A study was conducted of the effect on the geometric eccentricity due to the resulting indentation from impact. To prevent the interaction of any other damage, uncured sandwich panels were indented with a 25-mm-diameter steel up to a depth of 1.6, 3.2, and 4.8 mm and then cured, resulting in an indented facesheet. A total of 12 specimens with IM7/8552 [90/0]
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facesheets cocured to 25-mm thick Nomex core were tested. All specimens were 83 mm in width and 356 mm in length. The specimens were loaded in uniaxial compression and strain measurements were made. The strain gage data indicated that although the manufactured indentations displaced deeper into the core, little growth transverse to the load was observed. In a few cases, no growth was observed prior to ultimate failure. In all cases the ultimate strength of the specimens with manufactured indentations was greater than comparable specimens with impact damage. Also, the ultimate failure of the indented specimens initiated away from the indentation. Thus, the manufactured indentations do not accurately model the dominant damage mechanisms found in similar panels with damage resulting from impact.
