Experimental Testing of Composite Rings under Uniform External Hydrostatic Pressure

The results obtained from the experimental testing of hoop wound S-2 GlasdEpoxy and AS41 PPS composite rings are presented here. In this study, the effects of different material system and thickness on failure are investigated. A custom, volume controlled pressurization set-up was designed and built for the tests. Initial imperfection in the ring specimens were measured prior to testing and the hoop modulus of the rings tested were measured and compared with Classical Lamination Theory predictions. Results indicate that the failure mode is global ring buckling. The initial postbuckling behavior is stable for both S-2 GlassIEpoxy and AS4/PPS rings. The rings tested were elastic and no permanent deformation was observed. Out-of -plane twist buckling was observed in both the thick S-2 Glass1 Epoxy and AS4RPS rings (R/ t < 9.5). Mode three buckling was observed when the ring specimens were constrained by the sealing ring (rubber Oring) used in the experiment, however, mode two buckling was obtained when this constraint was removed, via a bladder type loading.