Testing of Production Prototypes of a self-protective Headband for Car Occupants

This publication is the third in a series of reports for the ATSB in which we have detailed the development of a protective headband for car occupants. In CR193, we documented the results of tests made to determine the energy absorbing characteristics of several candidate materials. CR205 reported further investigations of possible production grade materials and discussed aspects of the design that would determine the general form of the headband in a consumer version of the product.

This report details the results of tests made on the headband, which may be compared with the requirements of the United States Federal Motor Vehicle Safety Standard 201. That standard requires a certain level of head protection for the occupants of the vehicle from the upper interior of the car. The standard stipulates that a free motion headform be launched against the interior components of the car at a speed of up to 24 km/h. The requirement in these tests is that a modified value of the Head Injury Criterion, HIC(d), be less than 1000. The nature of the test required by FMVSS 201 provides a method by which the effectiveness of the headband may be assessed.

In this study, prototype headbands were fabricated according to a design developed in CR205. The energy absorbing element was machined from a solid block of expanded polypropylene and sandwiched between a styrene outer shell and a cloth liner. These prototypes were designed to be dimensionally and materially similar to a future consumer version of the product (should such a version arise).

The aim of the testing was to choose structures that would behave similarly to structures found in the interior of a car. The test structure was designed so that the impact stiffness could be varied. The structure was such that a straightforward execution of the test procedure (without the headband) produced HIC(d) results that ranged from a pass (717), to a moderate fail (1623). The tests were then repeated with a headband attached to the headform so that a comparison of impacts with and without the headband could be made.

Two grades of EPP were evaluated in this study; a 50 g/l density foam and a 70 g/l density foam. The tests showed that headbands manufactured from either grade of EPP provided substantial protection with the most severe impact producing a HIC(d) value of 601 (compared to 1623 for the bare headform in the same test). Further analysis of the dynamic crush characteristics of the headband showed that the 70 g/l EPP was a more efficient energy absorber than the lower density material. This was also reflected in lower HIC(d) values in tests that used the 70 g/l foam. The headband provided protection by limiting peak loads and absorbing significant amounts of energy.

In frontal impacts, the headband would provided significant head protection for car occupants. This would be particularly beneficial for the occupants of older vehicles. Parts of Australia have a median vehicle age around 10 years. That implies that, on current trends, it will take 10 years before a new vehicle safety feature, introduced today, will be present in half the car fleet in this country. The headband may provide the drivers of older cars some of the benefits of new safety features immediately. We expect that there would also be benefits for the occupants of newer cars, as the headband would provide protection from striking objects that are not protected by padding or airbags.