Material of the Day: Fiberglass

Material of the Day: Fiberglass by Moritz Koeppenkastrop-Lueker

Today's Material is fiberglass, more specifically, fiberglass cloths and how fiberglass is used in composites. Fiberglass is a strong lightweight material with a high strength and low cost which make it a perfect material for many products and applications.

My name is Moritz Koeppenkastrop-Lueker, and besides engineering, I love to surf and do other water sports. Surfboards are primarily made out of glass fibers and epoxy raisins, due to its high strength and light weight. Because of my vivid interests in water sports and the wide use of fiberglass in that field, I would like to use this web page to explain why fiberglass has the properties that it does.

Besides for making surfboards, fiberglass is used in air crafts, boats, insulation,automobiles, pipes, water tanks, bath tubs, swimming pools, roofing, casts, sporting equipment, body armor, clothes, kitchen appliances, and the list goes on and on.

Figure 1 - Examples of applications for fiber glass composites ||| http://www.vetrotextextiles.com/applications

History: Glass fibers have been around for centuries. However, the mass production of thin glass fibers was first discovered by U.S. engineering and inventor Games Slayter in 1932. At first, fiberglass was in form of light glass wool, which was used for insulation. Later, in 1936, with technological advancements in production and manufacturing methods, glass fibers were strung in little strings and woven into glass fiber cloths. When mixed with a thermoset polymer matrix, fiberglass forms a composite that has the unique properties that we seek in order to build ships, cars, and surfboards.

Properties:

Bulk glass has the properties that it is stiff, has a high strength in compression, is easy to manufacture, and cheap. However, it is also very brittle, and has very small yet inherent and inevitable cracks (flaws). This gives bulk glass a low tensile strength. When strung into very thin glass fibers, however, the glass does not allow for many of the inherent manufacturing flaws. Because of this, an individual glass fiber is much stronger in both, compression and tension along its axis compared to bulk glass.

Material Properties of Glass Fiber composite (GFRP) compared to Carbon fiber composite (CFRP), steel, and concrete:

Table 1 - Comparative list of properties of fiberglass composites, carbon fiber composites, steel A572, and concrete ||||| http://web.mit.edu/istgroup/ist/research/maglev.htm

As we can see in the chart above, Glass Fibers have a tensile strength of 1020 MPa, while steel only has a tensile strength of about 345 MPa. We can also see that the density of glass fibers is only 2.08 g/cm^3 (while steel has a very high density of 7.86 g/cm^3). This makes glass fibers a preferred material for high strength applications that require to be lightweight.

The high strength of the glass fiber composites come from the prevention of cracks mentioned above, as well as the strong covalent and ionic bonds within the ceramic. These bonds give it a very high yield strength, stiffness, and are also responsible for its brittle behavior.

Safety Concerns

There have been many tests on the health side effects of fiberglass by government agencies and private labs, with varying results. The generally agreed upon fact is that fiberglass is an irritant. When in contact with skin, fiberglass wool can cause skin irritation such as itchiness as well as redness and difficulty breathing and seeing. However, when fiberglass strands are embedded in a composite, fiberglass is no longer an irritant. Besides that there are no health concerns with fiber glass.

Picture Credit: http://betterwayproducts.com/wp-content/uploads/2012/02/fiberglass32inch2.jpg

Conclusion

Very high strength, low weight, low cost, relatively simple to manufacture, needs to be embedded in a raisin, very brittle. Great material!

Ever since I was young, surfing was my passion. I am so impressed by how glass fibers changed the sport and made it easier, more extreme, and more fun. I am excited to see how glass fiber technology will improve it even further in the future.

References:

US, "Method & Apparatus for Making Glass Wool", published 11 Nov 1933, issued 11 Oct 1938 ||||| https://en.wikipedia.org/wiki/Fiberglass ||||| http://www.azom.com/properties.aspx?ArticleID=764 |||| http://www.vetrotextextiles.com/applications/wind-energy

Appreciate