Biocomposites reinforced with natural fibers: 2000–2010

Recently, there has been a rapid growth in research and innovation in the natural fibre composite (NFC) area. Interest is warranted due to the advantages of these materials compared to others, such as synthetic fibre composites, including low environmental impact and low cost and support their potential across a wide range of applications. Much effort has gone into increasing their mechanical performance to extend the capabilities and applications of this group of materials. This review aims to provide an overview of the factors that affect the mechanical performance of NFCs and details achievements made with them.

A review of recent developments in natural fibre composites and their mechanical performance

A critical review of the literature on the various aspects of natural fibers and biocomposites with a particular reference to chemical modifications is presented in this paper. A notable disadvantage of natural fibers is their polarity which makes it incompatible with hydrophobic matrix. This incompatibility results in poor interfacial bonding between the fibers and the matrix. This in turn leads to impaired mechanical properties of the composites. This defect can be remedied by chemical modification of fibers so as to make it less hydrophilic. This paper reviews the latest trends in chemical modifications and characterizations of natural fibers. The structure and properties of natural fibers have been discussed. Common chemical modifications and their mechanisms have also been elaborated. The importance of chemical modifications and the resultant enhancement in the properties of the composites have also been reviewed. Recent investigations dealing with chemical modifications of natural fiber-reinforced composites have also been cited. POLYM. COMPOS., 29:187‐

Recent Developments in Chemical Modification and Characterization of Natural Fiber-Reinforced Composites

The growing ecological and environmental consciousness has driven efforts for development of new innovative materials for various end-use applications. Polymers synthesized from natural resources, have gained considerable research interest in the recent years. This review paper is intended to provide a brief outline of work that covers in the area of biocomposites, major class of biodegradable polymers, natural fibres, as well as their manufacturing techniques and properties has been highlighted. Various surface modification methods were incorporated to improve the fibre–matrix adhesion resulting in the enhancement of mechanical properties of the biocomposites. Moreover, an economical impact and future direction of these materials has been critically reviewed. This review concludes that the biocomposites form one of the emerging areas in polymer science that gain attention for use in various applications ranging from automobile to the building industries.

A review of the recent developments in biocomposites based on natural fibres and their application perspectives

This review article describes the recent developments of natural fiber reinforced polypropylene (PP) composites. Natural fibers are low-cost, recyclable, and eco-friendly materials. Due to eco-friendly and bio-degradability characteristics of these natural fibers, they are considered as strong candidates to replace the conventional glass and carbon fibers. The chemical, mechanical, and physical properties of natural fibers have distinct properties; depending upon the cellulosic content of the fibers which varies from fiber to fiber. The mechanical properties of composites are influenced mainly by the adhesion between matrix and fibers. Chemical and physical modification methods were incorporated to improve the fiber—matrix adhesion resulting in the enhancement of mechanical properties of the composites. The most important natural fibers are jute, flax, and coir and their novel processing technics to develop natural fiber reinforced composites are also described.

Recent Development in Natural Fiber Reinforced Polypropylene Composites

The optimisation of New Zealand grown hemp fibre for inclusion in composites has been investigated. The optimum growing period was found to be 114 days, producing fibres with an average tensile strength of 857 MPa and a Young’s modulus of 58 GPa. An alkali treatment with 10 wt% NaOH solution at a maximum processing temperature of 160 °C with a hold time of 45 min was found to produce strong fibres with a low lignin content and good fibre separation. Although a good fit with the Weibull distribution function was obtained for single fibre strength, this did not allow for accurate scaling to strengths at different lengths. Alkali treated fibres, polypropylene and a maleated polypropylene (MAPP) coupling agent were compounded in a twin-screw extruder, and injection moulded into composite tensile test specimens. The strongest composite consisted of polypropylene with 40 wt% fibre and 3 wt% MAPP, and had a tensile strength of 47.2 MPa, and a Young’s modulus of 4.88 GPa.

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Optimising industrial hemp fibre for composites

Hemp fibres were alkali treated to improve their suitability for use as reinforcements in composite materials. Improvements in tensile strength, Young’s modulus, fibre separation, crystallinity index, lignin reduction and thermal stability were observed for hemp fibres treated with a solution of 5 wt% NaOH/2 wt% Na 2 SO 3 . A range of hemp fibre reinforced polypropylene composites were produced by extrusion and injection moulding, and the effect of fibre treatments and MAPP content on the tensile strength and Young’s modulus of composites were investigated. The optimum composite, consisting of polypropylene, 40 wt% NaOH/Na 2 SO 3 treated hemp fibre and 4 wt% MAPP, was found to have a tensile strength of 50.5 MPa and a Young’s modulus of 5.31 GPa.

Engineering and evaluation of hemp fibre reinforced polypropylene composites: Fibre treatment and matrix modification

In this study, the effects of interleaved nanofibre veils on the Mode I and Mode II interlaminar fracture toughness (ILFT) of autoclave cured unidirectional carbon/epoxy composite laminates were investigated. Various electrospun nanofibre veils consisting of a range of different polymer types, fibre diameters and veil architectures were placed in the laminate mid-planes, which were subsequently subjected to double cantilever beam and end-notch flexure tests. It was found that the polymer type and veil areal weight were the most important factors contributing to laminate performance. A 4.5 g/m 2 PA66 veil provided the best all-round performance with fracture toughness improvements of 156% and 69% for Mode I and Mode II, respectively.

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Mode I and Mode II interlaminar fracture toughness of composite laminates interleaved with electrospun nanofibre veils

Mode I and Mode II interlaminar fracture toughness of composite laminates interleaved with electrospun nanofibre veils Part A Applied science and manufacturing

The strength of a composite consisting of 40 wt% NaOH/Na 2 SO 3 treated hemp fibre, polypropylene and 4 wt% MAPP was evaluated by means of mathematical modelling and mechanical testing Interfacial shear strength, single fibre tensile strength and fibre length distribution within the composite were obtained, and theoretical composite strengths were determined by means of the Modified Rule of Mixtures and Bowyer–Bader models The experimentally obtained composite tensile strength of 505 MPa was found to be one-third of the theoretical strength determined by means of the Bowyer–Bader model, and this difference was thought to be mainly due to the non-axial planar-random orientation of the fibres within the composite

Gareth W. Beckermann

Papers

Optimising industrial hemp fibre for composites

Engineering and evaluation of hemp fibre reinforced polypropylene composites: Fibre treatment and matrix modification

Mode I and Mode II interlaminar fracture toughness of composite laminates interleaved with electrospun nanofibre veils

Mode I and Mode II interlaminar fracture toughness of composite laminates interleaved with electrospun nanofibre veils Part A Applied science and manufacturing

Engineering and evaluation of hemp fibre reinforced polypropylene composites: Micro-mechanics and strength prediction modelling