Sealed, Blast-Resistant Windows for Retrofit Protection Against the Terrorist Threat

Abstract : Recent world events have drawn attention to threats that extend to the civilian population. A protective design approach for retrofit of existing structures has become increasingly palatable, despite the high costs, because of terror threats that were once considered "remote." Windows have always been one of the weakest points in most structures, primarily because of the requirement for transparency. Recent research at the Air Force Research Laboratory (AFRL) has addressed the difficult problem of retrofitting windows against the "combined threat" of a bomb blast followed by a chem-bio attack. In the recent Gulf War, several specific threats were highlighted for both US military forces and Israeli civilians. The most obvious threat to civilians in that conflict was explosive, as about forty SCUD missiles were launched into civilian areas of Israel. Less obvious, but even more potentially dangerous, was the threat of chem-bio weapons of mass destruction. Recognizing the weakness of entry points to chem-bio contamination, many Israeli civilians used plastic sheeting on the interior side of their windows during periods of increased threat. Recent research at AFRL has shown that, although cost-effective, this approach is woefully inadequate at the blast-pressures which would be expected in a terror attack, as clearly demonstrated by a sequence of still frames taken from blast test videotapes. The paper briefly discusses early pioneering work at AFRL that dealt with the use of clear polymer membranes (i.e., plastic sheets) to combat the combined threat, but the body of the paper focuses on recent developments in the evolution of "membrane" windows. The AFRL windows will resist blast high blast pressures, and will remain sealed against subsequent chem-bio attack, due to a patent-pending design which includes sever