Moving Beyond the Finite Elements: A Comparison between Finite Element Methods and Meshless Methods for Modeling Honeycomb Materials and Simulating Side Impact Moving Deformable Barriers

Movable Deformable Barriers (MDBs) are used in surrogate tests to represent the behavior of an average midsize vehicle. The main difficulty in MDB modeling is the prediction of frontal energy absorbing barrier, where honeycomb materials are used and usually expected to simulate complex failure modes. In side impact tests, the severe shear deformation of the honeycomb material, full densification of barrier edge, rupture of aluminum cover sheets, and tearing of honeycomb blocks are often observed. This complex pattern of honeycomb material failure mode makes it difficult to predict. Numerical instabilities, such as negative volume, severe hourglassing, and inaccurate predictions are often experienced. In this study, National Highway Transportation Safety Administration (NHTSA) side impact MDB is modeled by using a 3D non-linear explicit dynamics numerical solver, LS-DYNA. As a conventional modeling technique, both barriers are first modeled by using Lagrangian solid hexahedron finite elements (FEs). Mat-26 (*MAT_HONEYCOMB) is used as a constitutive model for the barrier construction. By using this Lagrangian model as a reference point, Eulerian and Arbitrary-Lagrangian Eulerian (ALE) models of the MDBs are also created. However, when the distortions become very severe, especially Lagrangian FE algorithms are not always adequate. Honeycomb material behavior is found to behave unstable in this type of impact problems. More recently meshless methods (or particle methods) have been developed and applied to solid mechanics problems since they can efficiently be used to represent severe distortions. In this study, Element Free Galarkin (EFG) model of the MDB is also created. Each MDB model is compared to a full scale crash test against a load cell wall. Accelerometer responses from the simulations are compared to the measured values from the test. Computational costs of the systems are also compared to provide a foresight for the usage of the meshless methods in transportation safety field related research. Dhafer Marzougui, FHWA/NHTSA National Crash Analysis Center, The George Washington University