Review on natural plant fibres and their hybrid composites for structural applications: Recent trends and future perspectives

© 2022 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Sustainability and environmental protection have given rise to the use of renewable and biobased materials in several application areas. Fibre reinforced composites are currently gaining a high market value in both structural and semi-structural applications. Making these materials environmentally friendly, renewable and lighter will protect the environment and increase resource use efficiency. Opposed to synthetic fibres such as carbon and glass, natural plant fibres are less expensive, lighter, degradable, easy to produce, non-toxic and environmentally friendly. However, natural plant fibres are inferior to their synthetic counterparts in both mechanical performance and tolerance to harsh environmental conditions. One method of compensating for these disadvantages is to combine natural and synthetic fibres in a single matrix forming a hybrid composite where the disadvantages of one are compensated by the other. In this way, sustainability and cost minimisation are achieved with acceptable mechanical and physical responses. However, successful implementation and advancement in the development of natural plant fibre reinforced polymer (FRP) hybrid composites require the development of workable conceptual design, suitable manufacturing techniques and understanding of the strengthening mechanisms. The main objectives of this review are to critically review the current state of knowledge in the development of natural FRP hybrid composites, outlining their properties and enhancing them while reducing environmental impact of the product through the hybridisation approach.Peer reviewe

A review: fibres, polymer matrices and composites

The growing interest, environmental consciousness and high performance demands on engineering have led to extensive research and development of new and improved materials. Among the most commonly used natural fibres are kenaf, oil palm, sugar palm, pineapple leaf fibre, flax, hemp, sisal, coir and jute. These fibres are used to reinforce thermoplastic polymer matrices such as polystyrene (PS), polypropylene (PP), polyethylene (PE) and polyvinyl chloride (PVC). Meanwhile, phenolic, unsaturated polyester vinyl ester and epoxy resin are for thermosetting polymer matrices. The objective of this paper is to solicit works that cover major class of natural fibres, thermosetting polymers matrices, which detail about unsaturated polyester resin and hybrid biocomposites industry

Hybrid biocomposites

Biocomposites are being explored by research communityfor the past few decades due to rising environmental concerns. Moisture uptake, poor interface and moderate to lower mechanical properties have proved to be a bottleneck for biocomposites to partially or fully replace synthetic composites. The concept of hybridising, i.e. incorporating two or more reinforcements instead of single reinforcement in a matrix, has the potential to overcome this bottleneck by exploiting the desired contribution of both the reinforcing phases. Although hybrid composites have already extensively explored for high-performance fibres, the studies on hybrid composites using biodegradable constituents still lag behind. This review addresses studies conducted on hybrid composites using at least one biodegradable component and the findings in terms of properties and factors affecting them are discussed. The analysis on synergistic effect reported by researchers along with the scope of ongoing research and prospects for hybrid biocomposites have also been discussed in detail

Recent progress in hybrid biocomposites: Mechanical properties, water absorption, and flame retardancy

This article belongs to the Special Issue Mechanical Properties of BiocompositesBio-based composites are reinforced polymeric materials in which one of the matrix and reinforcement components or both are from bio-based origins. The biocomposite industry has recently drawn great attention for diverse applications, from household articles to automobiles.This is owing to their low cost, biodegradability, being lightweight, availability, and environmental concerns over synthetic and nonrenewable materials derived from limited resources like fossil fuel. The focus has slowly shifted from traditional biocomposite systems, including thermoplastic polymers reinforced with natural fibers, to more advanced systems called hybrid biocomposites. Hybridization of bio-based fibers/matrices and synthetic ones offers a new strategy to overcome the shortcomings of purely natural fibers or matrices. By incorporating two or more reinforcement types into a single composite, it is possible to not only maintain the advantages of both types but also alleviate somedisadvantages of one type of reinforcement by another one. This approach leads to improvement of the mechanical and physical properties of biocomposites for extensive applications. The present review article intends to provide a general overview of selecting the materials to manufacture hybrid biocomposite systems with improved strength properties, water, and burning resistance in recent years

Natural Fiber-Reinforced Hybrid Composites

In the last few decades, natural fibers have received growing attention as an alternative to the synthetic fibers used in the reinforcement of polymeric composites, thanks to their specific properties, low price, health advantages, renewability, and recyclability. Furthermore, natural fibers have a CO2-neutral life cycle, in contrast to their synthetic counterparts. As is widely known, natural fibers also possess some drawbacks, e.g., a hydrophilic nature, low and variable mechanical properties, poor adhesion to polymeric matrices, high susceptibility to moisture absorption, low aging resistance, etc. This implies that their applications are limited to non-structural interior products. To overcome this problem, the hybridization of natural fibers with synthetic ones (i.e., glass, carbon, and basalt) or different natural fibers can be a solution. For this reason, extensive research concerning natural–synthetic and natural–natural hybrid composites has been done in the last years. In this context, this book aims to collect some interesting papers concerning the use of natural fibers together with synthetic ones with the aim of obtaining hybrid structures with good compromise between high properties (e.g., mechanical performances, thermal behavior, aging tolerance in humid or aggressive environments, and so on) and environment care

Determination of mean intrinsic flexural strength and coupling factor of natural fiber reinforcement in polylactic acid biocomposites

This paper is focused on the flexural properties of bleached kraft softwood fibers, bio-based, biodegradable, and a globally available reinforcement commonly used in papermaking, of reinforced polylactic acid (PLA) composites. The matrix, polylactic acid, is also a bio-based and biodegradable polymer. Flexural properties of composites incorporating percentages of reinforcement ranging from 15 to 30 wt % were measured and discussed. Another objective was to evaluate the strength of the interface between the matrix and the reinforcements, using the rule of mixtures to determine the coupling factor. Nonetheless, this rule of mixtures presents two unknowns, the coupling factor and the intrinsic flexural strength of the reinforcement. Hence, applying a ratio between the tensile and flexural intrinsic strengths and a defined fiber tensile and flexural strength factors, derived from the rule of mixtures is proposed. The literature lacks a precise evaluation of the intrinsic tensile strength of the reinforcements. In order to obtain such intrinsic tensile strength, we used the Kelly and Tyson modified equation as well as the solution provided by Bowyer and Bader. Finally, we were able to characterize the intrinsic flexural strengths of the fibers when used as reinforcement of polylactic acid.Peer ReviewedPostprint (published version

Hybrid biocomposites

224-246Biocomposites are being explored by research communityfor the past few decades due to rising environmental concerns. Moisture uptake, poor interface and moderate to lower mechanical properties have proved to be a bottleneck for biocomposites to partially or fully replace synthetic composites. The concept of hybridising, i.e. incorporating two or more reinforcements instead of single reinforcement in a matrix, has the potential to overcome this bottleneck by exploiting the desired contribution of both the reinforcing phases. Although hybrid composites have already extensively explored for high-performance fibres, the studies on hybrid composites using biodegradable constituents still lag behind. This review addresses studies conducted on hybrid composites using at least one biodegradable component and the findings in terms of properties and factors affecting them are discussed. The analysis on synergistic effect reported by researchers along with the scope of ongoing research and prospects for hybrid biocomposites have also been discussed in detail

Mechanical and water absorption properties of hybrid kenaf and pineapple composite added with epoxidized natural rubber

Wood polymer composites, WPC, is a competitive material which ranging from consumer products to engineering parts in various of application field. In this research, mechanical properties and water absorption were investigated on the hybrid WPC made from kenaf fibre and pineapple leaf fibres, PALF, as fillers at three level of total fibre loading of 30 %, 40 % and 50 % by weight, mixed in high density polyethylene, HDPE. The fibres hybrid ratio was kept constant at 60% kenaf to 40% PALF and the composite was compounded in a melt mixer and fabricated by compression moulding. The effect of different total fibres loading and addition 3% by weight epoxidized natural rubber, ENR, into the composite formulation was evaluated. For both with and without addition of ENR into kenaf-PALF/HDPE composite, tensile strength, tensile modulus, flexural modulus, impact strength and water absorption increased with an increase in total fibres loading, but the elongation at break of the composite decreased with increasing total fibres loading. Flexural strength only increased at lower fibre loading but decreased at highest fibre loading of this experiment. Meanwhile, overall effect of ENR addition was that it enhanced the tensile strength, impact strength and water absorption of the composite but only improved flexural strength and flexural modulus at lower fibre loadings of 30 and 40 %. On the other hand, ENR decreased the tensile modulus and elongation at break of the composites. At highest fibres loading from this study and with 3 % ENR-50 added, the composite, KP50PE2 is deformable and experienced a slight decreased in tensile strength. However, its enhanced impact property and higher toughness enabled the composite to withstand impact loading

Assessment of dimensional stability, biodegradability, and fracture energy of bio composites reinforced with novel pine cone

In this investigation, biodegradable composites were fabricated with polycaprolactone (PCL) matrix reinforced with pine cone powder (15%, 30%, and 45% by weight) and compatibilized with graphite powder (0%, 5%, 10%, and 15% by weight) in polycaprolactone matrix by compression molding technique. The samples were prepared as per ASTM standard and tested for dimensional stability, biodegradability, and fracture energy with scanning electron micrographs. Water-absorption and thickness-swelling were performed to examine the dimensional stability and tests were performed at 23 °C and 50% humidity. Results revealed that the composites with 15 wt % of pine cone powder (PCP) have shown higher dimensional stability as compared to other composites. Bio-composites containing 15–45 wt % of PCP with low graphite content have shown higher disintegration rate than neat PCL. Fracture energy for crack initiation in bio-composites was increased by 68% with 30% PCP. Scanning electron microscopy (SEM) of the composites have shown evenly-distributed PCP particles throughout PCL-matrix at significantly high-degrees or quantities of reinforcing