Stress intensity factor of through-wall-cracked steel pipe wrapped with prestressed CFRP composites

Externally wrapped prestressed carbon fiber reinforced polymer (CFRP) composites are effective in cracked steel pipe repairs. In this study, the effects of pipe and crack geometry, CFRP properties, and prestress levels on the Mode Ⅰ stress intensity factor (SIF) were addressed quantitatively for a prestressed CFRP-wrapped steel pipe with a through-walled crack through dimensional and finite element (FE) analysis. Five hundred and ten FE models were established to analyze the effects of the parameters. The effects of radius and wall thickness on the SIF were interactional. The SIF was negatively correlated with the CFRP stiffness and decreased linearly with the increasing prestress. The ratio between the SIFs of a CFRP-wrapped cracked pipe and a cracked pipe was determined by the dimensionless CFRP stiffness. The SIF decreases with the increasing crack angle following the cosine function mode. The ratio between the SIFs of an inclined crack and an axial crack was determined only by the crack angle. The influences of pipe geometry, crack angle, and CFRP properties on SIF were independent of each other. An empirical equation for calculating the Mode Ⅰ SIF was proposed for the CFRP-wrapped thin-walled pipe with a through-walled crack. An accurate mechanical method to calculate the decrement of pipe substrate bearing internal pressure caused by prestress was proposed.