SYMPOSIA PAPER Published: 01 January 1996

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


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.

Author Information

Blatt, D
Materials Directorate, Wright Laboratory, Wright-Patterson AFB, OH
Nicholas, T
Materials Directorate, Wright Laboratory, Wright-Patterson AFB, OH
Grandt, AF
School of Aeronautics and Astronautics, Purdue University, West Lafayette, IN
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Developed by Committee: E08
Pages: 352–370
DOI: 10.1520/STP16462S
ISBN-EB: 978-0-8031-5325-7
ISBN-13: 978-0-8031-2001-3