Experimentally investigating annealed glazing response to long-duration blast

This paper examines the response of annealed glazing panels when subject to long-duration blast loading. In particular, it quantifies glazing response metrics while varying glazing thickness, glazing area, aspect ratio, and edge conditions. With positive phases exceeding 100 ms long-duration blasts result in significant specific impulse and dynamic pressures. The transient dynamic response of annealed glazing during these events is a complex function of structural arrangement, material properties, and explosive proximity. Twelve full-scale air blast trials using a heavily armored test structure subjected 24 glazing panels to approximately 14-kPa free-field overpressure and approximately 110-ms positive-phase duration. Results are reported where it is shown that elastic-edge supports can prevent glazing breakage better than rigidly clamped arrangements when suitable panel dimensions are employed. Fragmentation modes are also demonstrated to be a function of edge conditions, with elastically supported panels producing large, angular fragments. In contrast, rigid arrangements are shown to induce localized impulsive stress transmission at clamped edges, leading to significant cracking and small fragments. Substantially different fragment masses and geometries demonstrate the need to accurately quantify edge supports when appraising fragment hazard. Quantification of peak panel deflection, breakage time, and applied breakage impulse is then presented, with results showing the influence of edge supports and aspect ratio on glazing response to be dependent on proximity to the threshold area for a particular thickness.