Biaxial monotonic behavior of a multidirectional glass fiber epoxy pipe

This paper presents the results of an experimental investigation into the b iaxial monotonic behavior of a filament wound multidirectional glass-fiber/ epoxy pipe. Tests were conducted to observe the leakage (functional) failur e of the composite pipe subjected to various hoop to axial stress ratios. T he change in stiffness in the axial and the hoop directions and change in t he Poisson's ratio are discussed. The results show that there is a signific ant nonlinear change in the stiffness and the Poisson's ratio prior to leak age. The nonlinear change in the Poisson's ratio proved to be a useful indi cator of damage, independent of the tested stress rate. Macro and micro obs ervations indicate that a dominant axial tension gave a uniform type of mat rix cracking within the specimen, where a dominant hoop stress induced dela mination within the laminate. (C) 2000 Elsevier Science Ltd. All rights res erved.