Global-local coupled analysis of fiber-reinforced composite pipes for application in deepwater considering the failure evaluation

A homogenization-FE method was proposed to study the global-local response of fiber-reinforced composite pipes in ocean environments. At first, fiber-reinforced composite pipes were homogenized to calculate stiffness parameters, in which isotropic and orthotropic materials could be considered simultaneously. Then, stiffness parameters were used as input to conduct the global FE analysis based on the theory of slender rods. After that, the homogenization method was reversely employed from the "fake" homogenous pipe to the "true" composite pipe. The stress distribution of every lamina was calculated according to the global internal forces and they were used to evaluate the damage of composites and isotropic layers by applying Tasi-Wu failure criterion and von Mises yield criterion. Experimental tests and numerical simulations were conducted to verify the homogenization theory and the global FE method. Compared with SCR, the study showed that CRPs (carbon-fiber reinforced pipes) have lower requirements for the strength design of connectors because of smaller internal forces. It also confirmed that CRPs could be designed as safe as steel pipes. Besides, the increase of composite laminates and the replacement of the steel sheath by applying titanium and aluminum allow a greater safety margin.