APPLICATION OF THE FINITE-ELEMENT METHOD TO SIMULATION OF DAMAGE TO THE HUMAN SKULL AS A CONSEQUENCE OF MISSILE IMPACT ON A MULTILAYERED COMPOSITE CRASH HELMET

Finite-element analysis is a powerful technique which could be applicable to the study of a wide range of circumstances where the frame and/or the vital organs of the body are subjected to extreme loading conditions. This paper reports the results of an exploratory investigation in which the performance of a crash helmet in protecting the skull from an impacting load is modelled. The immediate objective is to show how a typical crash helmet design of glass-reinforced plastic (GRP) outer casing with quasi-foam-like liner can, with a suitable choice of material properties, attenuate the transfer of energy from the impacting mass such that the damage intensity to the skull is minimized. A simplified structure for both helmet and skull shape is adopted and the skull is modelled as being supported on an elastic foundation. The material properties used are representative rather than being accurately matched to experimentally determined ones. Several aspects of the modelling technique are worthy of particular note: the simulation of material anisotropy by means of multiple reinforcement layers with varying orientation, the use of dashpot elements for energy attenuation and the incorporation of multipoint constraint between the skull and the helmet lining to ensure integrity of the model with correct stiffness matrix values and allowing independent monitoring of all stress levels at the mating interface region. The results of the modelling show that the specific limited objectives can be met but also indicate how vitally important information could be obtained from similar but more detailed studies which included representative modelling of the body organs and skeleton.