Damage Progression in Graphite-Epoxy by a Deplying Technique.

摘要

Open hole and mechanically fastened joint specimens employing three different symmetric stacking sequences were used for this project. Replicates for each specimen type and stacking sequence were loaded to ultimate and four load levels below ultimate to produce specimens containing progressive amounts of damage. During loading of each specimen Acoustic Emissions (AE) were monitored as a function of load. Specimens from each of the four load levels were inspected for matrix cracking, delamination and fiber bundle fractures using penetrant enhanced X-ray radiography and the deply technique. The deply technique, a unique but destructive inspection method, was used to separate the graphite-epoxy composite into its individual laminae while maintaining the integrity of each lamina. With the application of a gold chloride penetrant before deplying, the internal matrix damage as well as fiber bundle fracture could be readily observed on the surface of the individual laminae. These damage observations were recorded on a Lamina Damage Characterization Chart for each specimen. These charts contain pictorial sketches, with fiber orientations shown, for each lamina of the specimen segment deplied. A summary of the inspection results including photomacrographs of typical observed damage along with examples of charted damage is presented in the main body of the report. (Author)