A REVIEW OF THERMOMECHANICAL FATIGUE DAMAGE MECHANISMS IN 2 TITANIUM AND TITANIUM ALUMINIDE MATRIX COMPOSITES

Combined load and temperature cycling could limit the durability of co ntinuous fibre reinforced titanium matrix composites. The fatigue life and damage induced by combining load and temperature cycling in sever al different ways were examined in two representative 0-degrees unidir ectional titanium and titanium aluminide matrix composites. Load and t emperature were sequentially cycled and simultaneously cycled in therm omechanical fatigue tests. Sequential and simultaneous thermomechanica l fatigue tests in which maximum tensile loads occurred at minimum tem perature had comparable lives and damage, associated with environment- assisted surface cracking. Sequential and simultaneous thermomechanica l fatigue tests in which maximum loads occurred at maximum temperature each had different lives and damage, primarily because of differences in the extent of matrix-relaxation-induced load shedding from the mat rix to the fibres. These general results applied to both titanium matr ix composite systems.