Observation and prediction of damage evolution in continuous fiber titanium matrix composites Academic Article uri icon


  • Titanium matrix composites (TMC's)are known to undergo significant environmental degradation at elevated temperatures. As a part of this research effort the TMC SCS-6/Ti-21S [0]4 has been fatigue tested at 482C and 650C. Additional specimens have been oxidized at 700C and then fatigued at 482C to failure. The life limiting physical mechanisms identified from the experiments are material inelasticity, surface embrittlement and subsequent surface cracking, fiber/matrix debonding, fiber-bridging, and eventual fiber failure. A model incorporating all of these physical phenomena has been developed in an ongoing effort by the authors. This model will be briefly presented herein. The model utilizes the finite element method coupled with models for material inelasticity, surface embrittlement, and crack propagation. Material inelasticity is predicted using Bodner's unified viscoplastic model. Crack propagation is modeled via the inclusion of cohesive zone elements. Surface embrittlement is accounted for through the degradation of material properties. Both monotonic and fatigue loadings have been modeled at 482C and 650C for oxidized and unoxidized specimens. Results indicate that surface crack propagation rates are significantly slower when matrix viscoplasticity is included in the model instead of elasticity. Furthermore, surface cracking in degraded specimens enhances fiber stresses compared to undegraded specimens. This difference apparently causes premature failure of the degraded composite.

published proceedings

  • American Society of Mechanical Engineers, Materials Division (Publication) MD

author list (cited authors)

  • Allen, D. H., Foulk, J. W., & Helms, K.

complete list of authors

  • Allen, DH||Foulk, JW||Helms, KLE

publication date

  • January 1997