ABSTRACT
Composites have encompassed almost all material domains (house furnishing, packaging, car, aerospace, transportation, sport, leisure, and so on). All synthetic polymers (thermoplastics, thermosets, and elastomers) can be used as matrices. As fillers, besides inorganic powders, extensive use has been made of inorganic man-made fibers such as glass, silicium carbide, or organic fibers like carbon and aramid, in the form of individual fibers (chopped or continuous), mats, or 2D-3D fabrics. Except for glass fibers, these reinforcing fibers are expensive. Various fibers like cellulose, wool, silk, and composites thereof are produced in nature. Among others, wood is a good example of a natural composite where cellulosic fibers are in close association with hemicelluloses to reinforce the lignin matrix.1 Cellulosic fibers are located in cell walls and are referred to as bast fibers in the stems and stalks (flax, jute, ramie, etc.) as leaf fibers (sisal, banana, etc.) and as seed fibers (cotton, kapok, etc.). Besides its renewability, cellulose is available worldwide and it is biodegradable. Raw materials are often used as furnished by nature, but cellulose and wood present poor dimensional stability due to swelling by water, in relation to relative humidity, and a protection against weathering conditions is needed (paints, varnishes, etc.). The return to natural materials is based on many advantages present in the materials themselves, as well as in combination with other materials in composites. As composites, large quantities of waste arising from woodworking (chips and clippings) are reused in chipboards, where they are compounded using a thermosetting resin: formaldehyde associated with phenol, melamine, or urea.2
