Stress Model of Composite Pipe Joints under Bending

Abstract

Recently, composite pipe is becomingpopular in the offshore oil and gas industry due to the new “floating” designs of various platforms which have made deepwater oil and gas exploration and production more economical and affordable. The limited space in platforms emphasizes the needs for composite pipe joints in order to accommodate turns and bends. It has been estimated that there is one joint for every 4 ft of composite pipe installed for marine applications. The joints are the weakest link in a composite pipingsystem. Bending, one of the most common loads in a pipingsystem, was applied to the joint system and analyzed. An analytical model was developed usingthe first-order laminated anisotropic plate theory. Due to the asymmetric nature of the bendingload about the pipe central axis, a twodimensional model is necessary to simulate the system response. In this developed model, a three-component joint system consistingof coupling, adhesive, and pipe was used to model different types of composite pipe joints such as adhesive-bonded socket joints, butt-and-strap joints, and heat-activated couplingjoints. Good correlation was found between results from the developed model and finite element model including adhesive peel stress and shear stress distributions. This investigation has shown the effectiveness of the first-order laminated plate theory in modelingtwo-dimensional tubular geometries, includingthe surface displacements which are important in determiningthe adhesive peel and shear stresses in this study.