J. Compos. Sci., Volume 7, Issue 8 (August 2023) – 41 articles

The lightweight of structure is widely applied in industrial applications, and the conflict between both dynamic stability and structural lightweight is still prominent. In this paper, functionally graded porous (FGP) elliptic cylindrical shells and panels with general boundary conditions are analyzed to explore the effect of the FGP on dynamic performance. First, the FGP elliptic cylindrical shell and panel models are established. Therein, three kinds of porosity distribution are considered, including nonsymmetric, symmetric, and uniform distributions. The energy expressions of the FGP elliptic cylindrical shell and panel are established by the first-order shear deformation theory (FSDT). To simulate various boundary conditions, the artificial spring boundary technique is employed in this study. Then, the Jacobi orthogonal polynomials and Fourier series are adopted to express the admissible displacements. Finally, the accuracy of this model is verified by comparing it with open literature and ABAQUS software. Results show that the variations of the boundary conditions, linear springs, thickness ratio, and porosity have close relation with the dynamic performance of the structure by affecting the stiffness of the structure. Full article

Wound healing is a multifaceted biological process influenced by both intrinsic and extrinsic factors. The ability of Wnt signaling to activate cell proliferation appears to serve a central role in wound healing. Therefore, the direct activation of Wnt or inhibition of the Wnt antagonist could be an ideal approach for the stimulation of wound healing. This study aimed to investigate the underlying mechanism of small molecule-loaded nanofibrous matrix in inducing wound healing. Herein, a naturally derived small molecule, curcumin, was used to inhibit the GSK3-β, which is considered a negative regulator of the Wnt/β-catenin signaling pathway. The docking results demonstrated that curcumin makes a complex with GSK3-β at seven specific sites, thereby inhibiting its activity. Moreover, the stabilization of β-catenin appeared to be increased with the treatment of curcumin. Next, curcumin was incorporated in poly ε-caprolactone nanofibrous matrices for controlled–sustained drug release to induce cell function. Curcumin-loaded nanofibrous matrix not only enhanced fibroblast cell proliferation, but also induced the expression of the fibroblast growth factor (FGF) in vitro. Moreover, the in vivo results showed that these nanofibrous mats significantly induced wound closure in 12 mm critical-sized defect. Collectively, these results suggest that the developed nanofibrous matrix promotes impaired wound healing by modulating cell proliferation and enhancing FGF expression that promotes wound closure. Full article

The synthesis of new composite nanomaterials based on graphene oxide (GO)modified with cellulose and its derivatives, as well as nanocellulose, is currently an important direction and contributes toward solving many problems in various fields such as nanotechnology, information technology, medicine, high-dielectric materials, and nanoelectronics. In this work, for the first time, for the production of GO and its membrane with carboxymethylcellulose (CMC), local Kazakhstan “Ognevsky” graphite was used as the initial raw material. In this regard, the preparation of nanocomposites of GO modified with cellulose derivatives, including CMC, attracts great interest from scientists and expands its field of practical application due to the significant changes in its physicochemical properties. In this work, the GO obtained using the Hummers method was modified by CMC, and its physicochemical, structural, and electrical characteristics were studied. The GO/CMC membrane was synthesized by mixing 1% GO with crushed solid mass of CMC (0.03 g; 0.06 g; 0.15 g) and then processing using ultrasound. The surface morphology of the GO/CMC membrane was studied using scanning electron microscopy (SEM). It has been established that by increasing the mass of CMC (0.03 g; 0.06 g; 0.15 g), the polymerization of CMC occurs on the surface of GO nanosheets. Cross-sectional micrographs of GO/CMC show the formation of sandwich-like layered structures. The synthesis efficiency (yield) of GO from synthetic graphite is 10.8%, and GO from Ognevsky graphite is 11.9%, almost 1.1% more than GO from synthetic graphite. The mechanical tensile strength increases from 2.3 MPa to 14.3 MPa and the Young’s modulus from 2.3 MPa to 143 MPa. The electrical parameters of the humidity sensor based on GO and GO/CMC membranes (0.03 g; 0.06 g; 0.15 g) were studied as a function of humidity to determine the performance of the device. Full article

Bioinspired nanocomposites aim to mimic the structure of natural materials. These materials exhibit excellent mechanical properties such as high strength, toughness, and stiffness. Using modeling and simulation, we can gain insight into the underlying mechanisms that control the properties of these materials, study the impact of various parameters on their performance, and design new materials with high performance. This study investigates a bone-inspired nanocomposite that consists of two subunits: Subunit-A (Mineralized Collagen Fibril) and Subunit-B (Extrafibrillar Matrix). Subunit-B provides the composite with stiffness before yielding. After yielding, Subunit-A stretches to accommodate the deformation up to the final failure. The adhesive material in the interface plays an important role in this nanocomposite’s failure. The composite’s toughness is enhanced by multiple mechanisms: diffuse damage in Subunit-B, strain relaxation around crack tips through horizontal interface delamination between the subunits, and the crack bridging role of Subunit-A. This study provides insight into the mechanical behavior of bone-inspired nanocomposites under tensile loading conditions, highlighting the importance of the adhesive phase in optimizing the material performance in various applications. Full article

The issue of crystallization of silicon oxide at low temperatures is a topical issue for the electronics of the future. Organosilicon oligomers and polymers are “ideal” sources for obtaining ultrapure silicon ceramics and silicon nanoparticles. This paper presents the results of the synthesis of highly dispersed silicon-carbon powder from an organohydrosiloxane oligomer and the method for increasing its crystallinity at low temperatures. The diffraction pattern of the resulting powder corresponds to the amorphous–crystalline state of the components in this material, as evidenced by two intense and broadened amorphous halos in the region of Bragg angles 2θ = 7–11° and 18–25°. The resulting silicon–carbon powder was subjected to electron irradiation (E = 10 MeV; D = 10⁶–10⁷ Gy). This paper presents the data on the changes in powder properties via IR-Fourier spectroscopy, X-ray phase analysis, and scanning electron microscopy. Irradiation with fast electrons with an absorbed dose of 10⁶ Gy leads to a slight crystallization of the amorphous SiO₂ phase. An increase in the absorbed dose of fast electrons from D = 10⁶ to D = 10⁷ Gy leads to the opposite effect. An amorphization of silica is observed. This study showed the possibility of the crystallization of a silicon–carbon powder without a significant increase in temperature, acting only with electron irradiation. It is necessary to continue further research on expanding the boundaries of the optimal doses of absorbed radiation from fast electrons in order to achieve the maximum effect of the crystallization of silicon–carbon powder. Full article

Background: This in vitro study aimed to investigate and evaluate the values of water sorption and water solubility of four types of denture base polymers—3D-printed NextDent 3D Denture + (NextDent, 3D Systems, Soesterberg, The Netherlands), CAD/CAM milled Ivotion Base (Ivotion Denture System, Ivoclar Vivadent, Schaan, Liechtenstein), PMMA conventional Vertex BasiQ 20 (Vertex Dental, 3D Systems, Soesterberg, The Netherlands), and conventional heat-cured BMS (BMS Dental Srl, Rome, Italy)—which were subjected to artificial aging. Materials and methods: 200 specimens were created (n = 50), dried, and weighed accurately. They were immersed in artificial saliva (T1 = 7 days, T2 = 14 days, T3 = 1 month) and re-weighed after water absorption. After desiccation at 37 °C for 24 h and then at 23 ± 1 °C for 1 h, samples were weighed again. Next, thermocycling (100 h, 5000 cycles, 5–55 °C) was performed, and the water sorption and solubility were re-measured. IBM SPSS Statistics 0.26 was used for data analysis, revealing a direct correlation between water sorption and material type. Thermocycling at 55 °C increased water sorption for BMS and Vertex BasiQ 20. In conclusion, NextDent’s 3D-printed resin had higher water sorption values throughout the study. Water solubility averages decreased over time, reaching the lowest in the 30-day period for CAD/CAM milled dental resin Ivotion Base. The artificial aging had no effect on Ivotion Base and NextDent’s water sorption. Thermocycling did not affect the solubility of the materials tested. The conducted study acknowledges the great possibilities of dental resins for additive and subtractive manufacturing for the purposes of removable prosthetics in daily dental practice. Full article

Cold thermal energy storage (CTES) based on phase change materials (PCMs) has shown great promise in numerous energy-related applications. Due to its high energy storage density, CTES is able to balance the existing energy supply and demand imbalance. Given the rapidly growing demand for cold energy, the storage of hot and cold energy is emerging as a particularly attractive option. The main purpose of this study is to provide a comprehensive overview of the current research progress on the utilisation of PCMs in CTES. The greatest difficulties associated with using PCMs for CTES are also examined in this overview. In this regard, a critical evaluation of experimental and numerical studies of the heat transfer properties of various fundamental fluids using PCMs is conducted. Specifically, several aspects that affect the thermal conductivity of PCMs are investigated. These factors include nanoparticle-rich PCM, a form of encapsulated PCM, solids volume percentage, and particle size. Discussions focus on observations and conclusions are drawn from conducted studies on PCMs used in CTES. Based on the findings of this study, a set of plausible recommendations are made for future research initiatives. Full article

Sustainable hydrogels are an innovative biodegradable alternative to traditional packaging materials. They offer exceptional water absorption capacity and high biocompatibility, making them ideal food absorbents to reduce plastic waste, extend shelf life and ensure the safety and quality of packaged foods. In this study, hydrogels based on gelatin, microcrystalline cellulose (MCC), and nanocrystalline cellulose (NCC) were developed, characterized, and applied in the packaging of chicken breasts. For this, MCC was isolated from the banana pseudostem and commercial NCC was incorporated into a gelatin solution to produce the hydrogel materials by film casting. The resulting hydrogels were analyzed in terms of morphology, structural properties, water absorption capacity, mechanical strength, and color properties. The results showed that the incorporation of MCC and NCC significantly improved the mechanical integrity of the hydrogels, which prevented premature deformation of the hydrogels when they absorbed moisture. In addition, changes in the color properties of chicken breast samples in contact with the hydrogels were observed, indicating their ability to preserve food quality. Subsequently, the effectiveness of the hydrogels for chicken breast storage at 4 °C for 4 days was validated. The results demonstrated that the hydrogels developed in this study are a sustainable and environmentally friendly alternative to traditional packaging materials that can extend the shelf life of food products while maintaining their physical and microbiological integrity. Full article

Deformation behavior of the composite “eggshell–polymer plomb” was examined under bending. Hen eggs were taken as a biological material for experiments. It was shown that a viscoelastic polymer coating does not change the type of deformation behavior of the composite, given that the eggshell continued to be brittle despite its mechanical characteristics varying widely for a brittle solid. Joint “polymer plomb–eggshell” never cracked under bending and hence exhibited a high cohesion strength under the stresses applied in these experiments. It seems that the composite “eggshell—polymer plomb” could substitute for the composite “tooth enamel–polymer plomb” under elaboration of novel restorative materials for dentistry, namely, for examination of their mechanical properties, including cohesive strength. Full article

The surface behavior of ZnO-based films can be modulated via the postannealing and ultraviolet (UV) illumination of different strengths and durations, respectively. The present results could provide the basis for modulating their microstructures with respect to the grain-size distribution and photocatalytic behavior, and act as a potential guide in the field of wide-bandgap semiconducting oxides. ZnO films were prepared at room temperature onto Corning-1737 glass substrates by applying radio-frequency magnetron sputtering without supplying an oxygen source. With the purpose of obtaining modulational grain microstructures, the as-prepared ZnO films (Z0) were treated via a postannealing modification in a vacuum furnace at 300 °C for 30 min after deposition (Z300), accompanied by adjustable internal stress. The contact angle (CA) value of the ZnO films was reduced from 95° to 68°, owing to the different grain microstructure accompanied by a change in the size variation. In addition, UV light with different illumination strengths could be used to improve the hydrophilicity, which varied from a hydrophobic status to a superhydrophilic status due to the desirable surface characteristics of its photocatalytic action. In addition, the photocatalytic activity of the ZnO films exhibited an effectual photodegradation of methylene blue (MB) under UV illumination, with a chemical reaction constant of 2.93 × 10⁻³ min⁻¹. In this present work, we demonstrated that the CA value of the ZnO films not only caused a change from a hydrophobic to hydrophilic status, accompanied by a change in grain size combined with internal stress, but also, induced by the UV light illumination, was combined with photocatalytic activity simultaneously. On the other hand, an enhanced surface plasmonic resonance was observed, which was due to couple oscillations between the electrons and photons and was generated from the interface by using a flat, continuous Pt capping nanolayer. This designed structure may also be considered as a Pt electrode pattern onto ZnO (metal Pt/ceramic ZnO) for multifunctional, heterostructured sensors and devices in the near future. Full article

The article studies the effect of polynorbornene (PNB) in the composition of PNB with Norman 747 LV plasticizer (RC) on the curing characteristics of the rubber compound and the physico-mechanical, dynamic, dielectric properties and the thermal behavior of vulcanizates based on a combination of isoprene, α-methylstyrene-butadiene, and nitrile-butadiene rubbers. It is shown that vulcanizates containing PNB in the composition of the RC had lower conditional tensile strength, hardness, and tear resistance compared to the vulcanizate of the base version of the rubber compound. Studies of dynamic mechanical analysis indicate that an increase in the content of RC, and hence PNB, in the rubber compound contributes to an increase in the mechanical loss factor (tanδ) and a decrease in the storage modulus of vulcanizates. It was found that vulcanized rubber, containing 24.0 parts per hundred of rubber (phr) (8.98 wt. %) PNB as part of the RC, is characterized by stable physico-mechanical, improved vibration-absorbing properties, as well as increased dielectric parameters. This rubber compound can be used as a base for rail fasteners for railroad tracks. Full article

Nanocellulose is increasingly proposed as a sustainable raw material having strong interparticle bonding. However, cellulose alone has limited bending and impact resistance. We newly observe self-assembly between crystalline nanocellulose (CNC) and ultrafine ground chemical-free calcium carbonate nanoparticles (UGCC). The suspension displays an intrinsic gel-like state, and heterogeneous adsorption occurs under the specific conditions where Brownian motion of both species is arrested by application of ultralow shear (0.01 s⁻¹). In contrast, simple static aging of the mixture leads to autoflocculation of each species independently. The heterogeneous adsorption results in compound particle self-assembly leading to multi-level hierarchical structures depending on relative species size and concentration ratio. Fine particles from species 1 adsorb onto the coarser complementary particles of species 2 and vice versa. Depending also on whether CNC or UGCC particles are in excess, the structural assembly occurs primarily through either CNC–CNC hydrogen bonding or CaCO₃–CaCO₃ autogenous flocculation, respectively. Controlling the hierarchical composite structure bonding in this way, the resulting morphology can express dual or predominantly single either mineralic or cellulosic surface properties. Novel complex hybrid biocomposite materials can therefore be produced having designable compatibility across a broad range of both natural and oil-based polymeric materials. Both CNC and UGCC are exemplified here via commercial products. Full article

In this work, we propose a hybrid approach to solve the challenge of balancing strength and ductility in aluminum (Al) matrix composites. While some elements of our approach have been used in previous studies, such as in situ synthesis and ex situ augmentation, our work is innovative as it combines these techniques with specialized equipment to achieve success. We synthesized nanoscale Al₃BC particles in situ using ultra-fine particles by incorporating carbon nanotubes (CNTs) into elemental powder mixtures, followed by mechanical activation and annealing, to obtain granular (UFG) Al. The resulting in situ nanoscale Al₃BC particles are uniformly dispersed within the UFG Al particles, resulting in improved strength and strain hardening. By innovating the unique combination of nanoscale Al₃BC particles synthesized in situ in UFG Al, we enabled better integration with the matrix and a strong interface. This combination provides a balance of strength and flexibility, which represents a major breakthrough in the study of composites. (Al₃BC, CNT)/UFG Al composites exhibit simultaneous increases in strength (394 MPa) and total elongation (19.7%), indicating increased strength and suggesting that there are promising strengthening effects of in situ/ex situ reinforcement that benefit from the uniform dispersion and the strong interface with the matrix. Potential applications include lightweight and high-strength components for use in aerospace and automotive industries, as well as structural materials for use in advanced mechanical systems that require both high strength and toughness. Full article

Bottom slamming loads cause considerable local damage to a ship’s body and reduce the ship’s structural performance against harsh sea waves. Although extensive studies have worked on stiffening elements to compensate for local damage due to slamming loads, few studies have concentrated on the ship’s body itself while using new generations of composite plates. Accordingly, a numerical study is conducted to determine the effect of using ultra-lightweight high-ductility cementitious composite in steel–concrete–steel (SCS) composite plate to mitigate bottom slamming loads. A large-scale model of the ship using SCS composite plates is modelled in Abaqus software, and fluid–solid (FSI) interaction is precisely modelled using the Coupled Eulerian–Lagrangian (CEL) method. The results show that using the CEL method with a large-scale 3D model precisely simulates FSI by providing a 6.5% deviation from the experimental result. Moreover, using an SCS plate when considering ultra-lightweight high-ductility cementitious composite results in a considerable reduction (around 95%) in the maximum strain of the ship body and, accordingly, reduces local damage so that, although about 22% of the strain of the outer layer is transferred to the inner part of the ship body containing only steel plate, almost 0% stress transfer is observed for the SCS-based ship’s structure. Full article

Multiphase fluoride polycrystalline eutectics pRF₃ × qMF₂ forming in the MF₂–RF₃ (M = Ca, Sr, Ba; R = La–Nd) binary systems were synthesized by the directional crystallization technique from a melt. The phase composition, morphology, and temperature dependences of fluorine ionic conductivity in fabricated composites were studied in detail. The pRF₃ × qMF₂ (p and q are the mole percentages of components) eutectic composites consist of both extremely saturated fluorite-type structure M_1−xR_xF_2+x solid solutions and the tysonite-type R_1−yM_yF_3−y ones. Microsized growth blocks with a fine lamellar structure are typical for synthesized composites. The thinnest (from 3 μm) and longest lamellae are observed in the 68LaF₃ × 32BaF₂ composition. The ionic conductivity values of pRF₃ × qMF₂ composites are determined by the phase composition, practically do not depend on their morphological features, and reach 10⁻³–10⁻² S/cm at 500 K (with an ion transport activation enthalpy of about 0.5–0.6 eV). Crystallized eutectics are superior to any single-phase M_1−xR_xF_2+x solid solutions and ball-milling R_1−yM_yF_3−y nanoceramics in terms of ion-conducting properties. These fluoride materials represent an alternative to widely applied tysonite-type ceramic composites in various electrochemical devices and require further in-depth studies. Full article

The large demand of reinforcement systems for the rehabilitation of existing concrete and masonry structures, has recently increased the development of innovative methods and advanced systems where the structural mass and weight are reduced, possibly avoiding steel reinforcements, while using non-invasive and reversible reinforcements made of pre-impregnated fiber nets and mortars in the absence of cement, commonly known as composite-reinforced mortars (CRMs). To date, for such composite materials, few experimental studies have been performed. Their characterization typically follows the guidelines published by the Supreme Council of Public Works. In such a context, the present work aims at studying numerically the fracturing behavior of CRM single-lap shear tests by implementing a cohesive zone model and concrete damage plasticity, in a finite element setting. These specimens are characterized by the presence of a mortar whose mechanical behavior has been defined by means of an analytical approximation based on exponential or polynomial functions. Different fracturing modes are studied numerically within the CRM specimen, involving the matrix and reinforcement phases, as well as the substrate-to-CRM interface. Based on a systematic investigation, the proposed numerical modeling is verified to be a useful tool to predict the response of the entire reinforcement system, in lieu of more costly experimental tests, whose results could be useful for design purposes and could serve as reference numerical solutions for further analytical/experimental investigations on the topic. Full article

The search for new hydrogen evolution reaction (HER) electrocatalysts with lower cost and higher activity and stability than noble metal catalysts is essential. In this regard cobalt phosphide is considered one of the most promising nanomaterials. The present work proposes a simple and efficient method for the synthesis of a nanocomposite of graphene–phosphorene structures decorated with CoP nanoparticles 2–5 nm in size via the electrochemical exfoliation of black phosphorus carried out in the presence of nitrogen-doped few-layer graphene structures and followed by solvothermal synthesis in a Co²⁺-containing solution. The obtained CoP/EEBP/N-FLGS nanocomposite demonstrates high electrocatalytic activity and stability towards HER in an alkaline medium. The nanocomposite is characterized by an overpotential of 190 mV at a current density of 10 mA cm⁻² as well as a small Tafel slope (78 mV dec⁻¹). These characteristics make the CoP/EEBP/N-FLGS nanocomposite superior to most electrocatalysts based on cobalt phosphides. The results of this study could be in demand for the future design and improvement of HER electrocatalysts. Full article

In recent years, the trend of applying intelligent technologies at all stages of construction has become increasingly popular. Particular attention is paid to computer vision methods for detecting various aspects in monitoring the structural state of materials, products and structures. This paper considers the solution of a scientific problem in the area of construction flaw detection using the computer vision method. The convolutional neural network (CNN) U-Net to segment violations of the microstructure of the hardened cement paste that occurred after the application of the load is shown. The developed algorithm makes it possible to segment cracks and calculate their areas, which is necessary for the subsequent evaluation of the state of concrete by a process engineer. The proposed intelligent models, which are based on the U-Net CNN, allow segmentation of areas containing a defect with an accuracy level required for the researcher of 60%. It has been established that model 1 is able to detect both significant damage and small cracks. At the same time, model 2 demonstrates slightly better indicators of segmentation quality. The relationship between the formulation, the proportion of defects in the form of cracks in the microstructure of hardened cement paste samples and their compressive strength has been established. The use of crack segmentation in the microstructure of a hardened cement paste using a convolutional neural network makes it possible to automate the process of crack detection and calculation of their proportion in the studied samples of cement composites and can be used to assess the state of concrete. Full article

This work describes a systematic method for the analysis of the attrition and residual morphology of natural fibers during the compounding process by twin-screw extrusion. There are several methods for the assessment of fiber lengths and morphology, although they are usually based on the use of non-affordable apparatus or time-consuming methods. In this research, the variation of morphological features such as the length, diameter and aspect ratio of natural fibers were analyzed by affordable optical scanning methods and open-source software. This article presents the different steps to perform image acquisition, refining and measurement in an automated way, achieving statistically representative results, with thousands of fibers analyzed per scanned sample. The use of this technique for the measurement of giant reed fibers in polyethylene (PE) and polylactide (PLA)-based composite materials has proved that there are no significant differences in the output fiber morphology of the compound, regardless of the fiber feed sizes, extruder scale, or the polymer used as matrix. The ratio of fiber introduced for the production of composites also did not significantly affect the final fiber size. The greatest reduction in size was obtained in the first kneading zone during compounding. Pelletizing or injection molding did not significantly modify the fiber size distribution. Full article

Multiwalled carbon nanotube (MWCNT) nanopaper (NP)-reinforced in-mold coating (IMC) nanocomposites were fabricated by dip soaking without organic solvent. The thermally activated IMC resin was selected to provide electromagnetic interference shielding protection for sheet molding compound (SMC) material as well as other plastic materials due to the proven good adhesion of IMC resin to the substrate. In this work, the technical feasibility of a continuous fabrication process was evaluated for a nanopaper/IMC (NP/IMC) composite. The curing behavior of the candidate IMC resin was studied for a better understanding of the fabrication of NP/IMC nanotape as a prepreg (with 10% polymerization), as well as the final curing once the nanotape was applied to the substrate. The required limiting maximum temperature to prevent curing during infiltration was established. This allows the fabrication of multilayer nanotape or coatings by stacking several layers of tape to improve the EMI shielding protection. To be specific, the average EMI shielding effectiveness for a one-layer composite was 21 dB, while it increased to 48 dB on average for a six-layer composite. Full article

This study used a hybrid combination of kenaf and hemp fibers and the multi-walled carbon nanotube (MWCNT) reinforcements in the matrix phase to synthesize the composites. A kenaf/hemp fiber blend with MWCNTs in epoxy was used for the specific concentration. The procedure used three composite materials chosen from pilot trials. The ratio of MWCNT filler particles was altered up to the agglomeration limit based on initial trials. Two specimens (2 and 3) were supplemented with MWCNTs in a concentration range of 0.5 wt. % to 1 wt. %, with the fiber concentration being maintained in equilibrium with the epoxy resin, all of the materials were tested under the same conditions. The hybrid nanocomposite was characterized for its morphological and mechanical properties; the tensile properties were higher for 1% MWCNTs concentration (specimen 2), while the flexural properties were higher for 0.5% MWCNTs, with values of 43.24 MPa and 55.63 MPa, correspondingly. Once the MWCNT concentration was increased to 1 wt. %, the maximum impact strength was achieved (specimen 3). In the limits of the Shore-D scale, the kenaf fiber and hemp fiber matrix composite (specimen 1) gained a hardness index of 84. Scanning electron microscopy was carried out to analyze the morphological features of the fractured samples and to assess the adhesion between the fiber, matrix, and surface. Among the various fillers tested, the kenaf fiber/hemp/MWCNT composite (specimen 3) demonstrated superior binding and reduced the incidence of fiber pull-out, breakage, and voids. In addition to the comparative analysis, the addition of 0.5 wt. % MWCNTs resulted in better mechanical properties compared to the other two combinations. Full article

Research on polymer nanocomposite nanofibers has seen remarkable growth over the past several years. One of the main driving forces for this progress is the increasing applicability of polymer nanocomposite nanofibers for technological applications. This review basically aims to present the current state of manufacturing polymer/graphene nanofiber nanocomposites, using appropriate techniques. Consequently, various conducting and thermoplastic polymers have been processed with graphene nano-reinforcement to fabricate the nanocomposite nanofibers. Moreover, numerous methods have been adopted for the fabrication of polymer/graphene nanocomposites and nanofibers including interfacial polymerization, phase separation, freeze drying, template synthesis, drawing techniques, etc. For the formation of polymer/graphene nanocomposite nanofibers, electrospinning can be preferable due to various advantages such as the need for simple equipment, control over morphology, and superior properties of the obtained material. The techniques such as solution processing, melt spinning, and spin coating have also been used to manufacture nanofibers. Here, the choice of manufacturing techniques and parameters affects the final nanofiber morphology, texture, and properties. The manufactured nanocomposite nanofibers have been examined for exceptional structural, microstructure, thermal, and other physical properties. Moreover, the properties of polymer/graphene nanofiber rely on the graphene content, dispersion, and matrix–nanofiller interactions. The potential of polymer/graphene nanocomposite nanofibers has been investigated for radiation shielding, supercapacitors, membranes, and the biomedical field. Hence, this review explains the literature-driven significance of incorporating graphene in polymeric nanofibers. Conclusively, most of the studies focused on the electrospinning technique to design polymer/graphene nanofibers. Future research in this field may lead to advanced innovations in the design and technical applications of nanocomposite nanofibers. To the best of our knowledge, research reports are available on this topic; however, the stated literature is not in a compiled and updated form. Therefore, field researchers may encounter challenges in achieving future advancements in the area of graphene-based nanocomposite nanofibers without first consulting the recent literature, such as an assembled review, to gain necessary insights, etc. Consequently, this state-of-the-art review explores the manufacturing, properties, and potential of polymer/graphene nanocomposite nanofibers. Full article

This research attempts to investigate the thermal performance of solar air collectors with pin fins and turbulators. Incorporating carbon-nanotube-based fins and turbulators in solar collectors can enhance their performance due to their high thermal conductivity, low weight, and high aspect ratio. In the present study, numerical analyses of a solar collector with pin fins and turbulators are carried out to investigate its effect on the Nusselt number. The paper begins with the numerical analysis of conventional air collectors and compares them with theoretical results. This is followed by numerical analyses, which are carried out to examine different configurations of the absorber plate with pin fins of varying diameters (10 mm, 20 mm, and 30 mm) and turbulators of varying heights (20 mm, 40 mm, and 60 mm) in the base plate. The analyses include variations in the Reynolds number ranging from 3000 to 15,000. Subsequently, after the performance of the solar collector with pin fins is evaluated, the effect of turbulators of varying heights on the Nusselt number is analyzed, followed by the analysis of the combined effect of pin fins and turbulators. The results are compared with traditional solar collectors and show that the combined effect of pin fins and turbulators can significantly improve the thermal performance of solar air collectors. The findings of this study can contribute to the development of renewable energy-based air conditioning, ventilation, and heating systems. Full article

Statistical based reconstruction methods and signal processing tooling techniques are implemented and used to detect delaminations or debondings within composite complex items with very high precision. From the literature, it appears that although a single procedure for the estimation of structural health is a fast solution, multiple analyses based on different reconstruction methods or different damage parameters are the way to achieve maturation assessments of the methodology. This highlights the fact that the hardware and software parts of an SHM system need two different assessment and maturation ways. This work focuses on the software part by proposing a way to start assessing the outcomes. In this paper, the damage detection and localization strategy in CFRP plate-like structures with elastic guided waves excited and acquired with a circular array PWAS network is considered. Previous outcomes are compared by new analyses using a new post-processing approach based on a cross-correlation-based technique in terms of the BVID (Barely Visible Impact Damage) surface position and its center of mass. The advantage of this specific study is hopefully to enable confidence in the transition from R&D to field implementation. In addition, this work tries to evidence an improvement in terms of cost efficiency and reduced complexity while maintaining the same accuracy. Full article

High-density polyethylene (HDPE) is a highly versatile plastic utilized in various applicative fields such as packaging, agriculture, construction, and consumer goods. Unfortunately, the extensive use of polyethylene has resulted in a substantial accumulation of plastic waste, creating environmental and economic challenges. Consequently, the recycling of polyethylene has become a critical concern in recent times. This work focuses on the recycling of HDPE parts recovered from end-of-life boats into materials suitable for the marine environment with additive manufacturing technology via screw-assisted extrusion 3D printing. In particular, rigid materials are obtained by adding glass fibers to HDPE to mitigate the loss of mechanical performance upon recycling. Eventually, the properties obtained with two different production methods were compared, namely compression molding and screw-assisted extrusion 3D printing. Since the developed materials will be exposed to an aggressive environment, an extended thermos-mechanical characterization (including fatigue resistance) and investigation of the stability to UV exposure were performed. Full article

Among conducting polymers, polythiophene has gained an important stance due to its remarkable physical features. Graphene is a unique, two-dimensional, nanocarbon nanomaterial. As in other polymers, graphene has been reinforced in polythiophene to form advanced nanocomposites. This comprehensive review covers the design, essential features, and methodological potential of significant polythiophene and graphene-derived nanocomposites. In this context, various facile approaches, such as in situ processing, the solution method, and analogous simplistic means, have been applied. Consequently, polythiophene/graphene nanocomposites have been investigated for their notable electron conductivity, heat conduction, mechanical robustness, morphological profile, and other outstanding properties. Studies have revealed that graphene dispersion and interactions with the polythiophene matrix are responsible for enhancing the overall characteristics of nanocomposites. Fine graphene nanoparticle dispersal and linking with the matrix have led to several indispensable technical applications of these nanocomposites, such as supercapacitors, solar cells, sensors, and related devices. Further research on graphene nanocomposites with polythiophene may lead to remarkable achievements for advanced engineering and device-related materials. Full article

Polymeric floating photocatalysts based on polyethylene (PE)/TiO₂ compositions were synthesized by in situ ethylene polymerization in the presence of a titanium–magnesium catalyst synthesized by the sequential deposition of a magnesium–aluminum complex and TiCl₄ on commercial TiO₂ P25. The optical band gap of the synthesized PE/TiO₂ composites was shown to be 3.1–3.3 eV, which allowed for their use as photocatalysts for the utilization of solar light. The photocatalytic activity of the PE/TiO₂ composites was studied for the degradation of methyl orange (MO) under irradiation with UV light (λ_max = 384 nm). The composites containing 20–50 wt.% of PE were found to have an optimum combination between floatability and photocatalytic activity. The maximum photodegradation rate was observed at an MO concentration below 5 ppm. The polymeric PE/TiO₂ floating photocatalysts could be used repeatedly, but the long-term exposure of the composites to UV radiation was accompanied by oxidation of the polymer. Full article

Coupled shear walls (CSWs) are structural elements used in reinforced concrete (RC) buildings to provide lateral stability and resistance against seismic and wind forces. When subjected to high levels of seismic loading, CSWs exhibit nonlinear deformation through cracking and crushing in concrete and yielding in reinforcements, thereby dissipating a significant amount of energy, leading to their permanent deformation. Externally bonded fiber-reinforced polymer (EB-FRP) sheets have proven to be effective in strengthening RC structures against various loading and environmental conditions. In addition, their high strength-to-weight ratio makes them an attractive solution as they can be easily applied without significantly increasing the structure’s weight. This study investigates the effectiveness of using EB-FRP sheets to reduce residual displacement in CSWs during severe earthquake loadings. Two series of 15-story and 20-story CSWs in Western and Eastern Canadian seismic zones, which serve as representative models for medium- and high-rise structures, were evaluated through nonlinear time history analysis. The numerical simulation of all CSWs and strengthened elements was carried out using the RUAUMOKO 2D software. The findings of this study provided evidence of the effectiveness of EB-FRP sheets in reducing residual deformation in CSWs. Additionally, significant reductions in the rotation of the coupling beams (CBs) and the inter-story drift ratio were observed. The results also revealed that bonding vertical FRP sheets to boundary elements and confining enhancement by wrapping CBs and wall piers is a very effective configuration in mitigating residual deformations. Full article

The purpose of this study was to reveal the effect of printing direction and post-printing conditions on static and fatigue bending characteristics of Ultem 9085 at two stress levels. Right after the printing, the Ultem samples were subjected to three cooling conditions: cooling in the printer from 180 to 45 °C for 4 h, rapid removal from the printer and cooling in the oven from 200 to 45 °C during 4 h, and removal from the printer and cooling at room temperature. Static 3-point bending tests were performed to estimate the flexural characteristics of Ultem 9085 samples after subjecting them to different post-printing conditions. The flexural strain was evaluated and applied for the stress ratios such as 75% and 50% of σ_max. Thus, displacement-controlled fatigue tests were carried out to reveal the effect of post-printing conditions on fatigue bending characteristics. The results obtained for the X and Y printing directions proved that the Ultem samples subjected to the cooling conditions in the printer and the oven had a similar static and fatigue behavior, while a lower performance was obtained for the samples cooled at room temperature. Regardless of the cooling regime, significantly lower bending performance was revealed for the samples printed in the Z-direction since they have intra-layer filaments parallel to the stress plane, and, accordingly, intra-layer adhesion has a crucial influence on mechanical performance. Full article

In the context of energy efficiency and resource scarcity, lightweight construction has gained significant importance. Composite materials, particularly sandwich structures, have emerged as a key area within this field, finding numerous applications in various industries. The exceptional strength-to-weight ratio and the stiffness-to-weight ratio of sandwich structures allow the reduction in mass in components and structures without compromising strength. Among the widely used core designs, the honeycomb pattern, inspired by bee nests, has been extensively employed in the aviation and aerospace industry due to its lightweight and high resistance. The hexagonal cells of the honeycomb structure provide a dense arrangement, enhancing stiffness while reducing weight. However, nature offers a multitude of other structures that have evolved over time and hold great potential for lightweight construction. This paper focuses on the development, modeling, simulation, and testing of lightweight sandwich composites inspired by biological models, following the principles of biomimetics. Initially, natural and resilient design templates are researched and abstracted to create finished core structures. Numerical analysis is then employed to evaluate the structural and mechanical performance of these structures. The most promising designs are subsequently fabricated using 3D printing technology and subjected to three-point bending tests. Carbon-fiber-reinforced nylon filament was used for printing the face sheets, while polylactic acid (PLA+) was used as the core material. A honeycomb-core composite is also simulated and tested for comparative purposes, as it represents an established design in the market. Key properties such as stiffness, load-bearing capacity, and flexibility are assessed to determine the potential of the new core geometries. Several designs demonstrated improved characteristics compared to the honeycomb design, with the developed structures exhibiting a 38% increase in stiffness and an 18% enhancement in maximum load-bearing capacity. Full article