Effect of Localized Bending at Through-Flaws in Pressurized Composite Cylinders

An analytical and experimental investigation was conducted to determine the effect of localized bending at through-flaws in pressurized composite cylinders. A finite-difference solution was formulated to determine the stress, strain, and displacement fields in the vicinity of a slit. Tests were conducted on 305-mm-diameter cylinders made from graphite/epoxy fabric in a (0,45)s configuration, with axial slits. Surface-strain-field measurements made in the vicinity of the slit showed a significant bending, which verified the finite-difference solution. This significant bending near the slit tip results in a large magnification of the stresses there. An average stress criterion was employed to predict the failure response of these cylinders based on data obtained from coupon specimens. The finite-difference solution provided correction factors to account for the localized bending. The prediction utilizing this methodology was excellent in all cases. A generalized methodology to assess damage tolerance of structural configurations with notches is proposed.