Plant Fibre Composites Research Articles

A Comparative Study on Various Natural Plant Fiber Composites

A Comparative Study on Various Natural Plant Fiber Composites

Plant Fiber Composites for Biomedical Applications: Advances and Prospective.

Plant fibers are strong, robust, flexible, versatile, renewable, and sustainable, making them valuable for many applications. Fibers from plants are now utilized in biomedical applications as reinforcements for biological composites to enhance the mechanical characteristics of composite biological materials including rigidity, tensile strength, and endurance. Reinforcement composites with hybrid components were explored in biodevices for prospective utilization in orthopedics, prosthetics, tissue fabrication, and surgical dressings. This review presents an overview of plant fibers, including their characteristics, influencing variables, and numerous applications. The text explores several methods for creating synthetic composites using common, sustainable fibers and the distinct characteristics of the resulting biological materials. The text also analyses many instances of composite hybrids and their application in the biological field. The results are summarised and suggestions for potential improvements are presented. The current research primarily examines the concept, specifications, efficiency, and potential advancements of composites with hybrid characteristics made from plant fibers.

Investigating Polylactic Acid Foam–Plant Fiber Composites for Sound Absorption and Insulation

Investigating Polylactic Acid Foam–Plant Fiber Composites for Sound Absorption and Insulation

Research on properties and cellular structure of nano‐CaCO3/rice‐husk fiber/polypropylene three‐phase thermoplastic microcellular foaming composites

AbstractMicrocellular foamed plant fiber composites have the advantages of low density, low cost, and biodegradability, so it has great development potential in the industry. Nevertheless, the existence of cellular structures diminishes the mechanical performance of plant fiber composites. To overcome this problem, in this study, nano‐CaCO3 was used to enhance the microcellular foamed plant fiber composites, and the three‐phase thermoplastic composites, comprised of nano‐CaCO3, rice‐husk fiber, and polypropylene (PP), were fabricated using a chemical foaming injection molding technique. The study analyzed how the nano‐CaCO3 concentration affected the melt viscosity, crystallization characteristics, mechanical properties, and cellular structure of the composites. According to the findings, the mechanical characteristics of microcellular foamed three‐phase thermoplastic composites were enhanced initially and subsequently diminished as the nano‐CaCO3 content was augmented, and obtained optimal value at 2 wt% nano‐CaCO3 content. By observing the cells of microcellular foamed three‐phase thermoplastic composites in vertical and parallel melt flow directions, it was found that the nano‐CaCO3 content of 2 wt% three‐phase thermoplastic composite had the best cellular structure.Highlights The role of nano‐CaCO3 in plant fiber composite materials was explored. The relationship between the content of nano‐CaCO3 and the various properties of tri‐phasic plant fiber composite materials was demonstrated. The mechanisms by which nano‐CaCO3 enhances plant fiber composite materials were analyzed at both macroscopic and microscopic levels.

Closed-loop recyclability of a biomass-derived epoxy-amine thermoset by methanolysis.

Epoxy resin thermosets (ERTs) are an important class of polymeric materials. However, owing to their highly cross-linked nature, they suffer from poor recyclability, which contributes to an unacceptable level of environmental pollution. There is a clear need for the design of inherently recyclable ERTs that are based on renewable resources. We present the synthesis and closed-loop recycling of a fully lignocellulose-derivable epoxy resin (DGF/MBCA), prepared from dimethyl ester of 2,5-furandicarboxylic acid (DMFD), 4,4'-methylenebis(cyclohexylamine) (MBCA), and glycidol, which displays excellent thermomechanical properties (a glass transition temperature of 170°C, and a storage modulus at 25°C of 1.2 gigapascals). Notably, the material undergoes methanolysis in the absence of any catalyst, regenerating 90% of the original DMFD. The diamine MBCA and glycidol can subsequently be reformed by acetolysis. Application and recycling of DGF/MBCA in glass and plant fiber composites are demonstrated.

Weathering resistance of plant fiber‐reinforced high‐density polyethylene matrix composites: Effect of different pigments

AbstractThe effects of iron oxide red pigment, organic red 254 pigment, titanium white pigment, and carbon black pigment on the properties of wood fiber (WF)reinforced high‐density polyethylene (HDPE) composites under outdoor aging conditions were investigated. The results indicate the addition of pigments in the outdoor aging process has a certain physical protection effect on the composites, effectively preventing the damage of ultraviolet rays on the WF/HDPE composites, and the mechanical experiments show that the pigments protect the composites more obviously in the first 3 months. Among them, the carbon black pigment had the best color‐fixing effect on the composites, with the ∆E* value is only 4.1, and the protective effect on the composites was relatively good due to its special structure. The quality change also verified again that the carbon black pigment has a certain protective effect on the plant fiber composites in the pre‐aging period outdoors, in which the mass of the composites with added carbon black pigment increased by 0.14%. Comprehensively, it shows that the addition of pigment cannot completely prevent the photo‐oxidation reaction of the composites from occurring, but it can effectively slow down the aging process of the composites and prolong the service life.Highlights WF/HDPE‐modified composites were prepared by injection molding. The surface color of composites with pigment additions was analyzed. The addition of pigments effectively protects the composites. Mechanical and thermal properties have also been investigated.

Fatigue and Impact Properties of Kenaf/Glass-Reinforced Hybrid Pultruded Composites for Structural Applications.

To address the weight, cost, and sustainability associated with fibreglass application in structural composites, plant fibres serve as an alternative to reduce and replace the usage of glass fibres. However, there remains a gap in the comprehensive research on plant fibre composites, particularly in their durability for viable structural applications. This research investigates the fatigue and impact properties of pultruded kenaf/glass-reinforced hybrid polyester composites tailored for structural applications. Utilising kenaf fibres in mat form, unidirectional E-glass fibre direct roving yarns, and unsaturated polyester resin as key constituents, pultruded kenaf/glass hybrid profiles were fabricated. The study reveals that pultruded WK/UG alternate specimens exhibit commendable fatigue properties (18,630 cycles at 60% ultimate tensile strength, UTS) and fracture energy (261.3 kJ/m2), showcasing promise for moderate load structural applications. Notably, the pultruded 3 WK/UG/3WK variant emerges as a viable contender for low-load structural tasks recorded satisfactory fatigue properties (10,730 cycles at 60% UTS) and fracture energy (167.09 kJ/m2). Fatigue failure modes indicate that the stress applied is evenly distributed. Ductile failures and delaminations during impact test can be attributed to damping and energy absorbing properties of kenaf fibres. Moreover, incorporating kenaf as a hybrid alternative demonstrates substantial reductions in cost (35.7-50%) and weight (9.6-19.1%). This research establishes a foundation for advancing sustainable and efficient structural materials and highlights the significant role of materials design in shaping the future of engineering applications.

A comparative study of polylactic acid (PLA)-Based unidirectional green hybrid composites reinforced with natural fibers such as kenaf, bamboo and coir

Plant-based composites are considered as new generation materials that offer sustainability, eco-friendly and green chemistry, utilized by numerous sectors. Composites of green hybrid made from polylactic acid (PLA) and three different plant fibers were prepared using two symmetrical fibers stacking sequences; namely high modulus and brittle (HMB) fibers (kenaf-bamboo-coir/PLA) and low modulus and ductile (LMD) fibers (coir-bamboo-kenaf/PLA) in the outmost layers. The stacking sequence was prepared using a simple slot tool to properly align the fibers and it was dried at 50 °C before being compressed using hot press. It was found that the tensile strength and tensile modulus of both hybrid composites increased linearly up to 158 MPa and 7 GPa respectively. It shows that the stacking sequences had no significant effect on tensile strength, but fracture strain increased by 58% produced by LMD fibres. However, the use of HMB fibres in the outmost layers significantly improved flexural strength up to 49% higher than that of LMD fibres. In contrast, the impact strength of the green hybrid composites using LMD fibres in the outmost layers was 21% higher than that of its counterpart. Like other plant fiber composites, both composites had an increased water absorption capacity of up to 39% due to increased fibre content. These stacking sequence properties are essential to fabricate a specific application to ensure properties suitable for the job's features. High modulus and brittle composites require a high load to deform permanently, as well as low modulus and ductile composites. Both exhibit versatile mechanical characteristic, providing a balance of sealant toughness and the ability to retain overall shape, such as in sound absorption and vibration in transportation.

Influence of fiber orientation on the moisture adsorption of continuous bamboo fiber composites

Recently, a considerable interest is being shown in the use of plant fibers as reinforcement for polymer composites. Indeed, researchers and scientists are trying to overcome the environmental bias by using bio-composites in several engineering applications. Their attractive specific mechanical properties, low cost, lightness and biodegradability may promote them to substitute expensive and non-renewable fibers such as carbon, kevlar and glass fibers. However, the hydrophilic behavior of natural fibers is of a great concern for their possible outdoor applications. Indeed, the entrapment of water molecules at the fiber lumen, voids and porosities may reduce the tensile strength and modulus of plant fiber composites. Hence, this work aims to evaluate the moisture adsorption behavior of bamboo fiber epoxy composites at different fiber orientations (tangential and radial directions). Firstly, bamboo fibers are extracted using a combination of compression and manual techniques. Morphological and thermogravimetric analyses are carried out to deeply understand the physical properties of the extracted fibers. The findings show that the fibers consist of parallel microfibrils enclosed by some impurities and amorphous constituents. The moisture content of bamboo fibers at 50RH% is deduced from the moisture evaporation stage in the thermogravimetric curve and is about 8.07%. Thereafter, hand layup and compression techniques are used to manufacture the composite samples for the moisture adsorption test. The obtained results show that the equilibrium moisture capacity and diffusion rate values are higher along the fiber direction, which is mainly due to the exposure of the fiber lumen and interfacial voids. The mechanism of moisture transport into composites is found to follow Fick’s law.

3D strain fields in a plant fibre composite during fragmentation test: Micro-CT based DIC and DVC

This paper aims to study the evolution of the 3D strain fields in a single yarn composite during fragmentation test. The internal full-field strains were obtained by coupling micro-CT scans with digital image correlation (DIC) and digital volume correlation (DVC). An ex-situ step-by-step fragmentation test was carried out on a sample made of a hemp yarn and a polymer matrix filled with metal oxide powder, playing the role of a three dimensional speckle. Macroscopic markers were also added to enable a precise geometric alignment during the 3D reconstruction. The analysis of the tomographic images showed a stepwise progression of the damage occurrence: yarn breaks appeared first, followed by internal matrix cracks and then edge cracks occurred for high strain levels. DIC method allowed to easily and quickly determine 2D strain maps in selected planes. The use of DVC was more complex and needed powerful computing systems but it gave the volumetric strains in the whole sample. DVC calculations were compared and validated by DIC results in central planes. Experimental results were also compared with finite element simulations. This study demonstrates the viability and benefits of combining DVC and micro-CT for a deeper understanding of complex 3D strains in single yarn composites.

Durability of Plant Fiber Composites for Structural Application: A Brief Review.

Environmental sustainability and eco-efficiency stand as imperative benchmarks for the upcoming era of materials. The use of sustainable plant fiber composites (PFCs) in structural components has garnered significant interest within industrial community. The durability of PFCs is an important consideration and needs to be well understood before their widespread application. Moisture/water aging, creep properties, and fatigue properties are the most critical aspects of the durability of PFCs. Currently, proposed approaches, such as fiber surface treatments, can alleviate the impact of water uptake on the mechanical properties of PFCs, but complete elimination seems impossible, thus limiting the application of PFCs in moist environments. Creep in PFCs has not received as much attention as water/moisture aging. Existing research has already found the significant creep deformation of PFCs due to the unique microstructure of plant fibers, and fortunately, strengthening fiber-matrix bonding has been reported to effectively improve creep resistance, although data remain limited. Regarding fatigue research in PFCs, most research focuses on tension-tension fatigue properties, but more attention is required on compression-related fatigue properties. PFCs have demonstrated a high endurance of one million cycles under a tension-tension fatigue load at 40% of their ultimate tensile strength (UTS), regardless of plant fiber type and textile architecture. These findings bolster confidence in the use of PFCs for structural applications, provided special measures are taken to alleviate creep and water absorption. This article outlines the current state of the research on the durability of PFCs in terms of the three critical factors mentioned above, and also discusses the associated improvement methods, with the hope that it can provide readers with a comprehensive overview of PFCs' durability and highlight areas worthy of further research.

Viscoelastic properties of alkaline treated walnut shell/rice straw fiber/epoxy biocomposite

The increasing demand for an eco-friendly environment has led to the recent development of polymer matrix/green plant fiber composites. In this present study, the viscoelastic performance of walnut/rice straw fiber/epoxy biocomposites was examined using a dynamic mechanical analysis (DMA) in three-point bending mode at a constant frequency (1 Hz) and temperature (25 oC to 240 °C). The surface morphology of the developed composites was analyzed using field emission scanning electron microscopy (SEM). The epoxy resin was incorporated with walnut/rice straw fiber in five proportions (2-10 wt%) using the hand lay-up technique. The hybrids of rice straw fiber/walnut shell ash particulates were added in equal ratios. The DMA results showed that epoxy/6wt% walnut/rice straw fiber biocomposite recorded the maximum storage modulus (> 8 × 103 MPa) with low loss modulus and damping factor. This indicates excellent stiffness and high energy storage capacity resulting from excellent interfacial bonding of molecules of epoxy, walnut shell particulates, and rice straw fiber. The epoxy/rice straw fiber biocomposite showed a high rate of molecular mobility, leading to high heat dissipation and damping capacity. The glass transition temperature (Tg) of the developed composites ranges from 70 oC to 130 oC, indicating the working temperature of the materials to be below 70 oC. The tan-δ curves indicate that walnut/rice straw fiber/epoxy biocomposites are heterogeneous materials with separate viscoelastic phases and glass transition temperatures, resulting from the addition of walnut shell particulates and rice straw fiber. These reinforcers are finally noted as critical factors affecting the extent of macromolecular mobility within walnut/rice straw fiber/epoxy biocomposites.

A multiscale homogenization model on thermal conductivity of bio-based building composite considering anisotropy, imperfect interface and moisture

Bio-based materials are considered as one of the solutions to reduce energy consumption in buildings due to their excellent thermal insulation properties. However, previous studies often do not consider multiple complex microstructural characteristics in one model. In this study, a novel iterative multi-scale homogenization model was developed to predict the effective thermal conductivity of bio-based materials. This model is based on micro-geometric features at three scales and considers plant fiber orientation and shape, imperfect contact, moisture, and different pores’ size. Further, the model was verified by comparison with finite element models and experimental data from the literature. The results show that the present model demonstrates reliable predictions on the scale of binder, plant fiber, and bio-based composites. The application on hemp verified the accuracy of the imperfect contact in the model, while the application on wheat straw showed the non-negligibility of moisture. Additionally, this study also has good applicability to other plant fibers. In conclusion, this model links microstructure and macroscopic behavior, which can effectively predict and evaluate the thermal conductivity of a wide range of bio-based materials, and thus contribute to reducing building energy consumption.

A hierarchical analytical model for twisted yarn reinforced plant fiber composites considering dual-scale filler content, porosity and local aggregation effect

Plant fibers with length limited by natural growing usually require to be twisted into continuous yarns for reinforcing the host matrix. This makes such twisted yarn reinforced plant fiber composites (TYPCs) are hierarchical with two-scale reinforcements: the plant fibers compacted in the yarn and the twisted yarns at the mesoscale. In the present paper, to uncover the internal relationship between such hierarchical structure and the mechanical properties of TYPCs, a bottom-up theoretical model is established. Synergistic effects of the filler content, filler aggregation degree, and porosity at each level are underlined. Accordingly, a three-step homogenization method based on Mori-Tanaka method is applied. To validate the effectiveness and accuracy of this model, comparisons with existing prediction models and available experimental data are made. Furthermore, detailed parameter analysis indicates that the performance of TYPCs depends not only on the filler content, but also on the filler distribution. The enhancement of TYPCs’ properties with increasing filler content may be offset by the weakening effect caused by filler aggregations. Moreover, the helical structure of yarns should not be ignored. The increase of the yarn twisting angle will improve the transverse and shear moduli of TYPCs while sacrificing the modulus in the longitudinal direction to a certain extent.

Multi-objective optimization for improving printing efficiency and mechanical properties of 3D-printed continuous plant fibre composites

The mechanical properties and printing efficiency (i.e. the printing time) are often contradictory goals in 3D printing of continuous fibre composites. In this work, we presented a multi-objective optimization method for improving both the mechanical properties and printing efficiency of 3D-printed continuous flax-fibre-reinforced composites (CFFRCs). It was found that the printing efficiency of the CFFRCs with the optimal processing parameters was remarkably improved by 40% without sacrificing the tensile strength of the composites. This study provides an effective method for the improvement of the production efficiency of high-quality 3D-printed continuous fibre reinforced composites.

In situ damping identification of plant fiber composites using dynamic grid nanoindentation

Damping properties of plant fiber composites have been quite widely investigated based on macroscale techniques. Considering their heterogeneous and hierarchical microstructure, it is also necessary to study their damping behavior at the microscale to provide better insight into the dissipation origins and mechanisms. This article proposes a characterization of the dynamic mechanical properties of flax/GreenPoxy composites at microscale using dynamic grid nanoindentation technique. Two loading protocols are used: the classical Continuous Stiffness Measurement method (CSM) and a new method called Constant Amplitude Measurement method (CAM). Results show experimental protocols (CAM or CSM) do not have significant effect on storage modulus while they significantly affect the loss factor. The grid nanoindentation technique also provides an interesting map of the viscoelastic properties at the microscale in the cross-section of the composites and the damping contribution of the various components are highlighted.

Novel infrared-terahertz fusion 3D non-invasive imaging of plant fibre-reinforced polymer composites

The reinforcement of polymer composites using plant fibres has received vast and growing attention for investigation owing to their capability to serve as semi-structural materials, especially as a substitute for fiberglass. However, in this type of research, the structural complexity, due to geometrical mismatches and inherent variability to the properties of vegetable fibres and plant fibre composites would benefit from more effective non-invasive inspection techniques. In this work, a novel infrared-terahertz fused approach was proposed, and a new unsupervised deep residual fusion algorithm was developed in order to combine the outputs from two different physical mechanisms. Specifically, infrared imaging provided the details of the defects and the morphological information from the surface and subsurface, while terahertz imaging recorded the distribution of the fibres and the resin. Finally, the fused infrared-terahertz slices were reconstructed into a form of 3D exhibition for inspection and evaluation of two plant fibre-reinforced polymer composites in first time using multiphysical imaging and fusion.

Impact of cell wall non-cellulosic and cellulosic polymers on the mechanical properties of flax fibre bundles

Fibre bundles are groups of elementary fibres glued together thanks to the middle lamella, and are the main fraction in plant fibre composites. In this study, relationship between the mechanical properties of flax fibre bundles, chemical composition and cellulose structure were investigated. To do so, a sequential biopolymer extraction was implemented. Fibre bundles were first depectinated by oxalate extraction, and then the hemicelluloses were extracted by LiCl/dimethyl sulfoxide (DMSO) and KOH. The oxalate extract consisted of homogalacturonans and type I rhamnogalacturonans, while the LiCl extract was composed mainly of glucomannans and the KOH extract of xyloglucans. The KOH stage resulted in the appearance of cellulose II in flax bundles. The extraction of pectin and hemicelluloses led to the disappearance of the middle lamella concomitant with a decrease in the tensile Young's modulus and maximum strength. Finally, the fibre bundle composition, ultrastructure and mechanical properties are discussed together in view of the thin middle lamella.

Experimental investigation on the mechanical behavior of concrete reinforced with Alfa plant fibers

Currently, the reinforcement of ordinary concrete with synthetic fibers poses ecological problems because the manufacturing process of these products is very polluting. Plant fiber composites are a new challenge for environmental protection. The present article aims to investigate the mechanical behavior of concrete reinforced with natural fibers, called alfa fibers. Compression and three-point bending tests have been performed on cubic and prismatic samples, respectively. Different fiber lengths (2.5, 5, and 8 cm) and content (0.6, 1.2, and 1.8%by volume) of alfa fibers have been used to examine their influence on the mechanical behavior of the fiber-reinforced concrete. The obtained results show that for a volume content of 1.2% of plant fibers of 5 cm length, the tensile strength of the reinforced concrete increases up to 54.41% compared to the ordinary concrete (BT). However, for content of 1.8% of fibers with 8 cm length, both the compressive and tensile strength of the reinforced concrete decrease slightly. At this level, an excess of both fiber content and their length produces the formation of voids within concrete. Moreover, such an excess made the hydration reaction slower. It is worth noticing that the orientation of fibers also plays a significant role in the nucleation and propagation of microcracks. The fibers arranged both horizontally and obliquely are more resistant to microcracking than those oriented in the loading direction.

Experimental investigation on mechanical properties of alkali treated jute fibre reinforced sodium alginate composites

Plant fibre composite from renewable resources have emerged as one of the growing field in the engineering sectors. The present work investigating the effect of various concentration(1.5, 2 and 2.5%) of sodium alginate gum on the mechanical characteristics of jute fibre(untreated/treated) composites. Using hand layup process the materials were prepared. Experimental results revealed that alkali treated jute fibre sodium alginate gum composites have resulted in enhancement of mechanical strength(tensile-2.4 MPa, flexural-9.97 MPa and impact-20.3 J/m). The less moisture absorbing capacity of 0.84% was observed for the alkali treated composites. In addition to that biodegradability of the treated composite is found to be relatively superior to that of untreated one. SEM studies demonstrated that the improvement in properties was due to enhanced bonding between the fibre and matrix. Thus, the findings inferred that chemical treatment has established a good adhesion between the jute fibre and the matrix making these composite material as suitable for various domestic and industrial uses.