J. Compos. Sci., Volume 7, Issue 12 (December 2023) – 41 articles

Macromolecule entanglements are common in polymers. The first part of this review describes their influence on the properties of entangled polymers. Then, methods for reducing the entanglement density of macromolecule chains are discussed. It has been shown that research on partially disentangled polymers has provided a lot of new information about the relationship between the entangled state and properties of polymers. This research concerns, among others, mechanical and thermal properties and the crystallization process. A special disentangled polymer case, ultra-high-molecular-weight polyethylene, is also discussed. The results of research on polymer composites in which macromolecules were disentangled via processing and composites were produced using already disentangled polymers are presented in particular detail. It has been indicated that such composites and blends of disentangled polymers are promising and will probably be intensively researched in the near future. Full article

Polymer nanocomposites have been of great interest to packaging, energy, molding, and transportation industries due to several favorable properties including a higher resistance to stress and cracking even under flexed conditions, and also a chemical resistance to water, acids, and alkalis. The current work disseminates the studies on the mechanical and thermal properties of the polypropylene HHR102 polymer reinforced with nano dispersoids of silicon dioxide at varied weight fractions. The nanocomposites, fabricated via melt processing followed by injection molding, were tested for tensile strength, % elongation, tensile modulus, and impact toughness. Further, the samples were also subjected to dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) to determine the dynamic storage modulus and thermal stability. The addition of nano-silica in polypropylene HHR102 resulted in enhanced ductility and well-balanced tensile modulus; however, the tensile strength and impact toughness were found to be decreased. On the other hand, the storage modulus was significantly increased for all nano-silica (NS)-containing polypropylene HHR102 matrices. With the increased nano-silica content, the storage modulus was optimal. Further, with the lower weight loss of 30% and 50%, the thermal stability of the increased silica content PP nanocomposites was much affected. However, it improved at a weight loss of 30% for the lower silica content PP nanocomposite (PP-1%NS). The imbibition was found to increase with the increase in NS. The increase in imbibition is attributed to the micro-voids generated during ageing. These micro-voids act as channels for water absorption. Further, the degree of crystallinity of the nanocomposites was decreased as a result of inhibition by the nano-particles on the regular packing of polymer molecules. The structure–property correlations were explicated based on the achieved mechanical properties. Full article

Foam concrete is a popular energy-efficient construction material with a fairly wide range of usage in buildings and structures. Increasing ecological efficiency and reducing construction costs by the application of different types of industrial waste in the manufacturing technology of this composite is a promising direction. The main goal of this study is to investigate the possibility of coal dust (CD) waste inclusion in the technology of energy-efficient cellular concrete produced by foam concrete technology. Test samples of foam concrete were made using coal dust by partially replacing cement in the range of 0–10% in increments of 2%. The following primary characteristics of foam concrete were studied: fluidity of mixtures; compressive strength; density; thermal conductivity of foam concrete. An X-ray diffraction analysis of foam concrete composites was performed, which showed changes in their phase composition when using coal dust as a modifier. Coal dust in rational quantities from 2% to 6% improves the physical and mechanical characteristics of foam concrete and increases the structure uniformity. The optimal values of the foam concrete characteristics were recorded at a dosage of coal dust of 6%. At the same time, the density decreased by 2.3%, the compressive strength increased by 15.6%, and the thermal conductivity coefficient decreased by 8.9% compared to the ordinary composition. The use of the resulting foam concrete is advisable in enclosing structures to create high energy efficiency of buildings and structures due to the improved structure and properties. Full article

This study aims to ascertain the material characteristics that are intrinsic to the prepreg layer within a laminated composite structure. The elastic modulus of the lamina, a primary determinant of composite structural behavior, is the focal point of this analysis. This parameter has been assessed by employing reverse-engineering techniques on a composite composed of sequentially stacked prepregs. The investigation entailed simulating the behavior of the composite under static loads and conducting modal analyses to reflect both static and dynamic conditions. The findings indicate that the elastic modulus values derived from combined tensile and modal analysis simulations exhibit superior accuracy compared to those obtained through tensile simulation alone. Specifically, the maximum prediction error for E₁ (the tensile-direction elastic modulus of one lamina sheet) decreased from 1.17% to 0.28%, and that of E₂ (the transverse-direction elastic modulus of one lamina sheet) decreased from 12.01% to 7.30%. Further simulations incorporating fabrication error variances underscored the critical nature of precise E₂ analysis. The proposed methodology evidenced a more accurate assessment of E₂, underscoring its potential to enhance the reverse-engineering process in composite material design. Full article

This article discusses an effective method for obtaining superconducting composites based on Y₁Ba₂Cu₃O_7-δ (YBCO) by optimizing the total preparation time in comparison with similar scientific works while searching for effective modifying micro-additives. YBCO-based composites were doped with microparticles of aluminum, nickel, and iron. It was established that the initial ratio of green components, heat treatment, and holding time directly affect the qualitative and quantitative formation of the useful superconducting phase Y₁₂₃, which in turn affects the basic superconducting properties of the final material. Full article

The failure of composite laminates under cyclic fatigue loads is complex, as multiple failure mechanisms are in play at different scales and interact with each other. Predicting the remaining fatigue life as well as the residual capacities of a composite laminate or component is crucial, particularly for safety-critical applications. A progressive fatigue model is proposed to describe the catastrophic failure of open-hole laminates under tensile cyclic fatigue. To represent both intra-laminar and inter-laminar damage, a combination of a continuum damage mechanics model (CDM) and a discrete cohesive zone model (CZM) is implemented in the finite element (FE) software Abaqus. The CDM combines fibre- and matrix-dominated S-N curves with the Palmgren–Miner accumulation rule and Hashin’s residual strength to form a fatigue failure criterion differentiating between fibre failure (FF) and matrix failure (MF). The CZM implemented in this work is the CF20 model proposed by NASA. Fatigue cycling is simulated using an external cycle-jump scheme, where the stiffness degradation is conducted between the FE simulations outside of the implicit solver [90/0] s. Glass fibre reinforced polymer (GFRP) open-hole specimens were tested in tensile cyclic fatigue at a load ratio of 0.1. The experiments were reproduced numerically and the results compared. After calibration of a set of parameters based on one load level, the model was able to reproduce the experimental S-N curve very well, predicting a slope of −0.10, while the experimental value was −0.11. The failure sequence of the laminate was also successfully reproduced. The growth of the split from the hole, and its interaction with inter-laminar delamination, was successfully captured. The proposed approach was able to describe the fatigue failure of an open-hole laminate with a minimal set of material inputs using a simplified fatigue damage model while avoiding convergence issues. Full article

This review paper discusses the effect of polymers, especially thermoplastics, in environments with low earth orbits. Space weather in terms of low earth orbits has been characterized into seven main elements, namely microgravity, residual atmosphere, high vacuum, atomic oxygen, ultraviolet and ionization radiation, solar radiation, and space debris. Each element is discussed extensively. Its effect on polymers and composite materials has also been studied. Quantification of these effects can be evaluated by understanding the mechanisms of material degradation caused by each environmental factor along with its synergetic effect. Hence, the design elements to mitigate the material degradation can be identified. Finally, a cause-and-effect diagram (Ishikawa diagram) is designed to characterize the important design elements required to investigate while choosing a material for a satellite’s structure. This will help the designers to develop experimental methodologies to test the composite material for its suitability against the space environment. Some available testing facilities will be discussed. Some potential polymers will also be suggested for further evaluation. Full article

The effect of the melt cooling rate on the atomic ordering of austenite and, as a consequence, on the martensitic transformation of a nonstoichiometric alloy of the Ni-Mn-In system has been studied. In situ TEM observations revealed differences in the mechanism of phase transformations of the alloy subjected to different cooling conditions. It is shown that during quenching a high density of antiphase boundaries (APB) is formed and the alloy is in the austenite–martensitic (10M and 14M) state up to a temperature of 120 K. In a slowly cooled alloy, a lower APB density is observed, and a two-stage transformation, L21/B2 → 10M → 14M, occurs in the range of 150–120 K. Full article

The industrial application of UV curable coatings is being widely commercialized at a rapid pace with very diversified product markets. UV curing has existed for many years now, but the new commercial opportunities emerging for sustainable, and climate friendly technologies have driven demand for photo-curable coating systems. It is primarily attributed to its environmentally friendly solvent-free and energy-efficient method. Precedented UV light curable coatings are being commercialized and numerous lamp sources are being extensively studied. In such an era of predominant research evolving the UV curing technology horizon, we attempt to outline the state of the art, opportunities, and challenges. This contribution attempts to highlight, in a comprehensive way, sustainable UV coating on the basis of recent research advancements, existing challenges and prospective scope in this field. With a set of prerequisite foundational knowledge into UV curable coatings and mechanisms, the review has meticulously looked at the recent research advancements. This review contribution attempts to focus on three aspects: the known science behind UV curing coatings, coupled with the recent advancements, and future opportunities. Full article

Polylactic Acid (PLA) is a biodegradable polymer, but the cost of PLA is not competitive compared to polyolefins. The development of bioplastic composites by blending PLA with spent coffee grounds (SCG) and thermoplastic starch (TPS) is an effective way to reduce the cost of PLA. This study aimed to investigate and evaluate the feasibility of using SCG to develop bioplastic composite materials with a blend of PLA and TPS. Bioplastics were fabricated with various SCG contents (5, 10, 15 wt%). The physical and mechanical characteristics of the bioplastic composite decreased as the SCG content increased owing to the higher aggregation caused by SCG dust. However, the bioplastics manufactured with the addition of SCG exhibited enhanced crystallinity, resulting in enhanced thermal properties compared to the composites without SCG. The best characteristics of bioplastics, obtained with a 5% SCG addition, were as follows: water vapor transmission rate of 1276 g d/m², water vapor permeability (WVP) of 1.86256 × 10⁻⁷ g/ms Pa, Young’s modulus of 420 MPa, elongation of 2.59%, and tensile strength of 5 MPa. Based on the results obtained, it can be concluded that the addition of SCG is not recommended for improving the physical and mechanical properties of bioplastics. However, owing to its large content of organic compounds, SCG represents a promising and low-cost functional material that can be exploited in the development of various value-added products. Full article

In this theoretical study, the electronic, structural, and optical properties of copper-doped zinc oxide (CZO) were investigated using the full-potential linearized enhanced plane wave method (FP-LAPW) based on the density functional theory (DFT). The Tran–Blaha modified Becke–Johnson exchange potential approximation (TB-mBJ) was employed to enhance the accuracy of the electronic structure description. The introduction of copper atoms as donors in the ZnO resulted in a reduction in the material’s band gap from 2.82 eV to 2.72 eV, indicating enhanced conductivity. This reduction was attributed to the Co-3d intra-band transitions, primarily in the spin-down configuration, leading to increased optical absorption in the visible range. The Fermi level of the pure ZnO shifted towards the conduction band, indicating metal-like characteristics in the CZO. Additionally, the CZO nanowires displayed a significant blue shift in their optical properties, suggesting a change in the energy band structure. These findings not only contribute to a deeper understanding of the CZO’s fundamental properties but also open avenues for its potential applications in optoelectronic and photonic devices, where tailored electronic and optical characteristics are crucial. This study underscores the significance of computational techniques in predicting and understanding the behavior of doped semiconductors, offering valuable insights for the design and development of novel materials for advanced electronic applications. Full article

Coordination polymer (CP)-type adsorbents impregnated with ionic liquids that are used to remove phenol from wastewater must be regenerated. A simple washing of the adsorbent releases about 70% from the spent adsorbent. In order to increase and study the phenol release, an electrochemical method was used. For this purpose, an electrochemical commercial graphite electrode was used as the working electrode, and the electrolyte support was a 3% NaCl solution. During the electrochemical investigation, the spent CP was immersed in a saline solution. The PH content in the electrolyte affected the direct electrooxidation (EO); the formation of BQ appeared to be accelerated by a lower concentration and a slower release of PH. After 90 min, an efficiency of PH electrooxidation (EOPH) of 36.22% from Cu-PA and EOPH of 42.14% from Cu-PA-IL, respectively, was achieved. These results were significantly higher than the EOPH of the solution resulting from washing the wasted adsorbent with a saline solution (22.58%). This work highlights the potential for the simultaneous electrooxidation of desorbed PH and the recovery of spent adsorbent in this situation. The number of cycles in which the adsorbent can be used without losing its absorbance ability is three. Full article

In this study, polymer biocomposites based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) PHBV biopolymers with Arbocel C350 SR wood fiber filler with mass contents of 15%, 30%, and 45% were described. Samples for testing were produced using the injection molding process. The shrinkage of the produced composites was determined, as well as the basic mechanical properties on the basis of the uniaxial static tensile test, hardness, and impact tensile test. The dimensional stability of samples was subject to temperature and humidity in the water absorption test. This research was carried out in terms of the problems with composite processing and use of products. This paper contains many remarks and conclusions regarding the processing and exploitation of the tested products, which can be extended to a larger range of cellulose fillers. It was found that it was possible to produce the tested type of composites with a content of up to 45 wt. of filler. However, the mechanical properties of the tested composites made it possible to use them for the production of selected products. These conclusions allow for conducting future research toward the effective use of WPC composites with a PHBV matrix and fibrous fillers of natural origin. Full article

Calcium oxide plays an important role in alumina production by binding SiO₂ from aluminosilicate raw materials (bauxite, nepheline, kaolinite, etc.) in aluminum-free compounds. The efficiency of the hydrochemical technology depends on the activities of calcium oxide or its compounds introduced into the alkaline aluminosilicate slurry. In this paper, we considered the effects of different calcium compounds (calcium carbonate CaCO₃, gypsum CaSO₄·H₂O, calcium oxide CaO and calcium hydroxide Ca(OH)₂), introduced during the hydrothermal stripping of aluminosilicates with alkaline solutions, on the degree of aluminum oxide extraction, with the subsequent production of fillers for composites. Ca(OH)₂ was obtained by the CaO quenching method. Extraction of Al₂O₃ in an alkaline solution was only possible with Ca(OH)₂, and the degree of extraction depended on the conditions used for CaO quenching. The effects of temperature and of the duration of CaO quenching on particle size were investigated. In potassium solution, the best results for Al₂O₃ extraction were obtained using CaSO₄·H₂O gypsum. The obtained solutions were processed using the crystallization method. Full article

The physicochemical modification of the filler allows changing the hydrophilic–hydrophobic properties and effectively influencing the processes occurring at the filler–binder interface, on which the physicomechanical characteristics of composites largely depend. The paper presents studies related to the modification of limestone-based filler effect on the degree of its hydrophobicity and wetting with liquids of different polarity, establishing the relationship between the characteristics of hydrophobized mineral powders and the adsorption capacity in relation to water. Using mechanochemical processing with hydrophobic components GF-1 and GF-2, it was possible to obtain fillers with a sufficiently high content of hydrophobic particles (58.2% and 85.9%, respectively). It was found that the results of the contact angle (123.6° and 114.5°, respectively) and the degree of hydrophobicity do not quite correlate with each other. It was noticed that the contact angle on the powder modified with GF-1 decreases with time. Studies of the powders’ thermal effects wetting of different polarity liquids via microcalorimetry allows us to establish that with an increase in the filler hydrophobicity degree, the integral heat of immersion decreases due to a significant decrease in the probability of chemical interactions between water and powder due to the adsorption of applied surfactants molecules on the limestone active centers. The revealed endothermic effects indicate the occurrence of physical interactions due to non-polar dispersion forces. Differences in the nature of heat release and heat absorption in modified fillers indicate significant differences in the composition and mechanism of action of the used surfactants, which affected the efficiency of hydrophobization. At the same time, a linear dependence of the moisture absorption and moisture indicators, determined by independent experiments, on the degree of hydrophobicity was established. Full article

This comprehensive review explores the multifaceted world of natural fiber applications within the domain of composite materials. Natural fibers are meticulously examined in detail, considering their diverse origins, which encompass plant-derived fibers (cellulose-based), animal-derived fibers (protein-based), and even mineral-derived variations. This review conducts a profound analysis, not only scrutinizing their chemical compositions, intricate structures, and inherent physical properties but also highlighting their wide-ranging applications across various industries. The investigation extends to composites utilizing mineral or polymer matrices, delving into their synergistic interplay and the resulting material properties. Furthermore, this review does not limit itself to the intrinsic attributes of natural fibers but ventures into the realm of innovative enhancements. The exploration encompasses the augmentation of composites through the integration of natural fibers, including the incorporation of nano-fillers, offering a compelling avenue for further research and technological development. In conclusion, this review synthesizes a comprehensive understanding of the pivotal role of natural fibers in the realm of composite materials. It brings together insights from their diverse origins, intrinsic properties, and practical applications across sectors. As the final curtain is drawn, the discourse transcends the present to outline the trajectories of future work in the dynamic arena of natural fiber composites, shedding light on emerging trends that promise to shape the course of scientific and industrial advancements. Full article

Glass-containing materials are widely considered among the most reliable materials for the immobilization of radioactive waste materials. The present work considers the synthesis of glass–ceramic and glass crystalline composite materials based on borosilicate glasses. The synthesis of glass–ceramic materials was carried out by a gradual temperature decrease, followed by crystallization for several hours. Sintering of crushed samples with crystalline components was carried out as an alternative procedure. Porous glasses were produced from glass melts by quenching. After impregnating the resulting porous materials with aqueous solutions of cesium nitrate, compaction of the glass was carried out to form glass crystalline composites. The thermochemical characteristics of the parent glasses were determined using the differential scanning calorimetry method. The phase composition and structure of the glass-containing materials were determined using X-ray phase analysis, X-ray spectral microanalysis, and Raman spectroscopy. Full article

Conducting high-temperature tests on ceramics-containing lithium, which are employed as tritium breeding materials, plays a crucial role in comprehending their ability to withstand degradation and maintain their strength properties throughout operation. From the standpoint of fusion research, it is imperative to grasp these phenomena in order to guarantee the safety and effectiveness of reactors. Additionally, these factors could impact the choice of particular materials and designs for blanket materials. The primary objective of this research is to evaluate alterations in the strength characteristics of ceramics-containing lithium when subjected to high-temperature thermal stability tests, while also preserving the hardness stability and resistance to cracking in ceramics subjected to cyclic tests. Lithium-containing ceramics based on lithium titanate (Li₂TiO₃), lithium orthosilicate (Li₄SiO₄), and lithium methacyrconate (Li₂ZrO₃), having a high structural ordering degree and good strength properties, were chosen as objects for assessing resistance to high-temperature degradation. During the studies, it was discovered that the presence of interphase boundaries in the composition of ceramics linked to the development of impurity phases results in crack resistance growth during long-term high-temperature tests simulating the stress effect on the material. At the same time, an assessment of high-temperature aging as a result of modeling destruction processes showed that ceramics based on lithium metazirconate are the most resistant to degradation of strength properties. By simulating high-temperature aging processes, it became feasible to establish connections between structural alterations resulting from the thermal expansion of the crystal lattice and oxygen migration phenomena occurring at elevated temperatures. These factors collectively contribute to a detrimental reduction in the strength properties of ceramics-containing lithium. Full article

The effects of gamma radiation on the AC electrical properties of highly cross-linked epoxy resin/bisphenol A-based polycarbonate samples have been investigated as a function of concentrations of bisphenol A-based polycarbonate, frequency, and temperature. The composite samples contained different bisphenol A-based polycarbonate concentrations of 0, 4, 8, 10, and 15 by wt%. The gamma irradiation process was performed at different gamma doses of 0, 100, 300, and 500 Gy. The AC electrical properties of the tested samples were studied before and after gamma irradiation within a frequency range of 200 kHz to 1 MHz. The results show that after irradiation, a consistent decrease in complex impedance values ($Z^{\ast }$) was observed, indicating an increase in conductivity due to radiation-induced scission of the composite structure. Dielectric properties, including the dielectric constant (${\epsilon }_{\mathit{r}}$) and dielectric loss (${\epsilon }_{\mathit{i}}$), exhibited an increase with higher doses and higher polycarbonate concentrations, signifying the formation of defect sites and charge carrier trapping. AC electrical conductivity (${\sigma }_{ac}$) displayed a notable rise post irradiation, with temperatures ranging from 30 °C to 110 °C, and higher radiation doses and higher temperatures led to increased conductivity. The activation energy (${ E}_a$) decreased as the radiation dose increased, reflecting structural modifications induced by radiation. Full article

The current work shows the optimization of the preparation of nanosized titanium carbide in situ through mechanical alloying. Metallic titanium powders, along with two carbon sources, carbon nanotubes, and stearic acid, were used to reduce the particle size (around 11 nm) using an SPEX 800 high-energy mill. The combined use of 2 wt % of these carbon sources and n-heptane as a liquid process control agent proved crucial in generating nanoscale powder composites through a simple and scalable synthesis process within a 4 h timeframe. The uses of 20 wt % of both carbon sources were compared to determine the ability of carbon nanotubes to form carbides and the decomposition of process control agent during mechanical milling. The structure of the composites and starting materials were evaluated through X-ray diffraction and Raman spectroscopy, while the morphology features (average particle size and shape) were monitored via scanning electron microscopy and transmission electron microscopy. Full article

Ferrous metallurgy has been and remains one of the main types of production activities that enables humanity to extract, process and produce basic equipment for all types of activities. The growth of ore production as well as the reduction in world reserves of the raw material base have lead to the search for effective methods of processing and preparation of waste for metallurgical processing. The mining and metallurgical sector of the Republic of Kazakhstan, which has its an integrated mining and metallurgical complex with its own coal, iron ore, and energy base, uses iron ores from several deposits. It also includes ash and sludge storage tanks, which store valuable metallurgical waste, such as converter production sludge, rolling scale, and others, the use of which is hindered by the presence of certain harmful impurities in the composition (a rather high content of non-ferrous metals, especially zinc, a high content of oils, etc.). These valuable technological wastes require additional research that may contribute to their use as a charge or as iron-containing components of the charge. Based on the urgency of the tasks of dephosphorylation of iron ores and utilization of human-made waste (converter sludge and rolling scale), studies were conducted to try to eliminate existing problems. The results of the research work make it possible to obtain metals based on prepared pellets with a significantly low phosphorus content; this will enable the use of an oiled rolling scale and converter sludge for the production of a metalized product for steel smelting. The resulting metalized products make it possible to dispose of scale and converter sludge by 70%, and the degree of iron extraction exceeds existing methods by 1–3.5% (92.1–94% vs. 95.6%). Full article

Laser processing is an effective post-treatment method for modifying the structure and improving the properties of cold-sprayed coatings. In the present work, the possibility of fabricating a hard and wear-resistant Ti-based cermet coating by cold spray followed by laser remelting was studied. A mixture of titanium and chromium carbide powders in a ratio of 60/40 wt.% was deposited by cold spray onto a titanium alloy substrate, which ensured the formation of a composite coating with a residual chromium carbide content of about 12–13 wt.%. The optimal values of laser beam power (2 kW) and scanning speed (75 mm/s) leading to the qualitative fusion of the coating with the substrate with minimal porosity and absence of defects were revealed. The microstructure and phase composition of as-sprayed and remelted coatings were examined with SEM, EDS and XRD analysis. It was shown that the phase composition of the as-sprayed coating did not change compared to the feedstock mixture, while the remelted coating was transformed into a β-Ti(Cr) solid solution with uniformly distributed nonstoichiometric TiC_x particles. Due to the change in microstructure and phase composition, the remelted coating was characterized by an attractive combination of higher microhardness (437 HV_0.1) and lower specific wear rate (0.25 × 10⁻³ mm³/N × m) under dry sliding wear conditions compared to the as-sprayed coating and substrate. Laser remelting of the coating resulted in a change in the dominant wear mechanism from oxidative–abrasive to oxidative–adhesive with delamination. Full article

Natural rubber, sourced from Hevea brasiliensis trees mainly in southeast Asia, is a critically important resource for transportation, national security, and medical products, among other uses. The guayule shrub is a domestic alternative source of natural rubber that is emerging with advantages over Hevea since it is well-suited for many medical and consumer applications. Biochar is a sustainable form of carbon made from biomass that is a potential replacement for petroleum-sourced carbon black, the most common filler for rubber composites. The coppiced-wood species hybrid poplar (Populus × canadensis) and Paulownia elongata are both rapidly growing hardwoods that have shown promise as feedstocks for biochar that can be used as fillers in common rubber composites such as Hevea natural rubber, styrene-butadiene, and polybutadiene. In this work, poplar and paulownia biochars were used to partially replace carbon black as filler in guayule rubber composites. Guayule composites with up to 60% of the carbon black replaced with poplar or paulownia biochar had higher tensile strength, elongation, and toughness compared to the 100% carbon black-filled control. These composites would be excellent candidates for rubber applications such as gloves, belts, hoses, and seals, while reducing dependence on fossil fuels and Hevea natural rubber. Full article

Composites materials like jute/epoxy exhibit high hardness and are considered as difficult-to-machine materials. As a result, alternatives to conventional machining become essential to post-process the composites. Accordingly, due to its non-thermal nature, abrasive water jet machining has recently come to be seen as one of the most promising machining methods for composite materials. In the current study, the impact of machining parameters such as traverse speed (TS), standoff distance (SOD) and abrasive mass flow rate (MFR) on machined surface roughness (Ra) has been investigated. In addition, the optimum combination of process parameters to machine a jute fiber-reinforced polymer composite with minimum Ra is predicted. The experimental results are analyzed using Taguchi and Response Surface Methodology (RSM) approaches to determine the optimum set of process parameters to achieve the lowest roughness values. Without making any changes in the machining conditions, the optimum set of values is determined for two conditions by reinforcing the fiber with 45° inclination and 90° inclination. The results reflect the different optimum combinations for each fiber inclination. For 45° fiber inclination, to achieve the minimum Ra value, the predicted combination is TS = 30 mm/min, SOD = 2 mm and MFR = 0.35 kg/min. When the fiber inclination is 90°, the predicted optimum combination is TS = 25 mm/min, SOD = 2 mm, and MFR = 0.35 kg/min. It is evident from the results that the optimum combination will be changed according to the machining conditions as well as material properties. The results confirm the effect of fiber orientation on surface roughness. The specimen with 45° fiber inclination produces a lower Ra with an average of 4.116 µm, and the specimen with 90° fiber inclination generates a higher Ra with an average of 4.961 µm. Full article

Interest in the modification of zirconium-containing ceramics is rooted in their great prospects for application as materials for creating inert matrices of dispersed nuclear fuel, which can replace traditional fuel containing uranium dioxide, as well as increase the degree of its burnup. Moreover, among the variety of different types of ceramics offered, zirconium dioxide is the most promising, since it has higher thermal conductivity values compared to other types of ceramics, as well as low volumetric thermal expansion. Moreover, the key limitations in the application of these types of ceramics as materials for creating inert matrices are polymorphic transformations, which have a negative impact on changes in the properties of ceramics under external influences. The evaluation results of the impact of change in the ZrO₂ ceramics’ phase composition on the radiation damage resistance when subjected to irradiation with heavy ions, comparable in energy to fission fragments, are presented. The objects of study were samples of ZrO₂ ceramics doped with MgO, the variation in the concentration of which leads to an acceleration of the processes of polymorphic transformations during thermal sintering, as well as the formation of a ZrO₂/MgO-type structure with inclusions in the form of MgO grains. The results of the irradiation effect on the stability of the crystal structure of ceramics to deformation swelling due to the accumulation of deformation inclusions showed that ceramics with a monoclinic structure type are the least stable, for which, in the case of high irradiation fluences, the accumulation of deformation distortions leads to polymorphic transformations of the m—ZrO₂ → t—ZrO₂ type. During the evaluation of the irradiation effect on the change in mechanical properties and the softening degree, it was found that phase transformations of the m—ZrO₂ → t—ZrO₂ and t—ZrO₂ → c—ZrO₂ types lead to an increase in crack resistance by 1.5–2.0 times. Meanwhile, the formation of a structure of the ZrO₂/MgO type with inclusions in the form of MgO grains in the interboundary space results in a softening resistance growth by over 7-fold. During tests for determining thermophysical parameters, as well as maintaining stability to crystal structure thermal expansion during prolonged thermal exposure, it was found that phase transformations associated with polymorphic transformations of the t—ZrO₂ → c—ZrO₂ type led to the preservation of the stability of thermophysical properties, even in the case of high irradiation fluences. Full article

In this work, to obtain textile triboelectric layers for wearable flexible triboelectric nanogenerators (TENGs), we used two modes of growing nanostructured zinc oxide (ZnO) arrays on a carbon fabric (CF) using the automatic Successive Ionic Layer Adsorption and Reaction (SILAR) method. To produce a CF/ZnO_nr triboelectric textile with an array of intergrown short ZnO nanorods, we used a pre-coating of carbon fibers with ZnO seed layers. When the ZnO layer was fabricated by automatic SILAR on bare carbon fabric, we obtained the CF/ZnO_ns textile with an array of interconnected ZnO nanosheets 50–100 nm thick. As a proof of concept, we developed and tested two prototypes of flexible vertical contact–separation mode CF/ZnO_nr/PET/ITO and CF/ZnO_ns/PET/ITO TENGs, in which a gap was involuntarily formed between the smooth PET layer and the woven carbon textile coated with nanostructured ZnO films. In pressing tests with a force of ~5 N (pressure ~33 kPa), the CF/ZnO_ns/PET/ITO TENG created a higher open-circuit voltage up to 30 V and a higher maximum surface charge density of 1.3 μC/m². In the successive press–release tests, this TENG showed an output voltage of 3.6 V, a current density of 1.47 μA/cm², and a power density of 1.8 µW/cm², confirming its effectiveness. Full article

Composite booms for solar sails have been prototyped by using innovative smart materials. Shape memory polymer composites (SMPCs) have been manufactured by interposing SMP layers between carbon-fiber-reinforced (CFR) plies. A polyimide membrane has been embedded into the CFR-SMPC frame of the sail during lamination. The sail’s size has been limited to 250 × 250 mm² to allow its testing on Earth. The feasibility of large sail deployments has been shown by prototyping small CFR-SMPC elements to insert only in the folding zones. Numerical simulation by finite element modeling allowed for predicting the presence of wrinkles close to the frame’s vertexes in the cases of large sails under solar radiation pressures. Nevertheless, the frame’s configuration, with SMPC booms at all the edges of the sail membrane, seems to be suitable for drag sails instead of propulsion. On-Earth recovery tests have been performed on 180° folded sails by using flexible heaters. After an initial induction time, the maximum rate was reached with a following drop. In the case of two heaters per folding zone, the angular recovery rate reached the maximum value of about 30 deg/s at the power of 34 W, and full recovery was made in 20 s. Full article

Dry–wet cycling has a significant impact on the mechanical properties of rocks, and a series of problems such as rock collapse can occur in rock masses under long-term dry–wet cycling. Based on this, some mechanical tests were carried out on sandstone under different dry–wet cycles to analyze the evolution law of its physical and mechanical parameters. The results show that the internal connection of the mineral becomes looser, the drying quality of the sample decreases, and the water absorption quality increases gradually under different dry–wet cycles. The peak strength of the sample decreases first and then increases with increasing dry–wet cycles. The change trend of the elastic modulus and deformation modulus with the increase in dry–wet cycles are similar to the peak strength, which is mainly related to the change in the connection between particles. Furthermore, the specimens showed axial tensile failure under uniaxial action. With the increase in dry–wet cycles, the tensile crack on the surface of the specimen increased, and the fracture of the specimen became looser. The specimen exhibited block spalling when the number of dry–wet cycles was eight times. Full article

Banyan aerial root (BAR) powder was prepared from the aerial roots of a Banyan tree to modify epoxy resin using a magnetic stirrer. The modification was performed at different proportions of BAR powder, namely, 2%, 4%, 6%, and 8%, by weight. Composites were fabricated with modified and unmodified resins using a combination of hand lay-up and compression molding processes to evaluate the influence of BAR powders on their mechanical properties. The test results showed that BAR powder incorporation had a positive influence on the mechanical properties of the composites, as an increase in tensile, flexural, and impact strengths was observed, with the highest tensile and flexural properties of 407.81 MPa and 339 MPa, respectively, seen in composites with 4% BAR and the highest impact strength 194.02 kJ/m² observed in the specimen with 6% BAR powder. Though the properties saw a dipping trend at higher weight proportions of the particulate, they were still significantly higher than the properties of laminates prepared with unmodified resin. Gravimetric analysis and Fourier transform infrared spectroscopy (FTIR) on BAR powders confirmed cellulose to be the major constituent, followed by lignin and hemicellulose. A scanning electron microscope was used for studying the failure mechanisms of the laminates. Full article

Three-dimensional printing is a prototyping technique that is widely used in various fields, such as the electrical sector, to produce specific dielectric objects. Our study explores the mechanical and dielectric behavior of polylactic acid (PLA) and plasticized cellulose acetate (CA) blends manufactured via Fused Filament Fabrication (FFF). A preliminary optimization of 3D printing parameters showed that a print speed of 30 mm·s⁻¹ and a print temperature of 215 °C provided the best compromise between print quality and processing time. The dielectric properties were very sensitive to the three main parameters (CA content W_CA, infill ratio, and layer thickness). A Taguchi L9 3^3 experimental design revealed that the infill ratio and W_CA were the main parameters influencing dielectric properties. Increasing the infill ratio and W_CA increased the dielectric constant ε′ and electrical conductivity σ_AC. It would, therefore, be possible to promote the integration of CA in the dielectric domain through 3D printing while counterbalancing its greater polarity by reducing the infill ratio. The dielectric findings are promising for an electrical insulation application. Furthermore, the mechanical findings obtained through dynamic mechanical analysis are discussed. Full article