Identification of the LLDPE Constitutive Material Model for Energy Absorption in Impact Applications

Abstract

Current industrial trends bring new challenges in energy absorbing systems. Polymer materials as the traditional packaging materials seem to be promising due to their low weight, structure, and production price. Based on the review, the linear low-density polyethylene (LLDPE) material was identified as the most promising material for absorbing impact energy. The current paper addresses the identification of the material parameters and the development of a constitutive material model to be used in future designs by virtual prototyping. The paper deals with the experimental measurement of the stress-strain relations of linear low-density polyethylene under static and dynamic loading. The quasi-static measurement was realized in two perpendicular principal directions and was supplemented by a test measurement in the 45° direction, i.e., exactly between the principal directions. The quasi-static stress-strain curves were analyzed as an initial step for dynamic strain rate-dependent material behavior. The dynamic response was tested in a drop tower using a spherical impactor hitting a flat material multi-layered specimen at two different energy levels. The strain rate-dependent material model was identified by optimizing the static material response obtained in the dynamic experiments. The material model was validated by the virtual reconstruction of the experiments and by comparing the numerical results to the experimental ones.

Assessment of Nanobag as a New Safety System in the Frontal Sled Test

“…The nanobag concerns a thin foil (nanofoil) unrolled between side supports. The nanofoil is based on a linear low-density polyethylene (LLDPE), where the material properties were previously identified in both static and dynamic loading conditions [12]. The frontal scenario was chosen as the first step for assessing the performance of the nanobag system due to the ease of comparison to standard airbag performance.…”

“…The simplified geometry of the nanobag system was built based on the documentation provided by [6]. The study implements the previously identified linear low density polyethylene LLDPE nanofoil material [12]. Hynčík [12] performed the numerical optimization of material parameters to fit the performed experimental tests.…”

“…The study implements the previously identified linear low density polyethylene LLDPE nanofoil material [12]. Hynčík [12] performed the numerical optimization of material parameters to fit the performed experimental tests. Static and dynamical analysis were considered to model and validate the material behaviour for such loading.…”