According to helmet standards, the absorption capacity of helmets is assessed
through impact of a headform fitted with the helmet onto an anvil. It implies that the
effect of the rest of the body on impact outputs has been assumed to be negligible.
The purpose of this work was to investigate this effect. Full-body and detached-head
impacts were simulated using the Finite Element (FE) method. A detailed FE model
of a composite-shell helmet was developed and validated against experimental data. It
was coupled with an FE model of the Hybrid III dummy. To validate the full-body
impact model, a new test method was designed to drop test helmeted dummies. As a
consequence of the presence of the body, the crushing distance of the helmet liner was
drastically increased. This evidence indicated that the effect of the body should be
included in impact absorption tests in order to provide conditions that are more
realistic to real world accidents and more stringent.
The solution to an analytical model proposed for helmeted headform impacts
revealed that the influence of increasing the headform mass on impact outputs,
particularly the liner crushing distance, is the same as the influence of the body. The
added mass was calculated for various impact configurations by using a detailed FE
model of the human body. Finally, an added mass of 20% together with a 9%
reduction in the limit of head linear acceleration were proposed.
Full-body and detached-head oblique impacts were also simulated. The results
indicated that the body had a noticeable influence on head rotational acceleration.
Modifying the inertia matrix of the head to include this effect in the detached-head
drop tests was proposed. By using an FE model of the human head, intracranial injury
predictors were also evaluated in oblique impacts considering the complete
kinematics of the head.