Plant Fiber-reinforced Composites Research Articles

Examine the static and dynamic mechanical properties of alkali-treated Cannabis sativa plant fiber-reinforced composites

Examine the static and dynamic mechanical properties of alkali-treated Cannabis sativa plant fiber-reinforced composites

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 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.

Investigation of recovery behavior on 3D-printed continuous plant fiber-reinforced composites

The mechanical properties and accuracy of 3D-printed composites can be significantly affected by printing parameters. This work discovered a noteworthy recovery phenomenon during 3D printing of continuous flax fiber-reinforced composites (CFFRCs). The yarn count and printing speed are the critical factors that influence the recovery behavior, which, in turn, affects the thickness, the fiber volume fraction, and the void content of CFFRCs, ultimately impacting the mechanical properties. Smaller yarn counts have a greater effect on the recovery behavior of CFFRCs. Increasing the printing speed from 5 mm/s to 15 mm/s leads to the loss of tensile properties and flexural modulus in CFFRCs up to 30 % and 58 %, respectively. The recovery mechanism of the CFFRCs is further elucidated with the observation of temperature distribution during the printing process. This indicates that recovery is more likely to occur in the compressed yarn with a twisted structure when the deposited thermoplastic matrix exceeds the glass transition temperature. The results and findings have the potential to enhance the process optimization of 3D-printed continuous plant fiber composite parts, ensuring high mechanical properties and dimensional precision.

Plant fiber‐reinforced composites based on injection molding process: Manufacturing, service life, and remanufacturing

AbstractResource depletion and environmental degradation have become important issues affecting the human development process. Plant fiber‐reinforced composites (PFRCs) are characterized by high natural availability, good mechanical properties, low density, recyclability, and eco‐friendliness. Expanding human applications of plant fibers is an important measure to combat resource and environmental problems. The injection molding process has the characteristics of strong product size adaptability, high molding precision, and high production efficiency. It is suitable for large‐scale production in the industry and is one of the main molding methods of PFRCs. Currently, there are still challenges and opportunities for high‐performance manufacturing of PFRCs based on the injection molding process. This article reviews the complete process of manufacturing‐service life‐remanufacturing of PFRCs based on the injection molding process. Emphasis is placed on the pretreatment technology and selection strategy of multi‐phase blended raw materials, the molding process conditions, functional applications, and simulation analysis, the aging and degradation characteristics during service, and the remanufacturing characteristics of the composites. Finally, the future research focus is summarized and prospected. The research in this paper will help promote the continuous progress of key technologies in the production process of PFRCs and help the industry to truly realize high‐performance green manufacturing in the future.Highlights Plant fibers exhibit variability in morphology and properties. The link between the structure and performance of PFRCs is unclear. The degradability and durability of PFRCs are contradictory. The functionality and mechanical properties of PFRCs are contradictory. PFRCs have good characteristics for remanufacturing.

Physiochemical investigation of untreated and alkali treated agave plant fiber

Plant fiber-reinforced composites occupied an important role in the production of bio-degradable goods. Polymer composites with synthetic fiber as reinforcement produce adverse effects on the environment because of their higher decomposition rate. In most cases, natural fiber reinforced composites were used in the automotive industry to make body door parts, interior panels, bumpers, dashboard units, two-wheeler mudguards, doom parts, etc. During the reinforcement of fiber with matrix there are a lot of factors say moisture absorption, interfacial bonding, etc., involes in affecting the composite. So in order to reduce those risk factors, natural fiber has to be pre-treated before involving it in reinforcement. Chemical treatment was useful in the removal of impurities, wax, and other unwanted substances on the outer surface of the fiber. This paper deals with the novel study in identifying the optimum concentration of alkali solution for suitability in making the two-wheeler mudguard. Pre-treatment involves soaking of agave fiber at different concentrations of sodium hydroxide (NaOH) solution say 2, 4, 6, and 8%(w/v) for about 3 h. The impact on different concentrations of NaOH treatment was confirmed with the change in the diameter of the fiber using a digital microscope, chemical composition analysis was performed, a single fiber tensile test, and a scanning electron microscope was also conducted. From the test results, it was noted that sodium hydroxide treatment removes unwanted substances present on the fiber surface. Meanwhile, when the concentration of the sodium hydroxide was increased the fiber got damaged due to the abrasion of cellulosic constituents that reduces the property of fiber, making it unsuitable for reinforcement. At the end of this study, 4% of NaOH-treated fiber showed better results from all tests and that was used for making a mudguard.

Mechanical Performances Analysis and Prediction of Short Plant Fiber-Reinforced PLA Composites.

Plant fiber-reinforced polylactic acid (PLA) exhibits excellent mechanical properties and environmental friendliness and, therefore, has a wide range of applications. This study investigated the mechanical properties of three short plant fiber-reinforced PLA composites (flax, jute, and ramie) using mechanical testing and material characterization techniques (SEM, FTIR, and DSC). Additionally, we propose a methodology for predicting the mechanical properties of high-content short plant fiber-reinforced composite materials. Results indicate that flax fibers provide the optimal reinforcement effect due to differences in fiber composition and microstructure. Surface pretreatment of the fibers using alkali and silane coupling agents increases the fiber-matrix interface contact area, improves interface performance, and effectively enhances the mechanical properties of the composite. The mechanical properties of the composites increase with increasing fiber content, reaching the highest value at 40%, which is 38.79% higher than pure PLA. However, further increases in content lead to fiber agglomeration and decreased composite properties. When the content is relatively low (10%), the mechanical properties are degraded because of internal defects in the material, which is 40.42% lower than pure PLA. Through Micro-CT technology, the fiber was reconstructed, and it was found that the fiber was distributed mainly along the direction of injection molding, and the twin-screw process changes the shape and length of the fiber. By introducing the fiber agglomeration factor function and correcting the Halpin-Tsai criterion, the mechanical properties of composite materials with different contents were successfully predicted. Considering the complex stress state of composite materials in actual service processes, a numerical simulation method was established based on transversely isotropic material using the finite element method combined with theoretical analysis. The mechanical properties of high-content short plant fiber-reinforced composite materials were successfully predicted, and the simulation results showed strong agreement with the experimental results.

Tensile Performance Mechanism for Bamboo Fiber-Reinforced, Palm Oil-Based Resin Bio-Composites Using Finite Element Simulation and Machine Learning.

Plant fiber-reinforced composites have the advantages of environmental friendliness, sustainability, and high specific strength and modulus. They are widely used as low-carbon emission materials in automobiles, construction, and buildings. The prediction of their mechanical performance is critical for material optimal design and application. However, the variation in the physical structure of plant fibers, the randomness of meso-structures, and the multiple material parameters of composites limit the optimal design of the composite mechanical properties. Based on tensile experiments on bamboo fiber-reinforced, palm oil-based resin composites, finite element simulations were carried out and the effect of material parameters on the tensile performances of the composites was investigated. In addition, machine learning methods were used to predict the tensile properties of the composites. The numerical results showed that the resin type, contact interface, fiber volume fraction, and multi-factor coupling significantly influenced the tensile performance of the composites. The results of the machine learning analysis showed that the gradient boosting decision tree method had the best prediction performance for the tensile strength of the composites (R2 was 0.786) based on numerical simulation data from a small sample size. Furthermore, the machine learning analysis demonstrated that the resin performance and fiber volume fraction were critical parameters for the tensile strength of composites. This study provides an insightful understanding and effective route for investigating the tensile performance of complex bio-composites.

Behavior of the Flexural Strength of Hemp/Polypropylene Composites: Evaluation of the Intrinsic Flexural Strength of Untreated Hemp Strands.

The growing demand for plant fiber-reinforced composites offers new opportunities to compete against glass fiber (GF)-reinforced composites, but their performance must be assessed, revised, and improved as much as possible. This work reports on the production and the flexural strength of composites from polypropylene (PP) and hemp strands (20-50 wt.%), using maleic anhydride-grafted PP (MAPP) as a compatibilizer. A computational assessment of the reaction between cellulose and MAPP suggested the formation of only one ester bond per maleic anhydride unit as the most stable product. We determined the most favorable MAPP dosage to be 0.06 g per gram of fiber. The maximum enhancement in flexural strength that was attained with this proportion of MAPP was 148%, corresponding to the maximum fiber load. The modified rule of mixtures and the assumption of similar coupling factors for tensile and flexural strength allowed us to estimate the intrinsic flexural strength of hemp strands as 953 ± 116 MPa. While falling short of the values for sized GF (2415 MPa), the reinforcement efficiency parameter of the natural fibers (0.209) was found to be higher than that of GF (0.045).

Meso-micro-nanoscale experiments and simulations on the hierarchical interfaces of composites

<p indent="0mm">Plant fibers possess the advantages of green environmental protection and abundant sources. They exhibit specific mechanical properties comparable to man-made fibers and can become an important reinforcement of composites. Their unique hierarchical structures affect the load transfer mode of plant fiber reinforced composites (PFRCs). To serve the task of interfacial design of PFRCs, it is necessary to quantify their hierarchical interfacial properties. First, by applying the nanoindentation technology, the mechanical properties of the multi-layer interface of PFRCs, including the modulus, hardness, energy dissipation, and ability of crack initiation and propagation, were measured using the single-step and multi-step static nanoindentation methods. Subsequently, the fatigue characteristics of multiple interfaces in PFRCs under cyclic loading were evaluated via the nanoscale dynamic mechanical analysis. Finally, combined with the finite element simulation at the mesoscale, the multi-stage failure behavior of the hierarchical interfaces in the composites was presented by introducing multiple interface performance parameters obtained at the nanoscale. The results showed that the hierarchical structure of plant fibers was associated with the multi-stage failure behavior of PFRCs. The hierarchical interfacial failure caused by the crack initiation and propagation at the three types of interfaces occurred sequentially. The experimental results at the nanoscale provide support and basis for an in-depth analysis of the interfacial properties and failure mechanisms of composites on meso-microscale.

Effect of weight fraction on the mechanical properties of flax and jute fibers reinforced epoxy hybrid composites

Development of the plant fiber-reinforced composites from renewable sources is a sustainable alternative material for emerging engineering fields like automotive, aerospace and marine. This experimental work aims to study the effect of weight fraction on the mechanical properties of flax (Linum usitatissimum) and jute (Corchorus olitorius) fibers reinforced hybrid composites. Five different hybrid composites based on fiber weight fraction were prepared by compression molding method. The mechanical properties of hybrid composites such as tensile, flexural, impact and interlaminar shear strength were tested according to ASTM standard. Failure of hybrid composites generally occurs due to the reduced adhesion bonding between fibers and epoxy matrix and fibers pull out. It was observed that the maximum tensile strength, flexural strength, interlaminar shear strength and impact strength were obtained only for a composite having 30 wt% flax fiber reinforcement. The values for the same were recorded as 36.38 MPa, 112.25 MPa, 4.45 MPa and 36.78 kJ/m2 respectively. These composites are having high compatibility to be incorporated in the application like automobiles, sheet roofs, etc.

Improvement of the Mechanical Properties of Plant Fiber-reinforced Composites through Hybridization

ABSTRACT The most important reason why natural fibers are not sufficiently involved in applications is the large scattering of their properties. In addition, it is very difficult to find one kind of natural fiber which has perfect mechanical properties like synthetic fibers. Here, we aimed to find solutions by developing a hybrid composite according to the expectations in the field of application. With this method, desired mechanical properties can be designed, and the weak properties can be improved. To be able to examine this method, we used two different fibers which have different mechanical characteristics. The mechanical properties were measured with three-point bending and impact resistance tests. According to the results, the flexural strength of the jute-reinforced composites (JC) has been improved by 44–71% using luffa fiber hybridization method. On the other hand, it has been observed that the impact resistance of the same specimens of JC has been improved by 51–83%. These results revealed that it is possible to improve the mechanical properties of the composites with hybridization. In conclusion, our study shows that bio-composites can be designed according to the requirement of the application. Hence, the application areas of bio-composites can be widened with increased usage rates.

The Middle Lamella of Plant Fibers Used as Composite Reinforcement: Investigation by Atomic Force Microscopy.

Today, plant fibers are considered as an important new renewable resource that can compete with some synthetic fibers, such as glass, in fiber-reinforced composites. In previous works, it was noted that the pectin-enriched middle lamella (ML) is a weak point in the fiber bundles for plant fiber-reinforced composites. ML is strongly bonded to the primary walls of the cells to form a complex layer called the compound middle lamella (CML). In a composite, cracks preferentially propagate along and through this layer when a mechanical loading is applied. In this work, middle lamellae of several plant fibers of different origin (flax, hemp, jute, kenaf, nettle, and date palm leaf sheath), among the most used for composite reinforcement, are investigated by atomic force microscopy (AFM). The peak-force quantitative nanomechanical property mapping (PF-QNM) mode is used in order to estimate the indentation modulus of this layer. AFM PF-QNM confirmed its potential and suitability to mechanically characterize and compare the stiffness of small areas at the micro and nanoscale level, such as plant cell walls and middle lamellae. Our results suggest that the mean indentation modulus of ML is in the range from 6 GPa (date palm leaf sheath) to 16 GPa (hemp), depending on the plant considered. Moreover, local cell-wall layer architectures were finely evidenced and described.

Experimental and numerical investigation on the dynamic characteristics of thick laminated plant fiber-reinforced polymer composite plates

Although considerable attention has been devoted to the experimental research works of plant fiber-reinforced composites, theoretical determination of their structural characteristics is also much needed one in their evolution. But it is still considered as a difficult process due to the several factors such as short and discontinuous fiber form, plant fiber’s intrinsic characteristics, fiber anisotropy and porosity. In this study, vibration characteristics of woven jute/epoxy and woven aloe/epoxy laminated composite plate structures are investigated theoretically and experimentally. The elastic constants of the woven jute/epoxy and woven aloe/epoxy laminated composites are obtained through experimental testing. The governing differential equations of motion for the uniform woven jute/epoxy and woven aloe/epoxy laminated thick composite plates are carried out using the p-version finite element method based on higher-order shear deformation theory. The effectiveness of the developed finite element formulations is demonstrated by comparing the natural frequencies obtained using the present finite element method with those obtained from the experimental measurements. Also a comparative study is carried out between the results of h-version FEM and p-version FEM to check their accuracies and efficiencies. The effects of aspect ratio and angle of fiber orientation under various end conditions on the free vibration responses of the woven jute/epoxy laminated composite plate are also investigated. The forced vibration response of the woven jute/epoxy laminated composite plate under the harmonic force excitation is carried out under various end conditions.

Effect of physiochemical structure on energy absorption properties of plant fibers reinforced composites: Dielectric, thermal insulation, and sound absorption properties

Abstract Supported by life cycle assessment, plant fiber reinforced composites (PFRCs) have been acknowledged environmentally superior to man-made glass and carbon fibers reinforced composites (GFRCs and CFRCs). Endowed with an intrinsic multi-scale cell wall and lumen structure, plant fibers are expected to yield better energy absorption performances in their reinforced composites. In this research, the energy absorption properties: dielectric , thermal and acoustic properties, of PFRCs were evaluated via vector network analyzer, dielectric spectrometer, steady-state hot plate and acoustic impedance tube. It was demonstrated that PFRCs were beneficial for multi-functional applications, possessing lower dielectric constant and dielectric loss, lower thermal conductivity and higher sound absorption coefficient in comparison with man-made equivalents (carbon fiber and glass fiber reinforced composites). More specifically, the physiochemical structures of plant fibers (lumen, cell wall and crystalline structure) were correlated to analyze these energy absorption behaviors of PFRCs.

An overview of structural-functional-integrated composites based on the hierarchical microstructures of plant fibers

Plant fiber-reinforced composites have raised great attention among materials scientists and engineers during the past decade. Most of the efforts were put on the interfacial modifications to improve the mechanical properties of the composites so that they could partly replace the currently largely used glass fiber-reinforced composites. The modifications were mainly focused on the surface treatment of plant fibers so that mechanical or chemical bonding between plant fibers and polymeric matrices could be set up. However, the unique hierarchical microstructures of plant fibers make the building up of multiscale interfaces possible so that more forces or energies would be needed to fracture the plant fiber-reinforced composites. The additional hollow structures could also bring benefits for sound absorption and damping properties. Therefore, this article reviewed R&D efforts to develop structural and functional-integrated plant fiber-reinforced composites by fully taking advantage of the hierarchical microstructures of plant fibers. Firstly, the unique hierarchical structures of plant fibers were revealed and hierarchical theoretical models for mechanical properties were discussed. Then, the modification, characterization, and evaluation of plant fibers in terms of their interfacial properties with polymeric matrices, especially by nanotechnologies with the consideration of their unique hierarchical microstructures, were reviewed. Finally, the design and manufacture of quasi-structures and structural-damping components using technologies that have been fully adapted to state-of-the-art industrial processes for use in critical applications, such as aircraft interiors, rail transportation vehicles, and constructions, were also introduced.

Modeling the longitudinal tensile behavior of unidirectional twisted plant fiber yarns-reinforced composites

In this paper, a theoretical model among strain, stress, and surface twist angle of plant fiber yarns, for unidirectional twisted plant fiber-reinforced composites under tensile forces, was proposed with a piecewise function. That model focused on yarn twist angle’s effect on tensile modulus and stress–strain relations of composites, which was based on the widely used rule of mixtures, classical laminate theory, and revised Krenchel orientation efficiency factor cos22θ (θ is the surface twist angle of fiber yarns). In the model, a surface twist angel θe was regarded as the threshold value where ε1 = ε (ε1 is the longitudinal tensile strain, and e is its numerical value) for the piecewise function, which cut off the experimental stress–strain curve from nonlinearity into linearity. The model was validated by the tensile test results of sisal fiber-reinforced composites made from twisted sisal filament yarns. A good agreement between the theoretical values and experimental results was obtained. This study would form the fundamentals for building up the constitutive model of plant fiber yarns-reinforced composites.

A micromechanical model of interfacial debonding and elementary fiber pull-out for sisal fiber-reinforced composites

The interfacial failure behavior of sisal fiber-reinforced composites (SFRCs) was studied experimentally and theoretically. The residual pull-out strength of the SFRCs was observed to gradually decrease during the single sisal fiber pull-out test, after which the SFRCs presented multiple failure modes, including at the interface between technical fiber and matrix and at the interface between elementary fibers. To further investigate the failure mechanisms of SFRCs, using the traditional shear lag model, a double-interface model tailored to the unique multi-layer interface structure of plant fibers was developed to describe the fiber pull-out behavior and the interfacial adhesion status of single plant fiber-reinforced composites (PFRCs). By comparison with other existing models, using the experimental applied stress as reference, the proposed double-interface model was found to provide a more accurate quantitative theoretical prediction of the interfacial failure behavior of PFRCs during multi-stage fracture of the two interfaces.