Experimental testing of thick-walled graphite fiber composite rings

Test results are presented from pressurizing thick-walled, hoop-wound graphite fiber composite rings to very high internal radial pressures. Hydraulic pressures exceeding 275 MPa (40 000 psi) were obtained. The testing was performed on rings wound with two different resins: a cyanate ester and a bismaleimide (BMI) resin. To prevent axial delaminations at these high pressures, a thin bi-directional G11 cloth lining was used inside the rings. The rings were monitored with strain gages and acoustic probes as the pressure was applied. Flaw-free cyanate ester rings survived the testing, indicating that the nominal transverse (radial) compressive strength of hoop-wound rings is higher than 275 MPa (40 000 psi).