PERIODIC INSPECTION OF COMPOSITE WRAPPED PRESSURE VESSELS USING ACOUSTIC EMISSION

摘要

The most common type of composite containers used by the Navy to store compressed gases are Type 3 composite cylinders. Designs of this type of cylinder are carbon fiber full wrap of aluminum liners with 3,4 factor of safety. Under Department of Transportation (DOT) jurisdiction, the recertification procedure for the Navy Type 3 composite cylinders requires both a hydrostatic test and an internal visual inspection every five years over the allowable 15-year service life. Acoustic emission baseline tests were performed on over fifty "good" Naval Sea (NAVSEA) Systems Command Type 3 cylinders. Damage and/or fatigue cycling was then introduced into fourteen (14) of the cylinders. The types of damage included impact damage in thirteen cylinders, and an artificial cut in the Fiber Reinforced Polymer (FRP) overwrap in one cylinder. Tests were designed to degrade the structural condition of the cylinders in a fashion representative of service-induced damage, and to a degree that would significantly reduce the burst pressure. Once the cylinders had been subjected to damage and simulated service cycling, they were AE tested again. Testing of damaged cylinders resulted in a dramatic increase in the amount of AE activity compared to the AE activity prior to the damage. A consistent correlation was observed between burst pressure and AE activity observed. An accept/reject criterion was developed to differentiate those cylinders with acceptable burst strength from those with unacceptable burst strength.