study route corridor are recommended to remove and replace with suitable and non-expansive subgrade materials, since enormous amount of selected fill materials that fulfill the requirements for subgrade soils improvement are available nearby the study area.

Влияние тепловлажностного воздействия на прочностные свойства полимерных композиционных материалов

Влияние тепловлажностного воздействия на прочностные свойства полимерных композиционных материалов

Joint Work of Cement Concrete and Composite Reinforcement with Periodic Profile Winding

A study of the joint work of cement concrete and material winding fiberglass composite reinforcement with different types of coatings and types of windings was conducted. The type of periodic profile winding is presented, which increases the adhesion of the material of glass fiber reinforcement winding with cement concrete. It has been established that the winding of the periodic profile improves the strength properties of the composite reinforcement material. The influence of aggressive media on the adhesion of fiberglass rods with different types of surface preparation from cement concrete is estimated.

Safety assessment of a dam made of ground materials

The Rogun HPP dam stability from ground materials is studied on the basis of numerical calculations of its spatial stress-strain state. The deformation and strength properties of materials composing the dam body defined in the triaxial compression devices were used in the calculations. Limit values of strength materials properties and controlled values of diagnostic indicators of a dam at which safety of its work is provided are established.

Исследование триботехнических свойств композиционных полимерных материалов в период приработки

Results of research and development of composite polymer materials are presented. The aim of this work was the study and development of new composite polymer materials with optimal performance properties for the working bodies of machines and mechanisms. The surface grinding of the samples was carried out using an eccentric rotary brush according to the procedure previously presented by the authors. Tribological properties of polymeric materials and coatings were determined on a tribometer. The results of the study showed that the degree of influence of fillers on the strength and antifriction properties of composite polymer materials depends on the type and nature of the filler and binder.

Comparison of Some Properties of Selected Non-Wood Plants and Wood Species and Unbleached Kraft Pulps from These Materials

ABSTRACT The different properties of hemp stalks, hemp woody-core, and Miscanthus × giganteus stalks cultivated in Poland and physical properties of unbleached kraft pulps from these materials were compared with the ones of pulps from pine, birch and wheat straw. Research performed showed that in terms of oven-dried material density, bulk density, yield, morphological, structural, and strength properties of pulps, hemp stalks and Miscanthus stalks are more similar to birch and pine than hemp woody-core and wheat straw. Thus, it can be stated that hemp and Miscanthus stalks should be better papermaking fibrous raw materials than hemp woody-core and wheat straw and could be used for the production of a broader range of papers and boards.

Coupled Thermal-Mechanical Progressive Damage Model with Strain and Heating Rate Effects for Lightning Strike Damage Assessment

This paper proposes a progressive damage model incorporating strain and heating rate effects for the prediction of composite specimen damage resulting from simulated lightning strike test conditions. A mature and robust customised failure model has been developed. The method used a scaling factor approach and non-linear degradation models from published works to modify the material moduli, strength and stiffness properties to reflect the effects of combined strain and thermal loading. Hashin/Puck failure criteria was used prior to progressive damage modelling of the material. Each component of the method was benchmarked against appropriate literature. A three stage modelling framework was demonstrated where an initial plasma model predicts specimen surface loads (electrical, thermal, pressure); a coupled thermal-electric model predicts specimen temperature resulting from the electrical load; and a third, dynamic, coupled temperature-displacement, explicit model predicts the material state due to the thermal load, the resulting thermal-expansion and the lightning plasma applied pressure loading. Unprotected specimen damage results were presented for two SAE lightning test Waveforms (B & A); with the results illustrating how thermal and mechanical damage behaviour varied with waveform duration and peak current.

Electric treatment of alumina composite materials

A method of processing alumina composite materials using electric current is presented. Aluminum matrix composites based on aluminum alloy AK12 were obtained in a pass-through vessel with the addition of composite particles to the stream of molten material without the influence of an electric current and with the influence of a current. As a composite additive, graphite enriched with crystalline grade TG-1 and particles of titanium carbide (TiC) were used, the amount of the components being injected was 15 volume percent.Measurements of the mechanical properties of the original AK12 alloy and composite material based on the AK12 alloy with the addition of composite particles carried out without an electric field and with exposure showed that the greatest increase in strength properties of alloys treated with an electric field was recorded for an aluminum matrix composite material with TiC particles, which amounted to 20% for ultimate strength and 24.5% for hardness. An increase in ductility was found in a composite material with a TG-1 composite additive, for it an increase in the relative elongation was 15.6%, while the electric current treatment of the composite material with a filler in the form of TiC did not lead to a change in the relative elongation of the sample material. In general, the increase in the strength properties of an aluminum matrix composite material with titanium carbide particles (TiC), after it was treated with an electric current, turned out to be slightly larger than that of an aluminum matrix composite material with particles of TG-1 enriched crystalline graphite. The physical mechanism of the influence of electric current on the properties of ALCM is given.

An experimental research of the laminated composite plates stability

The article shows the results of experimental studies of stability, supercritical behaviour and fracture of plates of a layered composite material. Composite plates are made of fiberglass layers glued with epoxy resin. To reliably assess the bearing capacity of laminated plates, numerical and experimental methods are used. A methodology for experimental research of the deformation and strength properties of composite materials using testing equipment has been developed. The difference between the critical strength values of three-layer samples and the critical strength of four-layer samples was determined to be 2-3%. Thus, products from composite materials (unmanned aerial vehicles) can be made from three-layer plates to reduce their weight. Models of two-layer, three-layer, and four-layer plates were performed with the ANSYS program. The obtained experimental results were compared with numerical values. The possibility of using experimental data of the mechanical behaviour of layered composite materials in the design and calculation of unmanned aerial vehicles was estimated.

Electret and Strength Properties of Polymeric Materials Based on Epoxy Oligomer and Amine Curing Agents

Electret properties of polymeric materials based on DER-331 epoxy oligomer and amine curing agents, produced in the course of synthesis of the polymer in a constant electric field, were examined. It was shown that the presence of certain polar functional groups and fragments in the structure of the curing agent can both raise the electret characteristics of polymers (by making larger the number of polar groups capable of orientation) and diminish these characteristics (due to steric factors). To obtain polymeric epoxy materials possessing good electret characteristics, it is preferable to use diethylenetriamine as the amine curing agent. The hardness of epoxy polymers is determined by parameters of the network of chemical bonds and by their structural organization. Using N-aminoethylpiperazine in manufacturing polymeric materials based on the epoxy oligomer makes it possible to obtain 3D structures providing a higher hardness owing to the presence of a heterocyclic fragment in the structure of the curing agent. Converting the network polymeric structures to the polarized state results in hardness increases. This is due to the orientation of polar groups, which gives rise to a denser network of physical bonds.

Post Weld Annealing of Welded Joints of Refractory Titanium Alloys VT41 AND VT8-1

Mechanical properties and structure of butt welded pseudo-α-(VT41) and (α + β)-(VT8-1) refractory titanium alloys are studied as applied to electron-beam welding of rotor parts of gas turbine engine compressors. Welded joints of VT8-1 + VT8-1, VT8-1 + VT41 and VT41 + VT41 are studied. The effect of post weld annealing on the short-term and long-term strength and impact strength of matrix metal is studied in the operating temperature range. Partial annealing of welded joints is shown to have a favorable effect on matrix metal and weld material strength properties without a substantial reduction in high-temperature strength. Weld metal ductility remains at a low level, while that of the matrix metal hardly decreases.

Triaxial extension and tension tests on lime-cement-improved clay

This paper presents the results of a series of undrained and drained isotropic consolidated triaxial extension, tension and compression laboratory tests on lime-cement-improved very soft clay. The main objective of these tests was to investigate the material strength and stiffness properties for stress conditions similar to those expected on the passive side of excavations where a retaining structure is supported by Deep Mixing columns. The different stress paths to failure were obtained by varying the directions of the major and minor principal stresses in a conventional triaxial test cell. The undrained tests conducted at low consolidation stresses, corresponding to depths of approximately 0–10 m below the ground surface, revealed significant differences in undrained strength depending on the directions of the major and minor principal stresses, indicating anisotropic material behavior. Based on the undrained triaxial test results, the relationship among the undrained strength, the effective consolidation stress and the over-consolidation ratio (OCR) is presented for different stress paths to failure.The experimental data from the drained tests show that a failure surface comprised of a shear failure function based on the Mohr-Coulomb failure criterion and a tensile failure function based on the tensile strength and the confining stress can be applied for lime-cement-stabilized clay.

Characterisation of post-production raw material from the Raciszyn II deposit as a material suitable for the production of alkaline-activated materials

The clay is the basic raw material used in the production of a wide range of ceramic products. However, global guidelines encourage limiting the consumption of natural resources in the production process. For this reason, research is being conducted in developing technologies that enable the production of full-value products by using post-process materials. The article presents the properties of post-production clay sourced from the Jurassic limestone Raciszyn II deposit. In this study, the results of mineralogical (X-ray diffraction) and chemical (X-ray fluorescence) analysis of post-production raw material will be presented. In addition, the leachability in water and the natural radioactivity of the material were established, which determines the possibility of using the raw material in building applications. It was found that, because of the presence of minerals from the kaolinite group in the post-production raw material from Raciszyn II deposit, it is suitable for the production of alkaline-activated materials. However, it was necessary to determine the temperature range of its thermal treatment. The processes occurring in the post-production raw material during its heating were characterised by means of thermogravimetry, differential thermal analysis and mass spectroscopy thermal analysis-coupled techniques. The compressive strength properties of alkali-activated materials, produced from the post-process material from Raciszyn, analysed after 14 and 28 days of curing, were also presented.

Influence of Reinforcing Plant Fillers on the Strength Properties of Composite Materials with an Ice Matrix

This article describes a method of producing composite materials with an ice matrix from distilled water reinforced with plant fillers of different biological composition and morphology: coniferous needles, wood chips, cedar cone scales, cedar nut shells, luffa, and linen fibers. We studied the bending strength and strain of the composite samples and showed that the reinforcement of the ice matrix with plant fillers makes it possible to control their physical and mechanical properties by creating stronger materials as compared to ice. We identified the quantitative dependences of strength characteristics of the composite materials on the type and composition of the reinforcement component and determined the optimal variants of reinforcing ice with plant substances.