Stress and Strain
Today we spent our time discussing material strength – an important property in building materials if you want to make something that is able to withstand an earthquake! After a brief discussion of the various ways to stress and strain a material, the students experimented by bending paperclips, stretching rubber bands, and examining the light patterns in plastics as seen through polarizing films.
We learned that the strength of a material comes from its molecular structure. Students can explain why graphite is soft and diamond is hard even though they both have the same chemical formula: C (carbon). We also learned that introducing small flaws or impurities into a material’s crystal structure can actually strengthen the material, a fact blacksmiths have been exploiting for millennia.