A question and answer session with some interesting facts and answers to some of the most common questions about Materials Science
Question
Many fibers are synthesized from a petrochemical base (from oil---a fossil fuel). Is it possible to make a comfortable, durable polo shirt from fibers that are synthesized
from corn, a completely renewable chemical feedstock?
Answer
A Benson, MN company is making shirts from corn that you can wear for work or play. The shirts look and feel like cotton, but they wick moisture away from the body just like shirts made from high-end synthetic fabrics, says Don Lenz, CEO of Future Products, Inc. The fiber is called Ingeo (In-gee-o), which means "ingredients from the earth." A totally renewable product made from corn, Ingeo contains no petroleum byproducts like synthetics and other fabrics. It doesn't peel, shrink, wrinkle or stain. It's 100 percent biodegradable, making it the perfect "green" fabric, Lenz says. "It's the fabric of the century." Cargill Inc. makes Ingeo at its new $120 million NatureWorks plant near Blair, NE. It mills corn kernels into starch, then sugar. Enzymes ferment the sugar to produce lactic acid, which is transformed into pellets and extruded into a fiber that can be used in everything from clothing and carpets to packaging containers.
More Info:
http://www.cargill.com/
http://www.natureworksllc.com/
Question
I met a number of representatives from your organization at the ATE conference in Washington in October. At the time they mentioned a cake baking lab that could be used in material science. I have searched your web site but unfortunately have not been able to find it. Would it be possible to get a copy or a link?
Question
I am building the Strength Testing machine as shown in "Properties of Fibers and Fabrics" module. I am having a problem finding a luggage scale. Any suggestions?
Answer
A weight scale, found at a local hardware store, or a game scale that can be found at a sporting goods store could be substituted.
QuestionWith Boeing using more and more composite materials and drawing such interest for my students, I would like to demonstrate composite principles in my classroom. Any suggestions?
Answer There are several illustrative modules on the MatEdU website and we recommend starting with the Introduction to Composite Materials for Engineers and Technicians. Go to
MatEdU Modules and choose composites in the subject group.
Question
I have been recommended to a workshop you do for educators. How do I get more information?
Answer
Check the Materials in Stem website at
www.materialsinstem.org for more information on this annual educator’s event.
Question
I am looking for something to "grab" my students into the composites world and help them understand this technology and make a lasting impression. Do you have any ideas?
Question
As a teacher or parent, why would it be better to use experiments in solid materials in place of more standard chemistry experiments?
Answer
Since solids are less volatile, this reduces the potential exposure of students to harmful chemicals and fumes. Students can also identify more easily with solids than with liquids or gasses normally used in chemistry.
Question
When I bend a piece of metal like a paper clip or an aluminum rod, I can feel the bend portion getting warm. It also seems to get stronger. Why does this happen?
Answer
Bending a metal causes planes of atoms to slide over one another. This causes hardening as the planes slide and in some cases get tangled up with one another, giving increased strength. This process generates the heat that you feel. Many metals are strengthened by bending, rolling or hammering, all of which cause hardening. The increased strength remains until the metal is annealed by heating to a high temperature.
Question
Aluminum comes in a lot of forms. I know about aluminum foil but I read that airplanes are made of aluminum too. What is the difference in these forms of aluminum?
Answer
Pure aluminum is a relatively weak material, so that most aluminum products are alloys, containing other elements (called alloying elements). Aluminum foil is nearly pure aluminum, and is easily rolled into thin sheets, the form we use it in. Aluminum alloys can contain a variety of other elements in amounts from a few percent to 20 or more percent. Each alloy will have a specific set of properties such as strength, toughness, corrosion resistance, etc. Aluminum alloys may also be strengthened by heat treatments where they are heated and cooled in a specific manner. Each aluminum part on an airplane is chosen with specific properties in mind, and then matched to the correct alloy and heat treatment to produce those properties.
Question
When glass breaks it usually breaks into lots of sharp pieces. But there are some types of glass that don't do that, but rather break into small chunks. What is the difference?
Answer
The glass that breaks into small chunks is called tempered glass. It is "tempered" by heating to a very high temperature, followed by a rapid cooling to room temperature. This makes the glass 3 to 4 times stronger than regular glass; it also makes it brittle so that when it breaks, it breaks into the small chunks that you have seen. Automobile side and rear windows are usually tempered glass; windshields are not—they are a laminated layered glass, called "safety glass," in which 2 layers of glass are laminated with a sheet of plastic in between. When safety glass breaks, the pieces stick to the internal plastic sheet rather than separating from the windshield.
Question
I have heard of composite materials. What are they and how are they used?
Answer
Composites are materials made by combining two or more materials physically without combining them chemically. Fiberglass is an excellent example, where glass fibers are held in an epoxy resin, and the resulting combination is lighter and more flexible than glass, stronger than epoxy, and tougher than either. Plywood is also a composite, made of wood and glue, where the wood can be layered with the grain pointed in multiple directions, making it very hard for a crack to spread through it. Of course, wood itself is a natural composite made of the organic polymers cellulose and lignin. Composites are used wherever they are the right combination of properties and cost, just like any other material, and some have very high performance properties whereas others are valued for how inexpensive they are to produce. Their great advantage is the ability to get unusual combinations of properties, fitting different needs.
Question
I have used an epoxy casting module, but there are several problems, the worst being that the fumes bother some of the students. What can be done to alleviate this problem?
Answer
The material called Eurocast works better for a casting example and emits fewer fumes. Be sure to have good ventilation when this is done. Also, the best molds are cookie cutters or plaster molds‐‐ plastic tends to stick and paper is hard to remove.
Question
I've seen 3D printed things that are clear and have empty spaces inside them. How does that material get removed?
Answer
3D printing is what's called an additive manufacturing process, which means that material is added in layers. Each layer is fused on top of the previous layers, so we can build complex shapes inside an object layer-by-layer just as we build the walls around those shapes layer-by-layer, and leave any kind of hollow space we want behind. It's a completely different set of advantages from what we can do with machining or injection molding, for example!
Question
I have a 3D printer in my classroom and I constantly have to throw out filament that has gotten old and started jamming the printer. Is there a plastic that doesn't get old that I could use to waste less material?
Answer
Printing filament actually jams and sputters because it has absorbed moisture from the air, not because of its inherent age. The best way to save money, reduce waste, and keep using your filament is to keep it in a space with very low humidity. You can even pull the water back out of the plastic by keeping it dry enough. Our favorite method is to store our opened filament in a cabinet with very little airflow and a tray of rechargeable indicator silica desiccant. You can order a pound of it online for cheaper than a half kilo of PLA or ABS filament, and it'll save you a lot more than that.