Influence of the body on the response of the helmeted head during impact

Abstract

The most frequent type of injury that causes death or disability in motorcycle accidents is head injury. The only item of personal protective equipment that protects a motorcyclist's head in real-world accidents is the safety helmet. The protective capability of a helmet is assessed, according to international standards, through the impact of a headform fitted with the helmet onto an anvil. The purpose of the present work was to study the influence of the presence of the body on the impact response of the helmeted head. Full-body and detached-head impacts were simulated using the finite element (FE) method. 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 and stringent. The solution to an analytical model of the helmeted headform impact revealed that increasing the headform mass has the same influence on impact outputs, particularly the liner's crushing distance, as including the whole body in impact tests. The added mass was calculated by using a helmeted Hybrid III dummy for an impact configuration that frequently occurred in real-world accidents

Optimization of the Chin Bar of a Composite-Shell Helmet to Mitigate the Upper Neck Force

“…where isthe ratio of the limiting stress to the peak stress [49,50] and has been considered equal to 0.1 [43,44]for the present study. In this material model when an element fails, its moduli degrade to near zero but the element will not be deleted in order to avoid instability problems at the interfaces with other parts, like liner and anvil in the present work [44,45].…”

“…Test coupons were cut from different regions of the helmet in order to identify the ply layups and characterize their mechanical properties [44]. Table 2 and Figure 3 show different types of lamina used in the shell and the layups in different regions of the shell, respectively.…”

“…This model requires the definition of the compressive stress-strain curve. This curve was obtained using semiempirical equations provided in [46] and explained in [18,19,47].…”

“…4-node quadrilateral shell elements were used to generate the FE model of the composite shell and 4-node tetrahedral solid elements for the liner discretization as shown in Figure 1. The chin strap was modeled using 4-node quadrilateral shell elements with a Young's modulus of 1 GPa and a Poisson's ratio of 0.3 [44].…”

“…Other researchers have developed computational models of brain injury and used them to study the protection offered by helmets [13][14][15]. Computational models of helmets have also been developed and used to improve helmet design [16,17], to understand the performance of helmets in realistic impact conditions [18] and to investigate the effects of the head/neck interaction on impact performance of the helmet and head [18,19]. Some experimental studies have also been carried out in order to improve the head protection capability of motorcycle helmets.…”