AFRL entered into a Cooperative Research and Development Agreement (CRADA) with Dlubak Technologies, Inc., of Freeport, Pennsylvania, to pursue ongoing research in blast-resistant window and glazing technologies. Dlubak Technologies—a 50-year-old glass manufacturing company—provided fullscale window and frame products (see Figure 1) to AFRL for blast mitigation testing at AFRL's Sky Ten Range, Tyndall Air Force Base, Florida.
During recent conflicts, the US has seen a dramatic increase in terrorist bombings as instruments of warfare. AFRL engineers and scientists are actively exploring blast mitigation technologies that will help minimize the casualties caused by explosive attacks targeting buildings and expeditionary structures. Blast mitigation technology is particularly important, since flying glass and wall debris created by the detonation cause the vast majority of blast-related injuries and fatalities.
Research performed under this CRADA has produced a successful blast-resistant window that uses protective glazing in conjunction with a perimeter-anchored laminate. For these state-of-the- art windows, Dlubak Technologies fabricates glass with a polymer laminate layer that extends beyond the glass edges. Installers anchor these "laminate tails" in the window frame using one of several techniques. Dlubak is already marketing LAMLOK, its patent-pending laminate-locking system, for commercial sale, due in part to product performance demonstrated during AFRL research trials conducted under this CRADA. Throughout the effort, AFRL researchers studied various LAMLOK systems, including a polyvinyl butyral hinged-style window system for post-blast emergency exit and another variation for use in standard window frames having either flat or curved glass panels. Based on the research results, Dlubak created an improved version of the interlocking mechanism employed for standard window frames. The CRADA is intended both to facilitate further blast-resistant window research and to promote future investigations of related technologies.
In addition to engaging in the blast-resistant window research, AFRL engineers and scientists are investigating several systems designed to prevent wall fragments from penetrating a building's interior. As a result of this wall debris research, AFRL pioneered various techniques for retrofitting concrete block walls with blast-resistant polymers.1 Engineers can retrofit existing walls either by spraying or troweling the material onto the wall surface or by installing prepared façade panels to cover the existing surface. These alternatives allow engineers to better match the most suitable application method to the specific need, a determination that normally depends upon factors such as wall area, manpower skills, equipment availability, and budgetary resources. As part of an additional project focused on examining the blast resistance of insulated concrete products widely used in concrete construction, researchers are also evaluating the benefits of polymers for blast protection in new construction (as a stay-in-place concrete form).
AFRL has state-of-the-art facilities for conducting blast protection research activities. The lab's Range Operations and Support Group has two reaction structures at Sky Ten, each with the capability to simultaneously expose up to eight windows and/or wall systems to a 1,000 lb TNT charge (see Figure 2). Researchers monitor and control the blast from a master control board that provides over 100 channels for recording critical scientific data during and after the detonation. In addition, high-speed digital and traditional video cameras record the event to provide researchers with yet another tool for analyzing results.
Dr. Robert Dinan, Mr. Jeff Fisher (Applied Research Associates), and Ms. Mindy Cooper (General Dynamics), of the Air Force Research Laborator y's Materials and Manufacturing Directorate, wrote this article. For more information, visit http://www.afrl.af.mil/techconn_index.asp . Reference document ML-H-05-36.
1 Anderl, T., Dinan, R., and Porter, J. "Blast Protection Elastomer Coating." AFRL Technology Horizons®, vol 4, no 3 (Sep 03): 13. http://www.afrlhorizons.com/Briefs/ Sept03/feature1.html.