Glass fibre
Glass drawn thin enough to bend without breaking — and by far the most-used reinforcing fibre there is.
Glass fibre is ordinary glass chemistry drawn into filaments a few micrometres across, and the thinness is what changes everything. Bulk glass breaks at a low stress because it is full of surface flaws and a crack runs from the worst of them; a filament is too small to contain a large flaw, so it reaches a strength the bulk material never approaches, and it is thin enough to bend without the surface strain that would break a rod.
That is the whole principle, and it is why fibres of brittle materials are useful when the same material in a block is not.
Its stiffness is about that of aluminium — which is a fifth of carbon fibre's, and the reason carbon is worth its price where stiffness rather than strength is what is wanted.
Processing
Molten glass is drawn through a platinum-alloy bushing with hundreds of holes and pulled at high speed, thinning as it goes and cooling as it thins. A size — a coating — is applied immediately, and it does two jobs: protecting the filaments from abrading each other, and chemically coupling the glass to whatever resin will be used, which is what makes the composite work at all.
A mishandled or badly sized fibre gives a laminate a fraction of its potential strength, and the failure is at the interface rather than in either material.
Uses
As reinforcement, in more composite by tonnage than every other fibre combined: boat hulls, wind turbine blades, tanks and pipes, vehicle panels, circuit boards, and building panels.
As insulation, in the tangled wool form, which is a completely different product from the same material and is one of the highest-volume insulation materials in the world.
And as textile, in fabrics that must not burn.
History
Glass has been drawn into threads since antiquity as decoration. Continuous fibre for reinforcement is a 1930s development at Owens-Illinois and Corning, and the composite industry follows it immediately: the first glass fibre boat hulls date from the 1940s.
Environmental impact
Glass wool insulation is made with a high recycled glass content and saves many times its own embodied energy over a building's life, which is about as clear an environmental case as a material has.
The reinforcement is the opposite. A cured glass-reinforced thermoset cannot be separated back into fibre and resin, so a hull or a blade at end of life is ground for filler, burned in a cement kiln, or landfilled — which is the composite industry's standing problem and is discussed under the laminates rather than the fibre.
How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.
How this connects
Where a connection has been confirmed by an outside reference, that reference is named beside it.
contains
is sourced from
- Quartz — mineral · as silica sand, with limestone and clay for the rest of the E-glass batch
is a component of
- Glass fibre composite — material · the reinforcement, and the fibre's strength is not the laminate's
is used as
- Thermal insulation — application · as glass wool, which is a different product from the same material and one of the highest-volume insulations there is
is commonly confused with
- Glass fibre composite — material · 'fibreglass' means the fibre to a manufacturer and the composite to everybody else, and the two have entirely different properties
is used in
- Printed circuit board — object · the woven reinforcement, which is what stops the board moving as it is heated through a reflow oven
is produced by
- Glass melting — process · drawn through a bushing of hundreds of platinum-alloy holes, at a diameter of a few micrometres and a speed of tens of metres a second
Sources
- Material WorldOur own writing
- Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)