Safety Testing and Evaluation of Polycarbonate Vehicle Glazing Using Full Scale Crash Testing Procedures

This paper presents the results of a comprehensive research program addressing the safety issues pertaining to using Polycarbonate glazing for non-windshield vehicle glazing. A series of crash test procedures were used to evaluate the Polycarbonate glazing alternative. The test procedures utilized included High Speed Lateral Impact (HSLI), Narrow Object Intrusion or Pole Impact, Dynamic Rollover, and Inverted Vehicle Drop tests. It should be noted that component-level dynamic impact testing of a variety of Polycarbonate designs was previously conducted as part of this ongoing research program [1]. This testing included 40 lb guided headform and Free Motion Headform (FMH) testing.

In regard to vehicle glazing, there are a number of important occupant safety issues. These include occupant containment, injury due to occupant impact with glazing, and laceration. Throughout the project, emphasis was placed on the careful monitoring of the test results with regard to these three issues. The intent of this study was not to specifically highlight the safety benefits of Polycarbonate glazing, but more to fully investigate the Polycarbonate glazing alternatives to determine whether there are increased safety risks accompanying a switch to this type of glazing.

The vehicles that were used for this project are quite popular to the North American market. These vehicles included a 1997 Ford Taurus, a 1997 Chevrolet Cavalier, and a 1997 Dodge Grand Caravan. For each Polycarbonate test, the vehicle's non-windshield Tempered Glass glazing was replaced with 4 mm Polycarbonate glazing. The Polycarbonate glazing was bonded into the vehicle using an automotive adhesive common to the industry. Although this approach is not feasible for moveable window applications, one of the reasons it was chosen was to produce the highest possible loads on the Polycarbonate window.

Throughout this study, it became increasingly clear that there are many safety issues to consider with both Polycarbonate and Tempered Glass. From an injury standpoint, the three most common areas associated with glazing are laceration potential, impact injuries, and ejection. This project focused on these three areas. For the most part, the evaluation of the glazing performance with respect to these areas is direct and the techniques used for assessing these injuries is accepted by the safety industry. The difficulties arise when considering the relationship between impact injury and ejection. When considering overall safety, if there is glazing breakage, then there is higher potential for occupant ejection. Conversely, if there is not glazing breakage, then the potential for occupant ejection is eliminated (at least through the glazing), yet the injury potential due to glazing impact is increases. The issue arises as to how the injury due to the glazing impact compares to the injury potential when there is a partial or full ejection. Whenever there is an ejection of any kind, the range of objects that an occupant can strike is quite substantial and difficult to measure in laboratory testing. Therefore, one must carefully evaluate all potential and/or avoided injuries when considering the overall safety provided by one particular form of glazing compared to another.

In order to set the stage for the rest of the paper, it is important to briefly define a few terms as they are used here. A “Primary” impact is defined here as when there is direct glazing contact between the occupant and glazing.“Secondary” impact is defined as any occupant impact that is only possible when there is glazing breakage. The testing results revealed a number of significant trends. Based on the tests conducted in this study, the Polycarbonate glazing did not result in any major fractures due to the initial impact event in any of the test cases. Secondly, based on the testing, it has been shown that the impact injury potential of the Polycarbonate glazing appears to be no greater than other interior components of the vehicle. This is based upon film and data analysis in which contact between the occupant and glazing and other surfaces was studied.

Overall, the results of this testing indicate that there does not appear to be an added safety risk with Polycarbonate glazing when all the facets of occupant injury potential are considered, and, in addition, there may be a significant safety benefit in the form of occupant ejection containment.