J. Compos. Sci., Volume 6, Issue 9 (September 2022) – 36 articles

This study deals with the impact of the heating rate (HR), temperature (T), and the number of atoms (N) on the structural features of amorphous nanoparticles (ANPs) of Ni by molecular dynamics simulation (MDS) with the Pak–Doyama pair interaction potential field (PD). The obtained results showed that the structural features of ANPs of Ni are significantly affected by the studied factors. The correlation between the size (D) and the N was determined to be D~N^−1/3. The energy (E) was proportional to N⁻¹, and the Ni-Ni link length was 2.55 Å. The glass transition temperature (T_g) derived from the E-T graph was estimated to be 630 K. An increase in the HR induced a change in the shape of the ANPs of Ni. Furthermore, raising the HR caused an enhancement in the D and a decrement in the density of atoms. The obtained results are expected to contribute to future empirical studies. Full article

In this paper, several analyses were conducted to investigate the buckling behavior of Functionally Graded Material (FGM) thin plates with various circular cutout arrangements. The computer model was simulated using the Finite Element (FE) software ABAQUS. The developed model was validated by the authors in previous research. A parametric analysis was employed to investigate the effect of plate thickness and circular cutout diameter on the buckling behavior of the FGM thin plates. The normalized buckling load was also calculated to compare the buckling performance of FGM plates with various dimensions. Moreover, von Mises stress analysis was examined to understand the yield capability of the FGM plates in addition to the buckling modes that show the stress distribution of the critical buckling stress. Hence, this research provides a comprehensive analysis to display the relation between the critical buckling load and the arrangement of the circular cutouts. The results show that the critical buckling load heavily depends on the dimension of the plate and the cutout size. For instance, an increase in the plate thickness and a decrease in the cutout diameter increase the critical buckling load. Moreover, the circular cutout in a horizontal arrangement exhibited the best buckling performance, and as the arrangement shifts to a vertical arrangement, the buckling performance deteriorates. Full article

Osteoporosis increases the risk of bone fracture by reducing bone mass and thereby increasing bone fragility. The addition of strontium (Sr) nanoparticles in bone tissue results in a strengthening of the bone, induction bone formation by osteoblasts, and reduction of bone reabsorption by osteoclasts. The use of Sr for bone tissue regeneration has gained significant research interest in recent years due to its beneficial properties in treating osteoporotic-induced bone loss. We hypothesized that Sr-coated and antibiotic-doped HNTs could be used in antimicrobial coatings and as an antibacterial drug delivery vehicle. Accordingly, we coated HNTs with strontium carbonate (SrHNT) using a simple, novel, and effective electrodeposition method. We tested the antibacterial properties of SrHNT on Escherichia coli, Staphylococcus aureus, and Staphylococcus epidermis using the disc diffusion method. We assessed the potential cytotoxic and proliferative effects of SrHNTs on pre-osteoblasts using a Live/Dead cytotoxicity and cell proliferation assay. We successfully coated HNTs with strontium using a one-step benign coating method that does not produce any toxic waste, unlike most HNT metal-coating methods. Antibacterial tests showed that the SrHNTs had a pronounced growth inhibition effect, and cell culture studies using MC 3T3 cells concluded that SrHNTs are cytocompatible and enhance cell proliferation. Full article

The tensile properties of fabric-reinforced cementitious matrix (FRCM) composites are experimentally investigated through clevis-grip tensile tests (according to AC434 provisions) on FRCM coupons realized with customized (ad hoc developed in this paper) cement-based matrices. The tested FRCM coupons are reinforced with basalt, carbon, or steel fabrics, and are prepared with three different matrices: one-component mortar incorporating dispersible copolymer powders of vinyl acetate and ethylene (matrices A and B) and two-component mortar with carboxylated styrene–butadiene copolymer liquid resin (matrix C). This has made it possible to investigate the mechanical compatibility between different mortar matrices and fabrics and the resulting tensile properties of FRCM composites in the uncracked, cracking, and fully cracked phases. Experimental results are critically analyzed in terms of stress–strain curves and failure mechanisms comparatively for the analyzed FRCM systems. It has been shown that the matrix B exhibits a good compatibility with the basalt pre-impregnated fabric, while the matrix C appears to be the most suitable candidate to optimize the interfacial stress transfer at the fiber–matrix interface for all fabrics, thus exalting the mechanical performances in terms of tensile strength and ultimate strain. The results of this experimental program can be useful for designing optimized mortar mixes aimed at realizing novel FRCM composites or at improving existing FRCM systems by suitably accounting for compatibility behavior and slippage at the fabric–matrix interface. Full article

The increasing demands for more durable, lighter, and smarter structures have led to the development of new and advanced composites. Increased strength and simultaneous weight reduction have resulted in energy savings and applications in several manufacturing industries, such as the automotive and aerospace industries as well as in the production of everyday products. Their optimal design and utilization are a process, which requires their characterization and efficient modeling. The papers published in this Special Issue of the Journal of Composites Science will give composite engineers and scientists insight into what the existing challenges are in the characterization and modeling for the composites field, and how these challenges are being addressed by the research community. The papers present a balance between academic and industrial research, and clearly reflect the collaborative work that exists between the two communities, in a joint effort to solve the existing problems. Full article

One of the most essential building materials for sustainable development is concrete. However, there is a problem with a lack of inexpensive, efficient ways to make it high-strength and ultra-dense. A promising direction is the additional processing or activation of the cheapest component of the concrete mixture—inert aggregate. The article is devoted to a promising method for the simultaneous activation of both large and small aggregates using vibro-centrifuge technology. It has been established that the activation of concrete aggregates with aqueous solutions of natural bischofite at a concentration of 6 g of dry matter per 1 L of water is the most rational and contributes the maximum increase in strength characteristics and the best values of strain characteristics. Strength characteristics increased up to 16% and ultimate strains increased to 31%, respectively, and the modulus of elasticity increased to 9%. A new improved lightweight fiber-reinforced concrete was created and an innovative technology is proposed that makes it possible to achieve savings in manufacturing due to a significant improvement in structural properties and reducing the working sections of reinforced concrete elements. Regularities between the fundamental chemical processes of the surface activation of aggregates and the physical processes of structure formation of compacted and hardened concrete were revealed. An improvement in the structure of concrete at the micro- and macro-levels was recorded due to a point decrease in crack formation at the interfaces of the “cement matrix-aggregate” and “cement matrix-fiber” phases, and a decrease in the number of micropore defects was also found. Economic efficiency reached 25–27%. Full article

The use of boron nitride nanotubes (BNNTs) for fabrication of thermally conductive composites has been explored in the last years. Their elevated thermal conductivity and high mechanical properties make them ideal candidates for reinforcement in polymeric matrices. However, due to their high tendency to agglomerate, a physical or chemical treatment is typically required for their successful incorporation into polymer matrices. Our previous study about the dispersibility of BNNTs allowed determination of good solvents for dispersion. Here, we performed a similar characterization on styrene-butadiene rubber (SBR) to determine its solubility parameters. Although these two materials possess different solubility parameters, it was possible to bridge this gap by employing a binary mixture. The solvent casting approach followed by hot pressing was chosen as a suitable method to obtain thermally conductive SBR/BNNT composites. The resulting nanocomposites showed up to 35% of improvement in thermal conductivity and a 235% increase in storage modulus in the frequency sweep, when a BNNT loading of 10 wt% was used. However, the viscoelastic properties in the amplitude sweep showed a negative effect with the increase in BNNT loading. A good balance in thermal conductivity and viscoelastic properties was obtained for the composite at a BNNT loading of 5 wt%. Full article

Unfortunately, nearly the whole world came to a standstill due to the coronavirus disease 2019, i.e., the COVID-19 pandemic, which negatively and severely impacted almost all facets of society, systems, and lives on the planet during the last few years. During this time, a surge in the generation of a huge volume of diverse wastes at an unprecedented rate occurred due to the extensive use of disposables and personal shielding safety gear such as personal protective equipment (PPE) for both infected and uninfected people as well as frontline staff, etc., as corona protocols, especially in the form of “plastic wastes”. Consequently, all these factors induced a novel route for the pollution of air, soil, and water, inviting a great number of health hazards in addition to the pandemic. Beyond a doubt, the susceptibility of the spread of the coronavirus through polluted waste is high, an issue for which the waste management measures are comparatively not up to the mark. The spread of COVID-19 forced the world into lockdown, which had both constructive and unconstructive effects on not only the environment but also systems such as the waste management sector, etc. The unforeseen increase in the quantity of waste created a challenge concerning normal waste disposal facilities, negatively impacting the global waste management industry, and hence, leading to an urgent situation internationally. Still, in developing nations, the sector of waste management is at its nascent stage, and therefore, the sector of waste management during the pandemic period has been influenced severely in many parts of the world. The current comprehensive review provides not only an overview of the impacts and challenges of COVID-19 on the waste management sector but also extends the systematic data of waste generation that has been made accessible so far along with a discussion on the safety of the related workers and staff as well as suggestions for the possible approaches towards better waste management services, which are essential to manage the waste increase resultant of the COVID-19 pandemic in a majority of nations. Full article

The stiffness degradation of hybrid carbon/glass fibre composites are investigated under cyclic loading in three-point bending. The composites are compared to toughened composites interlayered with PA 6,6 nanofibre (veil) and a matrix toughened with 5% rubber particulate. With the incorporation of veil into the hybridised composite, the hybrid interface experienced extensive localised delamination, due to crack deflection, causing longitudinal cracking between the fibre and veil interface. It is observed that delamination was redirected and reduced by veil interlayering, due to crack bridging as the cracks propagated. The carbon fibre composites toughened by rubber particulate showed similar stiffness retention to carbon fibre after 1,000,000 cycles. The veil interlayering within carbon fibre improved the stiffness retention by 66.87% for the flexural modulus, compared to carbon fibre and rubber toughened carbon fibre laminates. In both glass and carbon fibre samples, the stiffness retention with veil showed a 10-fold increase in fatigue life, compared with untoughened controls. It is observed from the failure mechanics that veil acted as a randomly orientated fibre layer, rather than a matrix toughener. Full article

Hygroscopicity is an important technological property of composite materials for the conservation and treatment of water in modern technologies for sustainable green environment and agriculture. Using a thermodynamic approach, this study analyzes the hygroscopicity of composite gel-forming soil conditioners as a function of water activity and temperature. A simple and generally available method of water thermo-desorption is proposed for the quantitative assessment of hygroscopicity, dispersity and potential resistance of composite materials to osmotic collapse. It is based on the fundamental thermodynamic dependence of water potential and temperature of the dried material in a thermodynamic reservoir (laboratory) with constant relative humidity. The hygroscopicity of the studied composite materials in humid air (relative humidity over 90%) reaches a water content of 80–130% (wt); however, this water has too high retention energy and cannot be consumed by green plants, which calls into question the technology of obtaining water from the air using hygroscopic materials. The high hygroscopicity of hydrogels and its dynamics, depending on the controlling factors of temperature and air humidity, must necessarily be taken into account in the materials trade and in the technological calculation of doses for the use of these materials in sustainable agriculture and landscaping. Full article

One main global problem is the accumulation of a large amount of agricultural waste. This problem causes environmental pollution and requires an immediate comprehensive solution. The purpose of this study was scientific substantiation and experimental testing, at the micro- and macro levels, of the joint influence of electromagnetic activation of cement paste and nano-modification by rice straw biochar on the strength and strain properties of concrete. In addition to standard methods, the methods of electromagnetic activation, scanning electron microscopy, and energy dispersive spectrometry were used. The results of the joint influence of electro-magnetic activation and nano-modification by rice straw biochar on the strength and strain characteristics of concrete were experimentally verified and confirmed by microstructure analysis. Electromagnetic treatment of the cement paste increased the compressive strength, axial compressive strength, tensile strength in bending, and axial tensile strength of concrete. The best performance was demonstrated by electromagnetically-activated concrete containing 5 wt.% rice straw biochar. Strength characteristics increased from 23% to 28% depending on the type of strength, ultimate tensile strains decreased by 14%, and ultimate compressive strains by 8% in comparison with the control concrete composition. Replacing part of the cement with 10 wt.% and 15 wt.% rice straw biochar led to a strong drop in strength characteristics from 14 to 34% and an increase in strain characteristics from 9 to 21%. Scanning electron microscopy showed a denser and more uniform structure of electromagnetically activated samples. Full article

Preceramic samples were prepared from pastes based on the aqueous solution of sodium silicate and tricalcium phosphate with a given molar ratio of (Na₂O · 2,87SiO₂)_aq/Ca₃(PO₄)₂ = 1:3 after drying at 24 °C and then 60 °C for 24 h. It established the dependence of the plastic strength of these pastes on both time and temperature and the possibility of using them for extrusion 3D printing. The phase composition of ceramic was represented by unreacted β-TCP (β-Ca₃(PO₄)₂) and β-rhenanite (β-NaCaPO₄) after heat treatment at 500 °C. Further, an increase in temperature up to 700 °C led to the appearing phase of silicon dioxide (SiO₂) and up to 900 °C, of sodium calcium phosphate (Na₃Ca₆(PO₄)₅). After heat-treatment at 1100 °C, ceramic samples consisted of the β-TCP (β-Ca₃(PO₄)₂), sodium calcium phosphate (Na₃Ca₆(PO₄)₅), silicon dioxide (SiO₂) and β-wollastonite (β-CaSiO₃). The bending and compressive strength of the ceramics rose with increasing temperature from ≈6.8 MPa and ≈31.1 MPa at 500 °C to ≈10.6 MPa and ≈43.5 MPa at 1100 °C. The obtained composite ceramics consisted of biocompatible phases that are widely studied in the literature and may be used as a biomaterial for the treatment of bone tissue defects. Full article

We created a coke-repellent inner surface in a stainless steel (SS-321) tube using an enhanced chemical etching tactic. A water-borne etching solution was formulated by combining an ion sequestering ligand (L), hydrogen peroxide (H), hydrochloric acid (C), and a stabilizing agent (E or N). Three etchants, LHC, LHC-E, and LHC-N, were therefore formulated, respectively. The coke-repellent metal surfaces achieved by these etchants all show a characteristic topographic pattern on a micron scale, specifically with grooved spherulite and ridge-like topographic patterns. Fundamentally, these two topographic patterns prompt overhead micro turbulence fields whose agitation mitigates the surface entrapment of aromatic hydrocarbon flocs generated from the overhead lubricant. The surface entrapment of flocs is the crucial step to trigger coke growth. The coke repellency was assessed by placing an SS-321 tube filled with a lubricant in a heat soak. It was found that the topographic pattern and its surface roughness level have opposite effects on coke development. Hence, the three etchants give rise to different coke-resilient surfaces. Moreover, the plug flow rate of the etchant also affects the anti-coking performance, exhibiting an optimal flow rate that offers the highest coke-proof efficacy. Full article

The additive manufacturing process creates objects directly by stacking layers of material on each other until the required product is obtained. The application of additive manufacturing technology for teaching and research purposes is still limited and unpopular in developing countries, due to costs and lack of accessibility. In this study, an extruding-based 3D printing additive manufacturing technology was employed to design and construct a low-cost-high-accessibility 3D printing machine to manufacture plastic objects. The machine was designed using SolidWorks 2020 version with a 10 × 10 × 10 cm³ build volume. The fabrication was carried out using locally available materials, such as PVC pipes for the frame, plywood for the bed, and Zinc Oxide plaster for the bed surface. Repetier firmware was the operating environment for devices running on the computer operating system. Cura was used as the slicing software. The fabricated machine was tested, and the printer produced 3D components with desired structural dimensions. The fabricated 3D printer was used to manufacture some plastic objects using PLA filament. The recommended distance between the nozzle tip and the bed is 0.1 mm. The constructed 3D printer is affordable and accessible, especially in developing nations where 3D printing applications are limited and unpopular. Full article

In the present paper, the performance recovery under conditions of discontinuous exposure to a marine environment of a natural fiber-reinforced composite (NFRC) reinforced by flax fibers was assessed. In particular, this laminate was initially exposed to salt-fog for 15 and 30 days, and then stored in a controlled air condition for up to 21 days. The flax fiber-reinforced composite showed coupled reversible and irreversible aging phenomena during the wet stage, as well as evidencing a significant mechanical recovery during the dry stage. Unlike the stiffness, the laminate showed a noticeable recovery of its flexural strength. This behavior affected the composite material toughness. A simplified approach was applied to define a topological map of the material toughness at varying drying times. The results highlight that the composite shows maximum toughness at intermediate drying times thanks to the strength recovery, in addition to its residual plasticity. This approach allows us to better determine that the strength is more closely related to reversible degradation phenomena, whereas the stiffness is mainly correlated to irreversible ones, implying relevant effects on the toughness of the composite exposed to a wet/dry cycle. Full article

This study aims to investigate the flexural behavior of high-strength thin slabs externally strengthened with fiber-reinforced polymer (FRP) laminates through a numerical simulation. A three-dimensional (3D) finite element (FE) model is created to simulate the response of strengthened reinforced concrete (RC) slabs under a four-point bending test. The numerical model results in terms of load-deflection behavior, and ultimate loads are verified using previously published experimental data in the literature. The numerical results show a good agreement with the experimental results. The FE model is then employed in a parametric study to inspect the effect of concrete compressive strength on the performance of RC thin slabs strengthened with different FRP types, namely carbon fiber-reinforced polymers (CFRP), polyethylene terephthalate fiber-reinforced polymers (PET-FRP), basalt fiber-reinforced polymers (BFRP) and glass fiber-reinforced polymers (GFRP). The results showed that the highest strength enhancement was obtained by the slab that was strengthened by CFRP sheets. Slabs that were strengthened with other types of FRP sheets showed an almost similar flexural capacity. The effect of concrete compressive strength on the flexural behavior of the strengthened slabs was moderate, with the highest effect being a 15% increase in the ultimate load between two consecutive values of compressive strength, occurring in the CFRP-strengthened slabs. It can thus be concluded that the developed FE model could be used as a platform to predict the behavior of reinforced concrete slabs when strengthened with different types of FRP composites. It can also be concluded that the modulus of elasticity of the composite plays a major role in determining the flexural capacity of the strengthened slabs. Full article

Over the last few decades, polymers and their composites have shown a lot of promises in providing more viable alternatives to surgical procedures that require scaffolds and implants. With the advancement in biomaterial technologies, it is possible to overcome the limitations of current methods, including auto-transplantation, xeno-transplantation, and the implantation of artificial mechanical organs used to treat musculoskeletal conditions. The risks associated with these methods include complications, secondary injuries, and limited sources of donors. Three-dimensional (3D) printing technology has the potential to resolve some of these limitations. It can be used for the fabrication of tailored tissue-engineering scaffolds, and implants, repairing tissue defects in situ with cells, or even printing tissues and organs directly. In addition to perfectly matching the patient’s damaged tissue, printed biomaterials can have engineered microstructures and cellular arrangements to promote cell growth and differentiation. As a result, such biomaterials allow the desired tissue repair to be achieved, and could eventually alleviate the shortage of organ donors. As such, this paper provides an overview of different 3D-printed polymers and their composites for orthopedic applications reported in the literature since 2010. For the benefit of the readers, general information regarding the material, the type of manufacturing method, and the biomechanical tests are also reported. Full article

This paper investigates the structural performance of a new two-way profiled steel decking system for steel-concrete composite slabs. Several studies have investigated steel decking for steel-concrete composite slabs and focused on utilising the conventional deck as a one-way floor system. The newly developed deck consists of top-hat sections formed by bending corrugated sheets at 90°, which are attached to a corrugated base sheet. The deck is designed for improved composite and two-way action contributed by its unique geometry due to corrugations in the transverse and longitudinal directions. This paper experimentally tested a novel steel decking geometry under construction stage loading. It was in the absence of concrete to establish the deck’s suitability for construction and contribution towards loading capacity and performance for future use as a two-way composite slab. Ultimate load, two-way action, and failure modes were identified. A finite element model was also developed, and parameters assessed that could influence the performance when the deck is potentially used in the composite stage. It was concluded that, while increasing the thickness of the corrugated base sheet significantly affects the load-carrying capacity, the thickness of the top hats has no significant impact. Improved load transfer with two-way behaviour is observed when the bottom flanges of the top hats are continuously connected to the bottom flanges of the adjacent top hats to form a deck. This contrasts with the concept deck, where individual top hats are attached to a corrugated base sheet. In this case, decks with a corrugated base sheet perform 54% better in ultimate load capacity than decks without a corrugated base sheet. Full article

Here, nitrogen-doped carbon dots (N-doped CDs) were synthesized by the hydrothermal method embedded within poly(lactic acid-co-glycolic acid) ((PLGA)) films at different amounts. The N-doped CDs (or CD) that possess fluorescence properties also have antimicrobial properties against S. aureus and E. coli microorganisms, determined by the disc diffusion method with 19 ± 2 and 18 ± 1 mm zone diameters, respectively. The CD embedded PLGA films (CD@PLGA) with different CD contents revealed an increased fluorescence intensity with the increased amount of CD. Moreover, the antibacterial potency of 50% CD containing PLGA (50-CD@PLGA) films (by weight) against S. aureus and E. coli microorganisms was examined and the zone diameters were found to be 14 ± 1 and 13 ± 1 mm, respectively. In addition, CD release studies from different amounts of CD (2.5–50 by weight) containing composite films showed that 50-CD@PLGA film released 127 ± 16 mg/g CD dots, which is 38 ± 5% of the embedded CDs in about 12 days, suggesting their potential application in food packing and wound dressing. Moreover, all CD@PLGA films were found to be blood compatible via hemolysis and blood clotting index tests with <5% hemolysis and >90% blood clotting indices regardless of their CD content. Full article

In this study, hybrid boron nitride (BN)/titanium carbide (TiC)/epoxy resin composite nanodielectrics were manufactured and characterized. Their morphological and structural characterization was conducted via scanning electron microscopy (SEM) images and X-ray diffraction (XRD) patterns, whereas the dielectric behavior was studied by means of broadband dielectric spectroscopy (BDS). Dielectric measurements were carried out from 30 to 160 °C and from 10⁻¹ to 10⁶ Hz, respectively. The dielectric results revealed the existence of three relaxation mechanisms, which from high to low frequencies, at constant temperature, refer to re-arrangement of polar-side groups (β-relaxation) of the macromolecular chains, transition from glassy to rubbery state of the amorphous polymer matrix (α-relaxation) and interfacial polarization (IP) between the polymer matrix and the nanofillers. It was found that, in general, nanodielectrics exhibited enhanced dielectric properties mainly due to the high dielectric permittivity of TiC and the fine dispersion of the fillers, confirmed also by the SEM images. Dynamic analysis conducted for the α-relaxation showed a Vogel–Fulcher–Tammann dependence on temperature. The ability of energy storing of the nanocomposites was examined via their energy density. Optimum performance is exhibited by the 5 phr TiC/1 phr BN/epoxy nanocomposite, reaching an energy storing ability nine times greater than the unfilled matrix. Full article

This paper aims to propose an Industry 4.0 implementation model relevant to the composite manufacturing industry and offer it to academia and manufacturing practice in order to aid successful change and adoption. The research scope is defined at an intersection of challenges within the composites industry, as well as Industry 4.0. A critical review of relevant papers was used to establish key trends and gaps in professional practice. Exposed challenges and opportunities were then synthesized to propose a conceptual framework for implementing Industry 4.0. Findings suggest that the predicted growth of the composites sector depends on the paradigm shift in manufacturing. Industry 4.0, including automation, and horizontally and vertically integrated business models are seen as enablers. However, the value proposition or organizational resistance in establishing such integration is not sufficiently addressed or understood by the industry. Achieving a successful design for manufacturing (DFM), or, more generally, design for excellence (DFX), is identified as the target performance objectives and key business process enablers used to introduce Industry 4.0 technology. The identified key gap in professional practice indicate the lack of a model used for structuring and implementing Industry 4.0 technology into composite businesses. The existence of an identified gap, evidenced by the lack of literature and available knowledge, reinforces the need for further research. To enable further research, and to facilitate the introduction of Industry 4.0 in composite manufacturing firms, a conceptual implementation framework based on the systems engineering V model is proposed. The paper concludes with topics for further investigation. Full article

Bidimensional nanomaterials, such as graphene, respond to the rising demand for electromagnetic interference (EMI) shielding materials, followed by the advancements in wireless technology and increased signal sensitivity in electronic devices, especially for the safety of aircraft and other structures. Lightweight nanocomposites reinforced with 2D carbonaceous nanofillers can replace metals thanks to their ability to attenuate electromagnetic waves and low susceptibility to corrosion. In this work, the EMI shielding properties in the X band (8–12 GHz) of high content graphene nanoplatelets (GNPs) nanocomposites have been investigated. Both the effect of filler content and the nanoarchitecture have been studied. For this purpose, two different configurations have been considered, compact and porous, varying the filler content (from 10 wt% to 90 wt%) and the thickness of the samples. Specifically, four different systems have been tested: thin (i) and thick (ii) compact laminates and thin (iii) and thick (iv) porous coatings. The morphology of the material significantly influences its electromagnetic response in terms of reflection and absorption capacity. Maximum effective absorption of 80% was found for disordered structures, while a maximum reflection of about 90% was found for system highly aligned structures. Full article

Chromium ions released into aquatic environments pose major environmental risks, particularly in developing countries. Here, a low-cost N-cetyltrimethylammonium bromide (CTAB)-modified fly ash-based zeolite Na-A (CTAB@FZA) was prepared for the treatment of industrial wastewater contaminated with Cr(VI). CTAB@FZA was evaluated using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM), which showed that CTAB intercalation and coating of the modified zeolite were successful. The effects of influencing variables on the removal of Cr(VI) using CTAB@FZA were also evaluated, including pH, initial concentration, time, temperature, and coexisting ions. Fast adsorption equilibrium was observed after less than 10 min, and CTAB@FZA had a maximum adsorption capacity of 108.76 mg/g and was substantially greater than that of pristine FZA following modification. Furthermore, isothermal and kinetic data demonstrated that Cr(VI) adsorbed onto homogeneous surfaces via rate-limiting monolayer Langmuir adsorption, and according to thermodynamic data, the sorption of the targeted pollutant was exothermic and spontaneous. The application of CTAB@FZA to industrial wastewater treatment yielded Cr(VI) concentrations that were below the USEPA standards. Overall, the findings demonstrated that CTAB@FZA is an effective, promising, and economical adsorbent for the treatment of Cr(VI)-polluted water. Full article

Global environmental concerns, as well as the rapid depletion of non-renewable fossil fuel-based resources, have prompted research into the development of sustainable, environmentally friendly, and biodegradable materials for use in a variety of high-end applications. To mitigate the environmental setbacks caused by nonbiodegradable materials, the development of biocomposites with improved mechanical performance is gradually gaining momentum. Natural fibers such as hemp, flax, and sisal have been well incorporated into biocomposite development. Nonetheless, the impact of functional moieties in their life cycle cannot be underestimated. In this review paper, a detailed discussion of the characteristics and components of biocomposites is presented. The treatment of composite materials (alkali and acetylation), as well as several manufacturing processes (hand layup, 3D printing, extrusion, etc.) and the applications of biocomposites, which are not limited to the aerospace industry, packaging, biomedicine, etc., are presented. Biocomposites with excellent durability, performance, serviceability, and reliability must be produced to expand their applications. Full article

Calcium aluminates (CA) with a mayenite structure have attracted a growing interest during the last decades. The present paper reports the preparation of vanadia-mayenite composites performed via an impregnation of pure CA with ammonium vanadate solution. The properties of the prepared materials were explored by a low-temperature nitrogen adsorption/desorption technique, X-ray diffraction analysis, transmission electron microscopy, and spin probe method. As revealed, the addition of vanadium significantly affects the textural properties and the porous structure of mayenite. The blockage of micropores by vanadium species is supposed. The spin probe electron paramagnetic resonance technique based on the adsorption of 1,3,5-trinitrobenzene, phenothiazine, and diphenylamine has been applied to study the active sites on the surface of the composite samples. The results demonstrated an increase in the concentration of weak electron-acceptor sites when the vanadium loading was 10 wt%. X-ray diffraction analysis and transmission electron microscopy studies showed that the composites consist of few phases including mayenite, CaO, and calcium vanadates. Full article

Poly(vinylidene fluoride) (PVDF) membranes were fabricated using two different methods: the electro-spinning technique and the phase inversion process. The effect of a DMF/acetone solvent composition on the quality of the electrospun fibers of the PVDF membrane was investigated. The prepared PVDF membranes have been characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and contact angle. Uniform fibrous membranes with fiber diameters ranging mainly from 6 μm to 1.5 μm were formed from 16% (w/w) PVDF solutions in 50/50 (w/w) DMF/acetone at 30 kV voltage and 0.3 mL/h flow rate. The effect of surface morphology and hydrophilicity on anti-fouling potential was also studied and compared with flat-sheet membranes. It was found that the spun fibrous membranes exhibited the best hydrophilicity and antifouling properties with an average pure water permeability up to 400 L/m²/h, higher than that of the flat-sheet membranes, which exhibited 200 L/m²/h. Performance evaluation of the prepared PVDF membranes (water flux and organic matter retention) has been done through the use of a dead-end apparatus, where the results demonstrated the efficiency of electrospun membrane over the conventionally prepared flat-sheet membrane for utilization as a pretreatment stage of ultrafiltration and microfiltration (MF/UF), before reverse osmosis (RO) in the desalination plant. Full article

A new bundled glass fiber-reinforced resin post was developed to be used in post-endodontic restoration. We evaluated the bond strength of a single prefabricated glass fiber post (GFP) and a bundled glass fiber-reinforced resin post (GT), used alone or combined, to restore weakened roots. Fifty bovine incisors roots were weakened with a diamond bur, except for those from the control group. The root canals were endodontically treated (Pro Taper Next system, gutta-percha, and endodontic cement), and the roots were divided into five groups (n = 10): Reb—single prefabricated GFP (Rebilda Post—Voco); GT—bundled glass fiber-reinforced resin post (Rebilda Post GT—Voco); RebGT—association between the prefabricated GFP (Reb) and the bundled one (GT); CP—prefabricated GFP customized with composite resin; and Cont—singular post in a non-weakened root (Control). All posts were cemented using a universal adhesive system (Futurabond U) and dual-cure resin cement (Rebilda DC—Voco). Afterwards, two slices were obtained from each root third (cervical, middle, and apical) and submitted to a push-out bond strength test. Data were analyzed regarding the post system used and the root thirds by two-way ANOVA, followed by Tukey’s test (p < 0.05). There were higher bond strength means for the RebGT and CP groups, presenting values similar to the control. The Reb and GT groups showed lower values. The adhesion to deeper thirds of the root canal remains a challenge for adhesive dentistry and is not related to the design of the post. Additionally, the rehabilitation of teeth with weakened roots requires the customization of the glass fiber post with composite resin or the association between prefabricated options with multiple posts. Full article

The titica vine fiber (TVF) (Heteropsis flexuosa) is a natural lignocellulose fiber (NLF) from the Amazon rainforest that was, for the first time, investigated in terms of its basic properties such as dimensions, porosity, and density as well as its chemical composition, moisture content, crystallinity, and microfibrillar angle. In this study, the apparent density of TVF was determined as one of the lowest-ever reported for NLFs). Using both the geometric method and Archimedes’ principle, density values in the range of 0.5–0.6 g/cm³ were obtained. The moisture content was measured as around 11%, which is in accordance with the commonly reported values for NLFs. The TVF exhibited a high porosity, approximately 70%, which was confirmed by SEM images, where a highly porous morphological structure associated with the presence of many voids and lumens was observed. The crystallinity index and microfibrillar angle were determined as 78% and 7.95°, respectively, which are of interest for a stiff NLF. A preliminary assessment on the mechanical properties of the TVFs revealed a tensile strength, Young’s modulus, and elongation of 26 MPa, 1 GPa, and 7.4%, respectively. Furthermore, the fiber presented a critical length of 7.62 mm in epoxy matrix and an interfacial shear strength of 0.97 MPa. These results suggest the TVFs might favors applications where lighter materials with intermediate properties are required. Full article

In this research, the numerical calculation for elastic and nonlinear strains of Fe metal and FeC alloy under different pressures has been performed by the statistical moment method SMM with Mie–-Lennard–Jones potential (MLJ) and Embedded-Jones potential Atom Method (EAM). The analysis reveals that an enhancement in the concentration (cC) from 0 to 5% causes a decrement in the Young’s modulus (E) at room temperature (T = 300 K) for FeC. These calculated results are consistent with the experimental results. In addition, the obtained stress-strain curves for Fe are in perfect agreement with the experimental curves. Besides, increasing the cC for a continuous strain decreases the stress, showing that adding C to Fe to form FeC steel will increase strength and hardness, but decrease elasticity and hardness. The results obtained will be very useful not only for experimental studies but also for theoretical studies of metals and their interstitial alloys. Full article

The development of environmentally friendly polymeric composites holds great potential for agricultural leftovers. This study explores the effects of lignocellulosic corncob powder as a filler in a polyhydroxybutyrate (PHB)/polylactic acid (PLA) biopolymer matrix. The PHB-PLA matrix consists of a 55% to 45% blend, respectively, while the filler loadings range from 0 wt.% to 8 wt.%. The components are combined and directly extruded into fused filaments for three-dimensional (3D) printing. The tensile strength of both the filament and dog-bone samples, flexural strength, and Charpy impact toughness of the composites, all decreased as filler loading increased. The tensile and flexural modulus of all samples examined improved noticeably with increasing filler loading. The filler particles had dense, mildly elongated sheet-like shapes, whereas the fractured surfaces of the composite samples had flat features for the pure polymer blend, but became rougher and jagged as filler loading increased. The fractured surface of Charpy impact test samples had smoother morphology when tested at cryogenic temperatures, compared to room temperature testing. All attributes showed a fourth-degree polynomial relationship to filler loading and all improved as filler loading increased, with the best results obtained at 6 wt.% loading. Full article