Elastoplastic response of unidirectional graphite/aluminum under combined tension-compression cyclic loading
MetadataShow full item record
A test fixture for combined tension-compression cyclic testing of unidirectional composites was designed and characterized using 606l-O aluminum specimens. The elastoplastic response of graphite/aluminum l5Â° off-axis and 90Â° specimens under tension-compression cyclic loading was subsequently investigated at three temperatures, -l50Â°F, room temperature and 250Â°F. The test results showed that the tensile response was predominantly elastoplastic, whereas the compressive response could not be characterized exclusively on the basis of the classical plasticity theory. Secondary dissipative mechanisms caused by inherent voids in the materialâ s microstmcture had an apparent influence on the elastoplastic behavior in compression. At different test temperatures, the initial yield stress in tension and compression were translated in the tension direction with increasing temperature. This is believed to be caused by residual stresses induced inieach phase of the composite. The micromechanics model proposed by Aboudi was subsequently employed to correlate the experimental and analytical results at room temperature. A semi-inverse methodology was incorporated to determine the in-situ properties of the constituents. Comparison between the analytical and experimental results showed good agreement for monotonic tensile response. For tension-compression cyclic loading, fairly good correlation was obtained for l5Â° specimens, but poor for 90Â° specimens. The major cause of the discrepancy is suggested to be caused by the secondary dissipative mechanisms.
- Masters Theses