The effect of composite patch on stress intensity factor of semi-elliptical crack in a spherical pressure vessel

The purpose of this article is to investigate the effect of composite patch on stress intensity factor (SIF) for internal and external semi-elliptical crack located in spherical pressure vessel. The composite patch is wrapped only around the crack. The three dimensional analysis is done by Finite Element Method (FEM). ANSYS Parametric Design Language (APDL) codes are developed to facilitate modeling of semi-elliptical crack in spherical pressure vessel. By using these codes the effect of some parameters such as crack geometry (crack depth/thickness of vessel and crack depth/ half-length of crack), the ratio of composite thickness to metal thickness, the ratio of composite patch width to half-length of crack and composite material on stress intensity factor values are investigated and discussed in detail. The results show that composite patch has significant reduction in stress intensity factor at crack tip. Also it can be concluded that composite patch is more effective for deeper and slender crack. In addition composite patch is more effective to decrease stress intensity factor of external crack in comparison to internal crack.