Matrix fatigue cracking in {alpha}{sub 2} titanium matrix composites for hypersonic applications
- NASA Lewis Research Center, Cleveland, OH (United States)
The objective of this work was to understand matrix cracking mechanisms in a unidirectional {alpha}{sub 2} titanium matrix composite (TMC) in possible hypersonic applications. A [0]{sub 8} SCS-6/Ti-24Al-11Nb (atomic %) TMC was first subjected to a variety of simple isothermal and nonisothermal fatigue cycles to evaluate the damage mechanisms in simple conditions. A modified ascent mission cycle test was then performed to evaluate the combined effects of loading modes. This cycle mixes mechanical cycling at 150 and 483 C, sustained loads, and a slow thermal cycle to 815 C. At low cyclic stresses and strains more common in hypersonic applications, environment-assisted surface cracking limited fatigue resistance. This damage mechanism was most acute for out-of-phase nonisothermal cycles having extended cycle periods and the ascent mission cycle. A simple linear fraction damage model was employed to help understand this damage mechanism. Time-dependent environmental damage was found to strongly influence out-of-phase and mission life, with mechanical cycling damage due to the combination of external loading and CTE mismatch stresses playing a smaller role. The mechanical cycling and sustained loads in the mission cycle also had a smaller role.
- OSTI ID:
- 536395
- Report Number(s):
- CONF-940399-; ISBN 0-8031-2039-7; TRN: IM9745%%234
- Resource Relation:
- Conference: Life prediction methodology for titanium matrix composites symposium, Hilton Head, SC (United States), 22-24 Mar 1994; Other Information: PBD: 1996; Related Information: Is Part Of Life prediction methodology for titanium matrix composites; Johnson, W.S.; Larsen, J.M.; Cox, B.N. [eds.]; PB: 632 p.; ASTM special technical publication, 1253
- Country of Publication:
- United States
- Language:
- English
Similar Records
Damage accumulation in titanium matrix composites under generic hypersonic vehicle flight simulation and sustained loads
Damage evolution in creep of SCS-6/Ti-24Al-11Nb metal-matrix composites