Title page for ETD etd-11172012-040311

Type of Document Master's Thesis
Author Lin, Mark Wen-Yih
URN etd-11172012-040311
Title Elastoplastic response of unidirectional graphite/aluminum under combined tension-compression cyclic loading
Degree Master of Science
Department Engineering Mechanics
Advisory Committee
Advisor Name Title
Aboudi, Jacob Committee Member
Herakovich, Carl T. Committee Member
Pindera, Marek-Jerzy Committee Member
  • Elastoplasticity
Date of Defense 1987-08-05
Availability restricted

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 l5° off-axis and 90° specimens under tension-compression cyclic loading was subsequently investigated at three temperatures, -l50°F, room temperature and 250°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 material’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 l5° specimens, but poor for 90° specimens. The major cause of the discrepancy is suggested to be caused by the secondary dissipative mechanisms.

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