The biomechanical differences of shock absorption test methods in the US and European helmet standards

ABSTRACT

Nowadays crash helmets are tested by dropping a free or unrestrained headform in Europe but a guided or restrained headform in the United States. It remains unclear whether the free fall and the guided fall produce similar impact kinematics that cause head injury. A finite element helmet model is developed and compared with experimental tests. The resulting head kinematics from virtual tests are input for a finite element head model to compute the brain tissue strain. The guided fall produces higher peak force and linear acceleration than the free fall. Eccentric impact in the free fall test induces angular head motion which directs some of the impact energy into rotational kinetic energy. Consequently, the brain tissue strain in the free fall test is up to 6.3 times more than that in the guided fall. This study recommends a supplemental procedure that records angular head motion in the free fall test.

KEYWORDS:

• Helmet
• shock absorption test
• finite element analysis
• skull fracture
• traumatic brain injury

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the European Union's Horizon 2020 research and innovation programme under the Marie Skodowska-Curie [grant number 642662].