Search Results (1,481)

Textile composites are predestined for crash-loaded lightweight structures due to their adjustable energy absorption capacity, but they can exhibit different types of defects that occur during production (voids) and in operation (fatigue). The influence of such defects, especially the interaction of several defect types on the strain-rate-dependent material behaviour, is still insufficiently researched and can represent a safety risk. Therefore, this paper presents a phenomenological model that can be used to mathematically describe the strain-rate-dependent stress-strain behaviour of nominally defect-free and defect-affected textile composites. An adjunctive damage model in the sense of continuum damage mechanics is introduced, which also considers the interaction of both defect types for the first time. For the model validation, extensive experimental tests on glass fibre non-crimp fabrics reinforced epoxy (GF-NCF/EP) composites are performed. The focus is put on the influence of voids and fatigue-related pre-damage under subsequent tensile loading at strain rates up to 40 s${}^{-1}$. The theoretical studies show a good coincidence with the experimental results. The novel model provides a method for the efficient generation of material maps for numerical highly dynamic crash and impact analyses for defect-free and defective textile composites. As a result, a flexible and practice-oriented model approach is available, which makes a significant contribution to an improved understanding of materials and enables a future defect-tolerant design of textile composites. Full article

The determination of mechanical properties plays a crucial role in utilizing composite materials across multiple engineering disciplines. Recently, there has been substantial interest in employing artificial intelligence, particularly machine learning and deep learning, to accurately predict the mechanical properties of composite materials. This comprehensive review paper examines the applications of artificial intelligence in forecasting the mechanical properties of different types of composites. The review begins with an overview of artificial intelligence and then outlines the process of predicting material properties. The primary focus of this review lies in exploring various machine learning and deep learning techniques employed in predicting the mechanical properties of composites. Furthermore, the review highlights the theoretical foundations, strengths, and weaknesses of each method used for predicting different mechanical properties of composites. Finally, based on the findings, the review discusses key challenges and suggests future research directions in the field of material properties prediction, offering valuable insights for further exploration. This review is intended to serve as a significant reference for researchers engaging in future studies within this domain. Full article

Among the many radiochemical problems, the search for new materials and technologies for the immobilization of radioactive waste remains relevant, and the range continues to change and expand. The possibility of immobilizing the spent chloride electrolyte after the pyrochemical processing of the mixed uranium-plutonium spent nuclear fuel of the new fast reactor BREST-OD-300 on lead coolant into glass-composite phosphate materials synthesized at temperatures of 650–750 °C was studied. The structure of the obtained samples was studied using XRD and SEM/EDS methods. It has been shown that the spent electrolyte simulator components create stable mixed pyrophosphate phases in the glass composite structure. The materials were found to have high hydrolytic stability. This indicates the promise of using phosphate glass composites as materials for the reliable immobilization of the spent electrolyte. Full article

This research evaluates the use of organoclay/alginate hydrogels in removing Acid Yellow 23 in a fixed-bed column and contributes to the application of these composites in the context of the adsorption of anionic dyes that are present in wastewater. An organobentonite (OBent) was synthesized and encapsulated in an alginate matrix, using Ca²⁺ ions as a crosslinking agent. Experiments in fixed-bed columns showed that breakthrough and exhaustion times were longer with increasing bed height, which decreased with increases in flow rate and initial dye concentration. The Thomas, Yoon–Nelson, and Adams–Bohart models were well fitted to the experimental data for the breakthrough curves with high Adj. R² correlation coefficients and low values of χ². The theoretical adsorption capacity of the organobentonite/alginate hydrogel calculated from the Thomas model was 0.50 ± 0.01 mg/g (equivalent to 30.97 mg/g OBent), and this was obtained by using a 15 cm (10.10 g) bed height, 1 mL/min flow rate, and a 45 mg/L input dye concentration. The bed was regenerated with a 0.5 M NaOH solution, and the reuse of the saturated column bed was studied for two adsorption–desorption cycles. The results obtained in this study suggest the potential use of an organoclay/alginate hydrogel for the adsorption of pollutants in continuous systems. Full article

Biodiesel has gained a great deal of attention as a new sustainable energy alternative to petroleum-based fuels. The subsequent increased biodiesel production requires new utilization of glycerol, which is a byproduct of biodiesel synthesis. Photocatalytic biohydrogen generation using ZnO with the aid of simultaneous deposition of copper from an aqueous biomass-derivative glycerol solution was investigated. The effects of the concentration of glycerol solution, Cu ion concentration, and reaction temperature on biohydrogen generation were investigated. The photocatalytic biohydrogen production rate increased as the concentration of aqueous glycerol solution increased, and the observed data could be fitted to the Langmuire–Hinshelwood kinetic models. The photocatalytic H₂ production efficiency with ZnO could be significantly improved by simultaneous Cu deposition. The photocatalytic biohydrogen production rate was dependent on temperature, and increased as the temperature increased. Under the optimal conditions, the photocatalytic H₂ production rate was 72 µmol h⁻¹ g⁻¹ from the aqueous biomass-derivative glycerol solution. Possible mechanisms for the oxidation of glycerol solution and photocatalytic hydrogen generation were proposed. Full article

This research study’s purpose was to evaluate the mechanical and chemical surface treatment methods for self-cured acrylic resin repaired with a resin composite employing a universal adhesive agent. Eighty self-cured acrylic resins were built and designed into eight groups of ten specimens and surface conditioned using sandblasting (SB) and/or with methylmethacrylate monomer (MMA) and/or universal adhesive (UA) as follows: Group 1, non-surface modified; Group 2, SB; Group 3, UA; Group 4, SB + UA; Group 5, MMA; Group 6, SB + MMA; Group 7, MMA + UA; Group 8, SB + MMA + UA. A template was put on the specimen center, and the pushed resin composites. Mechanical testing machinery was used to examine the samples’ shear bond strength (SBS) values. To examine failure patterns, the debonded specimen surfaces were examined using a scanning electron microscope. The one-way ANOVA method was used to evaluate these data, and Tukey’s test was used to determine the significance level (p < 0.05). The highest SBS was obtained in Group 8 (27.47 ± 2.15 MPa); however, it was statistically equivalent to Group 7 (25.85 ± 0.34 MPa). Group 1 (4.45 ± 0.46 MPa) had the lowest SBS, but it was not statistically significant compared to Group 2 (5.26 ± 0.92 MPa). High SBS values were frequently correlated with cohesive patterns. The application of MMA prior to UA is the best method for increasing the SBS between self-cured acrylic resin and resin composite interfaces. However, the use of SB is not significantly different from not using SB. Full article

Nitrogen-containing polyphenylene type polymers containing pyridine rings were synthesized. The polymer-forming reaction is based on the interaction of diacetylarylene and triethylorthoformate with the formation of a pyrylium salt and subsequent treatment of the intermediate product with ammonia. The optimal ratios of the reagents for the formation of the pyridine fragment were determined. The mechanism of the main reaction is discussed. The formation of the pyridine ring and phentriyl (1,3,5-triphenylsubstituted benzene) fragments was confirmed using ¹H NMR data of the example of model reactions. After heating at a temperature of 450 °C, when a more complete polycondensation process occurs, the polymers reach high values of thermal characteristics—10% weight loss in an inert atmosphere corresponds to 600 °C. The structure of the synthesized polymers was confirmed using elemental analysis, IR, XPS, and EPR spectroscopy. The conjugation length in cross-linked polyphenylene pyridines can be controlled by varying the arylene bridge groups between the phentriyl fragments, which opens up opportunities for the development of new composite materials for electrical applications. Full article

Continuous efforts are being made to improve plain concrete compressive strength and ductility by applying carbon, glass fiber, or hybrid-reinforced epoxy resin composites. The investigation centers on analyzing the axial compressive strength and strain, compressive stress–strain behavior, failure morphology, and crack evolution of the reinforced cylinders. Besides the experiments, non-linear finite element analysis was performed using the finite element (FE) package ABAQUS 2021. The test results indicate that carbon fiber triaxial woven fabric (TWF-C) confinement result in the most significant improvement of 118% in compressive stress than the concrete specimens. On the other hand, glass fiber triaxial woven fabric (TWF-G) confinement shows the highest enhancement of 161% in ductility. The mechanical properties of the sample utilizing glass fiber as the weft yarn and carbon fiber as the warp yarn (TWF-GC2) exhibit superior improvements of 22% in compressive stress and 8% in axial strain compared to the sample using glass fiber as the warp yarn and carbon fiber as the weft yarn (TWF-CG2). Samples with glass fiber as weft yarn show gradual cracks during loading, while carbon fiber as weft yarn show instantaneous damage. The numerical finite element models accurately predict the experimental results of the tested specimens in this study. There were 1.2~3% and 5~10% discrepancies for compressive stress and axial strain, respectively, between experimental and FE results. Overall, the results suggest that Triaxial woven fabric confinement is a valuable technique to improve the strength and strain of concrete and that the type of fibers used could be tailored for appropriate performance characteristics. Full article

This article explores using biomass, namely rice husks, as a reinforcement material in thermoplastic copolyester (TPC) composites. Rice husks were subjected to three chemical pretreatments: single-stage sulfuric acid hydrolysis, first-stage sulfuric acid hydrolysis followed by a second-stage methanesulfonic acid (MSA) treatment, and first-stage sulfuric acid hydrolysis followed by a second-stage sodium hydroxide alkali treatment. We studied the effects of these treatments on the rheological, thermal, interfacial, and mechanical properties of composites. The fibers were mixed with polymers at high shear rates and temperatures, and 3D-printed filaments were produced using a desktop 3D printer. The printed parts were analyzed using tensile tests, torque and viscosity measurements, and thermogravimetric analysis to obtain their mechanical, rheological, and thermal properties. SEM imaging was performed to understand the fiber–polymer interface and how it affects the other properties. The results showed that first-stage sulfuric acid hydrolysis followed by a second-stage pretreatment of the fibers with MSA showed better fiber–polymer adhesion and a 20.4% increase in stress at 5% strain, a 30% increase in stress at 50% strain, and a 22.6% increase in the elastic modulus as compared to untreated rice husk composites. These findings indicate that readily available and inexpensive rice husks have significant potential for use in natural fiber-reinforced composites when pretreated using dilute sulfuric acid followed by methane sulfonic acid hydrolysis. Full article

Industrial waste usage in the technology of construction materials is currently in a relevant and promising direction. Materials made of industrial waste have a lower cost and are highly environmentally friendly. The objective of this study is to develop effective compositions of sulfur concrete based on the maximum possible number of various wastes of the local industry for this and to investigate the characteristics of this composite. Test samples of sulfur concrete were made from sulfur, fly ash, mineral aggregates and bitumen additive. The dosages of fly ash, sand and bitumen varied, while the content of sulfur and crushed stone remained constant. The following main characteristics of sulfur concrete were determined: density; compressive strength; and water absorption. Tests of sulfur concrete were carried out after 1 day and 28 days of hardening. The best values of compressive strength (24.8 MPa) and water absorption (0.9%) were recorded for the composition of sulfur concrete at the age of 28 days with the following content of components: sulfur—25%, modified with 4% bitumen of its mass; fly ash—10%; crushed stone—40%; and sand—25%. The optimal composition of modified sulfur concrete showed compressive strength up to 78% more and water absorption up to 53% less than the control composition. The characteristics of the sulfur concrete samples after 28 days of hardening differ slightly from the values after 1 day of hardening (up to 1.8%). An analysis of the structure confirmed the effectiveness of the developed composition of sulfur concrete in comparison with the control. Full article

Nowadays, the additive manufacturing of multifunctional materials is booming. The fused deposition modeling (FDM) process is widely used thanks to the ease with which multimaterial parts can be printed. The main limitation of this process is the mechanical properties of the parts obtained. New continuous-fiber FDM printers significantly improve mechanical properties. Another limitation is the repeatability of the process. This paper proposes to explore the feasibility of printing parts in continuous carbon fiber and using this fiber as an indicator thanks to the electrical properties of the carbon fiber. The placement of the fiber in the part is based on the paths of a strain gauge. The results show that the resistivity evolves linearly during the elastic period. The gauge factor (GF) increases when the number of passes in the manufacturing plane is low, but repeatability is impacted. However, no correlation is possible during the plastic deformation of the sample. For an equivalent length of carbon fiber, it is preferable to have a strategy of superimposing layers of carbon fiber rather than a single-plane strategy. The mechanical properties remain equivalent but the variation in the electrical signal is greater when the layers are superimposed. Full article

Biochar is a carbon-rich solid produced during the thermochemical processes of various biomass feedstocks. As a low-cost and environmentally friendly material, biochar has multiple significant advantages and potentials, and it can replace more expensive synthetic carbon materials for many applications in nanocomposites, energy storage, sensors, and biosensors. Due to biomass feedstock species, reactor types, operating conditions, and the interaction between different factors, the compositions, structure and function, and physicochemical properties of the biochar may vary greatly, traditional trial-and-error experimental approaches are time consuming, expensive, and sometimes impossible. Computer simulations, such as molecular dynamics (MD) simulations, are an alternative and powerful method for characterizing materials. Biomass pyrolysis is one of the most common processes to produce biochar. Since pyrolysis of decomposing biomass into biochar is based on the bond-order chemical reactions (the breakage and formation of bonds during carbonization reactions), an advanced reactive force field (ReaxFF)-based MD method is especially effective in simulating and/or analyzing the biomass pyrolysis process. This paper reviewed the fundamentals of the ReaxFF method and previous research on the characterization of biochar physicochemical properties and the biomass pyrolysis process via MD simulations based on ReaxFF. ReaxFF implicitly describes chemical bonds without requiring quantum mechanics calculations to disclose the complex reaction mechanisms at the nano/micro scale, thereby gaining insight into the carbonization reactions during the biomass pyrolysis process. The biomass pyrolysis and its carbonization reactions, including the reactivity of the major components of biomass, such as cellulose, lignin, and hemicellulose, were discussed. Potential applications of ReaxFF MD were also briefly discussed. MD simulations based on ReaxFF can be an effective method to understand the mechanisms of chemical reactions and to predict and/or improve the structure, functionality, and physicochemical properties of the products. Full article

Due to the advantages over other metallic materials, such as superior corrosion resistance, excellent biocompatibility, and favorable mechanical properties, titanium, its alloys and related composites, are frequently utilized in biomedical applications, particularly in orthopedics and dentistry. This work focuses on developing novel titanium-titanium diboride (TiB₂; ceramic material) composites for dental implants where TiB₂ additions were estimated to be 9 wt.%. In a steel mold, Ti-TiB₂ composites were fabricated using a powder metallurgy technique and sintered for five hours at 1200 °C. Microstructural and chemical properties were analyzed by energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and X-ray diffraction (XRD) to evaluate the impact of the TiB₂ ceramic addition. Compressive strength, Brinell hardness, porosity, and density, among other mechanical and physical properties, were also measured and characterized. It has been found that adding TiB₂ to Ti increases its porosity (35.53%), compressive strength (203.04 MPa), and surface hardness (296.3 kg/mm²) but decreases its density (3.79 gm/cm³). The lightweight and strong composite could be suitable for dental implant applications. Full article

Most concrete employs organic phase change materials (PCMs), although there are different types available for more specialised use. Organic PCMs are the material of choice for concrete due to their greater heat of fusion and lower cost in comparison to other PCMs. Phase transition materials are an example of latent heat storage materials (LHSMs) that may store or release thermal energy at certain temperatures. A phase transition occurs when a solid material changes from a solid state to a liquid state and back again when heat is added or removed. It is common knowledge that adding anything to concrete, including PCMs, will affect its performance. The goal of this review is to detail the ways in which PCMs affect certain concrete features. This overview also looks into the current challenges connected with employing PCMs in concrete. The review demonstrates a number of important findings along with the possible benefits that may pave the way for more research and broader applications of PCMs in construction. More importantly, it has been elucidated that the optimum PCM integrated percentage of 40% has doubled the quantity of thermal energy stored and released in concrete. Compared to conventional concrete, the macro-encapsulated PCMs showed thermal dependability, chemical compatibility, and thermal stability due to delaying temperature peaks. Furthermore, the maximum indoor temperature decreases by 1.85 °C and 3.76 °C in the test room due to the addition of 15% and 30% PCM composite, respectively. Last but not least, incorporating microencapsulated PCM has shown a positive effect on preventing freeze-thaw damage to concrete roads. Full article

The present work aims at studying the effect of the reinforcing fabric areal weight on the mechanical properties of composite laminates in carbon-fiber-reinforced polymers. Three different pre-impregnated 2 × 2 twill weaves, characterized by the different areal weight values of 380, 630, and 800 g/m² were used to produce laminates. These areal weights were selected to represent typical values used in structural application. A hand lay-up technique followed by an autoclave cycle curing was employed to produce the laminates. The desired final thickness of the laminates was obtained by laying-up a different ply number, as a function of the areal weight and thickness of each fabric. Uniaxial tensile and in-plane shear response tests were performed on samples obtained from laminates after curing. Furthermore, the presence of voids in composite materials were detected by performing resin digestion tests. Finally, light optical microscopy and stereomicroscopy analyses allowed observing the different arrangement of the plies in the cross-sections of laminates after curing and evaluating the degree of compaction as a function of the reinforcing fabric used. It was demonstrated that the fabric areal weight significantly affects the mechanical performances of the composite laminates; specifically, the decrease in the areal weight of the twill weave leads to an increase in tensile strength, elastic modulus, and in-plane shear stress, i.e., of about 56.9%, 26.6%, and 55.4%, respectively, if 380 g/m² and 800 g/m² fabrics are compared. These results are crucial for an optimal material selection during the design process for industrial applications and help to better understand composite material behavior. Full article