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Abstract

The high temperature fatigue behaviour of 2 2D reinforced ceramic matrix composites (CMC) is studied under high vacuum conditions. The mechanical loads imposed result in matrix cracking upon first loading, so that continued cyclic loading results in progressive interfacial debonding and/or matrix crack multiplication, as well as fibre failure. In order to investigate whether the fatigue life is mainly governed by time-dependent creep or by cyclically induced fatigue damage, a range of frequencies and 2 stress ratios are explored in stress controlled fatigue tests. The results obtained indicate that under pulsating fatigue (positive stress ratios or tension-tension) the material response is affected by both creep and fatigue mechanisms. The cyclic damage component gains in relative importance with increasing test frequency. Under reversed loading conditions (negative stress ratios), and depending on the creep strength mismatch between the fibres and the matrix, the time-dependent damage component can be largely suppressed, and the composite fatigue behaviour can become close to purely cycle-dependent. In both cases and for both composites fatigue failure is triggered by fibre failure.

Additional information

Authors: STEEN M, JRC Petten (NL);VALLES J-L, JRC Petten (NL)
Bibliographic Reference: Paper presented: ASME Turbo EXPO '96-Land, Sea and Air, 41st Gas Turbine and Aeroengine Congress, Birmingham (GB), June 10-13, 1996
Availability: Available from (1) as Paper EN 39621 ORA
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