Natural Fibre-Reinforced Structural Material

This chapter first gives an overview of cellulose raw materials and their molecular and supermolecular structures. The principles of shaping cellulose into fibres, films, and nonwovens by means of solution techniques are then outlined followed by a section on properties and market applications of these materials. Derivatives of cellulose are presented with special emphasis on thermoplastic cellulose esters, typical plasticizers, and promising reinforcing materials. Finally, recent developments and future prospects of cellulose materials are reviewed as far as the above applications are concerned. This book does not cover the important applications of cellulose and ligno cellulose fibres for reinforcing thermoplastics, like wood plastic composites (WPC) and natural fibre reinforced plastics (NFRP), since in these cases cellulose does not substitute a thermoplastic. 

The chapter demonstrates that in spite of the incompatibility between hydrophilic natural fibres and hydrophobic polymeric matrices, the properties of natural fibre composites can be enhanced through chemical modifications. The chemical treatments have therefore played a key role in the increased applications of natural fibre composites in the automotive sector. Recent work has also shown that if some of the drawbacks of natural fibres can be adequately addressed, these materials can easily replace glass fibres in many applications. The chapter has also shown that there have been attempts to use natural fibre composites in structural applications, an area which has been hitherto the reserve of synthetic fibres like glass and aramid. The use of polymer nanocomposites in applications of natural fibre-reinforced composites, though at infancy, may provide means to address these efficiencies. Evidence-based life-cycle assessment of natural fibre-reinforced composites is required to build confidence in the green composites applications in automotive sector. 

The performance of natural fibre reinforced polymer composites depends on several factors, including fibre chemical composition, cell dimensions, microfibrillar angle, defects, structure, physical and mechanical properties, and the interaction of a fibre with the polymeric matrix [28]. The knowledge about the characteristics of the fibre is essential in order to expand the effective use of lignocellulosic materials for polyethylene composites and to improve their performance. 

The presence of carbon fibres in ARBOFORM can also stabilize the structure and act as precursor. Unpyrolysed ARBOFORM F45 is a biocomposite with a low electrical conductivity - this means that it is an isolating material. The conductivity of the material can be adjusted on one hand by precipitation of metal particles onto the reinforcing natural fibres (see above) but on the other hand also by varying the pyrolysis temperature. When pyrolysed at 600 °C conductivity is still low, but pyrolysed at 1000 °C, a reasonable conductivity value is obtained, which substantially decreases when the material is pyrolysed at 1200 °C. A report on more detailed investigations can be found in ref. [76]. 

For consumers, natural fibre composites in automobiles provide better thermal and acoustic insulation than fibre glass and reduce irritation of the skin and respiratory system. The low density of plant fibres also reduces vehicle weight, which cuts fuel consumption [72]. Alves et al. [73] studied the life cycle assessment (LCA) analysis of the replacement of glass fibres by jute fibres as reinforcement of composite materials to produce automotive structural components in the structural frontal bonnet of an off-road vehicle (Buggy). 

The use of fibres and fabrics as additives to reinforce matrix materials in structures that are often referred to as composites goes back into prehistory, as in the use of straw to reinforce clay bricks. As usual, nature developed such structures first. Examples are wood (cellulosic fibres in a lignin matrix) and bone (collagen fibres in an inorganic matrix). A composite need not be based on fibres - it is a material or product formed by intimate combination of two or more distinct physical phases, so the sh ls of crustaceans (calcium carbonate in a chitin matrix) are composite structures. However, the word composite now commonly brings to mind structures consisting of fibres embedded in a matrix of some other material, whether plastic, ceramic or metal (i.e. fibrous composites), and even tends to be used particularly for structures in which the fibres are laid out in organized fashion before the matrix material is consolidated around them. 

Polymer composite materials which we investigated on failure occurrence are made on the basis of natural fibres, such as linen, cotton and jute. As the matrix material used epoxy resin R70 with hardener H71 often used for laminating contact while the texture is determined in advance. Jute fabric has a surface density in level 340 g- m , linen fabric 320 g-m and cotton fabric 130 g-m . For each reinforcement three components types have been prepared. Laminates structures with two, four and six layers have been prepared. 

The potential of these nano-sized structures can be found in different areas of application [33,37,38,40-43]. They are briefly referred as potential reinforcement in polyethylene, since the focus in this chapter is on the potential of different lignocellusic materials produced from natural fibres or agri-cultural/forest crops or residues. 

Aramid fibre mesh was also used as reinforcement of thin mortar sheets and subjected to impact by projectiles (Kyung and Meyer 2007). The problem of various body-armour products is of considerable importance because of the increased number and intensity of natural disasters, and more importantly, terrorist attacks. The results have shown that brittle matrix composite materials reinforced with fibres and composed of several thin layers have considerable capacity of energy absorption. There are ready-to-use design methods for such structures and already a vast amount of knowledge has been accumulated in this field. 

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