It is important to adopt proper countermeasure strategies, i.e. energy absorbers (EA), in order to meet the Upper Interior Head Impact requirements of FMVSS201 S6.2 (FMVSS201U) which assesses head injury by impacting a Free Motion Headform (FMH) to upper interior parts. The understanding of the energy absorbing characteristic for each kind of countermeasures is a stepping stone to optimize the head injury performance. This paper reviews general features of foam and plastic types of countermeasures with respect to raw material and manufacturing process, and highlights merits and demerits from the point of view of design flexibility. Energy absorbing characteristics based on static component crush testing are considered and these characteristics are also compared quantitatively by investigating energy absorbing efficiency of the countermeasures.

Lastly, sensitivity analysis is conducted to study the relationship between the space and head injury performance according to types of energy absorbers using finite element analysis (FEA).