An energy absorption performance index for cellular materials – development of a side-impact cork padding

Abstract

Owing to its combined properties and considering that it is a natural cellular material, cork can be widely used as a thermal and acoustic insulator and in various energy-absorbing applications (pavements, packaging, shoe industry, etc.). The goal of the research presented here is the development of an innovative application for cork and its derivatives in energy-absorbing and crashworthiness systems. Cork's efficiency as a material dedicated to energy absorption in automotive passive safety systems is studied numerically, specifically for the protection of the occupant's pelvic area in side-impact crash situations. Finite element analyses are performed with LS-DYNA in order to study the benefits and efficiency of the implementation of a microagglomerated cork padding in the interior of the vehicle's side door. For this purpose, a fully three-dimensional model of side-impact crash test is developed with the appropriate constitutive material models. Obtained results for the impacted system are thoroughly compared in situations with and without the cork padding. The numerical simulation results prove that there is a significant improvement in terms of either absorbed energy or intrusion and peak acceleration.

Keywords:

• cork
• cellular materials
• energy absorption
• crashworthiness
• impact performance
• numerical simulation
• finite element analysis
• LS-DYNA

Notes

1. Ratio of the actual volume to the initial volume.

2. The impactor block's mass is estimated in agreement with the average properties of the aluminium honeycomb.

3. This estimation of the intrusion is based on the empirical observation of lateral collisions between passenger vehicles. For this reason, this may be a value lacking qualitative confirmation, since it constitutes a determinant factor in the absolute results. However, for comparative purposes, intrusion level is not relevant.

4. The force acted by each group of springs is calculated by considering its average position in height within the door and the equilibrium of the horizontal momentum of these forces around the vehicle gravity centre.