Blast-Resistant Window Concepts

Terrorist bombs threaten American civilians and military personnel both at home and abroad. Analysis of data from previous terror attacks indicates the largest number of injuries result from projected glass shards from shattered windows and facades. Three key issues have led to increased interest in new window materials, as well as changes in building design codes: (1) actual terror attacks; (2) the threat of future terror attacks; and (3) monetary losses due to hurricanes. New protective products include a wide variation of films and laminated glasses for retrofit / replacement. Air Force Research Laboratory (AFRL) research has shown that these protective films will reduce the fragmentation of the enclosed glass. However, protective films that are not anchored will not provide retention of the film/glass system under the severe blast loadings expected from terror bombs. The paper introduces the Flex window, a patent-pending blast-resistant window developed at AFRL, along with key design concepts. In addition, the paper presents results from actual blast tests of the Flex window. Tabular data and photo-documentation is used to illustrate the ability of the Flex window to handle blast pressures a full order of magnitude greater than the typical commercial “blast proof” window. New AFRL methods for modeling both exterior and interior loading functions are presented. In addition, possible response modes are discussed, based on observations of high-speed video recordings.