Characterization of the Mechanical Properties and Fatigue Behaviour of a Three-Dimensional Braided Carbon-Fiber/Polyimide Composite

摘要

The characterization of the mechanical properties and the fatigue behaviour of arnthree-dimensional triaxial (0°/±60°) multi-layer interlock braided carbon-fiberrnthermosetting polyimide matrix composite material is examined. Uniaxial tensile staticrnand fatigue tests were conducted at room temperature on tabbed specimens. An edgernreplication technique was used to monitor damage development during both static andrnfatigue tests, and a scanning electron microscope was used to inspect the damagedrnmaterial microstructure upon completion of testing. Static tests reveal that the materialrnhas a bilinear stress-strain response, which has been observed to be caused by the lossrnin effectiveness of the off-axis braided fiber yarns due to an increase in the crackrndensity in these yarns at the transition stress. Tension-tension fatigue tests have furtherrnrevealed that the stress magnitude associated with the transition observed in the staticrnbilinear stress-strain behaviour is in fact the fatigue limit of the braided composite.rnStiffness degradation and stress-strain ratcheting was observed for all fatigued testrnspecimens regardless of the maximum stress magnitude. Examination of thernprogressive damage during fatigue was also directly correlated to the quantifiedrnspecimen hysteretic material behaviour.