Tension-Compression Fatigue of a Hybrid Polymer-Matrix/Ceramic-Matrix Composite at Elevated Temperature

Fully reversed tension-compression fatigue of a hybrid material comprising polymer matrix composite (PMC) co-cured with a ceramic matrix composite (CMC) was investigated. The PMC portion had a polyimide matrix reinforced with 15 plies of carbon fibers woven in an eight-harness satin weave (8HSW). The CMC portion had three plies of a quartz-fiber 8HSW fabric in a zirconia-based ceramic matrix. The hybrid PMC/CMC was developed for use in aerospace thermal protection systems (TPS). Hence, the experimental setup aimed to simulate the TPS service environment-the CMC side was kept at 329 degrees C, whereas the PMC side was open to laboratory air. Compression stress-strain response was studied, and compressive properties were measured at room and elevated temperature. Tension-compression fatigue tests were conducted at elevated temperature at 1.0 Hz. The evolution of tensile and compressive strains with fatigue cycles, as well as changes in the stress-strain hysteresis behavior and stiffness were examined. The tension-compression fatigue of a PMC with the same constituents and fiber architecture as the PMC portion of the PMC/CMC was studied for comparison. Tension-compression fatigue was found to be more damaging than tension-tension fatigue for both materials. The PMC outperformed the PMC/CMC in tension-compression fatigue. Post-test examination showed widespread delamination and striking non-uniform deformation modes of the PMC/CMC.