Prevention and prediction of head and neck injury in traffic accidents - using experimental and numerical methods

Abstract: Injuries to the head and neck system are potentially amongthe most serious injuries in humans, since they may damage thespinal cord. It is therefore important to develop safetysystems that can prevent injuries to the neuro- system, therebyreducing human suffering and costs to society. In thedevelopment of new and improved systems for injury preventionin car accidents, accurate criteria for predicting injury dueto mechanical forces in different impact loading situations areneeded to guide the development of improved safety systems.This thesis deals with three aspects related to theprevention of injury to the head and neck. First anexperimental and numerical study investigated how to reduce theforces on the head and neck in frontal car crashes. Secondly, afinite element model of the human neck was developed. Finally,head protection in oblique motorcycle crashes wasexperimentally and numerically studied.Specifically, the first study is focused on a headprotection system for reducing the forces to the head and neckduring frontal car accidents. An Experimental Head RestraintConcept (EHRC), a safety belt for the head, was designed to actas a complement or alternative to the conventional airbag. TheEHRC was evaluated experimentally in frontal collision for acrash severity of 11 m/s, and numerically in frontal collisionfor crash severities of 11 and 15 m/s. Experimental dataobtained from a frontal barrier test (11 m/s) showed a 67%reduction in the HIC value from 411 (without EHRC) to 136 (withEHRC). The EHRC clearly has a potential role in the search forprimary prevention of neurotrauma injuries in frontal carcrashes. However, it should only be seen as an experimentaltool, although it clearly has a potential market for transportof disabled people.The EHRC changed the characteristics of the response of theneck. The bending moment in the neck was shown to increase by afew percent when the EHRC was used. With available neck injurycriteria, it was not possible to determine whether this changein response is significantly negative. Therefore, there is astrong need for more advanced injury criteria for the neck inorder to optimize such a safety system.To improve the knowledge of injury mechanisms and injurycriteria of the neck, a research was initiated to develop adetailed finite element model of the cervical spine. The modelis aimed to predict injuries in the neck for different types ofload modes and to work as a tool to create global injurycriteria from local tissue-based failure criteria.The finite element model of the cervical spine excludingmuscles has been validated in compression-flexion where a goodcorrelation was found with experimental data. By the model itwas possible to predict experimentally found injuries as theHangman's fracture and the model was used to investigate a newcar roof structure.In the last study a new helmet design was presented with animproved protection against tangential impacts. In this worktwo new oblique helmet testing methods were used to investigatethe behavior of the helmet. This study showed thatit ispossible to reduce the rotational energy by up to 50% by addinga low friction layer between the shell and the liner.