Safety Performance Comparison of 30 MIL HPR Laminated and Monolithic Differentially Tempered Windshields

Conventional 30 mil HPR laminated and wide-zone monolithic tempered windshields are compared on a safety performance basis from the stand-points of occupant injuries from frontal force collisions and injury or loss of control from breakage from high speed external impact of stones. All experiments were conducted with the windshields installed by conventional methods in an automobile.

Occupant injury potential as measured by the Severity Index for brain damage at a 30 mph barrier impact simulation was approximately two times as high for the tempered as for the laminated windshields, although only one tempered windshield exceeded the recommended maximum value of 1,000. Severe lacerations resulted in all impacts in which the tempered glass broke. Less severe lacerations were found for the laminated windshield impacts at comparable speeds.

External stone impacts to the laminated windshields at speeds up to 75 mph resulted in only localized damage and had essentially no affect on the driver while each case of fracture of the tempered windshield resulted in 15 to 20 pounds of glass particles entering the vehicle and causing considerable driver distraction.

On the basis of the experimental results of this program, the authors conclude that the safety characteristics of laminated windshields are superior to those of the tempered windshields.