Читать книгу Encyclopedia of Glass Science, Technology, History, and Culture - Группа авторов - Страница 137

For military applications, R‐glass was first developed in the mid‐1960s within the quaternary SiO₂–Al₂O₃–CaO–MgO system. In its original chemistry, its production, like that of S‐glass, was limited because of the requirements imposed by its high melting temperature. The addition of CaO to the S‐glass ternary system improved the processing conditions required to make glass fibers while still providing a high level of strength, but conditions were still more challenging than E‐glass. Developments centered around the R‐glass compositional range increased in the mid‐00s, driven by the needs of wind‐turbine blade producers who required longer blades with higher‐modulus glass fibers to reduce the unit cost of electricity generation. Most of the improved technology made is based on reducing glass melting temperature while increasing fiber modulus, which has been realized by optimization of mixed alkaline earth oxides (MgO/CaO). As a result, large‐scale furnaces and large direct‐draw bushing operations are possible. [4]. These developments have provided a balance of mechanical performance, cost, and large‐volume production capability that is in good alignment with the scale of production and cost of energy drivers in the wind‐energy composites market. The speed at which these new high modulus fibers have been put on the market is unprecedented in glass‐fiber history.