Mechanical Properties and Fatigue Behavior of Unitized Composite Airframe Structures at Elevated Temperature
AIR FORCE INSTITUTE OF TECHNOLOGY WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
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The tension-tension fatigue behavior of newly developed polymer matrix composites PMCs and that of a unitized composite was studied. The PMCs investigated in this effort consisted of an NRPE a high-temperature polyimide matrix reinforced with carbon fibers. Two PMCs consisting of the aforementioned matrix with different fiber architectures were studied one reinforced with a 2D woven fiber fabric and another reinforced with a non-crimp 3D orthogonal woven fiber fabric. The unitized composite consisted of a PMC co-cured with a ceramic matrix composite CMC layer, which acts as a thermal barrier. The PMC portion of the unitized composite had the same constituent properties and weave as the aforementioned 2D PMC. The CMC layer consisted of a zirconia-based matrix reinforced with a 2D woven quartz fiber fabric. For all three material systems 3D PMC, 2D PMC, and unitized composite, material properties were investigated for both on-axis 090 deg and off-axis plus-minus 45 deg fiber orientations. Tensile properties were evaluated at 1 room temperature and 2 with one side of the specimen at 329 C and the other side exposed to ambient air. Tension-tension fatigue tests were conducted at elevated temperature at a frequency of 1.0 Hz with a ratio of minimum stress to maximum stress of R 0.05. Fatigue run-out for this effort was defined as 2x10 5 cycles.
- Laminates and Composite Materials