Investigation of Finite Element Material Models for Instrument Panel Head Impact Simulation 2014-01-1028

Motor vehicle safety standards are getting to be more demanding with time. For automotive interiors, instrument panel (IP) head impact protection is a key requirement of the Federal Motor Vehicle Safety Standard (FMVSS) 201. To ensure compliance of this requirement, head impact tests are conducted at 12 and 15 mph for performance verification.

Computer simulation has become more prevalent as the primary development tool due to the significant reduction in time and cost that it offers. LS-DYNA is one of the most commonly used non-linear solvers in the automotive industry, particularly for safety related simulations such as the head impact of automotive interiors. LS-DYNA offers a wide variety of material models, and material type 024 (MAT 024, piecewise linear plasticity) is one of the most popular ones [1]. Although it was initially developed for metals, it is commonly used for polymers as well. LS-DYNA also offers several other material models specifically developed to simulate polymers, such as material types 019, 089, 123, to name a few. These alternate material models have different requirements for input and resources required, and have advantages and disadvantages [2, 3].

The primary objective of this investigation is to compare various LS-DYNA material models for polymers - MAT 024, MAT 019, MAT 089 and MAT123, and recommend the appropriate model to use for predicting head impact performance. In an effort to give more functionality to these material models, this study proposes an effective way of estimating high strain rate properties based on existing low strain rate data. The simulation results are compared to IP head impact physical test data to arrive at conclusions on the benefits of these alternate material models.