Editing Fiberglass (section)

==Fiber==
[[File:Glass reinforcements.jpg|thumb|Glass reinforcements used for fiberglass are supplied in different physical forms: microspheres, chopped or woven [[glass cloth]].]]
Unlike glass fibers used for insulation, for the final structure to be strong, the fiber's surfaces must be almost entirely free of defects, as this permits the fibers to reach gigapascal [[tensile strength]]s. If a bulk piece of glass were defect-free, it would be as strong as glass fibers; however, it is generally impractical to produce and maintain bulk material in a defect-free state outside of laboratory conditions.<ref name=newscience>{{cite book |author=Gordon, J E |title=The New Science of Strong Materials: Or Why You Don't Fall Through the Floor|url=https://books.google.com/books?id=axW-iYrhQ1YC|date=1991|publisher=Penguin Books Limited|isbn=978-0-14-192770-1}}</ref>

=== Production ===
The process of manufacturing fiberglass is called [[pultrusion]]. The manufacturing process for glass fibers suitable for reinforcement uses large furnaces to gradually melt the [[silica]] sand, [[limestone]], [[kaolin clay]], [[fluorspar]], [[colemanite]], [[Dolomite (mineral)|dolomite]] and other [[minerals]] until a liquid forms. It is then extruded through bushings ([[Spinneret (polymers)|spinneret]]), which are bundles of very small orifices (typically 5–25 micrometres in diameter for E-Glass, 9 micrometres for S-Glass).<ref>{{Cite book|url=https://books.google.com/books?id=qZPBCQAAQBAJ&q=fiberglass+made+with+aluminosilicate+glass+fibers&pg=PA4|title=Lightweight Ballistic Composites: Military and Law-Enforcement Applications|last=Bhatnagar|first=Ashok|date=2016-04-19|publisher=Woodhead Publishing|isbn=9780081004258|language=en}}</ref>

These filaments are then ''sized'' (coated) with a chemical solution. The individual filaments are now bundled in large numbers to provide a [[roving]]. The diameter of the filaments, and the number of filaments in the roving, determine its ''weight'', typically expressed in one of two measurement systems:
*''yield'', or yards per pound (the number of yards of fiber in one pound of material; thus a smaller number means a heavier roving). Examples of standard yields are 225yield, 450yield, 675yield.
*''tex'', or grams per km (how many grams 1&nbsp;km of roving weighs, inverted from yield; thus a smaller number means a lighter roving). Examples of standard tex are 750tex, 1100tex, 2200tex.

These rovings are then either used directly in a composite application such as [[pultrusion]], [[filament winding]] (pipe), gun roving (where an automated gun chops the glass into short lengths and drops it into a jet of resin, projected onto the surface of a mold), or in an intermediary step, to manufacture fabrics such as ''chopped strand mat'' (CSM) (made of randomly oriented small cut lengths of fiber all bonded together), woven fabrics, knit fabrics or unidirectional fabrics.

====Chopped strand mat====
Chopped strand mat (CSM) is a form of reinforcement used in fiberglass. It consists of glass fibers laid randomly across each other and held together by a binder. It is typically processed using the hand lay-up technique, where sheets of material are placed on a mold and brushed with resin. Because the binder dissolves in resin, the material easily conforms to different shapes when wetted out. After the resin cures, the hardened product can be taken from the mold and finished. Using chopped strand mat gives the fiberglass [[isotropic]] in-plane material properties.{{citation needed|date=September 2024}}

===Sizing===
A coating or primer is applied to the roving to help protect the glass filaments for processing and manipulation and to  ensure proper bonding to the resin matrix, thus allowing for the transfer of shear loads from the glass fibers to the thermoset plastic. Without this bonding, the fibers can 'slip' in the matrix causing localized failure.<ref>{{cite web|title=The Fundamentals: Repairing Fiberglass And Ensuring Bonding|author=Reese Gibson|url=http://www.reesesfishhunt.com/how-to-repair-small-hole-fiberglass-boat/ |access-date=28 April 2017|date=2017-04-26}}</ref>