Biaxial fatigue behaviour of a multidirectional filament-wound glass-fiber/epoxy pipe

This paper presents the results of an experimental investigation into the biaxial fatigue behaviour of a filament-wound multidirectional glass-fiber/epoxy pipe. Tests were conducted to observe the leakage (functional) failure of the composite pipe subjected to various hoop to axial loadings. The stiffness change in the axial and hoop directions, fatigue life curves, biaxial fatigue envelopes at various lives, and failure mechanisms are discussed. It is noted that optimum fiber placement in principal directions may lead to a weak behaviour for an intermediate loading combination. It is also found that monotonic test data are not a good indicator of the fatigue behaviour. Furthermore, imperfections in the manufacturing process lead to early damage initiation under cyclic loading, and result in shorter Fatigue lives to leakage. (C) 2001 Elsevier Science Ltd. All rights reserved.