Kevlar - Randall Robert Social Student ID ME 2733 001...

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Randall Robert Social / Student ID : 437-51-9771 ME 2733 - 001 Materials Project – Kevlar April 28, 2005 1
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Abstract Composites have only been used for approximately forty years, industry being the first to incorporate the use of these advanced materials. Composites are now used everyday by the common civilian. It may go unnoticed but composites have become a huge part of our life. Composites are used as major critical parts of the automobiles we drive everyday, speakers, sporting equipment, gloves etcetera. One specific fiber used in all of the above mentioned composites is Kevlar. Background Kevlar was introduced by DuPont in the 1970’s. It was the first organic fiber with sufficient tensile strength and modulus to be used in advanced composites (About). Kevlar belongs to a group of materials called aramids, a term which represents an abbreviation for aromatic polyamide. The most common aramids are Kevlar and Nomex. Kevlar’s chemical composition is poly para-phenyleneterephthalamide, para-aramid or PPTA for short. Kevlar has specific gravity of 1.44, and a modulus of elasticity equal to 131[GPa]. This represents its outstanding strength to weight ratio which makes Kevlar far superior to other materials which could be considered as strong as Kevlar. There are currently three grades of Kevlar available: Kevlar 29, Kevlar 49, and Kevlar 149. The table in table 1 depicts the differences in properties among the three fore mentioned grades. Table 1.(properties of Kevlar) Kevlar Grade Density (g/cm 3 ) Tensile Modulus (GPa) Tensile Strength (GPa) Tensile Elongation (%) ~Melting Point (degrees F) 29 1.44 83 3.6 4.0 260 49 1.44 131 3.9 2.8 600 149 1.47 186 3.4 2.0 1000 Discovery / Origin Originally Kevlar was developed to replace the steel belting in radial automobile tires. Kevlar has advanced and is now used to produce “run flat” tires which can be driven on at fifty miles per hour with zero air pressure. Now it is used in a wide range of
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Kevlar - Randall Robert Social Student ID ME 2733 001...

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