J. Compos. Sci., Volume 5, Issue 7 (July 2021) – 31 articles

In this work, two urethane diols with different middle chain lengths were prepared by the non-isocyanate approach from 1,4-diaminobutane or 1,6-diaminohexane with ethylene cyclic carbonate at room temperature without the aid of a catalyst. Different weight percentages of hexa(methoxymethyl) melamine (HMMM) crosslinker was mixed with urethane diols then cured under elevated temperature to generate the melamine-formaldehyde (MF) coating films. Two different linear diols without urethane linkage were chosen to crosslink with HMMM as the control group. The mechanical properties of these MF coatings were investigated by tensile test, adhesion test, and conical mandrel bend test. It was found that coatings incorporated with urethane diols exhibited enhanced mechanical properties and flexibility. These properties were also influenced by the weight percentage of HMMM crosslinker. This study provided a facile non-isocyanate way to produce urethane diols and successfully applied them in MF coating. Full article

This work serves as a roadmap for the development of a Vanadium dioxide (VO₂)–Iridium composite based on the self-assembly of closely packed colloidal polystyrene microspheres (P-spheres) coupled with a Pulsed Laser Deposition (PLD) process. The self-assembly of a monolayer of PS is performed on an Al₂O₃-c substrate, using an adapted Langmuir–Blodgett (LB) process. Then, on the substrate covered with P-spheres, a 50-nanometer Iridium layer is deposited by PLD. The Iridium deposition is followed by the removal of PS with acetone, revealing an array of triangular shaped metallic elements formed on the underlaying substrate. In a last deposition step, 50-, 100- and 200-nanometer thin films of VO₂ are deposited by PLD on top of the substrates covered with the Iridium quasi-triangles, forming a composite. Adapting the size of the P-spheres leads to control of both the size of the Iridium micro-triangle and, consequently, the optical transmittance of the composite. Owing to their shape and size the Iridium micro-triangles exhibit localized surface plasmon resonance (LSPR) characterized by a selective absorption of light. Due to the temperature dependent properties of VO₂, the LSPR properties of the composite can be changeable and tunable. Full article

Recently, smart composites that serve as multi-functional materials have gained popularity for structural and infrastructural applications yielding condition assessment capabilities. An emerging application is the monitoring and prediction of the fatigue of road infrastructure, where these systems may benefit from the ability to detect and estimate vehicle loads via weigh-in-motion (WIM) sensing without interrupting the traffic flow. However, off-the-shelf applications of WIM can be improved in terms of cost and durability, both on the hardware and software sides. This study proposes a novel multi-functional pavement material that can be utilized as a pavement embedded weigh-in-motion system. The material consists of a composite fabricated using an eco-friendly synthetic binder material called EVIzero, doped with carbon microfiber inclusions. The composite material is piezoresistive and, therefore, has strain-sensing capabilities. Compared to other existing strain-sensing structural materials, it is not affected by polarization and exhibits a more rapid response time. The study evaluates the monitoring capabilities of the novel composite according to the needs of a WIM system. A tailored data acquisition setup with distributed line electrodes is developed for the detection of moving loads. The aim of the paper is to demonstrate the sensing capabilities of the newly proposed composite pavement material and the suitability of the proposed monitoring system for traffic detection and WIM. Results demonstrate that the material is promising in terms of sensing and ready to be implemented in the field for further validation in the real world. Full article

The functionalization of graphene has been reported widely, showing special physical and chemical properties. However, due to the lack of surface functional groups, the poor dispersibility of graphene in solvents strongly limits its engineering applications. This paper develops a novel green “in-situ titania intercalation” method to prepare a highly dispersed graphene, which is enabled by the generation of the titania precursor between the layer of graphene at room temperature to yield titania-graphene nanocomposites (TiO₂-RGO). The precursor of titania will produce amounts of nano titania between the graphene interlayers, which can effectively resist the interfacial van der Waals force of the interlamination in graphene for improved dispersion state. Such highly dispersed TiO₂-RGO nanocomposites were used to modify epoxy resin. Surprisingly, significant enhancement of the mechanical performance of epoxy resin was observed when incorporating the titania-graphene nanocomposites, especially the improvements in tensile strength and elongation at break, with 75.54% and 176.61% increases at optimal usage compared to the pure epoxy, respectively. The approach presented herein is easy and economical for industry production, which can be potentially applied to the research of high mechanical property graphene/epoxy composite system. Full article

The deadly Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) outbreak has become one of the most challenging pandemics in the last century. Clinical diagnosis reports a high infection rate within a large population and a rapid mutation rate upon every individual infection. The polymerase chain reaction has been a powerful and gold standard molecular diagnostic technique over the past few decades and hence a promising tool to detect the SARS-CoV-2 nucleic acid sequences. However, it can be costly and involved in complicated processes with a high demand for on-site tests. This pandemic emphasizes the critical need for designing cost-effective and fast diagnosis strategies to prevent a potential viral source by ultrasensitive and selective biosensors. Two-dimensional (2D) transition metal dichalcogenide (TMD) nanocomposites have been developed with unique physical and chemical properties crucial for building up nucleic acid and protein biosensors. In this review, we cover various types of 2D TMD biosensors available for virus detection via the mechanisms of photoluminescence/optical, field-effect transistor, surface plasmon resonance, and electrochemical signals. We summarize the current state-of-the-art applications of 2D TMD nanocomposite systems for sensing proteins/nucleic acid from different types of lethal viruses. Finally, we identify and discuss the advantages and limitations of TMD-based nanocomposites biosensors for viral recognition. Full article

Drilling two different materials in a layer, or stack-up, is being practiced widely in the aerospace industry to minimize critical dimension mismatch and error in the subsequent assembly process, but the compatibility of the drill to compensate the widely differing properties of composite is still a major challenge to the industry. In this paper, the effect of customized twist drill geometry and drilling parameters are being investigated based on the thrust force signature generated during the drilling of CFRP/Al7075-T6. Based on ANOVA, it is found that the maximum thrust force for both CFRP and Al7075-T6 are highly dependent on the feed rate. Through the analysis of maximum thrust force, supported by hole diameter error, hole surface roughness, and chip formation, it is found that the optimum tool parameters selection includes a helix angle of 30°, primary clearance angle of 6°, point angle of 130°, chisel edge angle of 30°, speed of 2600 rev/min and feed rate of 0.05 mm/rev. The optimum parameters obtained in this study are benchmarked against existing industry practice of the capability to produce higher hole quality and efficiency, which is set at 2600 rev/min for speed and 0.1 mm/rev for feed rate. Full article

Cycling stability is a key challenge for application of silicon (Si)-based composite anodes as the severe volume fluctuation of Si readily leads to fast capacity fading. The binder is a crucial component of the composite electrodes. Although only occupying a small amount of the total composite mass, the binder has major impact on the long-term electrochemical performance of Si-based anodes. In recent years, water-based binders including styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) have attracted wide research interest as eco-friendly and low-cost alternatives for the conventional poly(vinylidene difluoride) (PVDF) binder in Si anodes. In this study, Si-based composite anodes are fabricated by simple solid mixing of the active materials with subsequent addition of SBR and CMC binders. This approach bypasses the use of toxic and expansive organic solvents. The factors of binder, silicon, and graphite materials have been systematically investigated. It is found that the retained capacities of the anodes are more than 440 mAh/g after 400 cycles. These results indicate that organic solvent free process is a facile strategy for producing high performance silicon/graphite composite anodes. Full article

In this paper, micromechanical constitutive models are developed to predict the tensile and fatigue behavior of fiber-reinforced ceramic-matrix composites (CMCs) considering matrix fragmentation and closure. Damage models of matrix fragmentation, interface debonding, and fiber’s failure are considered in the micromechanical analysis of tensile response, and the matrix fragmentation closure, interface debonding and repeated sliding are considered in the hysteresis response. Relationships between the matrix fragmentation and closure, tensile and fatigue response, and interface debonding and fiber’s failure are established. Experimental matrix fragmentation density, tensile curves, and fatigue hysteresis loops of mini, unidirectional, cross-ply, and 2D plain-woven SiC/SiC composites are predicted using the developed constitutive models. Matrix fragmentation density changes with increasing or decreasing applied stress, which affects the nonlinear strain of SiC/SiC composite under tensile loading, and the interface debonding and sliding range of SiC/SiC composite under fatigue loading. Full article

Carbon-fiber-reinforced ultrahigh-temperature ceramic (C/UHTC) matrix composites are an attractive candidate for fabricating various hot structures. The present study aimed to establish a Si-free Zr–Ti melt-infiltration method for fabricating C/UHTC matrix composites. To achieve this, the wettability of Zr–Ti alloys on carbon and their reactivity to carbon were examined. The alloys were melted on graphite plates and infiltrated into model preforms, which were made of porous carbon and had median pore diameters of 3 μm. The results showed that the apparent contact angle between Zr–Ti and C measured from melted alloys on carbon in room temperature was ~20–42° and that the alloys infiltrated into the preforms regardless of the Zr or Ti content. However, with an increase in the Zr content in the alloys, carbon disappeared and was absorbed into the alloys since the reactivity of Zr was higher than that of Ti and the specific surface area of the porous preform was higher than that of carbon-fiber-reinforced carbon composites, which are a typical preform of C/UHTC matrix composites. These results clearly indicate that not only the capillary flow during infiltration but also the reactivity of alloys to preforms should be considered in the process design for fabricating high-density composites via Zr–Ti infiltration. Full article

The need for reliable methodologies for structural monitoring is certainly a current line of research in many engineering sectors. The detection of the impact on composite materials is in fact a recent subject of study, aimed at safeguarding the mechanical integrity and improving the useful life of structural components. In such a context, the work deals with evaluation of the use of neural algorithms for localizing the position of the impacts on composite structures. Starting from FE (finite element) simulations, representative of the dynamic response of a CFRP (Carbon Fiber Reinforced Polymer) panel as a benchmark, the approach has been finally validated experimentally by modal parameters identification. Full article

Hybridization of natural fiber with synthetic fiber to reinforce polymer matrix composites is an effective way of increasing fatigue strength of composites with substantial amount of bio-based content. Flax is the strongest type of bast natural fiber, possessing excellent mechanical and damping properties. Fatigue properties of flax fiber hybridized with synthetic carbon fiber reinforced polymer matrix composites were studied. Fatigue properties of inter-ply hybrid flax-carbon fiber reinforced composite were compared to intra-ply hybrid flax-carbon fiber reinforced composites through tensile fatigue testing at 70% load of ultimate tensile strength and with a loading frequency of 3 Hz. For similar amount (by mass) of flax and carbon fiber, intra-ply flax-carbon fiber hybrid reinforced composite exhibited a very large increase (>2000%) in fatigue life compared to inter-ply flax-carbon fiber hybrid reinforced composites. Suitable hybridization can produce hybrid composites that are as strong as synthetic fiber composites while containing a high bio-based content of natural fibers. Full article

Composite ionic conductors for intermediate temperature fuel cells (ITFC) were produced by a combination of yttrium-substituted barium zirconate (BaZr_0.9Y_0.1 O_2.95, BZY) and eutectic compositions of alkali carbonates (Li₂CO₃, Na₂CO₃, and K₂CO₃, abbreviated L, N, K). These materials were characterized by X-ray diffraction, scanning electron microscopy, and impedance spectroscopy. The combination of BZY with alkali metal carbonate promotes the densification and enhances the ionic conductivity, which reaches 87 mS·cm⁻¹ at 400 °C for the BZY–LNK40 composite. In addition, the increase of the conductivity as a function of hydrogen partial pressure suggests that protons are the main charge carriers. The results are interpreted in terms of the transfer of protons from the ceramic component to the carbonate phase in the interfacial region. Full article

Implanting scaffolds designed for the regeneration or the replacement of bone tissue damaged by diseases and injuries requires specially designed biomaterials that promote cell adhesion. However, the biodegradation rate of these scaffolds based on a single material is uniform. Four-dimensional printing appears to be a promising method to control this aspect by changing the shape and/or the intrinsic properties of 3D-printed objects under the influence of external stimuli. Two main classes of biomaterials and biocomposites based on biopolyesters, namely poly(lactic acid) (PLA) and poly(caprolactone) (PCL), were used in this study. Each of them was mixed with the inorganic filler hydroxyapatite (HA), which is a component of natural bone. The biocomposites and biomaterials were prepared using the melt extrusion process and then shaped using a 3D printer. Three-dimensional specimens showed a decrease in elongation at break and breaking strain due to variations of crystallinity. The crystallinity of irradiated samples increased slightly with irradiation and a new crystalline phase was observed in the case of the PLA. Four-dimensional printing of biomaterials using electron radiation shows great promise for bone tissue engineering based on biocomposite scaffolds and other medical applications. Full article

Graphene has accomplished huge notoriety and interest from the universe of science considering its exceptional mechanical physical and thermal properties. Graphene is an allotrope of carbon having one atom thick size and planar sheets thickly stuffed in a lattice structure resembling a honeycomb structure. Numerous methods to prepare graphene have been created throughout a limited span of time. Due to its fascinating properties, it has found some extensive applications to a wide variety of fields. So, we believe there is a necessity to produce a document of the outstanding methods and some of the novel applications of graphene. This article centres around the strategies to orchestrate graphene and its applications in an attempt to sum up the advancements that has taken place in the research of graphene. Full article

Herein, a facile, environment-friendly and cost-effective approach was followed for the preparation of metal sulfide-based supercapacitor electrodes. The effect of transition metal interrogation on the morphology and electrochemical performance of carbon-coated nickel sulfide composite electrode was investigated. Physicochemical characterization showed that the enhancement in electrical conductivity and electrochemical reaction sites with the introduction of copper (Cu) and cobalt (Co) was due to the variation in morphology. Fast ionic transformation and improvement in the number of redox active sites might improve the supercapacitor performance. The electrochemical experiment showed that the NCoSC electrode exhibited the highest capacitance value of ~760 F g⁻¹ at 2 A g⁻¹ current density as compared to the NCuSC and NSC electrodes. Therefore, a hybrid supercapacitor (HSC) device was fabricated by using NCoSC as the positive electrode and thermally reduced graphene oxide (TRGO) as the negative electrode. The fabricated device demonstrated maximum energy density of ~38.8 Wh Kg⁻¹ and power density of 9.8 kW Kg⁻¹. The HSC device also showed ~89.5% retention in specific capacitance after 10,000 charge–discharge cycles at 12 A g⁻¹ current density. So, the tuning of electronic and physical properties by the introduction of Cu and Co on nickel sulfide improved the supercapacitor performance. Full article

Ceramic matrix composites (CMCs) have been prepared and optimized as already described in part I of this paper. The fibrous preform made of Hi-Nicalon S fibers was densified by a matrix composed of Si₂N₂O prepared inside the CMC by reacting a mixture of Si and SiO₂ under high nitrogen pressure. This part describes the oxidation resistance and mechanical properties of the optimized CMC. The CMC submitted to oxidation in wet oxygen at 1400 °C for 170 h exhibited an oxidation gradient from the surface to almost the center of the sample. In the outer part of the sample, Si₂N₂O, Si₃N₄ and SiC were oxidized into silica in the cristobalite-crystallized form. The matrix microstructure looks similar to the original one at the center of the sample, while at the surface large pores are observed and the fiber/matrix interphase is consumed by oxidation. The elastic modulus and the hardness measured at room temperature by nano-indentation are, respectively, 100 and 8 GPa. The elastic modulus measured at room temperature by tensile tests ranges from 150 to 160 GPa and the ultimate yield strength from 320 to 390 MPa, which corresponds to a yield strain of about 0.6%. The yield strength identified by acoustic emission is about 40 MPa. Full article

Ceramic matrix composites (CMCs) have been designed and developed for extreme operating environments. The aim of the present study is to look for a rapid densification process providing a high level of material performance. The fibrous preform was made of Hi-Nicalon S fibers woven in a 3D interlock weave. The matrix was composed of Si₂N₂O prepared inside the CMCs by reacting a mixture of Si and SiO₂ under high nitrogen pressure (1 to 3 MPa). Silica was either impregnated by slurry or obtained by oxidation of silicon grains inside the preform. The synthesis reaction was initiated by heating the impregnated preform by means of a carbon resistor submitted to Joule effect. Composition, homogeneity and porosity of the formed matrix were studied and interpreted as a function of the experimental parameters (nitrogen pressure, heating rate of the preform) as well as the recorded thermal history of the process. The present results show that the matrix formation is almost completed in less than one minute. Melting of silicon has a major influence on the process. Competition was observed between the formation of Si₃N₄ and Si₂N₂O, which could be mainly controlled by the heating rate of the preform and the nitrogen partial pressure. Full article

This work reports on the production and characterization of recycled high density polyethylene (R-HDPE) composites reinforced with maple fibers. The composites were produced by a simple dry-blending technique followed by compression molding. Furthermore, a fiber surface treatment was performed using a coupling agent (maleated polyethylene, MAPE) in solution. FTIR, TGA/DTG, and density analyses were performed to confirm any changes in the functional groups on the fiber surface, which was confirmed by SEM-EDS. As expected, the composites based on treated fiber (TC) showed improved properties compared to composites based on untreated fiber (UC). In particular, MAPE was shown to substantially improve the polymer–fiber interface quality, thus leading to better mechanical properties in terms of tensile modulus (23%), flexural modulus (54%), tensile strength (26%), and flexural strength (46%) as compared to the neat matrix. The impact resistance also increased by up to 87% for TC as compared to UC. In addition, the maximum fiber content to produce good parts increased from 15 to 75 wt% when treated fiber was used. These composites can be seen as sustainable materials and possible alternatives for the development of low-cost building/construction/furniture applications. Full article

Multilayered fibre–metal laminates (FMLs) are composed of metal semifinished products and fibre-reinforced plastics, and benefit from the advantages of both material classes. Light metals in combination with fibre-reinforced thermoplastics are highly suitable for mass production of lightweight structures with good mechanical properties. As the formability of light metal sheets is sometimes limited at room temperature, increasing the process temperature is an appropriate approach to improve formability. However, the melting of thermoplastic materials and resulting loss of stiffness limit the processing temperature. Since single-ply layers have different through-thickness stiffnesses, the forming process changes the ply thickness of the multilayered laminate. In the present study, the deformation behaviour of multilayered FMLs was investigated using a two-dimensional finite-element model assuming plane strain. The thermoelastic-plastic finite-element analysis made investigation of the variation in thickness made possible by incorporating sufficient mesh layers in the thickness direction. The results indicate that a thermoelastic-plastic finite-element model can predict the delamination of plies during deformation, as well as in the final product. Additionally, the predicted changes in thickness of the plies are in good agreement with experimental results when a temperature-dependent friction coefficient is used. Full article

Environmental pollution, such as air, water, and soil pollution, has become the most serious issue. Soil pollution is a major concern as it generally affects the lands and makes them non-fertile. The main cause of soil pollution is agro-waste. It may be possible to mitigate the agro-waste pollution by re-utilizing this agro-waste, namely natural fibres (NFs), by blending into polymer-based material to reinforce the polymer composite. However, there are pros and cons to this approach. Consequently, the polymer composite materials fabricated using NFs are inferior to those polymer composites that are reinforced by, e.g., carbon or glass fibres from the mechanical properties’ perspectives. The limitations of utilizing natural fibres in polymer matrix are their high moisture absorption, resulting in high swelling rate and degradation, inferior resistance to fire and chemical, and inferior mechanical properties. In particular, the NF polymer composites exhibit inferior interfacial adhesion between the fibre and the matrix, which, if improved, ultimately overcome all the listed limitations and improve the mechanical properties of the developed composites. To improve the interfacial adhesion leading to the enhancement of the mechanical properties, optimum chemical treatment such as Alkalization/Mercerization of the fibres have been explored. This article discusses the Mercerization/Alkali surface treatment method for NFs and its effects on the fibres regarding the Mercerization/Alkali surface treatment method for NFs and its effect on the fibres regarding their utilization in the polymer composites, the morphological features, and mechanical properties of composites. Full article

Oil-in-water (O/W) emulsion has been a major concern for the petroleum industry. A cost-effective magnetite-reduced graphene oxide (MRGO) nanocomposite was synthesized to study the demulsification process of emulsion using said nanocomposite under solar illumination. Characterization data show that the magnetite was successfully deposited on reduced graphene oxide through redox reaction at varying loading amounts of magnetite. Demulsification of the O/W emulsion using MRGO nanocomposite shows that in general the demulsification efficiency was dependent on the loading amount of Fe₃O₄ on the RGO sheet. It was proposed that the surfactant hydroxyl groups have an affinity towards Fe₃O₄, which the loading amount was directly proportionate to available active site in Fe₃O₄. As the loading amount increases, charge recombination centers on the RGO sheet would increase, effectively affecting the charge distribution within MRGO structure. Full article

The development of sophisticated telecommunication equipment and other electro-electronic devices resulted in a kind of electromagnetic pollution that affects the performance of other equipment as well as the health of human beings. Intrinsically conducting polymers (ICP), mainly polyaniline and polypyrrole, have been considered as promising candidates for applications in efficient electromagnetic interference shielding (EMI) due to their ease of preparation, light weight, good conductivity and corrosion resistance. One of the important advantages of these materials is the capability to interact with the EM radiation through both absorption and reflection mechanisms thus enlarging the field of application. In this context, this review article describes a recent overview of the existing methods to produce intrinsically conducting polymers and their blends for electromagnetic shielding application. Additionally, it highlights the relationship between preparation methods reported in the literature with the structure and properties, such as electrical conductivity, electromagnetic shielding effectiveness (EMI SE), complex permittivity and permeability of these materials. Furthermore, a brief theory related to the electromagnetic mechanism and techniques for measuring the microwave absorbing properties are also discussed. Full article

Aluminum is one of the most abundant lightweight metals on Earth with broad practical applications, such as in electrical wires. Although traditional aluminum manufacturing by alloying, deformation and thermomechanical means addresses the balance between high strength and high conductivity, adding metallic ceramic nanoparticles into the aluminum matrix can be an exciting alternative approach to mass produce aluminum electrical wires. Here, we show a new class of aluminum nanocomposite electrical conductors (ANECs), with significantly higher hardness (130 HV) and good electrical conductivity (41% IACS). This ANEC is composed of Al and dispersed TiB₂ nanoparticles, as confirmed by XRD scanning and SEM imaging. We further observed an unusual ultra-fine grain (UFG) size when slow cooling ANEC samples, as a grain as small as 300 nm was clearly captured in FIB images. We believe that the significant hardness enhancement can be partially attributed to the UFG. Our investigation and theoretical analysis further validated that UFG can be achieved when nanoparticles are uniformly dispersed and distributed in the aluminum matrix, and this understanding is important for the development of Al nanocomposite wires with high strength and high electrical conductivity. Full article

Bird-strike failure of fan blades is one of the basic challenges for the safety of aircraft engines. Simplified flat blade-like plates are always used for damage mechanism study of composite laminates. One undesirable issue is the failure at the root of clamped flat plates under high-velocity impact. For this purpose, two different strategies were exploited to obtain desirable impact damage distributions, namely the impact location and the boundary condition. Numerical models of the simplified flat blade-like plate and the bird projectile were constructed by using finite element method (FEM) and smoothed particle hydrodynamics (SPH) approaches. The impact damage distributions were comparatively investigated in detail. The numerical results show that changing the boundary condition is the most effective way to obtain preferable impact damages for further failure analysis of real fan blades. Present results will be useful to the future surrogate experimental design of simplified bird-strike testing. Full article

In recent years, interest in low-cost seismic isolation systems has increased. The replacement of the steel reinforcement in conventional elastomeric bearings for a carbon fiber reinforcement is a possible solution and has garnered increasing attention. To investigate the response of fiber-reinforced elastomeric bearings (FREBs) under seismic loads, it is fundamental to understand its mechanical behavior under combined vertical and horizontal loads. An experimental investigation of the components presents complexities due to the high loads and displacements tested. The use of a finite element analysis can save time and resources by avoiding partially expensive experimental campaigns and by extending the number of geometries and topologies to be analyzed. In this work, a numerical model for carbon fiber-reinforced bearings is implemented, calibrated, and validated and a set of virtual experiments is designed to investigate the behavior of the bearings under combined compressive and lateral loading. Special focus is paid to detailed modeling of the constituent materials. The elastomeric matrix is modeled using a phenomenological rheological model based on the hyperelastic formulation developed by Yeoh and nonlinear viscoelasticity. The model aims to account for the hysteretic nonlinear hyper-viscoelastic behavior using a rheological formulation that takes into consideration hyperelasticity and nonlinear viscoelasticity and is calibrated using a series of experiments, including uniaxial tension tests, planar tests, and relaxation tests. Special interest is paid to capturing the energy dissipated in the unbonded fiber-reinforced elastomeric bearing in an accurate manner. The agreement between the numerical results and the experimental data is assessed, and the influence of parameters such as shape factor, aspect ratio, vertical pressure, and fiber reinforcement orientation on stress distribution in the bearings as well as in the mechanical properties is discussed. Full article

The aim of this study was to design a tooling system for manufacturing automotive components using a natural fiber polymer composite (NFPC) material. As a case study, an automotive battery cover was selected and a compression molding tool was designed, keeping in mind the need for the simplicity of the tool and ensuring the low cost of this process. However, since the original part was injection-molded with virgin polypropene, some vital changes made in the part and tool design process were documented as a guideline to show new designers how to approach the design of parts and tools using a natural fiber polymer composite material. Additionally, the challenges faced during the manufacturing of composite parts with the new tool were also documented and solutions to these challenges were suggested for large-scale production. Finally, compressive testing was performed to evaluate the performance of the structure of the designed part and to compare the recycled polymer with NFPC material. Both wood and palm fiber composite material perform better in compression testing compared to the recycled polymer material. Full article

The synergistic effect of pre-bond contamination by thermal degradation and de-icing fluid on the tensile behavior of scarf composite bonded joints has been investigated experimentally. The contamination types considered are related to the repair process of composite aircraft structures. Three contamination scenarios have been considered: namely, thermal degradation (TD) and a combination of thermal degradation with two different levels of de-icing fluid (TD+DI1 and TD+DI2). DI2 is more severe than DI1. Contamination has been applied to one of the adherents while the other one has been intentionally left intact. Tension tests have been conducted on single-lap shear specimens. The experimental results were compared with the reference samples (REF) showing an increase in tensile strength for the TD specimens and a decrease in tensile strength for the TD+DI1 and TD+DI2 specimens. After the tension tests, the failure surfaces were evaluated to get a better insight of the failure mechanisms of the bondline and to assess the effect of contamination. The TD specimens presented an increased cohesive failure which is consistent with the increase of the failure load, while the combined contamination caused the failure of the composite adherents which again is consistent with the decrease of tensile strength of the scarf specimens. Full article

During construction works, it is advisable to prevent strong thawing and an increase in the moisture content of the foundations of engineering structures in the summer. Since the density of water and ice differ, due to the difference bulging of the foundation sections can occur when it freezes back in winter. In this work, the effect of fiber-reinforced piles on the thermal field of the surrounding soil is investigated numerically; that is, the study of the influence of aggregates with high and low thermal-physical properties on the temperature of frozen soils is conducted. Basalt and steel fiber reinforcement are compared. The difficulty of this work is that the inclusions inside piles are too small compared to the pile itself. Therefore, to solve the Stefan problem, a generalized multiscale finite element method (GMsFEM) was used. In the GMsFEM, the usual conforming partition of the domain into a coarse grid was used. It allowed reducing problem size and, consequently, accelerating the calculations. Results of the multiscale solution were compared with fine-scale solution, the accuracy of GMsFEM was investigated, and the optimal solution parameters were defined. Therefore, GMsFEM was shown to be well suited for the designated task. Collation of basalt and steel fiber reinforcement showed a beneficial effect of high thermal conductive material inclusion on freezing of piles in winter. Full article

Thermites or composite energetic materials are mixtures made of fuel and oxidizer particles at micron-scale. Thermite reactions are characterized by high adiabatic flame temperatures (>1000 °C) and high heats of reaction (>kJ/cm³), sometimes combined with gas generation. These properties strongly depend on the chemical nature of the couple of components implemented. The present work focuses on the use of indium (III) oxide nanoparticles as oxidizer in the elaboration of nanothermites. Mixed with an aluminum nanopowder, heat of reaction of the resulting Al/In₂O₃ energetic nanocomposite was calculated and its reactive performance (sensitivity thresholds regarding different stimuli (impact, friction, and electrostatic discharge) and combustion velocity examined. The Al/In₂O₃ nanothermite, whose heat of reaction was determined of about 11.75 kJ/cm³, was defined as insensitive and moderately sensitive to impact and friction stimuli and extreme sensitive to spark with values >100 N, 324 N, and 0.31 mJ, respectively. The spark sensitivity was decreased by increasing In₂O₃ oxidizer (27.71 mJ). The combustion speed in confined geometries experiments was established near 500 m/s. The nature of the oxidizer implemented herein within a thermite formulation is reported for the first time. Full article

Multiferroic composites with enhanced magneto-electric coefficient are suitable candidates for various multifunctional devices. Here, we chose a particulate composite, which is the combination of multiferroic (PbFe_0.5Nb_0.5O₃, PFN) as matrix and magnetostrictive (Co_0.6Zn_0.4Fe_1.7Mn_0.3O₄, CZFMO) material as the dispersive phase. The X-ray diffraction analysis confirmed the formation of the composite having both perovskite PFN and magnetostrictive CZFMO phases. The scanning electron micrograph (SEM) showed dispersion of the CZFMO phase in the matrix of the PFN phase. The temperature-dependent magnetization curves suggested the transition arising due to PFN and CZFMO phase. The temperature-dependent dielectric study revealed a second-order ferroelectric to the paraelectric phase transition of the PFN phase in the composite with a small change in the transition temperature as compared to pure PFN. The magnetocapacitance (MC%) and magnetoimpedance (MI%) values (obtained from the magneto-dielectric study at room temperature (RT)) at 10 kHz were found to be 0.18% and 0.17% respectively. The intrinsic magneto-electric coupling value for this composite was calculated to be 0.14 mVcm⁻¹Oe⁻¹, which is comparable to other typical multiferroic composites in bulk form. The composite PFN-CZFMO exhibited a converse magneto-electric effect with a change in remanent magnetization value of −58.34% after electrical poling of the material. The obtained outcomes from the present study may be utilized in the understanding and development of new technologies of this composite for spintronics applications. Full article