Search

This review highlights potential application areas for carbon-based molecular nanoparticles, such as carbon dots, carbon nanotubes, graphene quantum dots, and carbon quantum dots. The success of nano-manufacturing hinges on robust collaboration between academia and industry to advance applicable manufacturing techniques. Choosing the right approach is crucial, one that integrates the carbon base of nanomaterials with the required properties and impurities, as well as the scalability of the process. Molecular, in this context, refers to the nanoscale carbon structures that form the basis of these materials, including their arrangement, bonding, and properties at the molecular level. The article also explores the characterization of different types of molecular nanomaterials. Nanomaterials are increasingly used in almost every contemporary industry, including construction, textiles, manufacturing, and computing. This article reviews the most prominent sectors globally that employ nanomaterials. Biomasses containing lignin, cellulose, and hemicellulose have become some of the most extensively studied. Initially, rice waste was utilized for bulk materials, but lately, the production of multifunctional materials has surged in interest. Carbon nanostructures derived from rice waste offer a broad spectrum of applications and enhanced biocompatibility. Recent advancements, challenges, and trends in the development of multifunctional carbon-based nanomaterials from renewable rice waste resources are considered.

Fibers collected from the husk of areca nut trees were chopped to a length of 30 mm and were either used as such or subjected to alkaline treatment by immersion in a 5% sodium hydroxide (NaOH) solution. The untreated and treated fibers were investigated using thermogravimetric analysis (TGA) before the fabrication of composites using an epoxy matrix. Different amounts of fibers were introduced in the matrix, fabricating the composite by compression molding. The composites were subjected to tensile, flexural, and Charpy impact and Shore D hardness testing, which all demonstrated the considerable advantage obtained with the growing quantity of fibers, especially when employing treated fibers, except in the case of hardness, where limited advantages were encountered. Wear tests were carried out on treated fiber composites and the surface morphology of the worn-out samples was studied, which also demonstrated the improvement in fiber-matrix bonding obtained with the growing amount of fibers. The main limitation of the fibers was their low elongation even after treatment. The fibers hardly reached 4%, which might represent a quite normal value for this kind of fibers, possibly due to with tendency to fibrillation. This would somehow compare these composites with others with similar amounts and lengths of natural fibers.

This study investigated the mechanical performance of hybrid tubes made via roll-wrapping and enhanced with an aluminum mesh and epoxy matrix (AL-DMEM). The specimens included Basalt + Jute (BJAJB), Basalt + Bamboo (BBmABmB), Basalt + Banana (BBaABaB), Basalt + Hemp (BHAHB), and Basalt (BAB). The BBmABmB specimen showed the best mechanical properties with the highest peak crushing force, specific energy absorption, mean crushing force, and total energy absorption. The AL-DMEM integration improved load-bearing capacity and energy absorption, reducing matrix cracking and fiber breakage. Scanning electron microscopy and energy-dispersive X-ray analysis highlighted BBmABmB's robust reinforcement. Its superior structural integrity and aluminum content make it suitable for applications requiring high structural integrity, such as micromobility vehicles, highlighting the potential of AL-DMEM-reinforced composites in advanced engineering applications.

This research explores natural fiber composites (NFCs) as alternatives to traditional materials such as fiberglass. By examining fibers like abaca, bamboo, banana, coir, flax, hemp, jute, kenaf, pineapple leaf (PALF), sisal, and others, we emphasize their lower weight, cost-effectiveness, competitive mechanical properties, commendable specific strength, and potential for biodegradability. NFCs offer practical and eco-friendly substitutes for conventional composite fibers in industries like construction, automotive, and packaging. The article provides a brief overview of NFCs, covering their chemical, physical, and mechanical characteristics, and highlights diverse applications. The comparative analysis underscores the potential of natural fibers as sustainable choices in various industries.

Natural fibers along with glass fibers were used as the reinforcement of an epoxy matrix for the betterment of mechanical and wear applications. The combination of overall wt% up to 20 resulted in 23.8 MPa of tensile strength compared to 15.5 MPa for untreated fibers. The wt% of areca fiber (AF) (20 wt%)/glass fibers (GF) (20 wt%) with 5% alkali treatment yielded a maximum tensile strength up to 62.6% in comparison to untreated fiber at lowest percentage of 10 wt%. The increase in flexural strength with alkali treatment was observed from 20 to 50 wt% hybrid fiber incorporation. The alkali treated fibers, untreated fiber combinations achieved 33.8% and 26.8% improvement with impact properties. A decrease in the wear loss was shown with the increase in wt% of hybrid fiber incorporation from 20 to 40 wt%. The interfacial adhesion of fiber with matrix created a pressure absorbing zone that was positively influenced with applying higher loads. The frictional rate was highly increasing with increase in hybrid fiber wt% and also with higher loads applied. The SEM results for treated 20 wt% AF+20 wt% GF with hybrid fiber incorporation observed better results due to improved adhesion of fiber with matrix phase.

This study explores how machining parameters affect Surface Roughness (SR), Tool Wear Rate (TWR), and Material Removal Rate (MRR) during Electrical Discharge Machining (EDM) of a hybrid aluminum metal matrix composite (AMMC). The composite includes 6 % Silicon carbide (SiC) and 6 % Boron carbide (B4C) in an Aluminum 7075 (Al7075) matrix. A combined optimization approach was used to balance these factors, evaluating Pulse ON time, Current, Voltage, and Pulse OFF time. Response Surface Methodology (RSM) optimized single responses, while multi-response optimization employed a hybrid method combining the Entropy Weight Method (EWM), Taguchi approach, TOPSIS, and GRA. Analysis of Variance (ANOVA) assessed parameter significance, revealing substantial impacts on SR, MRR, and EWR. Based on TOPSIS and GRA, optimized parameters achieved a desirable balance: high MRR (0.4172, 0.5240 mm³/min), minimal EWR (0.0068, 0.0103 mm³/min), and acceptable SR (10.3877, 9.1924 μm) based on EWM-weighted priorities. Confirmation experiments validated a 15 % improvement in the closeness coefficient, and a 16 % improvement in the Grey relational grade, which considers combined SR, MRR, and EWR performance. Scanning Electron Microscope (SEM) analysis of surfaces machined with optimal parameters showed minimal debris, cracks, and no recast layer, indicating high surface integrity. This research enhances EDM optimization for AMMC, achieving efficiency in machining, minimizing tool wear, and meeting surface quality requirements.

This work examines the mechanical properties and structural aspects of Al-Hybrid fibre metal laminates (HFMLs) reinforced with fibres from basalt, hemp, and bamboo, including commercial-grade Al6061 alloy mesh (Al-DMEM). Compression moulding of sustainable fibres into various stacking configurations, such as BAlB, BHAlHB, and BBbAlBbB, was required for fabrication. Using cutting-edge methods like SEM and EDX for microstructure investigation, extensive testing was carried out, including tensile, flexural, impact, interlaminar shear, hardness, and water absorption tests. Basalt/Bamboo/Aluminum/Basalt (BBbAlBbB) was the FML configuration with the best mechanical parameters, showing Vickers hardness (24.23 MPa), tensile strength (44.537 MPa), flexural strength (218.24 MPa), and impact resistance (2.01 J) (59.982 HV). In addition, BAlB showed 83.9 % Vickers hardness, 41.7 % flexural strength, and 90.4 % tensile strength of BBbAlBbB samples. BHAlHB displayed 92.9 % of the flexural strength, 65.3 % of the tensile strength, and 93.7 % of the Vickers hardness of BBbAlBbB. Bamboo is hydrophobic by nature, so adding bamboo fibres to BBbAlBbB significantly boosted its resistance to moisture. This study highlights the potential of hybrid FMLs as high-performance, eco friendly materials that are particularly well-suited for applications in interior and exterior panels for micro-mobility (E-vehicles), with AL-DMEM reinforcement offering significant benefits like improved fibre bonding and structural integrity.

Green composite materials are a means of reducing reliance on synthetic and especially single-use plastics (SUP) and raising public awareness of the need for urgent action to protect the planet. Natural (lignocellulosic) fibres are increasingly utilized as the reinforcement in polymer matrix composites, in search for increased renewability and sustainability. This work concerns the effect of washing ramie (Boehmeria nivea) fibres using sodium lauryl sulphate (SLS) surfactant. The SLS-treated ramie fibres were examined for their morphological, physical, thermal, structural, and mechanical properties by powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and tensile testing. SLS treated ramie fibres density and crystallinity index values were 1.23 g/cc and 84.5%, respectively, with a very high cellulose content of 81.3%, because hemicellulose and loose particles were dissolved. SEM images depicted the relevant changes, with no significant damage on treated fibre surfaces. With some assistance from the treatment, fibres initiated their degradation only above 250 °C, culminating at 327 °C, which appears suitable for the manufacturing of composites with the most common matrices.

Hollow hybrid structural tubes were evaluated using commercial-grade Diamond Micro Expanded Mesh (DMEM) thin mesh of aluminum (Al) as structural reinforcement. Axial, transverse (flexural), and radial compression tests were performed on four different layered hybrid structures using bamboo (Bm) and basalt (B). With a maximum force of 34.7 kN, compressive ultimate strength of 238 MPa, and strain of 12.6%, AlBmB (with layers labeled from inside to outside) was the best performer in the axial compression test. AlBmB’s adaptability was demonstrated by the flexural test, showing a maximum bending force of 4.7 kN, a flexural strength of 97.7 MPa, and a decreased deflection of 13.2 mm. Radial compression test results underscored the superior energy absorption characteristics of AlBmB. The varying material interfaces in the hybrid tubes yielded distinctive performances. AlBmB, incorporating bamboo and basalt layers, stood out with superior energy absorption and crush force characteristics, indicating enhanced crashworthiness. The other hybrids AlBm, AlB, and BmB also exhibited commendable performances, emphasizing the adaptability of different material combinations. The meticulous selection of DMEM and innovative roll wrapping method for fabrication reliably influenced the tubes’ mechanical properties. The study contributes to advancing the design of lightweight, durable, and high-strength components.

The physical and chemical attributes of Areca catechu fiber (ACF) were explored. ACF is attractive because of its high cellulose content at 63.2 wt%. The mechanical properties were evaluated for Areca catechu fiber-reinforced epoxy composites, in which silicon carbide (SiC) was used as filler. The studied properties included water absorption, flexural strength, impact strength, tensile strength, and hardness properties. The tensile and flexural properties improved when the filler content increased from 40 to 50 wt%, but further increment in the filler content reduced the strength values. The addition of SiC adversely affected the bending and flexural properties of the composites at 40 and 50 wt% filler content, but it positively affected the properties at 60 wt% filler content. The hardness of the composites increased with the addition of 10% silicon carbide. From the results of this study, it is recommended that the ratio of silicon carbide in the composite should not exceed 10 wt% due to agglomeration. The composites containing 10 wt% SiC can be used for outdoor applications such as decking, railing, garden fencing, cladding, and siding applications.

In this study the recent developments in raw materials, manufacturing processes, and applications of natural fiber composites (NFCs) were reviewed. Natural fibers can represent a substitute for man-made fibers (including glass, aramid, and carbon) in a variety of biocomposite applications. Physical and chemical properties of the natural fibers are given and compared with the synthetic fibers. Advantages and disadvantages of NFCs in comparison with synthetic fibers such as glass and carbon fibers have been proposed. Criteria are described for the selection and processing of natural fibers for polymer composites used in different sectors such as automotive and building industries. The nanocellulose production methods, unique properties, and its recent industrial application in various sectors are given. This short review on NFCs considers their chemical, physical, and mechanical characteristics, as well as their various applications.

Mycelium from fungi can serve as the matrix or as a self-grown binder in a biocomposite. The reinforcing component may consist of various combinations of agro-based waste in short fiber or powder form. The complexity of their development is linked not only to the selection of the substrate, but also to the growth conditions of the mycelial material and its consolidation in a final form by the temperature increase that takes place. These materials have initially been proposed as a replacement for polystyrene foams, and the characterization is concentrated on compression performance and acoustic and thermal insulation properties. The present review concentrates on substrates that originated from the large productive system based on hemp (shives or hurds, waste fibers, and mats). Attention is paid to the performance obtained and to the amount of waste that is possibly employed to serve as the substrate.

This work presents an investigation on the quality of parts manufactured using fused deposition modeling (FDM), which is influenced by a large number of different elements. Some of which are based on the materials used in the production of the part, though others are rather pertinent to the process parameters. The manufacturing process and filament formulation has also a significant impact on the cost of the final product, as well as its physical, mechanical, and thermal properties. As the result, judicious combination of parameters can effectively act toward fine-tuning FDM toward three-dimensional printing (3DP) of pieces with quality fit-for-application. In this sense, the use of design of experiments (DOEs) is often needed for the purpose. Printing process parameters, including layer height, wall thickness, temperature, printing velocity, and tool path, have been discussed, in the understanding that 3DP time increases with decreasing layer thickness, and in turn increases production time and overall cost. A specific account is given on recent developments increasingly and more thoroughly focused on recognizing the impact of the process parameters and raw materials on the final product.

This research focuses on hybrid woven fibre metal laminates (HWFMLs), specifically on the innovative hybridization of natural woven fibres (NWFs) with aluminium diamond microexpandable mesh (Al-DMEM) in thin laminates. More specifically, it investigates the effect on the mechanical and water absorption properties of incorporating basalt (B), jute (J), banana (Bn) fibres, and Al-DMEM as reinforcing materials in a traditional epoxy resin. Several stacking sequences were compared and discussed. The basalt-banana-aluminium-banana-basalt (BBnABnB) (five layers) laminate exhibited remarkable compressive strength (25.7 MPa), interlaminar shear strength (25.2 MPa), Izod impact strength (2.98 J), tensile strength (42.8 MPa), and tensile modulus (3.1 GPa). Other laminates, despite their limited tensile strain, still offered advantages in other loading modes. In particular, basalt-jute-aluminium-jute-basalt (BJAJB) (five layers) laminate showed notable performance with a compressive strength of 16.70 MPa and interlaminar shear strength of 20.85 MPa. In comparison, the basalt-aluminium-basalt (BAB) (three layers) demonstrated compressive strength equal to 6.87 MPa and interlaminar shear strength (ILSS) equal to 9.07 MPa.

New fibers extracted from plant barks are a recent subject of investigation as possible fillers for polymer composites. In this work, Grewia Monticola Sond (GMS) fibers have been characterized from a morphological, chemical, and thermal point of view. This involved using a number of techniques, including Fourier infrared spectroscopy (FTIR), X-ray diffraction (×RD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), atomic force microscopy (AFM), and 13C nuclear magnetic resonance (NMR). Results indicated that GMS fibers have relatively high cellulose (55%), with 33.5% crystallinity index and a crystallite size of 4.89 nm, and lower hemicellulose (14%) and lignin (15%) contents. The fibers showed cellulose degradation onset at around 324°C, while kinetic activation energy (74.18 kJ/mol) is quite low. The roughness of the fibers was in the range expected for similar natural fibers, and they may be considered silky according to their kurtosis values. As for possible application in composites, they would definitely withstand process temperatures with thermoplastics. However, their not very high crystallinity and low crystallite size might suggest a limited strength, to be verified in future after optimizing GMS fiber extraction from bark.

The stem bark of Acacia caesia, or Senegalia caesia, richly available in the Western Ghats of Tamilnadu and Kerala, India, does potentially offer a ligno-cellulosic fiber, which was characterized in this work, studying its chemical composition, morphology, and thermal degradation. The as-received fibers, which were extracted as technical fibers with diameters ranging between 100 and 150 µm, had a density of 1200 kg/m3. Their composition included 37% cellulose, 20% hemicellulose and 18% lignin, not very dissimilar, among other fibers, from alfa esparto and particularly coir. Their thermal degradation onset was at 308°C, which suggested a potential in composite application with traditional oil-based matrices and possibly also in the long run on bio-based ones. However, their high roughness and easy splitting of the fibers suggested that possible use as the filler for composites would require fiber treatment, namely, to remove undesired loose parts, hence regularizing their geometry. This would also serve to reduce the likeliness of longitudinal splitting, which is a widely recognized occurrence during stripping of bark fibers.

The tensile strength of fibers extracted by retting from Acacia Caesia bark was measured and their fracture morphology was examined, with the idea to propose their potential use as the reinforcement in polymer composites. Four categories of fibers were investigated, namely untreated and treated with a concentration of 5, 10 and 15% sodium hydroxide (NaOH) for 24 hours at ambient temperature. The increase of alkali concentration resulted in a gradual reduction of hemicellulose, wax, and moisture, which on the other side increased the fiber density. Single fiber tensile tests were performed according to ASTM D3822 standard. The fracture surfaces of the fibers were observed using an optical microscope and scanning electron microscope (SEM). The tensile tests revealed that the 10% NaOH treatment sample showed the highest performance, namely an average tensile strength of 16.2 (±5.63) N with an ultimate elongation of 4.6 (± 1.0)%. SEM evidenced the different possible morphologies of Acacia Caesia bark fiber fractures, including sliding and tearing, splitting and torsion of fibrils.

The optimization of heat transfer in heat exchanging equipment is paramount for the efficient management of energy resources in both industrial and residential settings. In pursuit of this goal, this empirical study embarked on enhancing the heat transfer performance of a double pipe heat exchanger (DPHX) by introducing silver (Ag)-graphene oxide (GO) hybrid nanofluids into the annulus of the heat exchanger. To achieve this, three distinct molar concentrations of Ag ornamented GO hybrid nanoparticles were synthesized by blending GO nanoparticles with silver nitrate at molarities of 0.03 M, 0.06 M, and 0.09 M. These Ag-GO hybrid nanoparticles were then dispersed in the base fluid, resulting in the formation of three distinct hybrid nanofluids, each with a consistent weight percentage of 0.05 wt%. Thorough characterization and evaluation of thermophysical properties were performed on the resulting hybrid nanomaterials and nanofluids, respectively. Remarkably, the most significant enhancement in heat transfer coefficient, Nusselt number, and thermal performance index (62.9%, 33.55%, and 1.29, respectively) was observed with the 0.09 M Ag-GO hybrid nanofluid, operating at a Reynolds number of 1,451 and a flow rate of 47 g/s. These findings highlight the substantial improvement in thermophysical properties of the base fluid and the intensification of heat transfer in the DPHX with increasing Ag molarity over GO. In summary, this study emphasizes the vital importance of optimizing the molarity of the material, which also plays a significant role in nanoparticle synthesis to achieve the optimal amplification of heat transfer.

The present work centers on aluminum-based metal matrix composites (AMCs), synthesized via stir casting and then processed by electrical discharge machining (EDM) in the case of Al7075 as a matrix and 6 wt.% boron carbide (B4C) as reinforcement. A design of experiment (DoE) approach, powered by hybrid optimization techniques (such as the entropy weight method (EWM), grey relational analysis (GRA) incorporated Taguchi method) was used to investigate the relationship between current (I), pulse ON time (Ton), pulse OFF time (Toff), and electrode gap (Gap) as input parameters and the material removal rate (MRR), tool wear rate (TWR), and surface roughness (SR) as response parameters. The results showed that an I = 140 A, Ton = 120 ms, Toff = 50 ms, and Gap = 0.4 mm combination gives the best response parameters of MRR = 0.5628 mm3/min, TWR = 0.0048 mm3/min, and SR = 4.4034 μs.

Natural rubber ( Hevea brasiliensis ) is generally a product of tropical countries such as Thailand, Malaysia and Indonesia. Due to its excellent physical properties, it is a widely used material in various industries, including tyre automotive, construction and medical. Natural rubber is often manufactured in wet form and must be dried to remove excess moisture and improve its mechanical properties. There are several methods for drying natural rubber, including vacuum drying, air drying, freeze drying and microwave drying. Microwave drying is a relatively new and promising method for drying natural rubber. This technology uses electromagnetic radiation in the microwave range to generate heat in the material, causing the moisture to evaporate. Microwave drying offers several advantages over traditional drying methods, including faster drying times, lower energy consumption and improved product quality. The natural rubber drying process is a complex process that consists of several factors such as humidity, temperature and drying time. Microwave drying is no exception and requires careful optimization of the process parameters to achieve optimal drying results. Research is currently underway to study the effects of microwave drying on natural rubber properties, including the physical, mechanical, chemical and thermal properties of the material. In this context, the article aims to provide an overview of the natural rubber drying process, with a particular focus on microwave drying. The article reviews the literature on the use of microwave drying for natural rubber and highlights the advantages and limitations of this method. The post also discusses the factors affecting the microwave drying process and their impact on the quality of the dried natural rubber. Finally, the paper identifies the gaps in our understanding of microwave drying of natural rubber and suggests potential areas for future research.

This study explores the effect of alkali treatment at ambient (25 °C) and elevated temperatures (100 °C) on the physicochemical, structural, morphological, and thermal properties of Calamus tenuis cane fibers (CTCFs) for the first time. Our purpose is to investigate their potential use as reinforcement in polymer composites, since cane fibers are generally known for their accurate and consistent geometrical orientation. Treatment with 8% (w/v) sodium hydroxide (NaOH) is carried out at ambient temperature and at 100 °C for 4 h. Chemical analysis and Fourier transform IR spectroscopy (FTIR) indicate some removal of non-cellulosic elements from CTCFs during alkali treatment, resulting in increased surface roughness, as confirmed by using SEM micrographs. This removal of non-cellulosic elements leads to an enhancement in the density of the treated CTCFs. Untreated and treated fibers are analyzed for maximum degradation temperature, thermal stability, and kinetic activation energy (Ea) using thermogravimetric analysis (TGA). In particular, Ea was considerably diminished with treatment and temperature. X-ray diffraction (XRD) results show an improved crystallinity index (37.38% to 44.02%) and crystallite size (2.73 nm to 2.98 nm) for fibers treated with 8% NaOH at ambient temperature. In conclusion, a general benefit was achieved by treating CTCFs, though the influence of increasing temperature treatment appears controversial.

In recent years, there has been growing interest in utilizing bark fibers as reinforcements for polymer composites. This study focused on the characterization of epoxy composites reinforced with Acacia caesia bark (ACB) fibers, considering their mechanical, morphological, and thermal properties. Various amounts of ACB fibers with three different lengths (10, 20, and 30 mm) were incorporated into the composites, ranging from 10 to 35 wt.% in 5% increments. This resulted in 18 sample categories, which were compared to neat epoxy samples. The findings demonstrated that the introduction of ACB fibers, even at the highest fiber content, led to improved mechanical performance. However, a transition in fiber length from 20 to 30 mm exhibited conflicting effects on the composite, likely due to the tendency of bark fibers to bend and split into fibrils during loading. Regarding thermal degradation, the advantages over neat epoxy were evident, particularly for 20 mm fibers, suggesting enhanced interfacial bonding between the matrix and the reinforcement. The epoxy adequately protected the bark fibers, enabling the composite to withstand degradation at temperatures comparable to pure resin, with minimal structural damage below 320 °C.

In this present investigation, Sansevieria cylindrica fiber was used as a reinforcement in a natural rubber matrix. Various biocomposite samples with different fiber contents (lengths and loadings) were fabricated, using compression molding process and vulcanizing technique by maintaining the temperature around 150 °C. From the results obtained, mechanical properties: tensile strength, modulus elongation at break and tear strength of 10.44 MPa, 2.36 MPa, 627.59% and 34.99 N respectively, were obtained from the optimum composite sample with length and loading of 6 mm and 20 wt% composition, respectively. The maximum hardness was observed at 76.85 Shore A from the composite sample of 6 mm and 40 wt%. The optimum properties can be attributed to the presence of strong interfacial adhesion between the Sansevieria cylindrica fiber and the natural rubber matrix. The mechanisms of failure of the biocomposites at their interfaces were examined and analyzed, using scanning electron microscopy (SEM). The micrographs obtained from SEM further confirmed that the Sansevieria cylindrica fibers were surrounded with more amount of natural rubber which can exhibit strong interfacial bonding between fiber and matrix. The optimal composites of this work can be used in general, abrasion resistant conveyor belt.

The specific interest for the use of bark in materials, instead than for energy recovery, is owed to circular economy considerations, since bark fibers are normally byproducts or even waste from other sectors, and therefore their use would globally reduce the amount of refuse by replacing other materials in the production of composites. For the purpose of promoting their application in polymer composites, mainly under a geometry of short random fibers, bark fibers are extracted and treated, normally chemically by alkali. Following this, investigations are increasingly carried out on their chemical composition. More specifically, this includes measuring cellulose, hemicellulose, and lignin content and their modification with treatment on their thermal properties and degradation profile, and on the mechanical performance of the fibers and of the tentatively obtained composites. This work aims at reviewing the current state of studies, trying to elicit which bark fibers might be most promising among the potentially enormous number of these, clarifying which of these have received some attention in literature and trying to elicit the reason for this specific interest. These can be more thoroughly characterized for the purpose of further use, also in competition with other fibers not from bark, but from bast, leaves, etc., and pertaining to developed production systems (cotton, hemp, flax, jute, etc.). The latter are already widely employed in the production of composites, a possibility scantly explored so far for bark fibers. However, some initial works on bark fiber composites and both thermoplastic and thermosetting are indicated and the importance of some parameters (aspect ratio, chemical treatment) is discussed.

Apart from the widely discussed pineapple leaf fibers, normally referred to as PALF, fibers from other parts of the plant also exist, particularly those in the fruit crown, which are known as pineapple crown leaf fibers (PCLF). In this work, PCLF were characterized using thermogravimetric analysis (TGA), Fourier transform IR spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The results indicated that the properties of PCLF do not greatly differ from those observed for PALF. In particular, a cellulose content of over 67% was observed, with approximately 76% crystallinity. The main degradation phenomena of the fibers took place between 230 and 380 °C, peaking at 324 °C, which is in line with observations in other fibers which have similar cellulose and crystalline contents. There was 13.4% residue at 680 °C. Bare mechanical retting of PCLF, although not allowing a full and thorough degumming, which would only be achieved through more aggressive chemical treatment, enabled aspect ratios of over 103 to be obtained. This indicates some potential for their application as short fibers in composites. In this respect, the considerable roughness of PCLF when compared to other leaf-extracted fibers, and in particular when compared to PALF, could suggest an ability to obtain a sufficiently sound fiber–matrix interface.

The wear performance of jute/coir unsaturated polyester composites, filled with eggshell powder (ESP) and nanoclay (NC), were examined, concentrating on two measured parameters, coefficient of friction (COF) and wear rate (WR). To assess the possibilities of this material, a Taguchi study, based on grey relational analysis (GRA), was carried out, based on three testing parameters of the wear performance, load (10, 20, and 30 N), speed (100, 150, and 200 rpm), and sliding distance (30, 40, and 50 m). The material showed promising characteristics especially at high load, low speed, and high sliding distance. When comparing the respective influence of the three different parameters, the speed proved to be the most critical, this suggested the possible application of the biocomposite only for very low values of it. On the other hand, it was also elucidated that the presence and interfacial adhesion of the two fillers considerably hindered the formation of ploughing during wear test, despite the fact that degradation might be continuous and critical as far as loading progresses.

The contribution of natural lignocellulosic fibers to the reduction in wear damage in polymer resins is of interest, especially when two of these fibers can combine their respective effects. Wear properties of hybrid kenaf/banana epoxy composites have been investigated using three different total amount of fibers, 20, 30 and 40 wt.%, at loading forces up to 30 N and to sliding distances of up to 75 m. This demonstrated that the introduction of the highest level of fibers proved the most suitable for consistency of results and containment of wear with increasing load, as was also found from the morphological evaluation of wear degradation using scanning electron microscopy (SEM). Subsequently, tensile, flexural and impact properties of as-received and post-water-saturation hybrid composites were examined. The tests revealed a limited reduction in tensile and flexural strength, not exceeding 10% of the initial values, which were very high compared to similar materials, almost reaching 140 MPa for tensile strength and exceeding 170 MPa for flexural strength. In contrast, a higher standard deviation of values was found for impact strength, although the decrease in average values was only slightly above 10%. The results suggest the availability of these hybrids for wear-resisting applications in high-moisture environments, and the even more limited water absorption conferred by banana fibers added to kenaf ones.

The introduction of natural fibers as a filler in a natural rubber (NR) matrix can be of relevance for their eco-friendly and sustainable nature as the substitute for carbon-based fillers. In this work, short Phormium tenax fibers were introduced in random orientation into a NR matrix in different lengths (6, 10, and 14 mm) and various amounts (10, 20, and 30%, taking 100 as the NR weight). The composite was fabricated using a two-roll mill according to American Society for Testing and Materials (ASTM) D3184-11 standard. Several properties were determined, namely tensile and tear characteristics, hardness, and abrasion resistance. The results suggest that the shortest fiber length used, 6 mm, offered the best combination between loss of mechanical (tensile and tear) properties and hardness and the most acceptable resistance to abrasion, with the properties increasing with the amount of fibers present in NR. As a consequence, it is indicated that a higher amount of fibers could be possibly introduced, especially to achieve harder composites, though this would require a more controlled mixing process not excessively reducing tensile elongation at break.

In the present study, a model is presented to optimize the fabrication parameters of natural fiber reinforced polyester matrix composites with dual fillers. In particular, jute fiber mat was chosen as reinforcement and eggshell powder (ESP) and montmorillonite nanoclay (NC) were selected as fillers. The weight per square meter (GSM) of the fiber, the weight percentage of ESP and NC have been chosen as independent variables and the influence of these variables on tensile, flexural and impact strength of the composite has been inspected. The permutations of the different combinations of factors are intended to accomplish higher interfacial strength with the lowest possible number of tested specimens. The experiments were designed by the Taguchi strategy and a novel multi-objective optimization technique named COPRAS (COmplex PRoportional ASsessment of alternatives) was used to determine the optimal parameter combinations. Affirmation tests were performed with the optimal parameter settings and the mechanical properties were evaluated and compared. Experimental results show that fiber GSM and eggshell powder content are significant variables that improve mechanical strength, while the nanoclay appears less important.