Natural organic fibers have been around for a very long time, from the beginning of the life on Earth. The archeological artifacts suggest that human beings used these materials in fabrics many thousand years ago. A direct use of the strength of natural fibers is in lines, ropes and other one-dimensional products; miscellaneous applications include early suspension bridges for on-foot passage of rivers and rigging for naval ships in early times and into the nineteenth century. Many kinds of textiles, ropes, canvas and paper produced form natural fibers are in use today.
It may seem surprising, but first natural fiber composites were used more than 100 years ago. For example, airplane seats and fuel-tanks were made of natural fibers with a small content of polymeric binders and the first composite materials were applied for the fabrication of large quantities of sheets, tubes and pipes for electronic purposes (paper or cotton to reinforce sheets, made of phenol- or melamine-formaldehyde resins) . However, these attempts were without recognition of the composite principles and the importance of fibers as the reinforcing part of composites. The use of natural fibers was suspended due to low cost and growing performance of technical plastics and, moreover, synthetic fibers. A renaissance in the use of natural fibers as reinforcements in technical applications began in 90s of 20th century.
OVERVIEW OF CELLULOSE-BASED NATURAL FIBERS:
Different types and examples of natural fibers classified according to their origin are presented in Figure 1. Asbestos is out of further consideration in this study due to its carcinogenic nature. In addition, asbestos does not possess most of advantages like other natural fibres
STRUCTURE AND CHEMICAL COMPOSITION:
Generally, plant or vegetable fibers are used to reinforce plastics. The main polymers involved in the composition of plant fibers are cellulose, hemicelluloses, lignin and pectin. Let us consider very popular flax fibers to understand the intricate structure of plant fibers. The ~1 meter long so-called technical fibers are isolated from the flax plant for the use in textile industry. These technical fibers consist of elementary fibers with lengths generally between 2 and 5 cm, and diameters between 10 and 25 m. The elementary fibers are glued together by a pectin interface. They are not circular but a polyhedron with 5 to 7 sides to improve the packing in the technical fiber.