J. Compos. Sci., Volume 7, Issue 9 (September 2023) – 59 articles

Different cuprous oxide (Cu₂O) particle forms, including the octahedron, truncated octahedron, cube, and star-like forms, are synthesized through chemical reduction under different reaction conditions. The correlation between the morphology and the catalytic activity of hydrogen evolution reactions (HERs) is investigated. It is discovered that the Cu₂O particles with a higher 111/100 facets (r) ratio have a higher oxidation resistance and higher activity in HER catalysis, as supported by the density functional theory (DFT) calculation results. This improvement is attributed to the fact that more Cu⁺ terminated atoms on facet 111 provide more active sites, as measured using their electroactive area, as well as the lower H₂ adsorption energy on that facet. To enhance Cu₂O’s HER performance, cuprous oxide particles are deposited on reduced graphene oxide (rGO) through a hydrothermal method. XPS and XRD show a CuO layer on the composite surface, which reduces the Cu₂O corrosion in the reaction. Overall, Cu₂O/rGO composites exhibit a better particle distribution, increased active sites, and improved charge separation. The best electrocatalyst in this study is the Cu₂O/rGO with a star-shaped form, with an overpotential of −458 mV. Its improved performance is attributed to the presence of unsaturated active sites with a higher reactivity, such as the edges and corners. SEM studies of this composite after catalysis indicate that Cu₂O undergoes structural reconstruction during the reaction and reaches a more stable structure. Full article

Managing disposable waste surgical face masks and plastic made from polyethylene (PE) resin is a real challenge. Thus, these are considered a great threat to the environment. Generally, surgical face masks are made of microplastic made of polypropylene materials. Both polypropylene and PE are not easily decomposable in the soil. Consequently, the presence of these waste materials can have detrimental effects on terrestrial and aquatic ecosystems, exacerbating the ongoing crisis faced by the animal kingdom and the broader biosphere. Hence, it is imperative to identify alternate and efficient methods for waste management. Given its significant economic importance, the construction industry holds a prominent position among many industries globally. Consequently, waste masks within the construction sector might assume a crucial role in mitigating plastic pollution. Concrete, one of the most widely used construction materials, is being adapted with various waste materials as the partial or complete substitutes for natural constituents, such as cement and aggregates. This study focused on using different percentages of used COVID-19 surgical masks in fiber form and PE as partial replacements of natural coarse aggregates in producing sustainable concrete. Mask fibers were used in concrete production at percentages of 0%, 0.5%, 1%, 1.5%, and 2% of the total volume of concrete. Similarly, PE aggregates replaced the coarse aggregates by volume at 0%, 5%, 10%, and 15% in concrete. The results showed that the strength of concrete reduced as the percentages of mask fiber and PE aggregates increased. However, the strength and crack-bridging capability of mask concrete are still acceptable for some structural and non-structural applications. The results obtained from this research could also help engineers to design sustainable concrete materials with mask fibers. Full article

Optoelectronic functional composite materials with porous structures are of great importance in various fields. A hybrid composite (SnP@SiA) composed of (trans-dihydroxo)(5,10,15,20-tetraphenylporphyrinato)tin(IV) (SnP) in silica aerogel (SiA) was successfully fabricated through the reaction of SnP with silanol groups of SiA in the presence of hexamethyldisilazane (HMDS). SnP@SiA was then characterized using various instrumental techniques. The zeta potential for SnP@SiA (−11.62 mV) was found to be less negative than that for SiA (−18.26 mV), indicating that the surface of SnP@SiA is covered by hydrophobic species such as SnP and trimethylsilyl groups. The Brunauer–Emmett–Teller (BET) surface area, pore volume, and average pore size of SnP@SiA are 697.07 m²/g, 1.69 cm³/g, and 8.45 nm, respectively, making it a suitable composite for catalytic applications. SnP@SiA, a photocatalyst with high porosity and a large surface area, yields promising performance in the photodegradation of acid orange 7 (AO7) under visible light irradiation in aqueous solution. This hybrid composite exhibited the desirable properties of aerogels along with the photoelectronic features of porphyrins. Therefore, this porphyrin-imbedded mesoporous material has valuable potential in various applications such as photocatalysis, light energy conversion, biochemical sensors, and gas storage. Full article

The new xMnAs/(1 − x)PMN–PT (x = 0.2, 0.3) multicaloric composites, consisting of the modified PMN–PT-based relaxor-type ferroelectric ceramics and ferromagnetic compound of MnAs were fabricated, and their structure, magnetic, dielectric properties, and caloric effects were studied. Both components of the multicaloric composite have phase transition temperatures around 315 K, and large electrocaloric (~0.27 K at 20 kV/cm) and magnetocaloric (~13 K at 5 T) effects around this temperature were observed. As expected, composite samples exhibit a decrease in magnetocaloric effect (<1.4 K at 4 T) in comparison with an initial MnAs magnetic component (6.7 K at 4 T), but some interesting phenomena associated with magnetoelectric interaction between ferromagnetic and ferroelectric components were observed. Thus, a composite with x = 0.2 exhibits a double maximum in isothermal magnetic entropy changes, while a composite with x = 0.3 demonstrates behavior more similar to MnAs. Based on the results of experiments, the model of the multicaloric effect in an MnAs/PMN–PT composite was developed and different scenario observations of multicaloric response were modeled. In the framework of the proposed model, it was shown that boosting of caloric effect could be achieved by (1) compilation of ferromagnetic and ferroelectric components with large caloric effects in selected mass ratio and phase transition temperature; and (2) choosing of magnetic and electric field coapplying protocol. The 0.3MnAs/0.7PMN–PT composite was concluded to be the optimal multicaloric composite and a phase shift ∆φ = −π/4 between applied manetic fields can provide a synergetic caloric effect at a working point of 316 K. Full article

The arrangement of a water thermal accumulator (WTA) containing phase change materials (PCM) is presented and analyzed. The hot or cool water is used as a working body. The accumulator contains two concentric cylindrical tubes. The inner tube is used for hot or cool water flowing, while the volume between the inner and outer tubes is filled with PCM. The thermal energy in the accumulator is stored as a result of flowing the hot water through the inner tube due to the phase transition in PCM. This accumulated energy can be extracted from PCM as a result of flowing the cool water through the inner tube. For the enhancement of the thermal conduction coefficient, the PCM is doped with the nanocarbon particles having a thermal conductivity coefficient exceeding that of PCM by 4–5 orders of magnitude. The thermal balance of the accumulator is calculated on the basis of the solution of the time-dependent heat conduction equation by taking into account the heat absorbed and released as a result of the phase transition as well as the convection thermal exchange in the melted PCM. The calculation results determine the interconnection between the thermal conductivity of PCM and the characteristic time of thermal exchange between PCM and the working body. The calculations indicate that the characteristic thermal exchange time decreases as the thermal conduction coefficient enhances, so that the dependence becomes close to saturation at the thermal conductivity coefficient of about 5 W/m K. Such a coefficient can be reached by doping the paraffin-based PCM with a reduced graphene oxide at a content of about 2% (weight). Full article

Carbon fiber composites are a popular design material due to their high specific strength. The directional strength of woven composites can be customized by changing the orientation and sequencing of individual lamina within the ply stack. This allows for the potential of specialized parts designed for specific applications, leading to both performance gains and weight savings. One challenge is the ability to characterize non-destructively the orientations of the individual lamina after the manufacturing process. Current industrial methods used to verify the ply stack are destructive to the part, increasing costs and material waste. This creates the need for a non-destructive technique capable of determining the ply stack, both for quality control and for in-service parts, including when there may be access to just a single side of the composite. This research introduces a procedure to scan a fabricated laminated composite using pulse-echo ultrasound coupled with an automated algorithm to determine the layer-by-layer orientation of the ply stack with a specific focus on woven composites. In this work, 12 unique plain-weave laminates ranging from 3 lamina to 18 lamina thick are studied. The orientations of each stacking sequence are different, with some following standard composite design methodologies and others randomly stacked. The mathematical technique presented in this work correctly characterizes non-destructively the orientation of each individual lamina to within 1° with 73% confidence and to within 3° with 98.3% confidence of the as-manufactured orientation. Full article

The development of a nanostructured copper–laser-induced graphene (LIG) composite that can catalyze the reduction of nitrate is described. The system was characterized using a range of surface analytical methods (SEM, Raman, DekTak profilometry). The electrochemical performance of the copper mesh in reducing nitrate was investigated, the nature of the catalytic response was elucidated, and the influence of potential interferences was critically appraised. The adaptation of the system as the basis of an electrochemical sensor for nitrate was assessed, which displayed a limit of detection of 4.7 μM nitrate. The analytical applicability in authentic media was evaluated through the analysis of two surface water samples and validated by standard spectroscopic (nitrate reductase–Griess methods). The LIG substrate offers a simple, scalable route towards the reduction of nitrate with a construction simplicity and sensitivity that is competitive with much more complex nanomaterials. Full article

Zirconia is a high-strength ceramic material that expands the design and application possibilities for all-ceramic restorations and dental implants. To enhance the bonding of zirconia restorations to tooth substrates and the osseointegration of implants with the surrounding bone, the surface should be modified by surface treatment. Unfortunately, the effective treatment of sintered zirconia is difficult. Surface treatment for presintered zirconia may be less difficult; thus, the effectiveness of surface treatments of presintered zirconia was investigated herein. The zirconia specimens were randomly divided into eight groups: (1) control (untreated) and seven treated groups subjected to surface treatment (s.ttt.) in the presintered stage, followed by sintering: (2) s.ttt. 1: hydrofluoric acid (HF) gel left during sintering; (3) s.ttt. 2: HF gel washed before sintering; (4) s.ttt. 3: coated with nanosilica; (5) s.ttt. 4: coated with microsilica; (6) s.ttt. 5: coat followed by airborne-particle abrasion; (7) s.ttt. 6: coat followed by partial etching; and (8) s.ttt. 7: coat followed by total etching. The surface microstructure was examined using scanning electron microscopy (SEM) and the crystalline phase was identified using X-ray diffraction (XRD). Biaxial flexural strength was also tested. The results of SEM for s.ttt. 1 and 2 displayed irregular surfaces. S.ttt. 3 showed deeper penetration of the nanosilica into zirconia (27 µm) compared to the microsilica used in s.ttt. 4. S.ttt. 5 and 6 showed irregular coats. S.ttt. 7 showed intergranular pores. The XRD of s.ttt. 1, 2, and 3 revealed tetragonal zirconia as the control group. S.ttt. 4 and 5 showed cristobalite silica and tetragonal zirconia. S.ttt. 6 and 7 contained amorphous silica and tetragonal zirconia, while s.ttt. 7 also showed monoclinic zirconia. The highest flexural strength was for s.ttt. 4 (982.4 MPa), while the lowest was for s.ttt. 7 (386.6 MPa). There was no significant difference in the flexural strength between the control, s.ttt. 1, and 2 (846.3 MPa, 830.0 MPa, and 835 MPa, respectively). Compared to the control group, s.ttt. 3 had a lower flexural strength (634.1 MPa), while s.ttt. 5 and 6 had higher flexural strengths (863.1 MPa and 872.2 MPa, respectively). It can be concluded that the surface modification of presintered zirconia is a promising method as long as no phase transformation or deep subsurface penetration occurs. Full article

The use of electromagnetic interference shielding materials in the mitigation of electromagnetic pollution requires a broader perspective, encompassing not only the enhancement of the overall shielding efficiency (SE_T), but also the distinct emphasis on the contribution of the absorption shielding efficiency within the total shielding efficiency (SE_A/SE_T). The development of lightweight, biodegradable electromagnetic interference shielding materials with dominant absorption mechanisms is of paramount importance in reducing electromagnetic pollution and the environmental impact. This study presents a successful fabrication strategy for a poly(lactic acid)/polycaprolactone/multi-walled carbon nanotube (PCL/PLA/MWCNT) composite foam, featuring a uniform porous structure. In this approach, melt mixing is combined with particle leaching techniques to create a co-continuous phase morphology when PCL and PLA are present in equal mass ratios. The MWCNT is selectively dispersed within the PCL matrix, which facilitates the formation of a robust conductive network within this morphology. In addition, the addition of the MWCNT content reduces the size of the phase domain in the PCL/PLA/MWCNT composite, showing an adept ability to construct a compact and stable conductive network. Based on its porous architecture and continuous conductive network, the composite foam with an 80% porosity and 7 wt% MWCNT content manifests an exceptional EMI shielding performance. The SE_T, specific SE_T, and SE_A/SE_T values achieved are 22.88 dB, 88.68 dB·cm³/g, and 85.80%, respectively. Additionally, the resulting composite foams exhibit a certain resistance to compression-induced deformations. In summary, this study introduces a practical solution that facilitates the production of absorption-dominated, lightweight, and biodegradable EMI shielding materials at scale. Full article

Research efforts seek to develop aluminium alloy composites to enhance the poor tribological performance of aluminium alloy base matrix. In this research, a hybrid metal matrix composite (HMMC) was developed by reinforcing an aluminium alloy (AA8011) with SiC and rice husk ash (RHA) using a stir casting technique. RHA was prepared by the cracking of rice husk, which is abundantly available in the Indian subcontinent. The samples were cast by keeping the amount of RHA constant at 2.5 wt.% and varying the amount of SiC from 0.0 wt.% to 8 wt.%. The samples were machined to manufacture pins for wear tests (at ambient temperature, 100 °C, and 200 °C) and hardness measurement. The microstructures of the cast samples were analysed using an X-ray diffractometer (XRD) and a scanning electron microscope (SEM), along with energy-dispersive X-ray spectroscopy (EDS). It was observed that the composites with greater reinforcement of SiC exhibited improved hardness and wear resistance, but the coefficient of friction increased with the addition of RHA and SiC, and the wear performance deteriorated with an increase in the operating temperature. The contribution of RHA alone to the improvement in wear performance was marginal compared to the pure alloy. It was also confirmed that the reinforced composites could be a better option for automotive applications to replace aluminium alloys. Full article

In this study, innovative nanocomposite materials for material extrusion (MEX) 3D printing were developed using a polypropylene (PP) polymer with tungsten carbide (WC) nanopowder. The raw materials were converted into filaments using thermomechanical extrusion. The samples were then fabricated for testing according to the international standards. Extensive mechanical testing was performed on the 3D-printed specimens, including tensile, impact, flexural, and microhardness assessments. In addition, the impact of ceramic additive loading was examined. The thermal and stoichiometric characteristics of the nanocomposites were examined using thermogravimetric analysis, energy-dispersive X-ray spectroscopy, differential scanning calorimetry, and Raman spectroscopy. The 3D-printed shape, quality, and fracture process of the specimens were examined using scanning electron microscopy. The results showed that the filler significantly enhanced the mechanical characteristics of the matrix polymer without reducing its thermal stability or processability. Notably, the highest level of nanocomposite mechanical responsiveness was achieved through the inclusion of 6.0 and 8.0 wt. % fillers. The 10.0 wt. % loading nanocomposite showed significantly increased microhardness, indicating a possible high resistance to wear. Full article

This paper presents modeling data to select the optimal industrial unit for the microwave modification of an epoxy basalt-filled oligomer (EBO) at electric field strength E of an electromagnetic wave equal to 11.9 × 10³ V/m and a uniform distribution of the temperature field over the entire volume of the modified object. A mathematical description of the electrodynamic and thermal processes occurring in the object under consideration subjected to microwave exposure includes the Helmholtz equation for the electric field strength vector and the heat conduction equation. The joint solution of this problem in a three-dimensional formulation is based on the use of the finite element method, which in this work was implemented in the COMSOL Multiphysics^® 6.1 software environment. According to the modeling results, the use of microwave chambers with a traveling wave of a waveguide type is inefficient because the required value of the electric field strength E is not achieved, while the modeled microwave chamber with a traveling wave on a quasi-coaxial waveguide makes it possible to achieve the required value of the electric field strength E and uniform distribution of the temperature field over the entire volume of the modified object by reducing the generated power for the modification of an EBO from 400 W up to 300 W. Optimal parameters for modifying an epoxy basalt-filled oligomer in the microwave electromagnetic field in the working chamber with a traveling wave on a quasi-coaxial waveguide have been developed, which provide a uniform microwave modification of an EBO with a microwave installation capacity of 11.6 kg/h. A sketch of an industrial microwave working chamber has been developed, which provides a mode of the uniform modification of the oligomer at electric field strength E = 12.3 × 10³ V/m. The proposed microwave chamber with a traveling wave on a quasi-coaxial waveguide can be replicated for the microwave modification of filled oligomers of various chemical compositions. Full article

This article reports the variation in incident and transmitted light through four different computer-aided-designed/computer-assisted-manufactured (CAD/CAM) resin-based composites (RBC) of thicknesses up to 4 mm after simulating clinically relevant but non-ideal curing conditions. A violet-blue light curing unit (LCU) was used to simulate 39 different curing conditions for each material and thickness, setting an exposure distance of up to 7 mm in the vertical direction and an additional 13 horizontally varying positions that included a central position and up to 3 mm off-center positions in mesial, distal, buccal, and lingual directions. The data clearly indicate that exposure distance has a stronger influence on the measured light characteristics than the directional and offset deviations from the center position. Increasing exposure distance leveled the differences and should be limited to 3 mm. In all materials, the parameters of the transmitted light follow the pattern of variation of the incident light. The attenuation of light while passing RBCs is high and increases exponentially with thickness to 95–96% of the incident light for 4-millimeter-thick samples. Significant differences in light transmission were observed between the materials, which are well related to chemical composition and refractive index differences between filler and organic matrix. Violet light is still measurable after passing through 4-millimeter-thick RBC layers, but its proportion relative to blue light is drastically reduced. Full article

This article deals with the ballistic impact of the 7.62 mm FMJ M80 rifle projectile into the laminated Twaron/UHMWPE composite armor. The armor composition consisted of composite panels made from Twaron CT 747 para-aramid fabric and ultra-high-molecular-weight Endumax Shield XF33 polyethylene. To analyze the ballistic impact and to verify the resistance of the designed armor according to the NATO AEP 4569 STANAG standard, protection level 1, 7.62 × 51 mm FMJ NATO M80 rifle cartridges with lead projectiles were used in the ballistic experiment. After the projectile impact, the damage failure mechanisms of the composite panels were documented. As part of the evaluation of the experiments, the initial microstructure of the composite panels was documented, and subsequently, the damaged areas of the composite armor after the ballistic experiment were also documented. Optical and scanning electron microscopy were used to document the structures. The important parameter of composite armor is its mechanical properties. The surface hardness of the composite panels was measured by the Shore D method using the hardness tester DIGI-Test II. The results obtained from the ballistic experiment demonstrate that the designed Twaron/Endumax armor was not penetrated. This armor has sustained multiple impacts for all three 7.62 mm FMJ M80 projectiles and is suitable for the construction of armor protection. Full article

Turbofan engine models for foreign object impact simulations must include a representation of fan blade interactions with surrounding components of the engine, including rubbing against the abradable lining. In this study, three numerical techniques, namely, the finite element method (FEM), smoothed particles hydrodynamics (SPH), and the adaptive (hybrid) FEM/SPH approach (ADT), were evaluated for their applicability to modeling of the blade–abradable rub strip (ARS) interaction. Models developed using these methods in the commercial code LS-DYNA were compared in terms of their computational cost, robustness, sensitivity to mesh density, and certain physical and non-physical parameters. As a result, the applicability of the models to represent the blade-ARS interaction was ranked as follows (1—most applicable, 3—least applicable): 1—SPH, 2—FEM, and 3—ADT. Full article

In this study, we prepared plastic films composed of modified layered double hydroxides (LDHs), which were incorporated into a low-density polyethylene (LDPE) matrix. The sunscreen additive sulfonic phenylbenzimidazole acid sodium salt was incorporated as counter-anion in the interlayer of a nanoclay by means of ion-exchange reactions to improve thermal and optical properties. The modified LDHs were characterized using FT-IR, XRF, TGA, and XRD techniques. Cast extrusion was employed to obtain the nanocomposites with the new LDH incorporated into LDPE. The mechanical, rheological, and optical properties of the films were assessed, and the influence of a non-ionic surfactant was also evaluated. In addition, accelerated ageing tests were carried out to evaluate the influence of UV light on the mechanical and optical properties of the films. Full article

Total hip arthroplasty (THA) is a common surgical procedure used to treat hip osteoarthritis and other joint conditions that cause pain and functional limitation. Traditionally, THA has been performed most often in elderly patients, but in recent years, there has been an increase in hip arthroplasties in young patients. Femoral prosthesis rupture is a rare but significant complication that can also occur in young patients undergoing total hip arthroplasty (THA). Some of the factors that can contribute to femoral prosthesis ruptures include abnormal overload, defects in the design, lack of geometric fit, and type of materials used in the stem and femoral head connection. The aim of this study is to analyze the criticalities in the contact between the femoral head and the stem neck. In particular, two types of contacts will be taken into consideration: proximal and distal, and through the finite element method (FEA), the criticalities will be defined. The results show that in the proximal contact, the stress levels exceeded 500 MPa in certain areas of the prosthesis. This stress could potentially lead to structural failure, such as rupture or deformation of the prosthesis. In addition, to prevent bacterial infiltration or debris from the outside, the distal connection is recommended. Full article

This study presents the results of the enlarged laboratory research on the melting of calcined composite pellets for ferrochrome obtained from fine-dispersed conditioned chrome concentrate containing 50.3% Cr₂O₃. This is a product of the gravitational beneficiation of waste sludge tailings from the Dubersay tailings dump at the Donskoy Mining and Processing Plant (DMPP) of JSC “TNC Kazchrome”. The composition of the charge for obtaining composite pellets consisted of 88.5% of chrome concentrate, 3% of mineral part of refined ferrochrome slag (RFC), 4% of ferruginous diatomite, 3% of coke and 1.5% of liquid glass. The initial charge was pelletized on a laboratory pelletizer to a size of 6–10 mm, dried at room temperature for 24 h and fired at 1200 °C for 60 min at a heating rate of 15 deg/min. On the basis of the developed composite annealed pellets, studies on the production of high-carbon ferrochrome at different melting temperatures were carried out. The results showed that with an increase in temperature from 1750 to 1850 °C, the iron–chromium phase in the composition of the alloy increases from 45.2 to 50.1%, the chromium carbide phase decreases from 23.7 to 11.3% and the chromium–iron phase increases from 7 to 11.2%. The carbon content in the alloys at temperatures from 1750 to 1850 °C varies from 7.2 to 8.94%, respectively. The maximum chromium content of the alloy is 64.82% with a melting point of 1850 °C; this alloy can be classified as FeCr60C90LP grade ferrochrome according to the international Chinese standard, which has no more than 0.03% phosphorus and no more than 0.1% sulfur. Full article

Modern research has evolved several approaches toward skin regeneration and one of the novel concerns is the use of polymer-based systems due to their excellent beneficial properties to the skin. Several polymers, such as cellulose, hyaluronan, alginate, chitosan, collagen, fibrin and fibroin, have been tested and have proven the benefits for skin regeneration, and most of them are derived from either polysaccharide- or protein-based materials. In order to understand the mode of action, several researchers investigated the cell–matrix interaction and possible signaling mechanism in skin regeneration. Not only the signaling mechanism but also the mode of cell communication determines the application of polysaccharide- and protein-based polymers in practice. Based on the above significance, this review disclosed the recent findings to compile a possible method of communication between cells and polymers derived from polysaccharide-based (such as cellulose, hyaluronan, chitosan, alginate, agar, and xanthan gum) and protein-based (such as collagen, gelatin, fibrin, and silk fibroin) materials along with other polymers, such as poly(vinyl alcohol), polyglycolide or poly(glycolic acid), or poly(lactic acid) in skin regeneration. Accordingly, this review addresses the fundamental concept of cell–matrix communication, which helps us to understand the basis of the polymer’s functions in the biomedical field. Full article

Electromagnetic interference is considered a serious threat to electrical devices, the environment, and human beings. In this regard, various shielding materials have been developed and investigated. Graphene is a two-dimensional, one-atom-thick nanocarbon nanomaterial. It possesses several remarkable structural and physical features, including transparency, electron conductivity, heat stability, mechanical properties, etc. Consequently, it has been used as an effective reinforcement to enhance electrical conductivity, dielectric properties, permittivity, and electromagnetic interference shielding characteristics. This is an overview of the utilization and efficacy of state-of-the-art graphene-derived nanocomposites for radiation shielding. The polymeric matrices discussed here include conducting polymers, thermoplastic polymers, as well as thermosets, for which the physical and electromagnetic interference shielding characteristics depend upon polymer/graphene interactions and interface formation. Improved graphene dispersion has been observed due to electrostatic, van der Waals, π-π stacking, or covalent interactions in the matrix nanofiller. Accordingly, low percolation thresholds and excellent electrical conductivity have been achieved with nanocomposites, offering enhanced shielding performance. Graphene has been filled in matrices like polyaniline, polythiophene, poly(methyl methacrylate), polyethylene, epoxy, and other polymers for the formation of radiation shielding nanocomposites. This process has been shown to improve the electromagnetic radiation shielding effectiveness. The future of graphene-based nanocomposites in this field relies on the design and facile processing of novel nanocomposites, as well as overcoming the remaining challenges in this field. Full article

Self-structural health monitoring (SHM) functionalities for fiber-reinforced polymer composites have become highly sought after to ensure the structural safety of newly advancing components in the automotive, civil, mechanical, and aerospace industries. This paper introduces a self-damage detection and memory (SDDM) hybrid composite material, where the structural carbon fiber tow is transformed into a piezoresistive sensor network, and the structural glass fiber operates as electrical insulation. In this study, SDDM specimens were fabricated, and tensile and impact tests were performed. The tensile tests of SDDM specimens find two distinct loading peaks: first where the carbon fiber fails, and second where the glass fiber fails. A linear correlation was observed between the carbon fiber resistance and composite strain up to a threshold, beyond which a sharp nonlinear increase in resistance occurred. The resistance then approached infinity, coinciding with the first loading peak and failure of the carbon fiber elements. This demonstrates the potential for a damage early warning threshold. Additionally, the effect of stitching the sensor tow in a zig-zag pattern over a large area was investigated using tailored fiber placement (TFP) of 1-loop, 3-loop, and 5-loop specimens. Tensile testing found that increasing the number of loops improved the sensor’s accuracy for strain sensing. Furthermore, impact tests were conducted, and as the impact energy progressively increased, the sensor resistance permanently increased. This illustrates a capability for self-memory of microdamage throughout the life cycle of the structure, potentially useful for predicting the remaining life of the composite. Full article

One of the drawbacks of natural fibers and their composites is their inherent hydrophilic nature. The effect of moisture on the mechanical properties of composites is irrefutable. This study deals with the hygroscopic characteristics of enset–PLA composites and their effect on the mechanical properties of the composites. To do this, injection-molded composite specimens with different fiber volume fractions, plasticizer ratios, fiber lengths, and fiber ages were considered. The specimens were exposed to distilled water, and the moisture absorption was monitored on a daily basis. Subsequently, the specimens were subjected to mechanical loading to determine the effect of moisture on their strength, stiffness, and strain at break strength. Lastly, the individual and joint effects of the considered factors were scrutinized using an optimal experimental design. The results of the study show that the maximum and minimum moisture uptakes were recorded for 25% and 15% fiber ratios, respectively. Due to the effect of moisture, the tensile and bending strength decreased by 11% and 5%, respectively, for the 15% fiber volume fraction and decreased by 16% and 13%, respectively, for the 25% fiber volume fraction. Increasing the amount of plasticizer increases the moisture resistance. The results indicate that Enset–PLA composites have competitive properties and stability when exposed to moisture. Full article

This paper deals with the application of statistical analysis in the study of the dependence of the flexural strength of sintered alumina (Al₂O₃) disks on the parameters (nozzle diameter of the printer print head, layer height, and filling pattern) of the fused deposition method (FDM) printing of ceramic–polymer filament containing 60 vol.% alumina and 40 vol.% polylactide. By means of a correlation analysis applied to the results of flexural tests, a linear relationship was found between the thickness of the printed layer and the strength of the sintered specimens. A statistically significant linear relationship was found between the geometric parameters and the weight of both printed ceramic–polymer and sintered ceramic samples, as well as the diameter of the nozzle used in the printing of the workpiece. It was found that the highest strength is achieved with a layer thickness equal to 0.4 mm, and the smallest scatter of mass values and geometric dimensions of ceramic samples is achieved using a nozzle diameter of 0.6 mm. As a result of the conducted research, linear equations allowing the prediction of changes in the geometry and mass of samples after sintering, as well as the strength properties of sintered samples, taking into account the geometry and mass of FDMed samples, were obtained. Full article

This research focuses on a comprehensive exploration of the experimental and mechanical aspects of the electrical discharge machining (EDM) process, specifically targeting the machining characteristics of AA2014/Si₃N₄/Mg/cenosphere hybrid composites. The aim is to optimize the process parameters for enhanced machining performance through a combination of testing, optimization, and modelling methodologies. The study examines the effects of key EDM variables—peak current, pulse on time, and pulse off time—on critical output responses: surface roughness (Ra), electrode wear rate (EWR), and material removal rate (MRR). Leveraging an L9 Taguchi orthogonal array experimental design, the impact of controllable factors on these responses is analysed. An integrated approach utilizing MATLAB’s logic toolbox and Mamdani’s technique is employed to model the EDM process, and a multiple-response performance index is calculated using fuzzy logic theory, enabling multiobjective optimizations. Furthermore, a mechanical behaviour evaluation of AA2014/Si₃N₄/Mg/cenosphere hybrid composites is performed through mechanical testing, with a comparison between experimental machining results and predicted values. Scanning electron microscopy (SEM) images reveal the presence of filler reinforcements within the base alloy, displaying an improved microstructure and uniform reinforcement dispersion. An X-ray diffraction (XRD) analysis confirms the major elemental constituents—aluminium, silicon, and magnesium—in the hybrid composites. A microstructural analysis of the hybrid metal matrix composites (MMCs) prepared for EDM showcases closely packed reinforcement structures, circular ash-coloured spots indicating silicon and nitrates, and a fine dispersion of cenosphere reinforcement particles. The study’s outcomes demonstrate a promising application potential for these hybrid composites in various fields. Full article

Holes and their effects on the fatigue behavior and damage propagation of thin-walled structural components remain objects of research. In this paper, the previously untreated effect of round holes in thin plain-woven carbon fiber-reinforced plastic plates subjected to simple block loading is examined, and the implication on both damage propagation and residual tensile strength is investigated. Using three-dimensional digital image correlation, the damage propagation in the performed experimental tests is acquired, and the damage size is quantified. The evaluations reveal a relationship between the damage propagation and applied load level, for which an empirical model has been previously established by the authors. As the number of cycles increases, a saturation behavior is found. Once the increased load is imposed on the plate, damage propagation resumes, leading to further damage propagation that can be described with the same empirical model as the initial damage propagation, including renewed saturation behavior. The subsequent experimental tests to determine the residual tensile strength reveal a positive effect of the existing damage size, as the ultimate load significantly exceeds the ultimate load of the non-damaged plate. Full article

The primary devices for extracting volatile components from dispersed materials in a vacuum are devices with the movement of raw materials by directed vibrations. During the analysis of the operation of such installations, some shortcomings were identified, due to the supply of heat flow to the processed raw material and the requirements for the choice of structural materials. In this article, the authors tested a heating method and a design of a sublimator with the supply of heat flow to the dispersed material by radiation from the heater. The sublimation zone is made in the form of a shaft formed by simple-shaped plates, the design and material of which involve the use of refractory and ceramic materials that are inert with respect to an aggressive vaporous sulfide medium. The movement of bulk material through the volume of the sublimator occurs due to rheological properties: sliding along inclined plates. Technological tests on the sublimation of arsenic sulfides from gravity and flotation composite concentrates of the Bakyrchik deposit (Kazakhstan) have shown the possibility of a high degree of sublimation of arsenic (more than 96–99%) while preserving precious metal composites in the sublimation residue and stable operation of equipment. Sublimation residues containing 0.14–0.30% As can be processed by known methods. The possibility of sufficiently complete removal of arsenic and its compounds from composite concentrates at a reduced pressure with the removal of the latter in the most environmentally friendly sulfide form has been established. Full article

In recent years, the use of functionally graded materials has been the focus of several studies due to their intrinsic ability to be tailored according to the requirements of structures while minimising abrupt stress transitions commonly found in laminated composites. In most studies, the materials’ mixture gradient is established through a structural component, i.e., thickness, which is known to visibly enhance structural behaviour. However, depending on the type of structure, it is important to exploit the possibility of building a structure using other gradient directions. The innovative characteristic of this work, which aims to study plane truss and frame-type structures made of functionally graded materials, lies in the specificity that the materials’ mixture gradient occurs as a function of a geometric structure feature, i.e., for example, the structure height, rather than the more usual approach, as a component dependence, i.e., through a member thickness or even along its length. The performance of the present model is illustrated through a set of case studies, and where possible, the results achieved are compared with more traditional solutions. Full article

Damage caused by the drilling process is the most common reason for the rejection of composite parts and components that include holes. This is especially true in the case of laminated composites. The purpose of the current experimental investigation is to investigate the efficiency of hole formation when the component is in the molding phase. The mechanical properties of molded and drilled holes in jute-fiber-reinforced epoxy composites have been compared in a study that was carried out with the purpose of conducting an examination of these features. It was discovered that the molded holes operate much better than the drilled holes when it comes to jute fiber/epoxy composite materials. This was the conclusion reached after observing both types of holes. The maximum tensile load that was taken by molded hole specimens of composites with hole diameters of 4 mm and 8 mm was reported to be 48.8% and 101.5% greater, respectively, than the maximum tensile load that was taken by drilled hole specimens of composites with the same diameter. In addition, the load-extension curves demonstrate that the specimens that were manufactured with molded holes were able to achieve a larger degree of extension when compared to those that were manufactured with drilled holes. Full article

The purpose of this paper is to evaluate the properties of Ethiopian bamboo fibre polymer composites as headliners in the automobile industry. Bamboo fibres are developed using the roll milling technique, and bamboo fibre epoxy composites (BFEPCS) are developed using a compression mould and a hot press machine. The mechanical properties are measured based on the recommended procedure of the ASTM. In total, 40% of the volume fraction of fibres is used to produce polymer composites. An accurate evaluation of its mechanical properties is thus critical for predicting its behaviour during a vehicle’s interior impact assessment. Conventional headliner materials are heavier, non-biodegradable, expensive, and non-sustainable during processing compared to the currently researched materials. Three representatives of bamboo plants are harvested in three regions of bamboo species, three groups of ages, and two harvesting months. Two-year-old bamboo fibres have the highest mechanical properties of all ages, and November has a higher mechanical properties compared to February. Inji-bara and Kom-bolcha have the highest and lowest mechanical properties, respectively. BFEPCs have high mechanical properties compared to BFPPCs. The mechanical properties of the current research findings have higher measured values compared to Jute felt PU, CFPU, GFMPU, BFPP, BFEP, PP foam, and TPU. The flexural strength of BFPCs has higher properties compared to their tensile strength. Ethiopian bamboo fibres and their polymer composites have the best mechanical properties for the composite industry, which is used for headliner materials in the automobile industry, compared to conventional headliner materials. Full article

Epoxy is the most prevalent thermosetting resin in the field of polymer composite materials. There has been a growing interest in the development of bio-based epoxy resins as a sustainable alternative to conventional petrochemical epoxy resins. Advances in this field in recent years have included the use of various renewable resources, such as vegetable oils, lignin, and sugars, as direct precursors to produce bio-based epoxy resins. In the meantime, bio-oils have been produced via the decomposition of biomass through thermochemical conversion and mainly being used as renewable liquid fuels. It is noteworthy that bio-oils can be used as a sustainable resource to produce epoxy resins. This review addresses research progress in producing bio-oil-based epoxy resins from thermochemical processing techniques including organic solvent liquefaction, fast pyrolysis, and hydrothermal liquefaction. The production of bio-oil from thermochemical processing and its use to inject sustainability into epoxy resins are discussed. Herein, we intend to provide an overall picture of current attempts in the research area of bio-oil-based epoxy resins, reveal their potential for sustainable epoxy resins, and stimulate research interests in green/renewable materials. Full article