Strong Materials

By: Fernando L. Reyes

Steel is one of the metal materials with very high tensile strength. The steel cable is use in the decks of U.S. naval aircraft careers to bring the planes when they are landing to a complete stop is just seconds.

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We live every day without worrying about what is around us. Have you asked yourself why things are made the way they are or about why we use them?

There is a diversity of materials in the world; most of them can be manipulated by humans. The strength of these materials can be measured in different ways. One of them is the tensile strength. This statement refers to the ability to withstand pulling of the material. Another one is the toughness; this refers to how much energy a material can absorb without breaking. Finally, is the compression strength, which is the ability to withstand squeezing. This can be explained better in the book “The Science and Engineering Materials 6th edition.”

NOVA series on PBS channel tried to explain the different types of strength of these materials in the episode named “Making Stuff: Stronger”. David Pogue, as host of the series, tried to explain different terms of the strongest materials in the world and their use. The materials investigated are steel, Kevlar, carbon nanotubes and the spider silk. David Pogue traveled to the deck of a U.S. naval aircraft carrier, rode in a crash car in a demolition derby and visited the top laboratories on the country searching for the strongest material in the world.

What determines the strength of the different materials is the atomic structure. For example, steel is an alloy of iron and carbon, which has a crystalline structure. The addition of carbon hardens the iron making a more rigid structure. David Pogue said on the episode that when we try to give the material more mechanical resistance, we sacrifice flexibility. “That is not totally true; there are some very special materials with both of these properties, especially the ones used to make the landing gears of the airplanes”, Prof. O. Marcelo Suráez said. Marcelo Suárez is a professor at the Science & Engineering Materials Department of the UPRM.

Material scientists can strengthen materials, such as steel, by manipulating how they are made. Material scientists create and combine materials to design new ones with specific properties. There are many different types of steel or plastics, each one with different properties. Each different material created in a different way covers a different use and purpose.

We can also create entirely new materials, such as Kevlar, a synthetic polymer with very high tensile strength and toughness. Kevlar is the material used to make bulletproof jackets for all different purposes. The creator of this synthetic fiber is Du Pont Corporation. Pogue made some test with Kevlar and it turns out that it has more tensile strength than steel. “Can we replace steel with Kevlar?” he asked, “surely this is a little preview of what we are going to see in the future.” mentioned David Pogue on the episode.

Another very strong material is the carbon nanotube. Maybe you don’t know what that is but you may have some idea, when we say Nano it means it is very small. One way to make this a strong material is creating a forest of carbon nanotubes. “The carbon nano tube is the darkest material, because it is dark, it can absorb more energy, so it is tough too,” Prof. O. Marcelo Suárez said.

Scientists study the natural world to learn how nature produces strong materials such as a spider silk. The composition of spider silk makes it one of the strongest materials in the world. Spider silk has even more tensile strength that iron and Kevlar but it does not overpass the carbon nanotube forest. The properties of the way atoms bond together are what makes spider silk so strong, as said on NOVA series Making Stuff: Stronger.

More than 25 people are watching NOVA series Making Stuff Stronger on the S-113. The video is from a computer that’s why it doesn’t have too much quality.

“The research of new materials to replace others is very important”, said Liliana Hernandez, an undergraduate student doing research in the Science & Engineering Materials area. Currently she is doing research under the guidance of Prof. Marcelo Suárez. Liliana focuses on the area of glass. Glass is a ceramic material with very low tensile strength or toughness. These properties are what make them break so easily, but in comparison to other materials, it has very high compression strength.

The next generation of strong materials may be very different from what we are used to. The problem is how to get this material in a large scale if they are so thin. Scientists are working to find the stronger materials in the world to replace others and improve and optimize existing ones.

Sources:
-Prof. O Marcelo Suarez, Professor of the Science & Engineering Materials Department.
-Liliana Hernandez, Civil engineering undergraduate student doing research on Engineering     Materials.
-Nova series page of Making Stuff: http://www.pbs.org/wgbh/nova/tech/making-stuff.html
-Book: Askeland, Fulay, Wrigth, The science and Engineering Materials 6th edition.
-2nd Picture downloaded from the internet and it is a scene of the episode.
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