Development and Evaluation of the Quadrant Ring Test Method

Testing of ring-shaped specimens often is required for determining the hoop-direction mechanical properties of cylindrical composite structures. A quadrant ring test method was developed in an effort to produce a relatively uniform stress distribution in the ring specimen using a conventional tensile testing machine. Finite element analysis results indicated that the four-sector quadrant test is capable of producing a more uniform stress distribution in the specimen than the split-disk test. However, similar tensile strengths were obtained using the quadrant and split-disk tests, both significantly below those obtained from tensile testing of flat specimens. The lack of improvement in tensile strength produced by the quadrant test was caused by small rotations of the fixture quadrants during loading, producing greater peak stresses than for the ideal case of radially displaced sectors. These results suggest that test fixturing that produces a true outward radial displacement of the fixture sectors is required to produce accurate tensile strengths.