Viscoelastic response of composite overwrapped cylinders

Creep and stress relaxation behavior of composite overwrapped cylinders are investigated based on anisotropic viscoelasticity. The analysis accounts f or ply-by-ply variations of material properties, ply orientations, and temp erature gradients through the thickness of cylinders. Fiber-reinforced comp osite materials generally illustrate extreme anisotropy in viscoelastic beh avior. The viscoelasticity exists mainly in matrix-dominant properties such as transverse and sheer, while the fiber-dominant properties behave more l ike elastic media. The study of thermal and mechanical stress relaxation in an overwrapped composite cylinder shows that the viscoelastic characterist ics of composite cylinders are quite different from those of isotropic cyli nders. Poisson effects from the creep behavior in the transverse properties of the composite can result in a drastic change of stress and strain state of the cylinder.