As the power density of advanced engines increases, the need for new materials that are capable of high operating temperatures, such as ceramic matrix composites (CMCs), is critical for turbine hot-section static and rotating components. Such advanced materials can significantly increase engine operating temperatures relative to those with conventional superalloy metallic blades. They also show the potential to enable longer life, growth margin, reduced emissions, reduced weight, and increased performance when compared with superalloy blade materials.
Improving Foreign Object Damage Performance for 2D Woven Ceramic Matrix Composites A model simulates high-speed impact response of ceramic matrix composites. John H. Glenn Research Center, Cleveland, Ohio The increased temperature capability and reduced weight, both from lower material density and the ability to eliminate the need for component cooling, enable CMCs in turbine engine airfoil applications to provide significant advantages in increased specific power output. To date, however, CMCs have achieved only limited use in these applications due to concerns about the relative ease of CMC airfoil degradation compared with that of conventional airfoil materials. Concerns remain regarding potentially inferior resistance to impact damage from foreign objects. Because of the brittle nature of CMCs and the thin configurations required in airfoil design, impact from sand, loosened metallic particles, and other foreign objects ingested into aero engines can do damage ranging from localized surface and subsurface damage, to complete penetration.
A custom material constitutive model was developed to simulate the high-speed impact response of 2D woven fabric-reinforced ceramic matrix composites. A combined analytical, fabrication, and experimental program was performed to improve foreign object damage (FOD) resistance of CMCs. Finite element math models of the CMC material specimens and the high-velocity metal projectiles were developed to simulate impact testing. The models have been verified by reproducing experimental data measured on impacted CMC specimens.
These situations were performed first on baseline, balanced, warp-aligned symmetric material samples. Thereafter, candidate methods for potential improvement of the FOD resistance were analytically investigated through mathematical simulations of impact tests. This provided the basis for proposing manufacturing methods that have analytically demonstrated promise in mitigating impact damage.
The analysis tool enables a shorter design cycle because of the ability to quickly and cost effectively evaluate material system modifications relative to their FOD resistance. Specifically, the tool is a custom, strain rate and pressure-dependent material constitutive model for impact of 2D fabric-reinforced ceramic matrix composites.
This work was done by Edward J. Klock- McCook and Brian J. Sullivan of Materials Research & Design for Glenn Research Center.
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