Fiberglass, (also called fiberglass and glass fiber), is material made
from extremely fine fibers of glass. It is used as a reinforcing agent
for many polymer products; the resulting composite material, properly
known as fiber-reinforced polymer (FRP) or glass-reinforced plastic
(GRP), is called "fiberglass" in popular usage. Glassmakers throughout
history have experimented with glass fibers, but mass manufacture of
fiberglass was only made possible with the invention of finer machine
tooling. In 1893, Edward Drummond Libbey exhibited a dress at the
World's Columbian Exposition incorporating glass fibers with the
diameter and texture of silk fibers. This was first worn by the popular
stage actress of the time Georgia Cayvan.
Uses for regular fiberglass include mats,
thermal insulation, electrical insulation, reinforcement of various
materials, tent poles, sound absorption, heat- and corrosion-resistant
fabrics, high-strength fabrics, arrows, bows and crossbows, translucent
roofing panels, automobile bodies, electrical insulation and boat hulls.
The Nature of Glass
- Glass is typically viewed as an elastic solid in which no significant crystallization has occurred. Thus there is no long-range ordering or extended formation of any Bravais lattice. It follows that glass, even as a fiber, has little crystalline structure (see amorphous solid). The properties of the structure of glass in its softened stage are very much like its properties when spun into fiber. One definition of glass is "an inorganic substance in a condition which is continuous with, and analogous to the liquid state of that substance, but which, as a result of a reversible change in viscosity during cooling, has attained so high a degree of viscosity as to be, for all practical purposes, rigid."
- Generally speaking, the atomic or molecular structure of glass exists in a metastable state with respect to its crystalline form. This essentially reflects their formation from a non-equilibrium supercooled liquid state. Fundamental principles of Gibbs free energy minimization dictate this thermodynamic driving force towards crystallinity, long-range symmetry and thermodynamic equilibrium.
Types of Fiber Glass
- Two types of fiberglass are most commonly used.
- They are S-glass and E-glass.
- E-glass has good insulation properties and it will maintain its properties up to 1500 degree F(815 deg C).
- S-glass has a high tensile strength and is stiffer than E-glass.
Properties of Glass
- Glass fibers are useful because of their high ratio of surface area to weight. However, the increased surface area makes them much more susceptible to chemical attack. By trapping air within them, blocks of glass fiber make good thermal insulation, with a thermal conductivity of the order of 0.05 W/(mK).
- The strength of glass is usually tested and reported for "virgin" or pristine fibers -- those which have just been manufactured. The freshest, thinnest fibers are the strongest because the thinner fibers are more ductile. The more the surface is scratched, the less the resulting tenacity. Because glass has an amorphous structure, its properties are the same along the fiber and across the fiber. Humidity is an important factor in the tensile strength. Moisture is easily adsorbed, and can worsen microscopic cracks and surface defects, and lessen tenacity.
- In contrast to carbon fiber, glass can undergo more elongation before it breaks. There is a correlation between bending diameter of the filament and the filament diameter. The viscosity of the molten glass is very important for manufacturing success. During drawing (pulling of the glass to reduce fiber circumference), the viscosity should be relatively low. If it is too high, the fiber will break during drawing. However, if it is too low, the glass will form droplets rather than drawing out into fiber.