LOW-VELOCITY IMPACT DAMAGE IN FILAMENT-WOUND COMPOSITE PRESSURE BOTTLES

In an effort to better understand the damage that develops in filament -wound composite structures when they are subjected to low velocity im pact loads, a series of low velocity impact experiments was performed on small (146 mm (5.75 in.) diameter) filament wound pressure bottles. Three different material systems, IM7/3501-6ATL, IM7/X8553-45, and IM 7/977-2, were evaluated. Three impact energy levels, 4.07 J (3.0 ft-lb ), 6.78 J (5.0 ft-lb), and 9.49 J (7.0 ft-lb), were applied. Dye penet rant enhanced X-ray radiography was used to assess the damage that res ulted from the impact loading. The through-the-thickness location of d amage was assessed by means of stereo radiography. The two material sy stems with toughened epoxy matrices (X8553-45, 977-2) generally develo ped smaller damage zones than the system with a standard epoxy matrix (3501-6ATL). Two distinct types of fiber fracture were observed. All o f the systems exhibited a tendency to develop fiber fracture in the in terior helical layers, usually at locations removed from the impact si te. Some of the specimens fabricated from the material systems with th e toughened epoxy matrices also developed fiber fracture in the exteri or hoop layers. This second fiber fracture mode appeared to originate at the point of contact between the impacting tup and the specimen.