Abstract: A burst panel assembly for normally covering a vent opening of structure which defines an area to be protected from the buildup of dangerously high internal pressures has two frangible panels disposed in spaced, face-to-face relationship along with a core of expanded polyurethane foam which functions to dampen vibrations received from the structure and transmitted to the frangible panels. The foam is introduced in an initially flowable condition into the space between the panels and thereafter expands while curing to a solidified configuration for continuously exerting pressure on both of the panels, to thereby substantially reduce the fatigue stress that would otherwise occur along lines of weakness of burst patterns that are formed in both of the panels.