Decrease In Impact Strength Research Articles

Influence of nano graphene filler on hardness, impact strength and density of glass epoxy composites

AbstractThis study investigates the effects of graphene reinforcement on the hardness and impact strength of glass epoxy composites. Four different materials were examined: pure epoxy (EP), glass epoxy (GE), glass epoxy with 1 wt.% graphene (GE1), and glass epoxy with 2 wt.% graphene (GE2). The results show that the incorporation of graphene significantly enhances the hardness of the composites. Pure epoxy (EP) exhibited a Shore D hardness of 60 and an impact strength of 0.09 J/m2. The glass epoxy (GE) showed a reduction in hardness to 56 but an increased impact strength of 0.15 J/m2 due to the inclusion of 33 wt.% glass fiber. Further addition of graphene in GE1 and GE2 led to notable improvements in hardness, reaching 68 and 74 Shore D, respectively. However, the impact strength displayed a decrease with the inclusion of graphene, with GE1 and GE2 showing values of 0.13 and 0.11 J/m2, respectively. When transitioning from pure epoxy (EP) to glass epoxy (GE), there is a 6.67% decrease in hardness, while the impact strength increases by 66.67%. Introducing 1 wt.% of graphene to the glass epoxy (GE1) results in a 21.43% increase in hardness but a 13.33% decrease in impact strength. Further adding 2 wt.% of graphene (GE2) leads to an additional 8.82% increase in hardness, though the impact strength decreases by 15.38%. X‐ray diffraction (XRD) analysis has revealed nano graphene presence and distribution, while fractography has revealed its effectiveness in enhancing interfacial adhesion and toughening mechanisms. Furthermore, XRD identifies potential changes in crystallinity or phase composition induced by nano graphene incorporation, further elucidating the composite's structure and properties. The study highlights the novel and significant trade‐offs encountered in optimizing the mechanical properties of epoxy‐based composites by incorporating graphene and glass fiber.

Development of PLA-Waste Paper Biocomposites with High Cellulose Content.

In this study, the integration of paper industry waste with high cellulose content into biocomposites of polylactic acid (PLA), a widely used biobased polymer material, was investigated. The PLA/waste biocomposite samples (0-25 wt.%) were manufactured using the extrusion and injection moulding techniques. The mechanical test results showed improvements in terms of tensile properties and a decrease in impact strength as the percentage of residue increased. The melting temperature decreased, and the crystallinity increased in all biocomposites according to the Differential Scanning Calorimetry (DSC) analysis. Water absorption increased proportionally with the percentage of residue, attributed to the higher cellulose content in the biocomposites, determined by Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) techniques. The scanning electron microscopy (SEM) fracture analysis demonstrated effective reinforcement-matrix cohesion, supporting the previously observed behaviour of the analysed materials. This work highlights the potential of using waste from the paper industry as reinforcement in PLA matrices, opening new perspectives for sustainable applications in the framework of the manufacture of composite materials.

Enhancement in mechanical properties of GFRP‐coal‐derived graphene oxide composites by addition of multiwalled carbon nanotubes and halloysite nanotubes: A comparative study

AbstractIn this study, we compare synergistic performance of two different nanofillers, namely halloysite nanotubes (HNT) clay and multiwalled carbon nanotubes (MWCNT), in conjunction with a fixed concentration (0.125 phr) of semi‐anthracite coal‐derived graphene oxide (AC‐GO) on mechanical properties improvement of EGFPs (E‐glass fiber‐based epoxy resin composites). The dispersion of AC‐GO with HNT clay (GO‐H) and AC‐GO with MWCNT (GO‐C) within epoxy matrix was achieved using sonication and homogenization. Further mixture was incorporated into mats of E‐glass fiber employing “vacuum‐assisted resin infusion molding” (VARIM). Significant enhancements (18.3% flexural strength, 14.6% tensile strength, and a slight increase of impact strength (1.8%)) were observed in EGFPs reinforced with GO‐H at 0.50 phr loading of HNT, with an AC‐GO concentration maintained at 0.125 phr. Correspondingly, optimal values for GO‐C reinforced EGFPs at 0.25 phr were 40.3%, 18.7%, and a 10.5% decrease in impact strength, respectively. Analytical techniques such as XRD, FESEM, EDX mapping, and FTIR reveal presence of relatively abundant functionalities and strong interfacial adhesion in GO‐H as well as GO‐C. The cost of HNT clay is approximately 15 times cheaper than industrial‐grade MWCNTs, therefore, these results underscore potential of GO‐H as a very economical nano‐reinforcement alternative to GO‐C for polymer nanocomposites.Highlights 0.50 phr HAGRP improves 18.3% flexural, 14.6% tensile, 1.8% impact strengths. Beyond 0.50 phr HAGRP and 0.25 phr CAGRP, mechanical properties decreased. 0.25 phr CAGRP improves 40.3% flexural, and18.7% tensile strengths. FESEM, FTIR reveal strong interfacial adhesion between nanofillers and epoxy. GO‐H has proven to be an inexpensive reinforcement for polymer nanocomposites.

A STUDY OF PROPERTIES OF AUSTENITIC STEEL IN THE INITIAL STATE

High-manganese steel is used in the rocket, space, and defense industries due to its low specific gravity, stable austenitic structure over a wide temperature range, and ability to strengthen under mechanical deformation. However, the wider application of this steel is hindered by such factors as: instability of mechanical properties in the initial state, tendency to thermal embrittlement and very poor machinability. Therefore, the work is aimed at solving the problems of eliminating the above-mentioned negative factors. Conducted studies of the effect of temperature-time parameters on the structure and properties of steel made it possible to establish the mechanism of thermal embrittlement of 9Г28Ю9МВБ steel. During slow cooling from hot deformation temperatures with speeds of the order of 0.03 º/s in steel, a large number of gray-blue coarse phase particles are released, which are located on the grain boundaries, which causes a sharp decrease in impact viscosity. It was established that in the temperature range of 500-800 ºС, the solid solution disintegrates with the release of particles of the strengthening K-phase - (Fe, Mn)3 AL, Cx. It was determined that the simultaneous decrease in hardness and impact strength in the temperature range of 750-950ºС provides a significant improvement in machinability. The lowest values of mechanical properties are achieved during aging at 700 ºС, the improvement of machinability in this case is maximal compared to exposure to other temperatures. So, for example, with an increase in the temperature of isothermal holding at 650ºС for 35 hours. machinability improves by almost 1.7 times, and for the same time at 700 ºС – by 2.4 times. When the holding temperature is increased to 950ºС for 35 hours. the machinability of steel increases only 1.6 times, which is due to the less intense decomposition of the saturated solid solution. Significant anisotropy of mechanical properties is formed as a result of the development of liquid chemical heterogeneity and its imitation during further thermomechanical processing. The value of the coefficient of anisotropy in sample bars of different grades of initial steel reaches values from 1.5 for a bar with a cross section of 105x105 mm to 3.9 units for a bar with a diameter of 120 mm. The study of the influence of the annealing temperature on the homogeneity of austenitic steel made it possible to develop a mode of heat treatment of austenitic steel 9Г28Ю9МВБ, which consists of heating to 1250°С, holding for 2 hours. at this temperature and subsequent cooling in water, in order to fix a homogeneous supersaturated solid solution. After such heat treatment, the striated microchemical heterogeneity is significantly reduced, the anisotropy coefficient does not exceed 1.1 units for all types of steel assortment.

Material recycling of acrylonitrile butadiene styrene (ABS) from wiring devices using mechanical recycling

Plastics play a significant role in various sectors by offering advantages such as durability, cost-effectiveness, and lightweight properties. However, the extensive production and consumption of plastics create significant environmental threats, leading to high carbon footprints, global warming, and the accumulation of hard-to-recycle waste. This study explores innovative recycling technologies, focusing on the circular economy and zero waste strategies. In line with this scope, the study aims to conduct research on the reuse of coated plastic materials in production, specifically selecting ABS materials that are difficult to recycle. In the study, wiring devices were prepared using 70% raw ABS (Acrylonitrile Butadiene Styrene) material and 30% recycled ABS (rABS) material, with this cycle being repeated three times. Experiments have been conducted to evaluate the suitability and performance of recycled ABS material for mass production. The results have revealed a slight decrease in tensile strength and impact strength compared to raw ABS material, yet significant mechanical performance has been maintained, thus demonstrating the viability of rABS in preserving product quality throughout successive recycling processes.

Mechanical behavior of epoxy resin with graphite additive subjected to water absorption

Abstract Epoxy resin-based composites find extensive applications across various industries due to their unique mechanical properties. They are commonly used in gas and petrochemical industries for pipes and fittings in transmission lines. The primary objective of this study is to investigate changes in the mechanical properties of epoxy resin-based composites under different environmental moisture conditions. To achieve this, epoxy resin with varying weight percentages of graphite additive (0, 5, 10, 15, and 25 wt%) was used. The water absorption characteristics of the specimens were assessed by immersing samples in potable water (PW), distilled water (DW), a 10 vol% alkaline solution (NaCl), and a 10 vol% acidic solution (HCl), following ASTM standards. Both dry and wet samples were examined for various mechanical strengths. The results indicate that, for all weight percentages of graphite additive, water absorption follows the increasing order: NaCl < PW < DW < HCl, as compared to the blank resin case. In terms of mechanical testing, increasing the weight percentage of graphite additive resulted in a 24 % decrease in Barcol hardness and a 39 % decrease in impact strength, while the hot deflection temperature (HDT) increased for 5 wt% and showed no significant effects for the other cases.

Mechanical and Thermal Properties of Aged Helmet Outer Shells Made of Acrylonitrile-Butadiene-Styrene

Acrylonitrile-butadiene-styrene (ABS) material is widely used as a protective rigid shell and impact absorber in bike helmets, providing vital protection against head injuries under specific working conditions. However, ABS aging in helmets could affect the safety factor of helmets and shorten the service life. Exploring the transformation during aging process for real assembled helmets made of ABS out shells is crucial for the investigation and fabrication of high performance helmets. Herein, the effect of long-term aging on the physical properties of practical helmets made of ABS outer shells has been discussed systematically. Four different types of helmets were subjected to different aging conditions, i.e., outdoor environment, ultraviolet exposure, hot air, and humid-heat conditions. The impact property and stiffness tests were carried out as a function of aging time and aging conditions. The measured helmets were capable of meeting engineering tolerances when aged under outdoor, ultraviolet, and hot air conditions, and could deliver competitive mechanical performance to their pristine helmets. Yet, after aging under humid-heat for 800 h, the helmets showed an obvious decrease in impact strength, gloss, and stiffness. The influence of different aging conditions was further investigated by thermal and spectral characterizations. The study might provide some valuable advice for helmet performance evaluation.

Effect of SiC addition in fabrication of Al/SiC metal matrix composite by stir casting

Aluminum alloys find extensive application in aerospace and automobile industries due to their advantageous attributes: low density, commendable mechanical properties, superior corrosion resistance, wear resistance, and a lower thermal coefficient of expansion compared to traditional metals and alloys. These materials boast excellent mechanical properties while maintaining a relatively cost-effective production, rendering them highly desirable across various scientific and technological applications. The objective of developing metal matrix composite materials is to combine the favorable characteristics of both metals and ceramics. This study focuses on investigating the behavior of Aluminum alloy 6063 combined with SiC composite produced through the stir casting method. A different percentage (3% & 5%) of SiC is added with Al6063, and the specimens were fabricated by a stir-casting process. Tensile tests, Hardness Tests, and impact test were conducted on the specimens obtained from the stir-casting process. The result showed that there is an increase in hardness and decrease in tensile and impact strength upon the addition of SiC with Al6063 to fabricate metal matrix composite.

The search for rigid, tough polyesters with high T g - renewable aromatic polyesters with high isosorbide content.

Renewable polyesters with a good balance between impact strength and elastic modulus (stiffness) are not very common, especially when combined with high glass transition temperature (T g). Achieving such high performance properties would enable the substitution of high performance polymers like ABS and polycarbonate with chemically recyclable polyesters from bio-based or recycled sources. One of the challenges in developing these materials is to select the right composition of the right monomers/comonomer ratios and making these materials with high molecular weight, which can be challenging since some of the most promising rigid diols, such as isosorbide, are unreactive. This study comprises aromatic polyesters from (potentially) renewable monomers, using bio-based isosorbide as a means to increase their T g and to inhibit their crystallization, while using flexible co-diols to improve impact strength. To incorporate a high amount of isosorbide into the targeted polyesters, we used the synthesis method with reactive phenolic solvents previously developed in our group. The selected compositions display high T g's (>90 °C) and high tensile modulus (>1850 MPa). We show that more polar monomers such as the stiffer 2,5-furandicarboxylic acid (FDCA) and diethylene glycol cause high stiffness but decreased impact strength (<5 kJ m-2). Combining terephthalic acid and isosorbide with more flexible diols like 1,4-butanediol, 1,4-cyclohexanedimethanol (CHDM) and 1,3-propanediol provides a better balance, including the combination of high tensile modulus (>1850 MPa) and high impact strength (>10 kJ m-2).

Mechanical and dynamic mechanical behavior of 3D printed waste slate particles filled acrylonitrile butadiene styrene composites

This study analyses the feasibility of utilizing waste slate particles as a strengthening component in affordable 3D-printed composite materials to address environmental issues associated with waste management. Composite filaments were created by incorporating waste slate particles (5 %, 10 %, and 15 % by weight) into an acrylonitrile butadiene styrene (ABS) matrix and subsequently evaluated for mechanical properties. A twin-screw extruder obtained the composite filaments, while test samples were produced using a 3D printer by fused deposition modelling. The developed composites have a gradual variation in evaluated properties, about an 8 % increment in hardness, and a 40 % increment in flexural and tensile modulus was noted on the inclusion of 15 wt% of waste slate particles in the ABS matrix. The composites filled with 10 wt% and 5 wt% waste slate particles exhibited the maximum flexural strength (65.24 MPa) and tensile strength (42.11 MPa), respectively. These values were 5 % and 8 % higher than those of unfilled ABS. Furthermore, it was shown that the ABS matrix saw a decrease in elongation and impact strength as the dosage of slate particles increased. The fractured surface morphology indicated that filament breaking, filler pullout, and the creation of voids between neighbouring layers were the primary causes of material failure. The dynamic mechanical analysis (DMA) results show the reinforcing effect of slate particles by an increase of storage modulus with 13 % at 35 °C for the composite with 10 wt% slate particles and 20 % for that with 15 wt% slate particles. DMA results analyzed the composite's adhesion factor, degree of entanglement, reinforcement efficiency factor, and effectiveness factor to clarify the reinforcing mechanism of slate particles. The study determines that the most effective utilization of waste slate particles in an ABS matrix is achieved by including 10 wt%. The results of this study enhance the concept of recycling waste slate powder and reveal the potential for their utilization in several industries, including the aerospace, automotive, healthcare, and architectural sectors of 3D printing.

Brittle fracture resistance of the Fe–17%Ni alloy of extraterrestrial origin (the chinga meteorite) under static and dynamic loading

The values of conditional yield strength, impact strength, and the parameters of static and dynamic crack resistance of the Chinga meteorite substance (the Fe–17%Ni alloy) are determined by mechanical testing for uniaxial tension and static bending and instrumented impact testing of V-notched prismatic samples at temperatures ranging between 20 and −196 °С. It is shown that the dynamic nature of material loading according to the three-point bending scheme contributes to a noticeable decrease in impact strength (KCV) and crack propagation energy (KCT) during low-temperature tests (−196 °С) and the appearance of brittle quasi-cleavage sites on the fracture surface. On the contrary, as the test temperatures decrease from room temperature to the temperature of liquid nitrogen during the static tests of the Chinga meteorite samples with induced cracks, the parameter of static crack resistance KC (K1C) increases and the fracture surface of the samples after low-temperature testing is characterized by predominantly viscous dimpled topography.

Mechanical, Thermal Properties of Virgin, Recycled and Mixed High-Density Polyethylene Matrices and Wood Plastic Composites with Plywood Sanding Dust

Virgin high-density polyethylene (vHDPE), recycled (rHDPE), and mixed vHDPE/rHDPE matrices and wood plastic composites based on these mixtures + 50 wt.% of plywood sanding dust (PSD) and 3 wt.% coupling agent maleated polyethylene (MAPE) physical-mechanical properties (tensile, flexural strength and modulus, impact strength, and microhardness) were investigated. It was observed that all defined properties depend on the content of rHDPE in the pure polymer matrix and corresponding WPCs. Tensile strength and modulus decreased a bit, but flexural modulus actually had no changes. At the same time, a decrease in impact strength and a significant increase (up to 2 times) in microhardness are observed. From all the investigated matrices, the most perspective seems to be the matrix with a vHDPE/rHDPE ratio of 75/25, whose mechanical properties are acceptable for the preparation of the WPCs based on plywood sanding dust. The compatibilization possibilities tests of different mixed matrices done by the DSC method in the air showed that the mixed vHDPE/rHDPE compositions compatibility is sufficiently good at different proportions. For all mixed matrices, only one relatively symmetric band with one peak of melting was observed. Differential scanning calorimetry (DSC) tests in an inert environment showed that during the first heating cycle, HDPE components are only partially compatible (two peaks of melting temperatures are possible to fix). On the contrary, after the cooling and crystallization processes, during the second heating of the same sample, these two bands completely merge, and like in the air, only one maximum melting temperature peak was observed. The values of thermal oxidation temperature and melting temperature are the highest for virgin vHDPE but the lowest for rHDPE. The values of all corresponding parameters of mixed matrices reduce proportionally with an increase in rHDPE content in the mixtures.

Thermosetting polymer composites: Manufacturing and properties study

Abstract In the proposed study, TiC is used in different sizes (i.e., 70–150 nm and 200–250 μm) and different ratios (e.g., 0, 10, 20, and 30 wt%) to reinforce the epoxy matrix. Micro- or nano-epoxy–TiC mixtures are poured into molds that have been prepared. The results obtained show a significant improvement in hardness, impact, creep, and tensile strength when the hard particles of nano- and micro-TiC are increased up to 20 wt%. This is due to the good dispersion of the TiC powder with minimal agglomeration and air bubbles. In addition, the results obtained show a decrease in hardness, impact, creep, and tensile strength when the ratio of the hard particles of nano- and micro-TiC is increased to 30 wt% due to agglomeration and air bubbles, which create a path for cracks to propagate. The results of the hardness, impact, creep, and tensile strength tests when 20 wt% nano-TiC composite specimens are used are 22.4, 67.55 J·m−2, 0.0132, and 34.7 MPa, respectively. These results show higher values than other composite specimens. A pin-on-disc wear testing process with various sliding lengths is used to analyze wear behavior. The maximum wear resistance of the 10 wt% of micro-epoxy–TiC composites is found at a load of 5 N and a 100 m sliding distance. Optical microscopy shows small scratches on the 10 wt% micro-epoxy–TiC composite specimens in comparison with the 10 wt% nano-epoxy–TiC composites at a load of 5 N and a 200 m sliding distance.

Fabrication, characterization and optimal selection of aluminium alloy 8011 composites reinforced with B 4 C-aloe vera ash

The aim of this study is to determine the use of B 4 C along with AVA as economical reinforcements to improve the mechanical properties of aluminium alloy 8011. The purpose of this investigation is the development of cost-effective hybrid metal matrix composites. The present investigation assessed the mechanical characteristics of Al-8011 alloy, Al-8011/3AVA, Al-8011/4B 4 C, Al-8011/2.5B 4 C/2.5AVA, and Al-8011/3B 4 C/3AVA composites, which were manufactured through stir-casting techniques. Scanning electron microscope (SEM) imaging with an energy-dispersive spectroscope (EDS) was performed on the fabricated composites to confirm the presence of reinforcements, and the images revealed a uniform distribution of reinforcements in the matrix. The density of the composite decreased with an increase in weight % of AVA-B 4 C in comparison with that of matrix aluminum alloy 8011. Results obtained for tensile strength and hardness exhibit the optimal results from adding 3 wt.% B 4 C with 3 wt.% AVA. The present paper also investigates the application of three multiple criteria decision-making (MCDM) methodological approaches to select the best option.

Numerical investigation of flow and heat transfer behavior on vortex cooling with an optimal convergent coolant chamber for different nozzle aspect ratio arrangement mode

A computational model including convergent coolant chamber, nozzles and vortex chamber is established. The vortex cooling flow and thermal exchange features are investigated under different nozzle aspect ratio arrangement mode based on an optimal convergent coolant chamber. The nozzle aspect ratio arrangement mode consists of two parts, namely eight nozzle aspect ratio sizes and three kinds of nozzle aspect ratio axial variations. Results indicate that the erosion velocity increases due to the smaller windward area with the increasing nozzle size. The convergent coolant chamber makes the mass flow and pressure increases, the reflux phenomenon appears. And the increasing nozzle size leads to the first increase and then decrease with high pressure and Nusselt number area. For the nozzle aspect ratio arranged from high to low, the airflow stiffness and turbulent kinetic energy at the sixth nozzle are the largest, the thermal transfer feature enhances. For the nozzle aspect ratio arranged from low to high, the airflow impact strength and heat exchange characteristic decreases. But the drag coefficient is minimal that has a positive effect on flow features. The thermal exchange capacity is the highest with the nozzle aspect ratio 2.0. Consequently, this study can provide reference for gas turbine design.

Thermal and Mechanical Properties of Biocomposites Based on Polylactide and Tall Wheatgrass.

Biocomposites based on polylactic acid (PLA), tall wheatgrass (TWG), and hemp (H) were made by injection molding. The article discusses the impact of the agrofiller content on the composite properties, including thermal (DSC, DMA, and TG) and mechanical characteristics (tensile modulus, tensile strength, and impact strength). Generally, the introduction of a plant filler into the polylactide matrix reduced the thermal resistance of the resulting composites. Plant fillers influenced primarily the cold crystallization process, probably due to their nucleating properties. The addition of fillers to the PLA matrix resulted in an increased storage modulus across all tested temperatures compared to pure PLA. In the case of a composite with 50% of plant fillers, it was almost 118%. The mechanical properties of the tested composites depended significantly on the amount of plant filler used. It was observed that adding 50% of plant filler to PLA led to a twofold increase in tensile modulus and a decrease in tensile strength and impact strength by an average of 23 and 70%, respectively. It was determined that composites incorporating tall wheatgrass (TWG) particles exhibited a slightly elevated tensile modulus while showcasing a marginally reduced strength and impact resistance in comparison to composites containing hemp (H) components.

Recycling PET Bottles for 3D-Printing Filament: Effect of Chain Extender

This study investigates the effect of a chain extender on the properties of recycled polyethylene terephthalate (rPET) for 3D printing filament. The research focuses on the melt flow index (MFI), mechanical properties, thermal behavior, and crystallinity of rPET blends with varying chain extender concentrations. MFI analysis reveals that the viscosity of rPET is influenced by the grade and sources of the PET bottles. The addition of the chain extender decreases MFI, indicating increased viscosity. Mechanical testing shows a slight decrease in impact strength with increasing chain extender concentration, suggesting the presence of limitations or constraints within the material. Thermal analysis demonstrates that the chain extender elevates the glass transition temperature (Tg) and melting temperature (Tm) of rPET, indicating enhanced rigidity and thermal resistance. However, the crystallinity (Xc) decreases as the chain extender disrupts the regular packing of polymer chains within the crystalline regions. These findings provide valuable insights into the influence of the chain extender on the properties of rPET for 3D printing filament. The research contributes to the development of sustainable manufacturing practices and promotes the utilization of recycled materials in additive manufacturing applications, furthering the goals of the circular economy and environmental sustainability.

Effect of Rice Husk and Wood Flour on the Structural, Mechanical, and Fire-Retardant Characteristics of Recycled High-Density Polyethylene.

Given the rising consumption of plastic products, it is becoming imperative to prioritize the recycling of plastic items as a solution to reducing plastic waste and environmental pollution. In this context, this research focuses on assessing the impact of incorporating rice husk and wood flour into recycled high-density polyethylene (rec-HDPE) to analyze its mechanical properties, flammability, and thermal stability. The combined rec-HDPE content of wood flour and rice husk varied between 0% and 20%. The rec-HDPE content of maleic anhydride grafted polyethylene (MAPE) was fixed at 3%. Mechanical characteristics such as flexural, tensile, and impact strengths were assessed. Cone calorimetry (CC) tests, limited oxygen index (LOI) tests, and horizontal and vertical burning tests were performed to determine the flammability or fire retardancy of these composites. On the other hand, to characterize the thermal characteristics of these composites, thermogravimetric analysis (TGA) was used. To further characterize the fluctuation in these characteristics, scanning electron microscopy (SEM) and infrared spectroscopy (FTIR) studies were carried out. The mechanical characteristics were found to be increased in response to adding rice husk or wood flour. An 8% increase in tensile strength and a 20% increase in elastic modulus enhancement were recorded for a 20% rice husk-added composite. SEM revealed the reason for the variation in tensile properties, based on the extent of agglomeration and the extent of uniform distribution of fillers in rec-HDPE. Following these lines, the 20% rice husk-added composite also showed a maximum increase of around 6% in its flexural strength and a maximum increase of 50% in its flexural modulus. A decrease in impact strength was recorded for rice husk and wood flour-reinforced composites, compared with unreinforced rec-HDPE. Hybrid composites displayed a lack of mechanical strength due to changes in their nature. FTIR tests were performed for a much more elaborate analysis to confirm these results. Twenty percent of rice husk-added rec-HDPE displayed the best thermal properties that were tested, based on TGA and derivative thermogravimetric (DTG) analysis. This 20% composite also displayed the best fire-retardancy characteristics according to UL 94 tests, cone calorimetry tests, and limited oxygen index tests, due to the barrier created by the silica protective layer. These tests demonstrated that the incorporation of both fillers-rice husk and wood flour-effectively enhanced the thermal, mechanical, and fire-retardant attributes of recycled HDPE.

Geri Dönüştürülmüş EPS ve Epoksi Kullanılarak Üretilen Kompozit Malzemeler: Sürdürülebilirlik ve Performansın Birleşimi

Epoxy composites are high-strength and lightweight materials created by combining epoxy matrix with reinforcing materials. Such composites have a wide range of applications in aviation, automotive, energy, and many other industrial sectors. In this study, the effects of surface-coated expanded polystyrene (rEPS) bubbles added to epoxy matrix at different ratios (%1, %3, %7, %11, and %14) on material properties were investigated. Material properties such as density, hardness, surface gloss at a 60° angle, and Charpy impact strength were measured according to varying rEPS ratios. The results showed that rEPS bubbles reduced density, thereby reducing the weight of the material, affected surface gloss, and decreased impact strength. There was no significant difference in hardness values, but impact strength decreased with increasing rEPS content. The effects of homogeneous distribution of rEPS bubbles on material properties were examined, and it was emphasized that the use of rEPS should be optimized with appropriate production processes. This study has been an important step in understanding the performance of rEPS in epoxy composite materials and has provided a foundation for future research.

Structural Anisotropy Parameters’ Effect on the Low-Temperature Impact Strength of Alloy Steels in Rolled Products

The present work is devoted to the study of the influence of the parameters of the structural anisotropy of rolled products on the low-temperature impact strength of alloyed steels. A quantitative metallographic analysis of the microstructure of rolled steel samples obtained after testing for low-temperature toughness was carried out. It was established that the main reason for the decrease in the low-temperature impact strength of rolled steel samples is a highly developed segregation band enriched with carbon films formed at the stage of steelmaking conversion in violation of the technology of continuous casting of steel. The microstructural analysis of rolled stock samples was used in the work, and studies of the fracture surface of rolled stock samples were carried out with a scanning electron microscope using X-ray microanalysis methods. The studies carried out showed that the metallurgical quality of sheets of one heat, as well as individual samples within one sheet, varied over a wide range, from satisfactory to unacceptably low. It was established that the main reason for the decreasing low-temperature impact strength of rolled products was a highly developed segregation band enriched with carbon films, formed at the stage of steelmaking in case of violation of the continuous casting of steel technology. The multivariate statistical analysis carried out showed that only the size of the segregation band has an effect on the low-temperature impact strength of 10 mm thick rolled coil samples.