Study of Fatigue Mechanisms in a 3D Carbon-Carbon Composite: Addendum, Torsion Test Results

摘要

Results are presented of torsion static and fatigue tests on three-dimensional carbon-carbon. The test set up and procedures are explained, and apparatus, including a power lift actuator, a rotary variable differential transformer, strain gauges, and a bridge amplifier meter, are listed. Stress and moduli calculations are discussed and attention is focused on each of the five tests performed. The torsion tests are shown to result in permanent deformation which increases with number of cycles and a torsional stiffness which decreases a small amount but approaches a stable value asymptotically as the number of cycles increases. It is concluded that this three-dimensional carbon-carbon has two torsional differences, one at very low angles of twist and one at high angles. This indicates a static shear behavior for the low shear strains and a 'bundle slip' or crack enlargement behavior in shear for high shear strains.