Investigation of helmet-to-helmet collisions in football: Experiments using a mechanical lumped element coupled harmonic oscillator model structure for the skull, fluid, and brain mass

Abstract

The study of extreme helmet to helmet football collisions may lead to future precautions to prevent serious head injuries. First, (a) oscillations of the helmet alone (much like a tuning fork) are investigated. Then (b) a thin walled 1/16 inch thick 2 inch tall by 6 inch diameter polycarbonate hoop is used to model the skull (in the n = 2 mode). Next, (c) the hoop is filled with a light weight polyurethane foam to model fluid in the structure. Then (d) a solid brass cylindrical 1 Kg weight is inserted in a carved out slot in the foam. The hoop-foam-brass weight structure is studied in transient vibration. Finally (e) the “skull”, “fluid”, “brain mass” structure is set in the helmet and cushioned with extraneous foam. A second identical helmet on a pendulum is released with some angular momentum and collides with the helmet (fitted with the structure (e)) that is suspended vertically by its own pendulum cord - initially at rest. In laboratory collision studies three single axis accelerometers are placed on (1) the helmet at rest, (2) the hoop and (3) the end of the cylindrical mass, in an effort to rudimentary model the vibration of the model brain mass.