Damage Initiation in Two-Dimensional, Woven, Carbon-Carbon Composites
Abstract
This thesis examines the failure initiation characteristics of uncoated, 2-D, warp-aligned, ACC-4 Carbon Carbon Composites in standard three- point bend experiments. ASTM-2344 short beam shear tests were run on specimens with a span-to-depth ratio of four, five, and fifteen. Failure load and indications of failure initiation were recorded on a load-displacement curve. Actual specimen mid-span displacement was recorded instead of the usual cross- head displacement. Specimens were micro photographed for pre- and post-test comparisons. Halftone reproductions of the photographs are included to show similarities and differences in failures of the various length specimens. A linear elastic NASTRAN finite element model was used to predict the global stress field. Displacements predicted by this model are within 5% of mean experimental values. Failure initiation sites and loads were predicted with contour plots of the Tsai-Wu and Tsai-Hill failure criteria. This model predicts failure initiation at loads near 50% of maximum load in the short specimens. A series of increasing step load test were run to collect photos of specimen damage at loads less than maximum. The results are consistent with model predictions with initial damage occurring at 45% of max load in the short beam. Theses.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1988
- Accession Number
- ADA202617
Entities
People
- James C. Dendis
Organizations
- Air Force Institute of Technology