Numerical simulations of motorcycle helmet impact tests

Abstract

The main objective of this study was to simulate experimental impact tests on a commercially available motorcycle helmet and to develop a virtual design tool. The mechanical properties of the shell and the foam liner of the helmet were estimated from existing material data taken from the open literature. The material data were adjusted to match the temperature conditioning of each impact test condition. All computational impact tests were performed using the explicit finite element code LS-DYNA3D with appropriate foam and composite material models. The European standards, ECE Regulation 22.05, were adopted in both experimental and numerical tests. The results demonstrate the possibility of accurately simulating the various types of standard impact tests, thus introducing the real possibility of using virtual testing techniques in the helmet design process, e.g. for motorbike helmets, and other helmet configurations

FEA of oblique impact tests on a motorcycle helmet

“…A comparison, of compression tests on a complete shell with FEA of the same loading geometry, showed that the Young's modulus of the GRP in the Mavet helmet was relatively low. This is almost certainly true for other helmets, suggesting that the moduli used in [11] and [12] were probably too high. GRP fracture and delamination does not occur in the flat anvil impacts, so these phenomena were not modelled.…”

“…GRP fracture and delamination does not occur in the flat anvil impacts, so these phenomena were not modelled. However, to model impacts on kerbstone anvils, these phenomena should be included in the FEA, as in [12]. If FEA is to replace prototype testing, in developing helmet designs to pass EC Regulation 22 or BS 6658, it is vital to model all the main protective foam components; the cheek pad foam was loaded in impacts at the helmet side, and the chin bar centre foam was loaded in frontal impacts.…”

“…Researchers often used GRP Young's moduli measured using flat test coupons, rather than values deduced from tests on helmet shells; Kostoupoulos et al [11] used an inplane Young's modulus of 19.7 GPa for a 2 mm thick prototype GRP shell. Aiello et al [12], who simulated direct impacts on a full-face Dainese helmet with a mixed-fibre composite shell, used an in-plane Young's modulus of 24 MPa at 50 °C. The consequent overestimation of the shell bending stiffness increased its load spreading to the EPS liner (the volume undergoing a high compressive strain), and hence gave erroneous predictions of helmet performance.…”

Measurement and simulation of energy absorption behaviour of motorcycle helmet materials

“…Due to its ease of calibration and accuracy in single impact events, these models are used in many studies where the focus is primarily on simulating shell material behaviour accurately such as in [40], [21] and [1].…”

“…Aiello et al [1] modelled contact between the outer shell and inner foam liner by defining a 'tiebreak' interface condition. This contact condition bonds the surfaces of two solid or surface meshes and prevents any sliding or separation between the surfaces.…”