# FE Analysis of Motorcycle Helmet Performance under Severe Accidents
###### Abstract  
A helmet is essential protective equipment for the safety of motorcyclists and their passengers. However, motorcycle accidents can cause severe injuries and fatalities, even when wearing helmets, because the strength of motorcycle helmets lacks head protectionly in actual impact accidents. Thus, this research investigates the structural performance of commercial motorcycle helmets in Thailand for head injury prevention using finite element analysis via LS-DYNA. The helmet structural model was firstly validated under impact analysis by comparing with the test according to the TIS 369-2557 standard. The finite element results showed that the difference in maximum acceleration was only 4.8%. The protective efficacy of the helmet structure was then studied and analyzed by simulation under various velocities and impact angles according to three cases of accidents. The structural strength was investigated by assessing energy absorption, HIC, and AIS. The worst case was caused when high impact speeds and angles were applied, which showed the highest impact force and HIC. It also enabled a 100% probability of head damage according to AIS 2+, which causes fatality to passengers during impact accidents. The safest conditions in terms of head injury severity occurred when the impact angle was 45 degrees. Finally, at least 75% energy absorption of foam was further recommended for safety design to reduce head injury from motorcycle accidents. motorcycle helmet; impact analysis; motorcyclist safety; head injury criteria; injury severity 2022125676. 2022125676. 2022125675 May 202213 May 20  
United States [9], the Economic Commission for Europe (ECE-R22.05) in European communities [10], and the Thai Industrial Standards no. 369-2557 (TIS 369-2557) in Thailand [11]. These regulators perform tests by simplifying cases of motorcycle accidents. One of the tests is the impact test, which has the highest potential to verify helmet structural performance by evaluating the peak acceleration and head injury criteria (HIC) at the assigned headform. Therefore, the impact test is typically used and studied as the essential requirement for helmet structure to ensure its strength for the head protection of passengers [12; 13; 14; 15]. The finite element model is prevalently applied to study and analyze motorcycle helmet structures under various impact test conditions according to the regulations for the preliminary design process [2; 16; 17]. The computational time and other costs of testing can be avoided by using a simulation procedure. The side impact test of the helmet structure is the worst scenario based on the fit effect, since the highest stress and HIC occur at the head, while the frontal position also causes severe head injury [18]. Modification of the material properties of the shell and foam components has been studied to reduce head damage [19; 20; 21], and reinforcement inside the structure must also efficiently absorb the impact force during an accident [22]. Composite materials were largely proposed to increase the energy absorption performance of the whole structure with a lightweight design [14; 23; 24; 25], but the cost of these materials was one of the drawbacks compared with that of a commercial helmet. All studies have focused on analyzing and designing for helmet structural strength when only impacting with flat or kerbstone anvils according to helmet testing standards. However, an impact test with anvils does not sufficiently represent actual motorcycle accidents when oblique conditions are considered by assigning different impact angles and normal and tangent velocities [26; 27; 28]. The characteristics of the headform under oblique collisions also presents a combination of translational and rotational behavior; however, the axial impact of each accredited agency does not concern these effects [29]. Thus, some limitations of the regulations should be discerned for representing actual accidents with motorcyclists and passengers.