amics.org/lAGS Glass Fiber-Reinforced Composit 123 for composites, pressure vessels an Raw discussed. Although very different Materials demand high strength, excellent ngth of the load-bear- Furnace g composite prevents a pressure vessel from exploding and prevents a projectile from penetration of an armor panel. In both cases, lives are at stake. The strength of the composite is critical for safety, Is imperative that the glass fiber reinforcement the source of Batch House Forehearth strength- be consistently high 自 Coating Fabrication Winding Glass Fiber Forming Process Fig. I. Fibergl As discussed in the previous paper, Strength of Formulation also governs whether a glass can be Higb Performance Glass Reinforcement Fiber, assuming fiberized. In some formulations, a small amount of fibers are treated equally and care important contributor to glass fiber tensile strength is strength or modulus may have to be sacrificed to widen formulation. There are a variety of glass fiber types as the forming temperature range there by allowing large defined in American Society for Testing and Materials scale industrial production by a direct melt process. (ASTM)D578: Standard Specification for Glass Fiber Direct melt furnaces of this type typically produce Strands and International Organization for Standardiza- 20,000 tons or more annually, and are preferred to tion(ISO)2078: Textile glass- Yarns- Designation maximize manufacturing efficiency and product consis- p standards describe key characteristics of each tency. A high-level schematic of direct-melt fiberglass manufacturing is given in Fig. I Raw materials that arrive by rail or truck ranges. Although there is a multitude of glass fiber batched on site and conveyed to the furnace for melt- types available, the most important from a tensile trength perspective are listed in Table I ing. Molten glass slowly cools as it travels through a channel and out to multiple forehearths, where it is further conditioned before fiberizing. Each forehearth Table L. Common Glass Fiber Types Used in feeds multiple forming positions ing or fibe ng fb Description through tiny orifices in a precious metal bushing. Labo- ratory bushings can have as few as one hole, whereas Alumino-borosilicate family of glasses high-throughput production bushings typically have inally developed for electrical 1000 or greater. Figure 2 shows a glowing hot glass applications; has found widespread fiber bushing and a close-up image of fibers exiting a use in nearly all glass fiber-reinforced bushing. The first direct-melt furnace for continuous fiber production, developed by Owens Corning in E-CR Corrosion-resistant E-glass; equal or 1961, had bushings with throughputs on the order of better mechanical properties and little 10 Ib/h. Bushing technology development at Owens or no cost disadvantage versus standard E Corning has focused on reducing the amount of High-strength glass with performance high-cost alloy required while increasing bushing ther intermediate to e and s mal-mechanical stability, and thus operational life and A family of glasses composed primarily of efficiency. Today, Advantex" glass fiber bushings are the oxides of magnesium, aluminum, capable of throughputs exceeding 300 Ib/h with life- and silicon; S-glass was developed for times greater than a year. high strength and modulus plus superior thermal and corrosion performance registered trademark of Owens Corningfor composites, pressure vessels and ballistic armor, are discussed. Although very different, both applications demand high strength, excellent durability, and most importantly, reliability. The strength of the load-bearing composite prevents a pressure vessel from exploding and prevents a projectile from penetration of an armor panel. In both cases, lives are at stake. The strength of the composite is critical for safety, so it is imperative that the glass fiber reinforcement — the source of strength — be consistently high. Glass Fiber Forming Process As discussed in the previous paper, Strength of High Performance Glass Reinforcement Fiber, assuming fibers are treated equally and carefully, the next most important contributor to glass fiber tensile strength is formulation. There are a variety of glass fiber types as defined in American Society for Testing and Materials (ASTM) D578: Standard Specification for Glass Fiber Strands and International Organization for Standardization (ISO) 2078: Textile glass — Yarns — Designation. These standards describe key characteristics of each glass type and prescribe acceptable compositional ranges. Although there is a multitude of glass fiber types available, the most important from a tensile strength perspective are listed in Table I. Formulation also governs whether a glass can be fiberized. In some formulations, a small amount of strength or modulus may have to be sacrificed to widen the forming temperature range there by allowing large scale industrial production by a direct melt process. Direct melt furnaces of this type typically produce 20,000 tons or more annually, and are preferred to maximize manufacturing efficiency and product consistency. A high-level schematic of direct-melt fiberglass manufacturing is given in Fig. 1. Raw materials that arrive by rail or truck are batched on site and conveyed to the furnace for melting. Molten glass slowly cools as it travels through a channel and out to multiple forehearths, where it is further conditioned before fiberizing. Each forehearth feeds multiple forming positions. Forming or fiberizing is achieved by pulling fibers through tiny orifices in a precious metal bushing. Laboratory bushings can have as few as one hole, whereas high-throughput production bushings typically have 1000 or greater. Figure 2 shows a glowing hot glass fiber bushing and a close-up image of fibers exiting a bushing. The first direct-melt furnace for continuous fiber production, developed by Owens Corning in 1961, had bushings with throughputs on the order of 10 lb/h. Bushing technology development at Owens Corning has focused on reducing the amount of high-cost alloy required while increasing bushing thermal-mechanical stability, and thus operational life and efficiency. Today, Advantex® glass fiber bushings are capable of throughputs exceeding 300 lb/h with lifetimes greater than a year.† Table I. Common Glass Fiber Types Used in Composite Applications1 Glass type Description E Alumino-borosilicate family of glasses originally developed for electrical applications; has found widespread use in nearly all glass fiber-reinforced composites E-CR Corrosion-resistant E-glass; equal or better mechanical properties and little or no cost disadvantage versus standard E R High-strength glass with performance intermediate to E and S S A family of glasses composed primarily of the oxides of magnesium, aluminum, and silicon; S-glass was developed for high strength and modulus plus superior thermal and corrosion performance Fig. 1. Fiberglass manufacturing schematic. † Advantex® is a registered trademark of Owens Corning. www.ceramics.org/IJAGS Glass Fiber-Reinforced Composites 123