Abstract
This paper deals with material property identification of a helmet lining consisting of an outer layer of an expanded polystyrene (EPS) and inner layer of an open-closed cell foam (OCCF). A combined numerical simulation and experimental testing was used for the material property identification. Compression and drop tests were performed. The ABAQUS finite element commercial code was used for numerical simulations in which the OOCF was modelled as a rate dependent viscoelastic material, while the EPS as a crushable foam. The reaction force time histories coming from the numerical simulation and the experiment have been used as a criterion for material parameter determination. After the identification of the material properties, numerical drop-tests were used to study the behaviour of a plate and a conical composite OOCF and EPS liners to decide which of them suits more for the helmet.
Highlights
Common property of composites and foams is their low specific weight
Open-closed cell foam (OCCF) is modern energy absorbing material having different viscoelastic mechanical response according to strain rate
The aim of this work is the identification of parameters of material models which would sufficiently characterize the foams for the thickness determination of a versatile sport helmet lining using the finite element method (FEM) model
Summary
A utilization of these two materials in suitable combination allows the creation of lightweight impact energy absorbers where composite layers advantageously distribute impact forces into foam layers. Expanded polystyrene (EPS) is a crushable foam which, in case of compression, absorbs energy during the plastic deformation stage when the stress reaches a roughly constant plateau value (plateau region in force compression diagram) over a large percentage of total strain (typically 60-70%)[1]. Open-closed cell foam (OCCF) is modern energy absorbing material having different viscoelastic mechanical response according to strain rate (produced e.g. by D3O®). The aim of this work is the identification of parameters of material models which would sufficiently characterize the foams for the thickness determination of a versatile sport helmet lining using the finite element method (FEM) model. The helmet should be suitable for cycling, inline skating, skateboarding, horse riding, paragliding and other similar sports
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