4. Nanotube-reinforced polymer matrix composites

4.1 Reinforcement with long fibers

Experience shows that, for the same mass of reinforcement, it is more effective to use fibers than spherical particles to increase the modulus of elasticity of a polymer. The effect is all the more pronounced when the fibers are oriented in the direction of stress. The result is an anisotropic composite material with a longitudinal modulus greater than the transverse modulus. Long-fibre composites are generally distinguished from short-fibre composites, as the methods used to prepare them and model their properties are significantly different. Long-fiber composites are manufactured by impregnation of a woven fibrous matrix, whereas short-fiber composites are made by mixing liquid polymer and short fibers, usually followed by extrusion to orient the...