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FMVSS 223 and 224 set standards for “Rear Impact Protection” for trailers and semi-trailers with a gross weight rating greater than 10000 pounds. A limited amount of experimental data is available for evaluating the different performance attributes of rear impact guards. The crash tests are usually limited to fixed parameters such as impact speed, guard height, strength and energy absorption, etc. There also seems to be some misunderstanding of the interdependence of guard strength and energy absorption, and their combined effect on the guard's ability to limit underride while keeping occupant acceleration forces in a safe range. In this paper, we validated the Finite Element (FE) model of an existing rear impact guard against actual FMVSS 223 tests. We also modified a previously evaluated FE model of a 1990 Ford Taurus by updating its hood geometry and material properties.

Truck-trailers are required to have rear impact protection guards per Federal Motor Vehicle Safety Standards 223 and 224. The standards define the minimum strength and energy absorption requirements at the guard component level, while allowing the guard manufacturer to use a rigid test fixture when certifying the guard. Due to the limitations inherent in “rigidizing” the under-structure of a trailer, often some amount of deformation in the supporting structures is tolerated when certifying a guard. Hence there is a tendency to certify the impact guard as a “guard system” composed of guard members and the support (mounting) structures. In this paper, a previously validated 1990 Ford Taurus FE model was used to analyze the effect of compliance in the guard support members on its dynamic performance. Two guard systems, one with rigid supports and another with some compliance in the supports were modeled.