Abstract
Creep and stress relaxation behavior of composite overwrapped cylinders are investigated based on anisotropic viscoelasticity. The analysis accounts for ply-by-ply variations of material properties, ply orientations, and temperature gradients through the thickness of cylinders. Fiber-reinforced composite materials generally illustrate extreme anisotropy in viscoelastic behavior. The viscoelasticity exists mainly in matrix-dominant properties such as transverse and shear, while the fiber-dominant properties behave more like elastic media. The study of thermal and mechanical stress relaxation in an overwrapped composite cylinder shows that the viscoelastic characteristics of composite cylinders are quite different from those of isotropic cylinders. 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.