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In the last several years the Finite-Element Method has been successfully used in assessing and optimizing vehicle crash performance. Occupant modelling however, has remained the domain of gross motion simulators which make use of rigid body dynamics. New passive restraint systems like the airbag, have raised demands to mathematical modelling which cannot be satisfied with the existing models. The simulation of ‘out-of-position’ vehicle occupants is a prime example. A new approach to occupant simulation using the Finite Element Method is presented. The three-dimensional modelling of an airbag using the modified explicit dynamic FE-Code PAM-CRASH is the first step in this direction. An airbag inflation model has been added to the PAM-CRASH code. It incorporates tabular input of the mass flow, calculation of the airbag's thermodynamics and gas flow out of the bag via vents and leakages. The airbag fabric is modelled with a newly implemented membrane element.

The present paper outlines basic material models for composite strength and failure analysis, based on ESI's PAM-FISS/Bi-Phase composite material model. The new material models have been ported into the PAM-CRASH™ crashworthiness simulation code and applied to the crashworthiness simulation of axially compressed box columns made of hybrid Carbon-Kevlar-Aramid sandwich walls. After calibration of the models on laboratory coupon tests and validation on simple component crash tests, the methodology can be used to predict the crash behaviour of a prototype passenger car compartment structure, made entirely of composite sandwich material.

The paper describes an engineering project carried out to optimize the crashworthiness of an existing passenger car for frontal crash using a procedure relying on numerical simulation. An optimization target is defined in terms of an ideal acceleration pulse at the seats anchors. The acceleration time history and structural members are scanned in parallel to correlate the local acceleration peaks to specific structural members. Members details are iteratively modified in order to alter the accelerations and get closer to the target.