Cylindrical discrete-layer model for analysis of circumferential cracked pipes with externally bonded composite materials

This study concerns circumferentially cracked pipes repaired by composite materials subjected to an axial tension. For this purpose, a cylindrical discrete-layer model with a simple and efficient approximation approach is proposed to implement parametric studies on properties of composite materials for patch repair, patch thickness, adhesive shear modulus, adhesive thickness, and thickness of the pipes. Elements of the cylindrical discrete-layer model have a subparametric concept that considers linear mapping of geometry fields on a cylindrical coordinate, and hierarchical approximating functions of displacement fields. The approximating functions are based on one- and two-dimensional integrals of Legendre polynomials, allowing accurate simulation of three-dimensional behavior. Also, a virtual crack closure technique (VCCT) is formulated for the proposed elements to obtain the strain energy release rates (SERR) of pipes with crack-like flaws. The easy-to-use modeling scheme is applied to single-patch repaired pipes with crack. Convergence tests of the elements and sensitivity tests of the modified VCCT are implemented and then some of the present analysis results are verified through comparison with some reference values.