Link of the Moment: STF Fabric

One of the more impressive applications of shear-thickening fluids is as a additive to body armor.  A collaboration between the University of Delaware and the U.S. Army Research Laboratory has improved the protective properties of Kevlar.  The home page is here, and pictures and video are here.

You Cannot Change the Laws of Physics, Captain

Brooks Sports is advertising its new cushioning system by highlighting its viscoelastic properties.  The new system (called DNA [1]) uses a "highly-viscous non-Newtonian fluid."  The shock absorber uses a semi-liquid filling instead of a semi-solid filling.  The company blog interviews a material engineer who talks a little about basic non-Newtonian behavior.  He uses ketchup as an example.  So far, so good.

The web page that discusses the technology (link here) does have a mistake.  In the video at the bottom of the page, the material engineer states that a "non-Newtonian fluid does not obey the laws of physics." [2,3]

It is precisely because a non-Newtonian fluid obeys the laws of physics that we observe unusual physical behavior like shear-thinning or shear-thickening.  A fluid that did not obey the laws of physics would defy gravity, or it would spontaneously separate into its individual elemental components.  

[1]  I could not find an explanation for this abbreviation.

[2]  Brooks is traveling the country with a vat of cornstarch and water advertising the new technology.  For other videos of shear-thickening behavior, go here.
[3]  I left a comment on the Brooks blog, but either it was not approved, or was removed.

Links of the Moment: Shear-Thickening Fluids

The 2008 Rheology Bulletin had links to movies that showed off the shear-thickening properties of cornstarch/water solutions.  The mixture of 1 part water to 1.5-2 parts cornstarch has become known as oobleck, which was a fanciful fluid invented by Dr. Seuss.  After the jump, several videos of oobleck experiments.

Hat tip: Rheology Bulletin