Carbon fiber based composites are an essential material in weight-critical applications
such as in the aerospace industry. However, these materials are susceptible to
damage such as matrix microcracking and fiber/matrix debonding (diffuse damage),
which occurs at stresses much lower than the failure stress.
A T700/M21 [0/90]s laminate was tensile loaded to introduce diffuse damage and
prepared for a study on the initiation of transverse microcracks. The material was
tensile loaded in a [+45/-45]s orientation to induce diffuse damage. A diffuse damage
indicator was developed by measuring the decrease in shear stiffness. Samples with
diffuse damage levels of 0, 0.05, 0.10, 0.15, 0.20, and 0.25 were prepared to be tensile
tested in a [0/90]s orientation to induce microcracks.
A successful development of the microcracking test procedure was performed. The
edge of the material was studied with optical microscopy and x-ray to establish the
structure of the fiber bundle geometry when undamaged. A sample containing microcracks
was treated with diiodomethane dye penetrant, which successfully highlighted
microcracks during x-ray imaging. The application time was not sufficient to produce consistent x-ray images over time, so a 45 minute soak time was recommended
instead. The same damaged sample was subjected to a tomographic scan without
a dye penetrant and while unloaded. Transverse microcracks were successfully identified from the data, although the results were not clean enough and likely omitted
some smaller microcracks. Results are expected to be cleaner if performed during
tensile testing.
Future tensile testing will quantify the induced crack density of samples containing
various degrees of initial diffuse damage, either using x-rays with a dye penetrant or
using x-ray microtomography.
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/235331 |
| Date | 07 1900 |
| Creators | Traudes, Daniel |
| Contributors | Lubineau, Gilles, Physical Science and Engineering (PSE) Division, Amassian, Aram, Farooq, Aamir |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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