Modeling the Crack Growth Rates of a Titanium Matrix Composite Under Thermomechanical Fatigue

Abstract

The crack growth characteristics of a 4-ply, unidirectional, titanium matrix composite, SCS-6/Ti-6Al-2Sn-4Zr-2Mo, subjected to thermomechanical fatigue were investigated. A linear summation model was developed to predict the isothermal and thermomechanical fatigue (TMF) crack growth rates of the composite. The linear summation approach assumes the total fatigue crack growth rate is a combination of a cycle-dependent and a time-dependent component. To assist the modeling effort, a series of isothermal, in-phase, and out-of-phase crack growth tests were conducted. The test temperatures ranged from 150‡C to 538‡C and the fastest thermal frequency was 0.0083 Hz. With the exception of the 150‡C isothermal test, the model was able to correlate all the baseline fatigue crack growth test data between δK of 50 to 90 MPa √m. In addition, the model was able to predict the fatigue crack growth rate of a proof test which involved a continual change in temperature range and load range to produce a constant crack growth rate. The proof test began under isothermal conditions at the maximum temperature and ended under in-phase TMF conditions.

Fracture Toughness Analysis of Delamineted Composites under Variable Temperatures

“…1 and Tab. 2, measured in a previous investigation [17,18,19], With a nominal ply thickness of 0.0626 mm and the reference stacking sequence considered in the study is [90-0]8 s. The values for tensile and compressive fiber fracture can be obtained from compact tension (CT) and compact compression (CC) tests as proposed by Pinho et al [20]. According to this formulation, the value depends on the laminate stacking configuration.…”

Evaluation of Damage Evolution and Material Behavior in a Sigma/Ti-6242 Composite Using Nondestructive Methods

“…The lamellar regions are most likely the result of non-uniform cooling rates during the plasma spraying operation. In general, the equiaxed structure is a desirable microstructure for fatigue crack initiation resistance; whereas, the lamellar structure is beneficial for fatigue crack propagation resistance [45].…”