Green Composites for Potential Substitution of E-Glass Composites and Plastics

This chapter provides a comparative study of the mechanical properties for different natural fiber composites. These composites consist of natural fiber 8-harness stain weave fabric reinforcing an epoxy matrix. The analytical model discussed in Chapter 5 is used to evaluate the elastic and ultimate strengths properties. The comparison is made according to the calculated specific modulus and specific strength. The Natural Fiber Reinforced Polymer (NFRP) composites are compared together according to their categories and yet compared to a similar E-glass/epoxy composite. In addition, a polypropylene and a thermoplastic composite are used also as reference materials. It is shown that some NFRP especially those belonging to the Bast and Leaf categories provide better properties than the plastics and also the E-glass/epoxy composite. Overall the Flax/epoxy composite could be considered the optimum choice in terms of properties since it has high specific modulus and strength.

Available Mechanical and Chemical Properties of Natural Fibers

Natural fibers are so attracting in comparison to synthetic fibers since they exhibit good properties like the low cost, good specific mechanical properties and their requirements of low energy during production. However, natural fibers hold some drawbacks which must be consider in comparison to the synthetic fibers like their high moisture absorption, low mechanical properties, heat resistance and durability and the variation in their prices and quality. In order to choose the suitable natural fiber for the selected application, their mechanical and chemical properties can be helpful for taking the right decision. In this chapter, a wide research is done in order to provide as much as possible the available mechanical and chemical properties of natural fibers of bast, leaf, seed, stalk, and wood categories from the most trusted publications. The specific mechanical properties of natural fibers are then calculated for a better comparison at the level of composites.

History and Origin of Natural Plant Fibers

A detailed review about different types of natural plant fibers: the family to which each fiber belongs, the historical background, their availability, weather conditions, the producer countries, and the usage are provided in this chapter. Good knowledge about the plants leads to characterize and obtain extracted fibers of high quality. Non-wood or vegetable fibers are obtained from a range of sources, including four main categories: bast, leaf, seed and stalk. The plant fibers have a lot of utilization such as in textile, handicraft industry, marine applications, reinforcement of composite, packaging material (bags), carpet backing, cordage, ropes, wall decoration, automotive components, fabrics, clothes, etc.

Composite Materials Types and Applications

A composite is composed from two or more different materials that are combined together to create a superior and unique material. Composites are divided into three main categories according to the matrix type; Metal Matrix Composites, Ceramic Matrix Composites and Fiber Reinforced Polymeric Composites. In this chapter, a general overview of these categories will be done. More emphasis is on polymeric composites reinforced by textile fabrics. A brief introduction of synthetic and natural fibers is presented. Also, a general investigation on the world market of natural fiber concerning the production, development, research fields and main applications will be provided.

Harvesting, Processing, and Modification Techniques of Natural Fibers

The goal of this chapter is to provide a wide overview of the available processing techniques followed in order to produce natural fibers of high quality. Obtaining the desired level of refined fiber without causing its excessive damage is an important consideration. So, the provided information typically begins from the cultivation, maturity level and harvesting of the plant till reaching the yarns ready for the usage. The details of the machinery used to produce several types of bast, leaf, and stalk plant fibers are well described. It includes also the definition of different terms utilized in the processing steps, in addition to the techniques used for improving the adhesion between the natural fiber and the polymer matrix.

Analytical Modeling

The large number of available natural fibers emphasizes the use of a reliable, non-costly and easy to use, predictive tool with short computation time. In order to predict the ultimate strengths and Young's moduli of green composites, an analytical model known as the three Stages Homogenization Model (3SHM) is used. The model relies on three main parts: a geometrical model, a homogenization method and a strength model. Moreover, the last two models consist of four main parts: a micro-mechanical modeling for elastic properties and ultimate strengths for unidirectional (UD) composites, a homogenization method at meso and macro levels to determine the composite stiffness and stress-strain fields throughout the composite, two 3D failure criteria for the matrix and unidirectional composites and a damaged stiffness model. This model enables the prediction of the ultimate strengths and the 3D elastic properties; Young's and Shear moduli, in addition to the in plane and out plane tensile and shear strengths.