Three main types of synthetic fibers are used in the United Satates to reinforce plastic materials:glass,aramid and carbon.Glass is by far the most widely used reinforcement fiber and is the lowest in cost.Aramid and carbon fibers have high strengths and low densitise and so are used in many applications,particularly aerospace,in spite of teir higher cost.
Glass fibers are used to reinforce plastic matrices to form structural composites and molding compounds.Glass-fiber plastic composite materials have the following favorable charcteristics:high strength-to-weight ratio;good dimensional stability;good resistance to heat,cold,moisture,and corrosion;good electrical insulation properties;ease of fabrication;and relatively low cost.
The to most important types of glass used to produce glass fibers for composites are E(electrical)and S(high-strength)glasses.
E glass is the most commonly used glass for continuous fiber.Basically,E glass is a limealuminum-borosilicate glass with zero or low sodium and potassium levels.The basic composition of E glass ranges from 52 to 56 percent SiO2 12 to 16 percent Al2O3,16 to 25 percent CaO,and 8 to 13 percent B2O3.E glass has a tensile strength of about 500 ksi(3.44 GPa)in the virgin condition and a modulus of elasticity of 10.5 Msi(72.3 GPa).