The objective of this research was to determine the effect of thermal cycling
combined with mechanical loading on the development of microcracks in M40J/PMR-II-
50, the second generation aerospace application material. The objective was pursued by
finding the critical controlling parameters for microcrack formation from mechanical
stress-thermal cycling test.
Three different in-plane strains (0%, 0.175~0.350%, and 0.325~0.650%) were applied
to the composites by clamping composite specimens (M40J/PMR-II-50, [0,90]s, a unitape
cross-ply) on the radial sides of half cylinders having two different radii (78.74mm
and 37.96mm). Three different thermal loading experiments, 1) 23oC to âÂÂ196oC to 250oC,
2) 23oC to 250oC, and 3) 23oC to -196oC, were performed as a function of mechanical inplane
strain levels, heating rates, and number of thermal cycles. The apparatus generated
cracks related to the in-plane stresses (or strains) on plies. The design and analysis
concept of the synergistic stress-thermal cycling experiment was simplified to obtain main and interaction factors by applying 2k factorial design from the various factors
affecting microcrack density of M40J/PMR-II-50.
Observations indicate that the higher temperature portion of the cycle under load
causes fiber/matrix interface failure. Subsequent exposure to higher stresses in the
cryogenic temperature region results in composite matrix microcracking due to the
additional stresses associated with the fiber-matrix thermal expansion mismatch.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/4213 |
| Date | 30 October 2006 |
| Creators | Ju, Jaehyung |
| Contributors | Morgan, Roger J. |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | 10238867 bytes, electronic, application/pdf, born digital |
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