Helmet Test Fixture

Our Customer: Chesapeake Testing

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Background

 

The helmet fixture would be used to conduct a military-specific compression test on composite helmets used in the armed forces. The motivation behind our design stems from the habit of soldiers sitting on their helmets when out in the field. It was speculated that repeated use of the helmet in this particular way could potentially delaminate the layers of the helmet and ruin its integrity, which could in turn weaken its material properties. The previous design was constructed of several wood 2 x 4" planks secured together. The planks were machined and hand sanded to match the contours of the helmets periphery. The main issues with the previous design were the gaps by the earflaps of the helmet, and deformation in the fixture created by the helmets after several tests.

 

Design Process

 

Our design objective was to design a fixture that supported helmet sizes small to XXL, support the periphery of the helmet, and rigidly hold it in place during testing. The final design would be a working fixture that would not restrict the helmet from expanding during testing. 

 

Our final design consisted a base plate and fixture to fit each required helmet size. The surface of each fixture matched the profile of the crown of each respective helmet size, while pins in the fixture fix the helmet in place during height measurements. The pins are removable to allow for expansion during compression tests. Our group chose to have the fixture machined from Aluminum 6061, which is lightweight, inexpensive, and, most importantly, has an ultimate strength which is well above our target. Once our design was machined, we tested our helmet to validate our top performance metrics: deformation and gap.