Plant Fibre Composites Research Articles

Quantitative analysis by micro-CT of damage during tensile test in a woven hemp/epoxy composite after water ageing

The influence of water ageing on the evolution of damage during tensile loading in woven hemp/epoxy composites is studied. First, the water uptakes of several types of samples are compared. Micro-CT observations show that, from the beginning of desorption but not during the water ageing, damage appears in the composites. At macroscopic scale, tensile tests reveal a significant modification of mechanical properties of the composite after water ageing. Then, an original test, combining tensile loading and X-ray microtomography, is performed on a ±45 hemp/epoxy composite material. The volume of damage inside two specimens (with and without water ageing) at several steps during a tensile test can be quantified. Results highlight significant differences in the evolution of the volume of damage between the two samples. This work shows how the mechanisms of deformation and damage of plant fibre composites are governed by their moisture exposure history.

Effect of gamma irradiation aging on mechanical and thermal properties of alfa fiber–reinforced polypropylene composites

Recently, the interest in plant fiber composites has considerably increased due to the new environmental legislation as well as consumer pressure that forced manufacturing industries to search substitutes to the conventional materials. The aim of this article is to assess the effects of different does of gamma irradiation on the physico-mechanical properties of the composites PP / alfa fiber treated and untreated. The Young’s modulus of composites increases in the presence of alfa fiber and it was more pronounced with untreated ones resulting by the cross-linking, whereas elongation and maximum strain decreased as dose irradiation raised. Fourier transform infrared spectroscopy results showed that the virgin PP has better stability to gamma irradiation than treated and untreated composites. Thermogravimetric analysis showed that the addition of the treated and untreated fiber greatly improves the thermal stability of the polymer matrix before and after gamma irradiation. Composites based on treated and untreated fiber have better storage modulus than virgin matrix.

Tensile properties of plant fibre‐polymer composites in fire

SummaryThe structural performance of polymer composites reinforced with plant fibres when exposed to fire was experimentally evaluated and compared against an E‐glass fibre laminate. Fire testing under combined one‐sided radiant heating and static tensile loading revealed that flax, jute, or hemp fibre composites experience more rapid thermal softening and fail within much shorter times than the fibreglass laminate, which is indicative of vastly inferior structural performance in fire. The plant fibre composites soften and fail before the onset of thermal decomposition of the plant fibres and polymer matrix, whereas the E‐glass fibres provide the composite with superior tensile properties to higher temperatures and higher applied tensile stresses. The tensile performance of the three types of plant fibre composites in fire was not identical. When exposed to the same radiant heat flux, the flax fibre composite could withstand higher tensile stresses for longer times than the hemp and jute laminates, which showed similar performance.

Natural Plant Fiber Composites - Constituent Properties and Challenges in Numerical Modelling and Simulations

Natural fibers are extracted from natural resources such as stems of plants. In contrast to synthetic fibers (e.g., carbon fibers), natural fibers are from renewable resources and are eco-friendlie...

Natural Plant Fiber Composites-Constituent Properties and Challenges in Numerical Modeling and Simulations

Natural fibers are extracted from natural resources such as stems of plants. In contrast to synthetic fibers (e.g., carbon fibers), natural fibers are from renewable resources and are eco-friendlier. Plant fibers are important members of natural fibers. Review papers discussing the microstructures, performances and applications of natural plant fiber composites are available in the literature. However, there are relatively fewer review reports focusing on the modeling of the mechanical properties of plant fiber composites. The microstructures and mechanical behavior of plant fiber composites are briefly introduced by highlighting their characteristics that need to be considered prior to modeling. Numerical works that have already been carried out are discussed and summarized. Unlike synthetic fibers, natural plant fiber composites have not received sufficient attention in terms of numerical simulations. Existing technical challenges in this subject are summarized to provide potential opportunities for future research.

Development of Electroless Ni-P Coatings on Sisal Fiber

Improving the properties of natural fibers can be interesting from a technological point of view. Modifications can result in a high specific strength, electromagnetic interference (EMI) shielding, antistatic brush etc. Plant fiber composites would make them an option for use in components such as rifle stocks and knife handles etc. The greatest challenge would be to ensure that the components are all weather capable, but today several materials exist that have a high moisture tolerance. Moreover with proper surface coating techniques, most natural fibers materials can be toughened up to use as reinforcement. An attempt was made using a proprietary experimental set-up to coat natural fiber with electroless nickel phosphorus (ENi-P), since sisal fiber is a non-conducting material. In this article the surface morphology, ingredients and cross-section images of the modified natural fibers were characterised by a scanning electron microscope equipped with EDAX.

Composites Based on Thermoset Resin and <i>Orbignya phalerata</i> (Babassu Coconut): Evaluation of Mechanical Properties, Morphology and Water Sorption

Researches in plant fiber composites have been developed with greater frequency during the last years, especially on environmental issues. The opening of the market, especially in the automotive sector, points to the replacement of synthetic additives by natural reinforcements. Characteristics such as low density and abrasiveness, superior mechanical properties and low cost are the most sought in these composites. The aim of this study was to evaluate the behavior of composites based polyester matrix and fiber of the babassu coconut epicarp, at levels of 5, 7.5 and 10% under testing of tensile strength and impact, as well as the morphology by microscopy scanning electron and water absorption. All composites were prepared raw fibers and fiber with treated with alkaline solution of 5% NaOH. As regards the mechanical properties, an increasing of the rigidity of the system was observed, and the kinetics of water absorption increased levels indicated for compounds with high content of fibrous reinforcement. By SEM there was greater interaction between fiber and matrix.

Interface and bonding mechanisms of plant fibre composites: An overview

Abstract The development of plant fibre composite is on the rise for a wide range of applications. Probably a single most important aspect with respect to the formulation of plant fibre composites with superior mechanical performance is the optimization of the interfacial bonding between the reinforcing plant fibre and polymer matrix. While the interface plays a pivotal role in determining the mechanical properties, e.g. transferring the stress and distributing the bond, it is among the least understood components of the composite. This paper presents an overview of the compatibility between the heterogeneous constituents of plant fibre composite, various modification approaches aiming at overcoming the incompatibility and refining the interfacial adhesion of the composite, interfacial bonding mechanisms, and the assessment of interface structure and bonding. It has been found that 1) the physical and chemical incompatibility between the fibre and matrix, leading to poor dispersion, weak interfacial adhesion and ultimately inferior composite quality, could be overcome through strategical modifications; 2) inter-diffusion, electrostatic adhesion, chemical reactions and mechanical interlocking are in general responsible for the interfacial bonding and adhesion of plant fibre composites; and 3) a thorough knowledge of structure-property relationship of the composite could be established by conducting a set of direct and indirect interfacial assessments. This paper finishes with some critical suggestions and future perspectives, underscoring the roles of composite material researchers and engineers for the further in-depth studies and up-scale commercialization of plant fibre composite.

Why do we observe significant differences between measured and ‘back-calculated’ properties of natural fibres?

The drive towards sustainability, even in materials technologies, has fuelled an increasing interest in bio-based composites. Cellulosic fibres, such as flax and jute, are being considered as alternatives to technical synthetic fibres, such as glass, as reinforcements in fibre reinforced polymer composites for a wide range of applications. A critical bottleneck in the advancement of plant fibre composites (PFRPs) is our current inability to predict PFRP properties from data on fibre properties. This is highly desirable in the cost- and time-effective development and design of optimised PFRP materials with reliable behaviour. This study, alongside limited other studies in literature, have found that the experimentally determined (through single fibre tests) fibre properties are significantly different from the predicted (‘backcalculated’ using the popular rule-of-mixtures) fibre properties for plant fibres. In this note, we explore potential sources of the observed discrepancy and identify the more likely origins relating to both measurement and errors in predictions based on the rule of-mixtures. The explored content in this discussion facilitates the design of a future investigation to (1) identify the sensitivity of the discrepancy between measured and predicted fibre properties to the various potential origins, (2) form a unified hypothesis on the observed phenomenon, and (3) determine whether the rule-of-mixtures model (in specific cases) can be improved and may be able to predict properties precisely.

Recycling of L-Poly-(lactide)-Poly-(butylene-succinate)-flax biocomposite

The development of new plant fibre composites is a key point in the development of semi-structural biodegradable or biobased parts, especially for automotive applications. The aim of this original and innovating work is to study, at different scales, the recycling ability of a fully biodegradable L-Poly-(lactide)-Poly-(butylene-succinate)-flax (PLLA-PBS-flax) biocomposite. The biocomposites were manufactured by twin-screw extrusion followed by injection moulding, then the recycling behaviour was studied during successive injection moulding cycles. Firstly, we investigated the length of the flax fibre after compounding and injection, as well as the cell wall stiffness and hardness, by in-situ nanoindentation tests. Secondly, we focused on the effects of recycling on thermal, rheological and tensile properties. We highlighted a severe evolution of the cell wall properties, especially concerning the polysaccharidic matrix after the first thermal cycle, nanoindentation properties remaining quasi-stable after this first drop. Furthermore, the biocomposites did not show any significant evolution of their mechanical performances during cycle three or four of the first injection cycles; after this plateau, the tensile strength and strain as well as impact energy were significantly altered due to the conjugated fibre length decrease and degradation of the PLLA, the latter being emphasized when the flax fibre is embedded. Nevertheless, this fully biodegradable composite exhibits a suitable recycling behaviour for 3 or 4 cycles, which is sufficient for industrial applications.

Life Cycle of Plant Fiber Composites: A Qualitative Analysis of Greenhouse Gases (GHG) Emissions of Polypropylene Composite with Sisal Fiber

Life Cycle of Plant Fiber Composites: A Qualitative Analysis of Greenhouse Gases (GHG) Emissions of Polypropylene Composite with Sisal Fiber

Effects of Processing Method, Moisture Content, and Resin System on Physical and Mechanical Properties of Woven Kenaf Plant Fiber Composites

Effects of the processing method, moisture content, and polymer type were evaluated relative to the physical and mechanical properties of composites based on natural plants. When kenaf was heated above the glass transition temperature of lignin, there was a reduction in moisture content by more than 8% of the total weight of the raw material. To investigate polymer behavior, the raw material was reinforced with three types of polymers: epoxy, unsaturated polyester (UP), and vinyl ester fabricated using hand lay-up with cold press (HCP) and vacuum infusion (VI). The results of (HCP) showed a noticeable improvement in tensile and flexural strength and their moduli for all types of polymer used compared with (VI), in ascending order from UP and vinyl ester to epoxy. Using the HCP method, the tensile strength improved considerably, by 60% for epoxy, 59% for UP, and 250% for vinyl ester, while flexural strength was enhanced by 16% for epoxy, 126% for UP, and 117% for vinyl ester compared to VI. Impact results showed a slight or no improvement in absorbed energy.

Damage in biocomposites: Stiffness evolution of aligned plant fibre composites during monotonic and cyclic fatigue loading

The non-linear stress–strain behaviour of plant fibre composites is well-known in the scientific community. Yet, the important consequences of this, in terms of the evolution of stiffness as a function of applied strain and cycles to failure, are not well-studied in literature. This is despite the fact that stiffness degradation is a well-accepted indicator of damage in a composite material, and is regularly used as a component failure criterion. This article systematically explores the evolution of stiffness of various aligned plant fibre composites, subjected to (i) monotonic loading, (ii) low-cycle, repeated progressive loading, and (iii) fatigue loading. The evolution in stiffness in plant fibre composites is found to be complex: structural changes in the elementary fibre cell wall and damage development in the composite have often competing effects on stress–strain behaviour. Indeed, the evolution in stiffness of plant fibre composites is found to be unlike that typically observed in traditional composites, and therefore needs to be taken into account in the design of structural components.

Mechanical performance of Cissus quadrangularis/polyester composite

This work describes the reinforcement ability of newly harvested plant stem fibers named veldt grape bast fiber (Cissus quadrangularis) in a thermoset matrix. The stamped fibers are extracted using the water immersion technique, followed by a manual shaving operation. The tensile, chemical and morphological properties of the veldt grape fiber were studied. The mechanical performance of the compression molded veldt grape/polyester composite was studied, for the effects of the fiber length and fiber loading. A non-linear trend in mechanical properties was noticed with the varying parameters. However, better mechanical properties were observed for the optimum fiber length of 40mm and 40wt% of fiber loading. A comparative study was performed between the various existing plant fiber composites and the newly developed one. Further, the morphological analysis was also done on the tensile and impact fractured composites, using the scanning electron microscope.

Flax/polypropylene composites for lightened structures: Multiscale analysis of process and fibre parameters

Abstract The optimization of the processing method for poly-(propylene) (PP)/plant fibre composites compounding is a key point in the development of semi-structural parts, especially for automotive applications. The aim of this original and innovating work is to study, at different scales, the impact of extrusion equipment and fibre length on the composite's mechanical performances. Firstly, we studied the flax fibre morphology after compounding and injection as well as their individualization in injected specimens. Secondly, we focused on the effects they had on tensile properties. The impact of the processing tool was observed on fibre morphology and division; as well as the use of a BUSS system instead of a twin-screw extruder, which enhances the fibre individualization, however, the number of kneading areas should be reduced in order to preserve the reinforcement aspect ratio. We highlight the fact that the composite's mechanical performances are highly impacted by the fibre division and cell wall stiffness, as demonstrated by in-situ nanoindentation tests. Finally, the use of longer fibres is not a priority for the improvement of mechanical performances; it induces a more difficult fibre division and an increase in the compound viscosity, which could endanger the moulding process of the final part.

Comparison of damage behaviour of different plant fibre composites under laser impact loading

The high strain rate behaviour of the eco-composites, when submitted to laser impact loading, is not well known yet. Crucial questions are still open: influence of plant fiber length and distribution on the composite impact behaviour, types of damage induced by impact loading, the way the failure occurs, etc. We present the very first results of a collaborative research involving the institutions PPRIME- Poitiers and PIMM-Paris, and IMP PAN-Gdansk-Poland. A comparison of laser shock induced damage is realised, based on observations of sample back faces for several types of eco-composites. Spallation, residual blister and inside delamination, depending on the fibre length in tested composites have been observed. The ability of the Terahertz technique for internal damage detection is demonstrated.

Processing of plant fiber composites by liquid molding techniques: An overview

Lately, researchers around the world have developed effective chemical and physical treatments on plant fibers to improve their compatibility with polymeric matrices. In addition, the need of high performance fabrics produced from plant fibers has been addressed by many manufacturers of textile reinforcements. These facts have increased the use of natural fibers in the composite industry. Liquid composite molding (LCM) techniques are suitable for mass production of high‐quality composite parts. Basically, the reinforcement is compressed inside a mold and a thermosetting resin is injected to impregnate the fibers and fill the empty spaces in the mold. After the resin cures, the composite part is demolded. However, the processing of plant fiber–reinforced composites by the traditional techniques is not trivial, because the structure of plant fibers is more complex than that of synthetic fibers and due to their chemical composition rich in cellulose and hemicellulose, they are highly hydrophilic. This work presents a review on the main issues that arise during the processing of plant fiber reinforced composites by traditional liquid composite molding techniques. POLYM. COMPOS., 37:718–733, 2016. © 2014 Society of Plastics Engineers

Can silk become an effective reinforcing fibre? A property comparison with flax and glass reinforced composites

Abstract With the growing interest in bio-based composites as alternatives to traditional glass fibre reinforced composites (GFRPs), there has been a persistent rise in the commercial use of plant fibre composites (PFRPs). In contrast, nature’s ‘wonder-fibre’ silk has had no commercial applications, and only limited scientific investigations, as a composite reinforcement. To produce silk fibre composites (SFRPs) with useful properties, three key recommendations from our critical literature review were followed: (i) a high-failure strain, low-processing temperature thermoset matrix was used to (a) maximise the reinforcing effect of low-stiffness, ductile silk, and (b) facilitate impregnation and avoid fibre degradation, (ii) high fibre volume fractions were employed to ensure that fibres carried a larger fraction of the load, and (iii) given the lack of studies investigating fracture energy dissipation mechanisms in SFRPs, interface modification was avoided due to its complex, sometimes detrimental, effects on toughness. In directly addressing the question, ‘is there a case for silks as polymer reinforcements?’, we evaluated various mechanical properties of nonwoven and plain woven SFRPs against similar flax and glass composites. In all cases, woven composites performed better than nonwoven composites. While SFRPs were weak in terms of stiffness, their flexural and tensile strength was comparable to PFRPs, but much below that of GFRPs. Notably, the low density of SFRPs, like PFRPs, made them comparable to GFRPs in terms of specific flexural properties. Woven SFRPs exhibited much higher fracture strain capacities than both flax and glass composites, making SFRPs suitable for applications where high compliance is required. The Achilles’ heels of PFRPs have been their reportedly (i) inadequate interfacial properties, (ii) inferior impact properties, (iii) poor strength performance, and (iv) high moisture sensitivity. We found that SFRPs outperformed their flax counterparts in areas (i)–(iii), and were more comparable to, but not better than, GFRPs. While concerns such as cost and ‘sustainability’ of silk are acknowledged, potential applications for SFRPs are discussed.

Extraction and preparation of bamboo fibre-reinforced composites

Natural plant fibre composites have been developed for the production of a variety of industrial products, with benefits including biodegradability and environmental protection. Bamboo fibre materials have attracted broad attention as reinforcement polymer composites due to their environmental sustainability, mechanical properties, and recyclability, and they can be compared with glass fibres. This review classifies and describes the various procedures that have been developed to extract fibres from raw bamboo culm. There are three main types of procedures: mechanical, chemical and combined mechanical and chemical extraction. Composite preparation from extracted bamboo fibres and various thermal analysis methods are also classified and analysed. Many parameters affect the mechanical properties and composite characteristics of bamboo fibres and bamboo composites, including fibre extraction methods, fibre length, fibre size, resin application, temperature, moisture content and composite preparation techniques. Mechanical extraction methods are more eco-friendly than chemical methods, and steam explosion and chemical methods significantly affect the microstructure of bamboo fibres. The development of bamboo fibre-reinforced composites and interfacial adhesion fabrication techniques must consider the type of matrix, the microstructure of bamboo and fibre extraction methods.

Mechanical Property Characterization of Aligned Plant Yarn Reinforced Thermoset Matrix Composites Manufactured via Vacuum Infusion

This article evaluates the mechanical properties of vacuum-infused unidirectional plant fiber composites (PFRPs), composing of bast fiber yarns and thermoset matrices. PFRPs are found to have lower fiber volume fractions than E-glass composites (GFRPs). Apart from the expected (30–40%) lower density of PFRPs, they have 60–80% lower tensile strength, 30–60% lower tensile stiffness, 5–10 times lower impact strength, and 20–30% lower interlaminar shear strength than GFRPs. Importantly, critical fiber lengths are of the same order (0.2–0.5 mm). Composites reinforced with flax rovings exhibit exceptional fiber tensile modulus of 65–75 GPa and fiber tensile strength of about 800 MPa.