The high modulus aramid organic fibers were first introduced commercially in the seventies by Du Pont. Initially referred to as Fiber B and PRD-49, these fibers are now produced and sold by Du Pont under the trade name Kevlar. These fibers belong to a type known under the generic title of aramid fibers defined as “fibers in which the fiber-forming substance is a long-chain synthetic polyamide in which at least 85% of the amide linkages are attached directly to two aromatic rings” [1]. They were developed as high modulus, high-strength fibers whose properties can be varied depending on the spinning and drawing conditions and are presently available as Kevlar and Kevlar-29, both formerly Fiber B, and Kevlar-49, formerly PRD-49, as continuous-filament fiber or fabric. All of them are characterized by their high tensile strength and high modulus compared with other organic fibers (Table 1 [1]).