J. Compos. Sci., Volume 6, Issue 8 (August 2022) – 26 articles

This paper presents an implementation of a robust control LQG-Kalman model applied to composite Kirchhoff plate dynamics. A reduced model of a finite element method and control procedure is considered in the modeling of a structure because of the important number of piezoelectric patches used in control. Replacing the full model with a short model reduces the computational and time costs, especially when the number of degrees of freedom is significant. In robust control, the measurement of all states is not necessary and the observability and estimability criteria can be exploited, while conventional LQR control assumes that the data accessibility of all states is available. For this reason, robust control is proposed to control the random external disturbances and is compared to LQR control to illustrate its practicability and efficiency. The sensors and actuators in the thermo-piezoelectric material are randomly distributed on both sides of the plate to establish the control procedure. A Monte Carlo simulation is used in the selection of the degrees of freedom of sensors presenting high electrical outputs. Numerical simulations are performed to demonstrate the effectiveness of the proposed control procedure in a reduced model and under mechanical and thermal disturbances in comparison with the LQR control. Full article

The science and technology of electrical equipment for communication experience a rapid growth rate. However, the unwanted interference of electromagnetic waves of different electronic devices brought serious anxiety about human health as well as the lifetime and performance of the systems. To combat these consequences, we need to lessen the electromagnetic wave emission by making our devices more noise-sensitive. Herein, we incorporated carbon nanotubes (CNTs) at different ratios into natural rubber (NR) and chlorobutyl rubber (CIIR) to achieve shielding efficiency, along with carbon nanofibers (CNFs), nanoclay (NC), and carbon black (CB) to manipulate EMI shielding performance. The blend of CIIR/NR in a 70/30 (w/w) ratio also mixed with CNT, CNF, CB and NC. The effect of different fillers and their concentration/combination was analyzed by UV spectroscopy, demonstrating an absorbance peak in CIIR in 320 nm. From FTIR spectroscopy, it was evident that CIIR/CNT (5 phr), NR (30 wt.%)/CIIR (70 wt.%)/CB (5 phr), and NR (30 wt.%)/CIIR (70 wt.%)/CNT (5 phr) new bonding signatures were detected. The dielectric spectroscopic analyses were reflected in dielectric loss, dielectric permittivity and AC conductivity, where NR (30 wt.%)/CIIR (70 wt.%)/CB (5 phr) blend nanocomposite with 5 dB showed significantly higher EMI shielding performance compared to CIIR/CNT (5 phr) and CIIR/CNF (5 phr) with 29 and 15 dB, respectively. The greater the concentration of nanofiller, the lower the electromagnetic interference (EMI) shielding, i.e., CIIR/CNT (10 phr) with 15 dB (≈−48% dB), but with more agglomeration. Surprisingly, even a combination of fillers did not lead to higher EMI performance, such that CIIR/CNT (5 phr)-CB (20 phr) showed an EMI shielding value of 59 dB. Full article

Building construction contributes a significant portion to the global consumption of energy and greenhouse gas (GHG) emissions, and decarbonization has become one of the main targets. This has turned much attention to renewable materials, particularly timber construction. Wood is a natural composite, and it causes challenges in its natural state due to its mechanical properties and functionality, which has constrained its use in construction. Laminating wood sections into glue-laminated (glulam) and cross-laminated timber (CLT) components overcomes limitations in dimensions and inconsistencies in its properties. We went beyond these technologies and explored the potential of combining timber of the radiata pine species with synthetic fibers, aiming for hybrid natural–synthetic composite beams. This research illustrated various reinforcement mechanisms and analyzed their structural properties. The results from the experiments showed that carbon fiber-reinforced timber composites have up to 49% additional increase in load-bearing capacity compared to unreinforced beams. An identical amount of strain required less stress, and the composite portrayed a metal-like ductility property, a characteristic referred to as pseudo-ductility. It reduces the material consumption in beams through a more efficient use of materials, particularly around compression areas before tensile rupture. The resulting composites are sustainable yet structurally capable, contributing to the reduction in CO₂ emissions in timber construction systems. Full article

Growing environmental concerns are becoming significant challenges for large-scale applications in the automotive industry. Replacing and hybridizing glass fibers with natural fibers for non-structural applications is one effective way to address this challenge, while retaining the useful properties of both. This paper investigates the mechanical and damping performance of four types of compression-molded materials: polyester matrix (reference), nettle (6% by weight), hybrid 1 (6% glass and 6% nettle by weight), and hybrid 2 (12% glass and 6% nettle by weight), with polyester matrix at an ambient temperature. The tensile tests using digital image correlation (DIC) showed that by adding 6% by weight nettle fibers for polymer matrix tensile modulus increases by 21%. For the hybrid 1 two-layer composite (6% by weight glass and 6% by weight nettle) and the hybrid 2 three-layer composite (12% by weight glass and 6% by weight nettle), it increases by 80% and 101%, respectively. On the other hand, dynamic mechanical analysis (DMA) has been used to assess the damping properties of the materials. The results showed that the loss factor increased by 6~14% for nettle reinforced composite, by 8~25% for hybrid 1 glass-nettle reinforced composite and by 2~15% for hybrid 2 glass-nettle reinforced composite for frequencies around 1.0~2.0 Hz and around 12 Hz corresponding to vehicle body and suspension natural frequencies, respectively. These results showed that glass fibers can be replaced by nettle fibers without compromising performance. Full article

Biomass–fungi composites, an emerging class of sustainable materials, have potential applications in the construction and packaging industries. Molding-based manufacturing methods are typically employed to make products from these composites. Recently, a 3D printing-based method was developed for biomass–fungi composites to eliminate the need for making molds and to facilitate customized product design compared with manufacturing methods based on molding and hot-pressing. This method has six stages: biomass–fungi material preparation; primary colonization; mixture preparation; printing; secondary colonization; and drying. This paper reports a study about the effects of waiting time between the mixture preparation and 3D printing using biomass–fungi composites. As the waiting time increased from 0.25 to 3 h, the hardness and compressibility of the prepared mixture increased. As the waiting time increased from 0.25 to 8 h, the shear viscosity showed a decreasing trend; the yield stress of the prepared mixture increased at the beginning, then significantly decreased until the waiting time reached 3 h, and then did not significantly vary after 3 h. As the waiting time increased, the storage modulus and loss modulus decreased, the loss tangent delta increased, and the minimum required printing pressure for continuous extrusion during extrusion-based 3D printing increased. The print quality (in terms of layer-height shrinkage and filament-width uniformity) was reasonably good when the waiting time did not exceed 4.5 h. Full article

It is well known that a proton conductor is needed as an electrolyte of hydrogen fuel cells, which are attracting attention as an environmentally friendly next-generation device. In particular, anhydrous proton-conducting electrolytes are highly desired because of their advantages, such as high catalytic efficiency and the ability to operate at high temperatures, which will lead to the further development of fuel cells. In this study, we have investigated the proton-conducting properties of the hydroxyapatite (HAp)-collagen composite without external humidification conditions. It was found that, by injecting HAp into collagen, the electrical conductivity becomes higher than that of the HAp or the collagen. Moreover, the motional narrowing of the proton NMR line is observed above 130 °C. These results indicate that the electrical conductivity observed in the HAp-collagen composite is caused by mobile protons. Furthermore, we measured the proton conduction of HAp-collagen composite films with different HAp contents and investigated the necessity of the appearance of proton conductivity in HAp-collagen composites. HAp content (n = 0–0.38) is the number of HAp per collagen peptide representing Gly-Pro-Hyp. These results indicate that injection of HAp into collagen decreases the activation energy of proton conduction which becomes almost constant above a HAp content n of 0.3. It is deduced that the proton-conduction pathway in the HAp-collagen composite is fully formed above n = 0.3. Furthermore, these results indicate that the value of the activation energy of proton conductivity was lowered, accompanied by the formation of the HAp-collagen composite, and saturated at n > 0.3. From these results, the HAp-collagen composite forms the proton-conduction pathway n > 0.3 and becomes the proton conductor with no external humidification in the condition of n > 0.3 above 130 °C. Full article

Metal fiber hybrids (MFH) exhibit outstanding mechanical properties. They combine the advantages of ductile metallic materials with the well-known advantages of classical glass or carbon fibers in polymer matrices. Previous research has shown that these hybrid material concepts can improve structural integrity and energy absorption while maintaining their excellent weight-specific mechanical properties as well as allowing a wider range of multifunctional applications. In today’s component design process, simulation is a powerful tool for engineers to exploit the full mechanical potential of the material used. However, describing the material behavior including its multifunctional usability in numerically aided design processes of components is currently one of the major challenges for MFH. Against this background, this work focuses on the development and evaluation of a description method for MFH in the finite element analysis (FEA). A steel and carbon fiber reinforced epoxy resin (SCFRP) with hybridization at the laminate level is chosen as the reference material. To describe the behavior of unidirectional steel fiber reinforced plastic (SFRP) layers, a material model combining an orthotropic damage model and a 1D-plasticity model is proposed and implemented as a user-defined subroutine for LS-Dyna. In addition, SCFRP laminates are manufactured, tested under tensile loading, and used to parameterize the material models and to validate the description method for SCFRP. In this study, it is shown that the description method in combination with the newly developed material model is able to describe the complex failure mechanism of SCFRP. In particular, with respect to the material behavior up to the failure of the carbon fibers, a very good mapping accuracy can be achieved. Strain localization effects occur in both numerically predicted and experimentally measured post-failure behavior. Therefore, it could be concluded that the accuracy of the numerical predictions strongly depends on the geometric resolution of the discretization. Full article

In this paper, the structure and phase transition temperature of bulk silicate materials are studied by the simulation method (SM) of molecular dynamics (MD). In this research, all samples are prepared on the same nanoscale material model with the atomic number of 3000 atoms, for which the SM of MD is performed with Beest-Kramer-van Santen and van Santen pair interaction potentials under cyclic boundary conditions. The obtained results show that both the model size (l) and the total energy of the system (E_tot) increase slowly in the low temperature (T) region (negative T values) at pressure (P), P = 0 GPa. However, the increase of l determines the E_tot value with very large values in the high T region. It is found that l decreases greatly in the high T region with increasing P, and vice versa. In addition, when P increases, the decrease in the E_tot value is small in the low T region, but large in the high T region. As a consequence, a change appears in the lengths of the Si-Si, Si-O, and O-O bonds, which are very large in the high T and high P regions, but insignificant in the low T and low P regions. Furthermore, the structural unit number of SiO₇ appears at T > 2974 K in the high P region. The obtained results will serve as the basis for future experimental studies to exploit the stored energy used in semiconductor devices. Full article

Chemical treatment is a significant factor in improving the natural fiber quality for composite materials production. In this study, the alkaline treatment of Ethiopian Arabica coffee husk by sodium hydroxide (NaOH) was performed to improve the fiber quality. A total of 10% (w/w) NaOH has been applied for the alkaline treatment. Comprehensive physicochemical characterizations, such as proximate analysis, cellulosic composition, porosity, and structural analysis of treated and untreated coffee husk, have been conducted and compared. The experimental results showed that lignin and hemicellulose were reduced by 72% and 52%, respectively, thus improving the overall fiber quality. Therefore, this study indicated alkaline treatment of Ethiopian coffee husk is effective for fiber quality enhancement. It can be applied as a potential feedstock for fiber production in the composite production sector. Full article

Most of the studies involving composite slabs under fire follow the standard fire scenario described by the ISO 834 curve, disregarding the cooling-phase. However, recent studies show that this phase is equally important, as it can lead to the collapse of the structure. Therefore, the present research carried out a parametric study, using numerical models, validated through experimental tests, to evaluate the thermal behaviour of the composite slabs components under natural fire. The results showed that the maximum temperatures in the reinforcement bars occur during the cooling-phase, reaching temperatures up to 300% higher than at the heating-phase, on the steel deck occur at the end of heating, and that the concrete thickness above the steel deck influences the temperature of these components. Also, during the cooling-phase, a “heat bubble” effect is observed on the ribs of the composite slabs, where the reinforcement bars are normally placed. These results highlight the importance of considering different natural fire scenarios, in the structural performance and safety of composite slabs, since during the cooling-phase there is still heat transfer between the elements, which can lead to slab failure. New parameters are proposed to find the temperature of each component for different fire ratings. Full article

The Aloe vera (L.) Burman f. pulp extract (AE), obtained from the inner parts of Aloe vera leaves, is rich in polysaccharides, including glucomannans, acemannans, pectic compounds, cellulose, and hemicelluloses; acemannan and glucomannan are considered the two main components responsible for most of the plant’s therapeutical properties. Besides having anti-inflammatory activity, these polysaccharides accelerate wound healing and promote skin regeneration, thus they can be utilized in healing products. The objective of this study was to develop Aloe vera mucilaginous-based hydrogels for topical use in psoriasis treatment. The hydrogels were prepared with 80% w/w of A. vera mucilaginous gel, evaluating two distinct polymers as the gelling agent: 1% carbopol 940 (FC1 and FC2) or 2% hydroxyethylcellulose (FH3 and FH4). FC1, FC2, FH3 and FH4 were evaluated for their organoleptic characteristics, rheological properties, pH and glucomannan content. Polysaccharide fractions (PFs) were extracted from the AE and used as a group of chemical markers and characterized by infrared (IR) spectroscopy and 1H nuclear magnetic resonance (₁H NMR). The quantification of these markers in the raw material (AE) and in the hydrogels was carried out using spectrophotometric techniques in the UV-VIS region. The hydrogels-based hydroxyethylcellulose (FH3 and FH4) had glucomannan contents of 6.76 and 4.01 mg/g, respectively. Formulations with carbopol, FC1 and FC2, had glucomannan contents of 8.69 and 9.17 mg/g, respectively, an ideal pH for application on psoriasis, in addition to good spreadability and pseudoplastic and thixotropic behavior. Considering these results, hydrogel FC1 was evaluated for its keratolytic activity in a murine model of hyperkeratinization. For that, 0.5 mL of test formulations FC1 and FPC (0.05% clobetasol propionate cream) were topically applied to the proximal region of adult rats daily for 13 days. After euthanasia, approximately 2.5 cm of the proximal portion of each animal’s tail was cut and placed in 10% buffered formalin. Then, each tail fragment was processed and stained with hematoxylin and eosin (HE), and the results obtained from the histological sections indicated a 61% reduction in stratum corneum for animals treated with the A. vera hydrogel (FC1G) and 66% for animals treated with clobetasol propionate (PCG), compared to the group of animals that did not receive treatment (WTG). This study led to the conclusion that compared to the classic treatment (clobetasol propionate), the 80% A. vera hydrogel showed no significant difference, being effective in controlling hyperkeratinization. Full article

Plastic has transformed the world; however, it generates a huge amount of waste plastics. It is well evident that, if urgent action is not undertaken on plastic pollution, it will pose threats to not only the environment, but also human life. Just simply discarding waste plastics will result in wasting a lot of valuable materials that could be recycled. Recently, the use of waste plastics has been considered for producing wood plastic composites (WPCs), which are superior to normal wood. Waste plastics are pelletized using an extruder and are then subjected to injection molding. In this study, investigations were carried out to determine the possibility of producing WPCs without the palletization of waste plastic to turn WPC production into a shorter, simple, and easy-to-achieve process. Here, a waste milk bottle, a familiar single-use plastic, was picked as a case study. Waste plastic granules and wood particles were mixed and directly injection molded to produce valuable WPCs. The water absorption of WPCs with 20% wood is 0.35%, and this increased to 0.37% when wood content was increased to 40%. The tensile strength at yield, elongation at break, and impact strength of WPCs with 20% wood content are 19.54 MPa, 5.21%, and 33.92 KJ/m², respectively, whereas it was 17.23 MPa, 4.05%, and 26.61 KJ/m² for the WPCs with 40% wood content. This process can be a potential solution for two problematic wastes at the same time. Full article

Composite Overwrapped Pressure Vessels (COPVs) are widely used in fields including aeronautics and by companies such as SpaceX to hold high pressure fluids. They are favored for these applications because they are far lighter than all-metal vessels, although they demand special design, manufacturing, and testing requirements. In this study, finite element modeling was used to conducted stress and damage assessments on a composite overwrapped pressure vessel that has a 4 mm thick aluminum core cylinder. To develop the optimum COPV, the lamina sequences, thickness, and fiber winding angle were considered. The relationship between these variables and the composite-overwrapped structure’s maximum burst pressure bearing capacity was assessed. The ABAQUS composite modeler was used to design and generate 14 models of COPVs from carbon fiber/epoxy plies with a consistent thickness of 6.5 mm and various fiber angle orientations. The effects of the ply stacking order were analyzed by the finite element analysis approach for all designed models, which had 13 layers of uniform thickness but a varying fiber orientation. A ply stacking sequence of [55°, −55°] PP winding pattern had an optimum COPV design profile, with a burst pressure bearing capacity of 24 MPa. The stress–strain distribution along the geometry of the COPV was also obtained using the finite element method, and it was found that the distribution is uniform over the surface of the COPV and that its peak values are found towards the polar boss section of the COPV. Extreme stress gradients were noticed when the boss nears its geometrical transition to the dome phase. This factor is evident from the change in the ply thickness caused by the overlapped fiber orientation. The results obtained from this study are useful for the design and application of composite overwrapped pressure vessels. Full article

In this paper, biobased carbons were used as fillers in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). The mechanical and electrical properties of these 100% biocomposites were analyzed. First, biocarbons were prepared from wood dust and cellulose fibers using carbonization temperatures ranging 900–2300 °C. XRD revealed significant improvements of the graphitic structure with increasing temperatures for both precursors, with slightly higher ordering in wood-dust-based carbons. An increase of the carbon content with continuous removal of other elements was observed with increasing temperature. The carbonized cellulose fiber showed an accumulation of Na and O on the fiber surface at a carbonization temperature of 1500 °C. Significant degradation of PHBV was observed when mixed with this specific filler, which can, most probably, be attributed to this exceptional surface chemistry. With any other fillers, the preparation of injection-molded PHBV composites was possible without any difficulties. Small improvements in the mechanical performance were observed, with carbonized fibers being slightly superior to the wood dust analogues. Improvements at higher filler content were observed. These effects were even more pronounced in the electrical conductivity. In the range of 15–20 vol.% carbonized fibers, the percolation threshold could be reached, resulting in an electrical conductivity of 0.7 S/cm. For comparison, polypropylene composites were prepared using cellulose fibers carbonized at 2000 °C. Due to longer fibers retained in the composites, percolation could be reached in the range of 5–10 vol.%. The electrical conductivity was even higher compared to that of composites using commercial carbon fibers, showing a great potential for carbonized cellulose fibers in electrical applications. Full article

Tissue engineering is a promising area that is aimed at tissue regeneration and wound repair. Sodium alginate (SA) has been widely used as one of the most biocompatible materials for tissue engineering. The cost-efficiency and rapid gel ability made SA attractive in would healing and regeneration area. To improve printability and elasticity, many hydrogel-based bioinks were developed by mixing SA with other natural or synthetic polymers. In this paper, composite SA/COL bioink was used for the bioprinting of artificial cartilage tissue mimicries. The results showed that the concentration of both SA and COL has significant effects on filament diameter and merging. A higher concentration of the bioink solution led to better printing fidelity and less deformation. Overall, a higher SA concentration and a lower COL concentration contributed to a lower shrinkage ratio after crosslinking. In summary, the SA/COL composite bioink has favorable rheological properties and this study provided material composition optimization for future bioprinting of engineered tissues. Full article

Hemodialysis (HD) is a life-sustaining treatment of crucial importance in managing end-stage renal disease (ESRD). However, this membrane-based therapy is associated with acute side-effects due to bioincompatibility issues and limitations on the removal of uremic toxins. The present study assessed the influence of hydrodynamic conditions applied during HD treatment on protein-mediated inflammatory and thrombotic responses. The membrane modules considered are commonly used in Canadian hospitals and are comprised of a polymer blend of polyarylether sulfone-polyvinylpyrrolidone (PAES). The membranes morphology and hydrophilicity were assessed using SEM, AFM, BET, and zeta potential. An in vitro study evaluated the adsorptive behavior of fibrinogen (FB) to the membrane under different flow conditions. Lower rates of 200 mL/min promoted slower and significant FB adsorption, leading to more severe inflammatory and thrombotic responses. Hydrodynamic conditions also affected the concentration of all inflammatory biomarkers. Lower flow rates triggered more complement activation as well as coagulation, clotting, and inflammatory responses compared to higher flow rates. At the end of the dialysis session, patients treated with a Qb of 200 mL/min presented a significant increase in the concentration of C5a (232%), properdin (114%), serpin (545%), IL-1α (50%), IL-6 (450%), and vWF (212%). IL-1β and TNF-α concentrations declined by 12.5 and 35.5%, respectively. Male patients experienced more severe inflammatory responses than female patients at the operating conditions considered. Comparing the pre- and post-dialysis levels of female and male patients, female patients experienced significantly higher levels of IL-6 and properdin, while male patients presented higher levels of C5a, IL-1α, and IL-6. The results of this study will help clinical doctors evaluate the impact of HD operating conditions on blood activations before prescribing treatment and inform expectations for outcomes in female and male patients. Full article

Rubber recycling attracts considerable attention by a variety of industries around the world due to shrinking resources, increasing cost of raw materials, growing awareness of sustainable development, and environmental issues. Recycled rubber is commonly used in aeronautic, automotive, and transportation industries. In this study, recycled rubber composites designed with different reinforcements in the literature are scrutinized by means of toughening mechanisms, mechanical and physical properties, as well as microstructural and fracture surface analysis. Microscale reinforcements (glass bubbles, alumina fiber, etc.) and nanoscale reinforcements (nanosilica, graphene nanoplatelets, etc.) utilized as reinforcements in rubber composites are thoroughly reviewed. The general mechanical properties reported by previous studies, such as tensile, compressive, and flexural strength, are investigated with the main goal of optimizing the amount of reinforcement used. The majority of the studies on recycled rubber composites show that recycled rubber reinforced with microscale particles leads to the development of physical and mechanical properties of the structures and also provides low-cost and lightweight composites for several application areas. Moreover, recycled rubber containing composites can be suitable for applications where high toughness and high resistance to impact are desirable. The present review aims to demonstrate research on reinforced recycled rubber composites in the literature and prospective outcomes. Full article

Non-crimp fabrics (NCFs) are increasingly used in industry for manufacturing of composite structures due to a combination of high mechanical properties and excellent manufacturability. As with other composites, in-service damage can be a cause for severe reduction in load-carrying capacity of NCF-reinforced plastics. In this experimental and numerical study, two constitutive material models previously used only for damage prediction in unidirectional (UD) tape and woven fabric-reinforced materials (LS-DYNA’s *MAT_ENHANCED_COMPOSITE_DAMAGE—MAT54 and *MAT_LAMINATED_COMPOSITE_FABRIC—MAT58) were evaluated for simulating transverse crushing of composite parts processed from a non-crimp carbon fabric. For this purpose, UD NCF components of tubular shape were subjected to transverse crushing through a controlled indentation of a metallic cylinder, and results of the experiment were compared with numerical modeling. Considered verification metrics included the observed and the predicted patterns of interlaminar damage, the extent of delamination, as well as the ability of the models to replicate force-displacement response exhibited by the tested specimens. Full article

A novel bio-based nanocomposite film was developed using the combination of gelatine and cellulose nanofiber (CNF) as a polymer matrix and zinc oxide nanoparticles (ZnONP) as nanofillers. The nanocomposite film solution was developed using simple solution mixing and film prepared by the following casting methods. The fabricated nanocomposite film containing 2 wt% of ZnONP shows excellent UV-light barrier properties (>95%) and high transparency (>75%). The presence of ZnONP also improves the mechanical strength of the film by ~30% compared to pristine gelatin/CNF-based film, while the flexibility and rigidity of the nanocomposite film were also slightly improved. The addition of ZnONP slightly increased (~10%) the hydrophobicity while the water vapor barrier properties remain unaltered. The hydrodynamic properties of the bio-based film were also changed in the presence of ZnONP, moisture content and the swelling ratio slightly enhanced, whereas water solubility was decreased. Moreover, the integration of ZnONP introduced antibacterial activity toward foodborne pathogens. The fabricated bio-based nanocomposite film could be useful in active packaging applications. Full article

The quality of Liquid Composite Molding (LCM) manufactured components is strictly related to the fibrous preform impregnation. As Darcy’s law suggests, the resin flow is influenced by the pressure gradient, geometrical features of the reinforcement, and resin viscosity. The former two parameters are dictated by the requirements of the component and other constraints; therefore, they are hardly modifiable during the process. Resin preheating increases its fluency, thus enhancing the impregnation and saturation flow, and reducing the mold filling time. In the present work, a microwave heating system has been integrated within a vacuum bag resin infusion process, to analyze the effect of the online preheating on the fiber impregnation. To monitor the resin flow a dielectric sensors-based system is used. Results from resin infusion tests conducted with and without the resin pre-heating were compared: the outcomes indicated an advance of approximately 190 s of the flow front when microwave heating is applied with respect to the unheated tests. Full article

An iron oxide/reduced graphene oxide (ION-RGO) nanocomposite has been fabricated to functionalize a low-cost electrochemical nitrite sensor realized by light-scribed reduced graphene oxide (LRGO) electrodes on a PET substrate. To enhance the stability and adhesion of the electrode, the PET substrate was modified by RF oxygen plasma, and a thin layer of the cationic poly (diallyl dimethyl ammonium chloride) was deposited. Raman spectroscopy and scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy (SEM-EDX) reveal that the light-scribing process successfully reduces graphene oxide while forming a porous multilayered structure. As confirmed by cyclic voltammetry, the LRGO electrochemical response to ferri-ferrocyanide and nitrite is significantly improved after functionalization with the ION-RGO nanocomposite film. Under optimized differential pulse voltammetry conditions, the LRGO/ION-RGO electrode responds linearly (R2 = 0.97) to nitrite in the range of 10–400 µM, achieving a limit of detection of 7.2 μM and sensitivity of 0.14 µA/µM. A single LRGO/ION-RGO electrode stands for 11 consecutive runs. The novel fabrication process leads to highly stable and reproducible electrodes for electrochemical sensors and thus offers a low-cost option for the rapid and sensitive detection of nitrite. Full article

The use of waste materials to make eco-friendly wood-polymer composites has been explored by many researchers for academic and industrial purposes due to the low cost, biodegradability, and availability of waste wood flour. Polypropylene (PP)/ground tyre rubber (GTR)/wood flour (WF) composites were prepared using an internal batch mixer at a temperature of 165 °C for 8 min, and the samples were injection-moulded at 190 °C with a pressure of 6 MPa. The design of the experimental approach was used to determine and optimize the proportions of each component in the composites. The morphology of the untreated composites showed more voids and the agglomeration of fillers, namely WF and GTR, in the PP matrix. Fewer voids, as well as improved distribution, were observed in the compatibilized composites. The incorporation of ethylene-1-butene as a compatibilizer improved the thermal stability and elongation at the break of the composites. The addition of WF increased the elongation at break and decreased the tensile strength of the composites. Overall, the use of statistically designed experiments has aided in attaining the optimum formulations of the wood flour–polymer composites. Full article

The discovery of an innovative category of inorganic geopolymer composites has generated extensive scientific attention and the kaleidoscopic development of their applications. The escalating concerns over global warming owing to emissions of carbon dioxide (CO₂), a primary greenhouse gas, from the ordinary Portland cement industry, may hopefully be mitigated by the development of geopolymer construction composites with a lower carbon footprint. The current manuscript comprehensively reviews the rheological, strength and durability properties of geopolymer composites, along with shedding light on their recent key advancements viz., micro-structures, state-of-the-art applications such as the immobilization of toxic or radioactive wastes, digital geopolymer concrete, 3D-printed fly ash-based geopolymers, hot-pressed and foam geopolymers, etc. They have a crystal-clear role to play in offering a sustainable prospect to the construction industry, as part of the accessible toolkit of building materials—binders, cements, mortars, concretes, etc. Consequently, the present scientometric review manuscript is grist for the mill and aims to contribute as a single key note document assessing exhaustive research findings for establishing the viability of fly ash-based geopolymer composites as the most promising, durable, sustainable, affordable, user and eco-benevolent building materials for the future. Full article

Metals have been investigated as biomaterials for a wide range of medical applications. At nanoscale, some metals, such as gold nanoparticles, exhibit plasmonics, which have motivated researchers’ focus on biosensor development. At the device level, some metals, such as titanium, exhibit good physical properties, which could allow them to act as biomedical implants for physical support. Despite these attractive features, the non-specific delivery of metallic nanoparticles and poor tissue–device compatibility have greatly limited their performance. This review aims to illustrate the interplay between polymers and metals, and to highlight the pivotal role of polymer–metal composite/nanocomposite healthcare materials in different biomedical applications. Here, we revisit the recent plasmonic engineered platforms for biomolecules detection in cell-free samples and highlight updated nanocomposite design for (1) intracellular RNA detection, (2) photothermal therapy, and (3) nanomedicine for neurodegenerative diseases, as selected significant live cell–interactive biomedical applications. At the device scale, the rational design of polymer–metallic medical devices is of importance for dental and cardiovascular implantation to overcome the poor physical load transfer between tissues and devices, as well as implant compatibility under a dynamic fluidic environment, respectively. Finally, we conclude the treatment of these innovative polymer–metal biomedical composite designs and provide a future perspective on the aforementioned research areas. Full article

We developed a new Bach-type reaction in the presence of oxy-hemoglobin as an oxygen supplier to synthesize polyazobenzene by traditional Bach reaction. The resultant product is a form of polymeric dye/hemoglobin copolymer. The advantage of this research is that it involves a new reaction using the function of biomolecules, as well as the formation of plastics and biomaterials. The bio-based material may have good affinity with life forms, which may lead to applications in medical science. Full article