Fatigue Characterization of SiC/SiC Ceramic Matrix Composites in Combustion Environment

2020 ◽  
Author(s):  
Ragav P. Panakarajupally ◽  
Joseph Elrassi ◽  
K. Manigandan ◽  
Gregory N. Morscher
Keyword(s):  
Electrical Resistance ◽  
Fatigue Behavior ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Fatigue Tests ◽  
Matrix Composites ◽  
Residual Properties ◽  
Sic Ceramic ◽  
Post Test ◽  
Combustion Environment

Abstract Fatigue behavior of woven melt infiltrated (MI) SiC/SiC ceramic matrix composites (CMCs) was investigated under a tension-tension fatigue condition in a combustion environment. A special experimental facility is designed to subject the CMCs under simultaneous mechanical and combustion conditions which is more representative of some conditions experienced by the hot section components of a jet engine. The MI SiC/SiC ceramic matrix composites considered in this study consists of a SiC matrix densified with liquid Si infiltration, BN interphase and reinforced with two different fibers namely Hi-Nicalon type S and Tyranno SA fibers. A high velocity oxygen fuel (HVOF) gun is used to create the representative combustion condition and a horizontal hydraulic MTS machine to apply the mechanical loading. Several fatigue tests were conducted at different stress levels with a stress ratio of 0.1, frequency of 1 Hz and the specimen surface temperature at 1200 °C. Similar tests were conducted in an isothermal furnace condition at 1200°C for comparison. Electrical resistance (ER) was used to monitor the tests. A reduction in the fatigue life was observed for the two MI systems under combustion conditions in comparison to the isothermal furnace condition at the same applied stress level. This is attributed to the presence of harsh combustion environment present in the burner rig. Electrical resistance showed some promising results in monitoring the temperature and detecting damage in the specimen. Runout condition was set as 24 H (86400 cycles) in burner rig and 100 H (360000 cycles) in furnace environment. Specimens that achieved the runout condition were subsequently tested under monotonic tension testing at room temperature after cooldown to evaluate the residual properties. Residual strength results showed a significant strength reduction in both the furnace and burner rig environments. Post-test microscopy was conducted on the fracture surfaces and longitudinal polished sections of the failed specimens to understand the oxidation behavior and damage mechanisms.

scholarly journals Fatigue Characterization of SiC/SiC Ceramic Matrix Composites in Combustion Environment

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Ragav P. Panakarajupally ◽  
Joseph El Rassi ◽  
K. Manigandan ◽  
Gregory N. Morscher
Keyword(s):  
Fatigue Behavior ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Fatigue Tests ◽  
Matrix Composites ◽  
Residual Properties ◽  
Significant Strength ◽  
Sic Ceramic ◽  
Post Test ◽  
Combustion Environment

Abstract Fatigue behavior of woven melt infiltrated (MI) SiC/SiC ceramic matrix composites (CMCs) was investigated under a tension–tension fatigue condition in a combustion environment. A special experimental facility is designed to subject the CMCs under simultaneous mechanical and combustion conditions which is more representative of some conditions experienced by the hot section components of a jet engine. The MI SiC/SiC CMCs considered in this study consists of a SiC matrix densified with liquid Si infiltration, BN interphase, and reinforced with two different fibers, namely, Hi–Nicalon type S and Tyranno SA fibers. A high velocity oxygen fuel (HVOF) gun is used to create the representative combustion condition and a horizontal hydraulic MTS machine to apply the mechanical loading. Several fatigue tests were conducted at different stress levels with a stress ratio of 0.1, frequency of 1 Hz, and the specimen surface temperature at 1200 °C. Similar tests were conducted in an isothermal furnace condition at 1200 °C for comparison. Electrical resistance (ER) was used to monitor the tests. A reduction in the fatigue life was observed for the two MI systems under combustion conditions in comparison to the isothermal furnace condition at the same applied stress level. This is attributed to the presence of harsh combustion environment present in the burner rig. ER showed some promising results in monitoring the temperature and detecting damage in the specimen. Runout condition was set as 24 H (86400 cycles) in burner rig and 100 H (360000 cycles) in furnace environment. Specimens that achieved the runout condition were subsequently tested under monotonic tension testing at room temperature after cooldown to evaluate the residual properties. Residual strength results showed a significant strength reduction in both the furnace and burner rig environments. Post-test microscopy was conducted on the fracture surfaces of the failed specimens to understand the oxidation behavior and damage mechanisms.

scholarly journals Thermomechanical Characterization of SiC/SiC Ceramic Matrix Composites in a Combustion Facility

Ceramics ◽  
2019 ◽  
Vol 2 (2) ◽  
pp. 407-425 ◽  
Author(s):  
Ragav P. Panakarajupally ◽  
Michael J. Presby ◽  
K. Manigandan ◽  
Jianyu Zhou ◽  
George G. Chase ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Mechanical Loading ◽  
High Velocity ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Fatigue Loading ◽  
Matrix Composites ◽  
Front Side ◽  
Sic Ceramic ◽  
Combustion Environment

A combustion facility which includes uniaxial mechanical loading was implemented that enables environmental conditions more akin to jet engine environments compared to conventional static environment tests. Two types of woven SiC/SiC ceramic matrix composites (CMCs), melt-infiltrated (MI) and chemical vapor infiltrated (CVI), were subjected to fatigue loading in the combustion facility and under isothermal furnace conditions. Some CVI test coupons were coated with a multilayer environmental barrier coating (EBC) of mullite + ytterbium monosilicate using slurry infiltration process to demonstrate the performance with a coating. Combustion conditions were applied using a high velocity oxy fuel gun on the front side of the specimen and mechanical loading was applied using a horizontal hydraulic MTS machine. All the specimens considered were subjected to tension-tension fatigue loading at 100 MPa, stress ratio of 0.1 and specimen front-side surface temperature of 1200 ± 20 °C. Nondestructive evaluation (NDE) methods, such as electrical resistance (ER), was used as an in-situ health monitoring technique. Similar fatigue tests were performed in an isothermal furnace for comparison. A much lower fatigue life was observed for the uncoated specimens tested under combustion conditions in comparison to isothermal furnace condition. This difference in fatigue life was attributed to damage associated with added thermal stress due to the thermal gradient and higher rate of oxidative embrittlement due to the presence of high velocity combustion gases in the combustion environment. EBC coating increased the fatigue life in combustion environment. However, EBC coated specimens experienced spallation in the high-velocity flame due to the presence of micro cracks in the coating surface. Fracture surfaces of the failed specimens were investigated under the scanning electron microscope (SEM) to determine the extent of oxidation and damage.

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