Conventional Composite Materials Research Articles

Micromechanics stiffness upscaling of plant fiber-reinforced composites

Fiber-reinforced green composites made from natural plant fibers are an increasingly popular sustainable alternative to conventional high-performance composite materials. Given the variety of natural fibers themselves, and the even larger variety of possible composites with specific fiber dosage, fiber orientation distribution, fiber length distribution, and fiber-matrix bond characteristics, micromechanics-based modeling is essential for characterizing the macroscopic response of these composites. Herein, an analytical multiscale micromechanics model for elastic homogenization is developed, capable of capturing the this variety. The model features (i) a nanoscopic representation of the natural fibers to predict the fiber stiffness from the universal stiffness of the fiber constituents, mainly cellulose, (ii) a spring-interface model to quantify the compliance of the fiber-matrix bond, and (iii) the ability to model any (and any combination of) orientation distribution and aspect ratio distribution. Validation is performed by comparing the predicted stiffness to experimental results for as many as 73 composites available in the literature. Extensive sensitivity analyses quantify the composite stiffening upon increasing fiber volume fraction, fiber alignment, fiber length, and fiber-matrix interface stiffness, respectively.

Dual emissive and stable surface-capped silica based nanoparticles for white light emission

There is an emerging thrust to develop intrinsic white light emitting materials that surpass critical issues of color balance, low color-rendering index, thermal stability, and a bluish tinge displayed by conventional multi-phosphor composite materials. In particular, the luminescent Silica-based nanoparticles (NPs) have drawn attention owing to their abundance and potential applications, such as in optoelectronic devices, solar cells, and batteries. In this work, stable phenothiazine capped-SiO2 nanoparticles (PTZ capped-SiO2 NPs) with an average size of 24 ± 2 nm have been synthesized that exhibit intrinsic white light emission and have comprehensively investigated interactions of ligands on Silica core and underlying charge transfer mechanism. The dual emission has been observed, spanning over 400 to beyond 800 nm (visible to the NIR region). The emission measured at different excitation wavelengths reveals enhancement of red emission, indicating efficient CT emission, which is facilitated by strong electron donor and conformational changes capability of the phenothiazine ligand. Taking into account the excellent photo/thermal stability of PTZ capped-SiO2 NPs (up to 30 days) observed, a white LED prototype was successfully fabricated that exhibits cool white light (CIE: 0.31, 0.32) with excellent CRI (Ra) 91 and CCT 7029 K.

Mechanical Performance of Extensive Restorations Made with Short Fiber-Reinforced Composites without Coverage: A Systematic Review of In Vitro Studies.

In recent years, composite resin materials have been the most frequently used materials for direct restorations of posterior teeth. These materials have some clinically relevant limitations due to their lack of fracture toughness, especially when used in larger cavities with high volume factors or when utilized as direct or indirect overlays or crown restorations. Recently, short-fiber-reinforced composite materials have been used in bi-structure restorations as a dentine substituting material due to their superior mechanical properties; however, there is no scientific consensus as to whether they can be used as full restorations. The aim of our review was to examine the available literature and gather scientific evidence on this matter. Two independent authors performed a thorough literature search using PubMed and ScienceDirect up until December 2023. This study followed the PRISMA guidelines, and the risk of bias was assessed using the QUIN tool. The authors selected in vitro studies that used short-fiber-reinforced composite materials as complete restorations, with a conventional composite material as a comparison group. Out of 2079 potentially relevant articles, 16 met our inclusion criteria. All of the included studies reported that the usage of short-fiber-reinforced composites improved the restoration's load-bearing capacity. Fifteen of the included publications examined the fracture pattern, and thirteen of them reported a more favorable fracture outcome for the short-fiber-reinforced group. Only one article reported a more favorable fracture pattern for the control group; however, the difference between groups was not significant. Within the limitations of this review, the evidence suggests that short-fiber-reinforced composites can be used effectively as complete restorations to reinforce structurally compromised teeth.

Static Convergence Behaviour of Discrete Kirchhoff-Mindlin Triangular Element on Rectangular Functionally Graded Material Plates

Rapid infrastructure development is consistent with the increase in innovation in structural elements. One of the main parameters in infrastructure development is materials. An advanced composite material called Functionally Graded Material (FGM) has been widely used. FGM is composed of the combination of two or more materials. FGM increases the bond strength between the layers compared to conventional composite materials, eliminating stress at the interface layers, and reducing cracks. However, further studies are required to understand the behaviour of the FGM plate. Finite element analysis (FEA) was considered to evaluate the convergence behaviour of the FGM plates. The Discrete Kirchhoff-Mindlin Triangular (DKMT) element is employed in the analysis. Studies regarding the FGM plates with the DKMT element were limited to square shapes and skew shapes. Thus, this study aims to study the convergence behaviour of the rectangular FGM plates composed of ceramic and metal. The FEA was carried out in different types of meshing, ratio a/h, ratio a/b, the power-law index, and boundary conditions. The analysis results indicate that the application of the DKMT element in analyzing the FGM plates gives good asymptotic and convergence behaviour. Thus, this method has proved reliable and sustainable.

Lightweight Composite Applications in the Structural Design of Quadricycles

Due to the increasing number of internal combustion engine vehicles, fossil fuel sources have decreased drastically in the last century. In addition, the concerns about global warming caused by vehicle emissions have led automotive manufacturers to search for new alternatives to transport. Quadricycles have started to be seen as future transport vehicles due to their smaller design and lower energy consumption when compared to conventional vehicles. Furthermore, they are also considered to prevent increasing traffic jams in metropolitan areas. The lightweight design of a quadricycle is crucial since its weight would affect energy consumption. On the other hand, because of their minimalistic design, crashworthiness is another factor that must be considered in the structural design of quadricycles for the safety of occupants in case of a collision. Composites are one of the most promising materials for manufacturing lightweight structures due to having a high strength-to-weight ratio compared to conventional metals. In this study, different body designs and optimizations of quadricycles are introduced. Comparisons are made between conventional metals and composite materials used in quadricycles in terms of weight and stiffness.

Structural Batteries – the Best or Worst of Two Worlds

The electrification of road transport is continuously progressing, and concomitantly lithium-ion batteries are developing towards higher energy densities. However, the theoretical limitations of this technology are expected to be reached in the coming years [1], leaving more demanding applications, like aeronautic ones, with high challenges regarding fully battery electric propulsion of commercial aircrafts. Structural batteries (or multifunctional energy storage), i.e. batteries which show sufficient mechanical stability to substitute conventional composite materials in load bearing structures, show a promising way to resolve this issue. Due to their multifunctional properties, structural batteries can replace interior and exterior elements of e.g. an airplane, and thus provide at best energy storage without weight increase [2].The idea of structural batteries emerged around 20 years ago, and different cell designs have been proposed including coaxial wires [3] and planar reinforced stacks [4]. Nevertheless, high degrees of multifunctionality could not be realized and the approach was never industrially applied [5]. Recently, the need to electrify the mobility sector and the prospect of massless energy storage has reincited a lot of new research activities around this topic.The main challenge at electrochemistry level for the development of structural batteries is to find an alternative electrolyte for the conventionally used carbonate-based liquid ones which provide only negligible mechanical stability. Apart from high ionic conductivities and safety, the additional requirements for the structural electrolyte include high mechanical capabilities (e.g. high Young’s modulus), good adhesion to all cell components, as well as high thermal stability. The latter is especially important for implementation of the structural batteries in composite structures, which are usually cured at elevated temperatures well beyond the stability range of conventional electrolytes. These demanding specifications render the use of conventional lithium-ion battery components formassless energy storage as futile.In this work, two different approaches for the development of electrolytes for structural batteries are discussed. The first one employs a bi-continuous electrolyte based on thermoset materials, whereas the second one uses a gel electrolyte. For the former two separate phases form percolating networks with different properties throughout the electrolyte membrane. One phase provides high ionic conductivity to achieve high electrochemical performance of the cells, whereas the other one yields high mechanical strength. The second approach uses a mono-phasic electrolyte which provides both, electrochemical as well as mechanical performance. The two approaches are further compared and discussed, focusing on their applicability for structural batteries. Important parameters like processability and feasibility for implementation into a composite structure, which are often neglected, are addressed, enabling a holistic view on this technology.

Evaluation of microhardness of short fiber-reinforced composites inside the root canal after different light curing methods – An in vitro study

ObjectivesShort fiber-reinforced composite (SFRC) materials make it possible to reinforce root canal treated teeth with individualized, directly layered intraradicular posts (the Bioblock technique). The question arises, however, as to whether the photopolymerization of the material is sufficient deep within the root canal space and if it can be improved through different light-conducting options. Our study aimed to investigate the hardness of intraradicular SFRC material applied using the Bioblock technique and cured with various illumination methods, as measured through nanoindentation. Materials and methodsFor this investigation, thirty plastic artificial teeth that had undergone root canal treatment were selected. These teeth were randomly divided into six study groups (Group 1–6; each group consisting of 5 teeth). The restoration procedures involved the use of SFRC or conventional composite materials, placed 6 mm apically from the root canal orifice. In Group 1 and 2, a conventional composite was used, whereas in Group 3–6, SFRC was employed for interradicular reinforcement (with a layered technique in Group 3 and 4 and a bulk-fill technique in Group 5 and 6). A modified light source was utilized for photopolymerization in Group 2, 4, and 6, whereas in Group 3 and 5, the polymerization light was directed through a prefabricated glass fiber posts. The control group (Group 1) utilized conventional composite material with a standard light-curing method. Following embedding and sectioning, the hardness of the composite materials was measured at 2 mm intervals within the root canal (1st, 2nd, 3rd measurements, in the coronal to apical direction). ResultsDuring the 1st measurement, light curing conducted through the glass fiber posts (Group 3 and 5) led to markedly higher hardness levels compared to the groups restored with conventional composite (control group with p = 0.002, p = 0.001, and Group 2 with p = 0.043, p = 0.034, respectively). In the 2nd measurement, only Group 5 demonstrated significantly greater hardness in comparison to the control group (p = 0.003) and Group 2 (p = 0.015). However, in the 3rd measurement, no statistically significant differences were observed among the groups. Conclusionlight curing through the glass fiber post provides outstanding hardness for the SFRC material in the apical layer in the root canal.

12-Month flexural mechanical properties of conventional and self-adhesive flowable resin composite materials.

The aim of this study was to investigate the 12-month flexural mechanical properties of 23 flowable resin-based composites (FRBC) that included 5 self-adhesive FRBC materials. Specimens were evaluated following ISO 4049:2019 guidelines, but additionally stored in physiologic 0.2M phosphate buffered saline solution being tested at 24 h, 1 week, 1 month, and at 3-, 6-, 9-, and 12-months. While some deviation and degradation were noted at testing intervals, conventional FRBC materials overall demonstrated greater flexural strength than the self-adhesive and compomer materials. Three self-adhesive materials and the compomer were below recommended ISO 4049:2019 flexural strength values at 24 h with another after 6 months storage. Conventional FRBC materials, except at 1 month, overall demonstrated increased flexural modulus than the self-adhesive FRBC materials. Although results were material dependent, conventional FRBC materials demonstrated overall greater flexural mechanical properties as compared to the self-adhesive FRBC materials and the compomer evaluated.

An Overview of Nanocomposites with Recent Advancements

The research in nanocomposites is accelerating with greater velocity due to its wide range of properties and applications in various sectors like construction, marine, automobile, aerospace, defense, and biomedical fields. Most of the researchers are trying to improve the properties further by dispersing various nanomaterials to the matrix to improve the matrix properties. In the present review article, we have discussed in brief the nanocomposites and their various synthesis routes along with their advantages and disadvantages. Why nanocomposites are more preferable over conventional composite materials is also discussed. Important characterization techniques like X-Ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetry (TG) and differential scanning calorimetry (DSC) used to investigate the nanocomposites are also discussed.

Thickness-Dependent Light Transmittance and Temperature Rise in Dual-Cure Bioactive and Light-Cure Bulk-Fill Composite Resins.

This study aimed to assess the light transmittance (T) and temperature increase through different increments of dual-cure bioactive bulk-fill restorative material (ACTIVA), light-cure bulk-fill, and conventional composite resin materials. Cylindrical specimens with a diameter of 8 mm and heights of 1, 2, 3, and 4 mm of ACTIVA, Tetric-N-Ceram bulk-fill (TBF), Filtek One bulk-fill (FBF), and Filtek Z250 (FZ) (n = 6 per group, 96 in total) were light-cured with a visible blue low-intensity light-emitting diode (LED) (650-800 mW/cm2 irradiance). T, and the temperature increase, were measured using an optical power meter and a digital thermometer during curing. The T mean values ranged between 0.012 and 0.239 (76.02 to 98.81% light attenuation), while the temperature rise mean values ranged between 9.02 and 20.80 °C. The parameters, including material type (partial eta squared (ηp2) = 0.284, p < 0.0001), thickness (ηp2 = 0.284, p < 0.0001), and their interaction (ηp2 = 0.185, p = 0.047), significantly affected the T values, whereas only the material type (ηp2 = 0.352, p = 0.047) affected the temperature rise values. The T and temperature rise mean values were highest in ACTIVA increments of 1-mm increments, in particular, showing the highest T mean values, followed by similar increments of TBF. A significantly higher T was found in 1-mm increments compared to thicker increments for all materials (p < 0.0001), and a significant positive correlation existed between T and temperature rise values (r = 0.348, p = 0.001). These findings show that the bioactive material ACTIVA and TBF allow for better T than the other materials, with ACTIVA recording a higher temperature rise. However, the large light attenuation observed for all materials, irrespective of thickness, suggests that curing in more than one location with a low-intensity LED is necessary to optimize the curing process. Furthermore, incremental filling of bulk-fill materials using a low intensity LED could be beneficial.

Study of Hybrid Composite Joints with Thin-Ply-Reinforced Adherends.

It has been demonstrated that a possible solution to reducing delamination in a unidirectional composite laminate lies in the replacement of conventional carbon-fibre-reinforced polymer layers with optimized thin-ply layers, thus creating hybrid laminates. This leads to an increase in the transverse tensile strength of the hybrid composite laminate. This study investigates the performance of a hybrid composite laminate reinforced by thin plies used as adherends in bonded single lap joints. Two different composites with the commercial references Texipreg HS 160 T700 and NTPT-TP415 were used as the conventional composite and thin-ply material, respectively. Three configurations were considered in this study: two reference single lap joints with a conventional composite or thin ply used as the adherends and a hybrid single lap. The joints were quasi-statically loaded and recorded with a high-speed camera, allowing for the determination of damage initiation sites. Numerical models of the joints were also created, allowing for a better understanding of the underlying failure mechanisms and the identification of the damage initiation sites. The results show a significant increase in tensile strength for the hybrid joints compared to the conventional ones as a result of changes in the damage initiation sites and the level of delamination present in the joint.

Microstructural properties and impact behavior of AA5083/Al2O3 functionally graded composite material with surface foam layer produced through powder metallurgy

The development of technology requires new generation materials that can hold different concentrations together, unlike conventional composite materials that are only reinforced. Functionally graded composite materials (FGCMs) are open to development because they are lightweight and hold concentrations with different mechanical properties. For this reason, in this study, a new generation FGCMs and aluminum foam material were combined. A new generation of functionally graded composite foam materials (FGCFMs) consisting of AA5083 alloy aluminum foam on one surface and AA5083 matrix on the other surface, and a graded composite structure with Al2O3 contents varying from 10% to 20%, 30%, 40%, 50%, and 60% were produced. AA5083, Al2O3 and TiH2 powders were weighed on a precision scale and mixed in a three-dimensional mixer for 1 h. The mixed powders were compressed under 300 MPa pressure at 500 °C and to obtain block samples of different step thicknesses (2, 4, and 6 mm). The foamable preform materials were foamed at 750 °C for about 10 min. The highest value of macro hardness value was obtained with 167 HB in the sample with a step thickness of 2 mm. In samples with step thicknesses of 4 and 6 mm, puncture did not occur at an impact energy of 300 J.

Teeth Restored with Bulk-Fill Composites and Conventional Resin Composites; Investigation of Stress Distribution and Fracture Lifespan on Enamel, Dentin, and Restorative Materials via Three-Dimensional Finite Element Analysis.

the aim of this study was to examine the stress distribution of enamel, dentin, and restorative materials in sound first molar teeth with restored cavities with conventional resin composites and bulk-fill composites, as well as to determine their fracture lifetimes by using the three-dimensional finite element stress analysis method. an extracted sound number 26 tooth was scanned with a dental tomography device and recorded. Images were obtained as dicom files, and these files were transferred to the Mimics 12.00 program. In this program, different masks were created for each tooth tissue, and the density thresholds were adjusted manually to create a three-dimensional image of the tooth, and these were converted to a STL file. The obtained STL files were transferred to the Geomagic Design X program, and some necessary adjustments, such as smoothing, were made, and STP files were created. Cavity preparation and adhesive material layers were created by transferring STP files to the Solidworks program. Finally, a FE model was created in the ABAQUS program, and stress distributions were analyzed. when the bulk-fill composite and conventional resin composite materials were used in the restoration of the cavity, the structures that were exposed to the most stress as a result of occlusal forces on the tooth were enamel, dentin, restorative material, and adhesive material. When the bulk-fill composite material was used in restoration, while the restorative material had the longest fracture life as a result of stresses, the enamel tissue had the shortest fracture life. When the conventional resin composite material was used as the restorative material, it had the longest fracture life, followed by dentin and enamel. when the bulk-fill composite material was used instead of the conventional resin composite material in the cavity, the stress values on enamel, dentin, and adhesive material increased as a result of occlusal forces, while the amount of stress on the restorative material decreased. In the fracture analysis, when the bulk-fill composite material was used instead of the conventional resin composite material, a decrease in the number of cycles required for the fracture of enamel, dentin, and restorative materials was observed as a result of the forces generated in the oral cavity.

Effect of polymerization mode on shrinkage kinetics and degree of conversion of dual-curing bulk-fill resin composites

ObjectivesTo assess the behavior of dual-cure and conventional bulk-fill composite materials on real-time linear shrinkage, shrinkage stress, and degree of conversion.Materials and methodsTwo dual-cure bulk-fill materials (Cention, Ivoclar Vivadent (with ion-releasing properties) and Fill-Up!, Coltene) and two conventional bulk-fill composites (Tetric PowerFill, Ivoclar Vivadent; SDR flow + , Dentsply Sirona) were compared to conventional reference materials (Ceram.x Spectra ST (HV), Dentsply Sirona; X-flow; Dentsply Sirona). Light curing was performed for 20 s, or specimens were left to self-cure only. Linear shrinkage, shrinkage stress, and degree of conversion were measured in real time for 4 h (n = 8 per group), and kinetic parameters were determined for shrinkage stress and degree of conversion. Data were statistically analyzed by ANOVA followed by post hoc tests (α = 0.05). Pearson’s analysis was used for correlating linear shrinkage and shrinkage force.ResultsSignificantly higher linear shrinkage and shrinkage stress were found for the low-viscosity materials compared to the high-viscosity materials. No significant difference in degree of conversion was revealed between the polymerization modes of the dual-cure bulk-fill composite Fill-Up!, but the time to achieve maximum polymerization rate was significantly longer for the self-cure mode. Significant differences in degree of conversion were however found between the polymerization modes of the ion-releasing bulk-fill material Cention, which also exhibited the significantly slowest polymerization rate of all materials when chemically cured.ConclusionsWhile some of the parameters tested were found to be consistent across all materials studied, heterogeneity increased for others.Clinical relevanceWith the introduction of new classes of composite materials, predicting the effects of individual parameters on final clinically relevant properties becomes more difficult.

Comparison of performance enhancement in a shell and tube based latent heat thermal energy storage device containing different structured fins

In this paper, the enhancement of melting behaviour in a shell and tube thermal energy storage (TES) device containing various structured fins is numerically investigated. Five innovative enhancement structures involving topology optimized fin, tree-shaped fin, snowflake fin, spiderweb fin, and a combined conventional fin and composite phase change material (CPCM) are quantitatively compared and evaluated. Two groups of experiments are carried out to validate the simulation codes for the devices containing topology optimized fin and CPCM, while the numerical models for the devices with longitudinal fin and pure PCM are verified by two sets of literature data. A comprehensive comparison is performed for these five enhanced configurations from multiple perspectives with the emphasis of investigation being placed on assessment of the economic efficiency of these structures through introducing a parameter of TES rate per unit cost. The results show that the use of enhanced structures achieves remarkable enhancement on the melting rate in a shell and tube device. Compared to the device containing no enhancement structure, the complete melting process can be accelerated respectively by 97.2%, 93.6%, 93%, 88% and 83.6% for the devices containing tree-shaped fin, spiderweb fin, snowflake fin, topology optimization fin, and joint longitudinal fin and CPCM. The implementation of tree-shaped fin provides the optimal economical solution to acquire the best utilization efficiency among the five structures, but the enhancement degree on the economic efficiency is intimately tied to the cost ratio of fin to PCM. In order to highlight the advantage of using tree-shaped fin on the improvement of heat transfer rate and economic efficiency, the cost ratio of fin to PCM in such enhanced structure is suggested to be controlled to less than 6.5. Moreover, fin material also presents a significant influence on the selection of performance enhanced structure since it affects not only the melting rate but also the material utilization efficiency within the device. Substituting aluminium alloy with cheaper steel as the fin manufacturing material makes the economic efficiency a whole declined. This indicates for achieving a combined improvement of melting performance and economic efficiency, the enhanced structure should be selected to have a high thermal conductivity and controllable cost that easy to manufacture.

Design and advanced computational approaches based comprehensive structural parametric investigations of rotary-wing UAV imposed with conventional and hybrid computational composite materials: A validated investigation

This work aims to design a rotary-wing unmanned aerial system (RUAS) that monitors the pollutants and minimizes their concentration in the atmosphere. This RUAS could be well suited for implementation in cities such as New Delhi and Ghaziabad, where air pollution is a major concern. This RUAV’s well-thought-out design and use would be good for the environment also a step forward in the technology of UASs. Therefore, an advanced approach in design as well as innovative computational composite materials development based on structural analysis of this RUAS has been made. The major components involved in this comprehensive investigation are the fuselage, main rotor and tail rotor of RUAS. The aerodynamic parameters on RUAS have been estimated through the advanced technique adopted computational fluid dynamics approach using ANSYS Fluent 17.2. The finite element analysis (FEA) of the RUAS imposed under two different approaches enforced on lightweight composite materials has been estimated through ANSYS Structural 17.2. Firstly, the advanced computational platform for the development of composite materials has been created through the ANSYS Composite Preprocessor tool 17.2, wherein computational moldings of the fuselages of RUAV are framed. The computational moldings are greatly supported and so the conventional polymer matrix composites, metal matrix based composites, and advanced hybrid composites are well prepared. A ll of these uniquely framed materials have undergone computational structural investigations, and the material suitable for RUAVs has thus been selected. The computational tests are validated with advanced experimental outcomes, which furthermore enhanced the reliability of this proposed work. Additionally, the main rotor and entire RUAV are also computationally investigated under aerodynamic loading conditions through fluid structure interaction (FSI) approach. At last, the suitable lightweight material for all the parts of RUAS is shortlisted through innovative integrated computational engineering analyses.

Detection of Leachable Components from Conventional and Dental Bulk-Fill Resin Composites (High and Low Viscosity) Using Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) Method.

The aim of this study was to investigate leachable components (monomers) in high and low viscosity dental bulk-fill resin composites and conventional resin composite materials after polymerization. Six bulk-fill and six conventional dental resin composite materials were used in this study. The samples of each material (three sets of triplicates) were cured for 20 s with irradiance of 1200 mW/cm2 with a LED curing unit and immersed in a 75% ethanol solution at 37 °C. The eluates from each triplicate set were analyzed after 24 h, 7 days or 28 days using liquid chromatography coupled with triple quadrupole tandem mass spectrometry (LC-MS/MS). Detectable amounts of 2-Hydroxyethyl methacrylate (HEMA) were found in both Gradia materials and the amount observed across different time points was statistically different (p ˂ 0.05), with the amount in solution increasing for Gradia and decreasing for Gradia Direct flo. Bisphenol A diglycidildimethacrylate (BIS GMA) was found in Filtek and Tetric materials. Triethylene glycol dimethacrylate (TEGDMA) was detected in all materials. On the other hand, there were no statistically significant differences in the amounts of TEGDMA detected across different time points in either of the tested materials. Monomers HEMA, TEGDMA, 4-dimethylaminobenzoic acid ethyl ester (DMA BEE) and BIS GMA in bulk-fill and conventional composites (high and low viscosity) can be eluted after polymerization. The good selection of composite material and proper handling, the following of the manufacturer's instructions for polymerization and the use of finishing and polishing procedures may reduce the elution of the unpolymerized monomers> responsible for the possible allergic and genotoxic potential of dental resin composites.

Preparation of CuO@humic acid@carbon nanotube composite material using humic acid as a coupling agent and its lithium-ion storage performance.

The conventional Li-ion battery composite electrode material composed of CuO and carbon nanotubes (CNTs) suffer from poor contact between CuO and CNTs. This results in high electrode resistance and poor electrochemical performance. To solve this problem, CuO@humic acid (HA) @CNT anode material with cross-linked network structure was generated by linking CuO and CNT with HA as a coupling agent. For comparison, CuO@HA or CuO@CNT were also prepared in the absence of CNT or HA, respectively. The results showed that CuO@HA@CNT had lower charge transfer resistance, higher conductivity, lithium-ion diffusion coefficient, specific capacity, and rate capability than CuO@HA and CuO@CNT. The specific capacity of the CuO@HA@CNT electrode was significantly better than that of the composite electrode materials of CuO and CNT, which have been prepared by scientists using various methods. Due to the introduction of HA, not only was the uniformly distributed flower-like CuO obtained, but also the specific capacity and rate capability of the electrode material were substantially improved. This study thus provides a good strategy to optimize the capability of transition metal oxide lithium-ion anode materials.

Statistical Modeling and Optimization of Surface Roughness for PLA and PLA/Wood FDM Fabricated Items

During last decades fused deposition modeling (FDM) has emerged as a widely applied additive manufacturing technology for numerous engineering applications. The present work investigates the effects of two independent variables during FDM fabrication of conventional polylactic acid (PLA) and organic biocompatible composite material with coconut flour (PLA/w) on mean surface roughness (Ra) of fabricated items. The parameter optimization adopts a customized response surface (RSM) design, based on an L9 orthogonal array. The independent variables investigated, were nozzle temperature, NT (oC) and layer thickness, LT (mm) whilst regression models for Ra concerning both materials; PLA and PLA/W, were developed to correlate the independent parameters. Proper analysis was preceded, based on response surface analysis through contour plots. The regression models were further utilized as objective functions to minimize Ra for both filament materials with the use of grey-wolf optimization genetic algorithm (GWO)

Experimental investigations on the tribological behaviour of thermoplastic composites with partial sand replacements

The present study investigates the effect of filler reinforcement on the tribological performances of polymer-based composite materials. The composites were developed by using waste plastic of low-density polyethylene as matrix and natural sand as fillers. The evaluation of sliding wear rate and three-body abrasive wear were carried out. The structural analysis of the developed composite surfaces verified the homogeneity of the mixture. The density and hardened were found in the ranges of 0.8404–1.5304 (g/cm3), and 4.6 – 15.8 HV respectively. The wear performance improves with the incorporation of fillers. The minimum value for the sliding wear rate and three-body abrasive wear were found to be 0.885 × 10−8 kg/meter and 0.07495 cm3 respectively for the specimen LDPE50. Whereas, the maximum values of sliding wear rate and abrasive wear were 5.311 × 10−8 kg/meter and 0.09822 cm3 respectively, for the specimen LDPE100. The study showed an irregular behaviour for wear with replacement of low-density polyethylene. Moreover, the interactions of several encountering forces makes the wear response a complex process. The structural analysis revealed that the fillers are completely encapsulated with matrix, resulting in optimum strength at 50 wt% replacement of low-density polyethylene. The study successfully provides a sustainable composite to replace the conventional composite materials and the results and discussions pave the way for future research.