Abstract
Fatigue crack growth testing has been applied to boron/Ti-6Al-4V composites in order to investigate simultaneously crack propagation mechanisms during the fatigue and overload portion of the experiments. It is concluded that linear elastic fracture mechanics (LEFM) for heterogeneous and anisotropic materials facilitates understanding of the rupture mechanisms and the assessment of failure work and toughness. The influence of isothermal exposure on crack propagation mechanisms has been pointed out. A short duration heat treatment at 850‡ C improves the composite toughness and reduces the fatigue crack growth rate although the fibrematrix (FM) interfacial bonding is increased. This effect has been related to a damage mechanism initiated in the interfacial reaction zone. In any case, the fatigue behaviour of the composite is controlled by the matrix and the capability of the fibres to function as crack arrestors. The impeding effect of the fibres is no longer effective when the thermal exposure duration is significant.
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