From inverted drop height of 18 inches.

Vehicle Crashworthiness in Inverted Drop Tests

Inverted drop testing of vehicles to test the integrity of roof structures is a methodology that has long been used by the automotive industry. In the late 1960's, SAE developed a standardized procedure to perform full vehicle inverted drop testing. Mercedes-Benz uses inverted drop testing as one of their many standard crash tests and has recommended inverted drop tests in its Comments to the Docket regarding roof strength rulemaking. The ESV projects in the 1970's had a design goal based upon performance of the vehicles in a two-foot drop. The National Highway Traffic Safety Administration (NHTSA) is currently evaluating inverted drop testing as an upgrade to FMVSS 216.

In our laboratory, we have employed the inverted drop test methodology on a late model production sport utility to simulate the damage incurred by a real world rollover accident. The extent and shape of residual damage was matched to the accident damage. A second vehicle was reinforced based upon techniques and methods published in SAE paper 980209. These practical techniques include unique reinforcing approaches such as a composite sandwich panel roof, increasing internal metal gage and filling existing roof pillars and headers with rigid composite materials. These reinforcements enhance the original structures by increasing load capacity, energy absorption and reducing section collapse. The reinforcements also proved to be effective in reducing the effects of stress risers inherent in the production structure. The composite sandwich panel roof creates a substantial load carrying and energy absorbing structure where previously there was none. Incorporation of these techniques demonstrated an increase in roof strength of approximately four-fold, resulting in improved resistance to intrusion with a minor weight addition.