Development of a Damage Based Design Criterion for Fiber Reinforced Vessels

The objective of this investigation was to develop a damage based criterion for the design of fiber reinforced vessels. The investigation involved the use of acoustic emission to determine the onset of damage in coupon specimens. The variables investigated were fiber architecture and resin type. Damage was determined with the well-established Felicity effect.

The data gathered from the acoustic emission testing was used to develop a damage based design criterion. The damage based criterion addresses the onset of damage as opposed to the ultimate stress approach that is used in the governing codes and standards. The damage based approach provides additional insight into the behavior of the composite.

Laminas made with flexible and brittle resins are compared. Laminas made with flexible resins were found to sustain higher levels of stress prior to damage than laminas made with more brittle resins for matrix dominated behavior. Little difference was observed between laminas made with brittle resins and those made with flexible resins for fiber dominated behavior.

The damage criterion was used in conjunction with finite element analysis to design modifications to a 21’-6” tall by 7’-0” diameter filament wound pressure vessel. The modifications made were a 24”diameter manway and an 8” diameter nozzle.

The modifications to the vessel were implemented. The vessel was tested to a superposed pressure of 23.0 psi. Acoustic emission monitoring was performed during re-loadings and no signs of significant distress were found.