Axisymmetric delamination in deposited multi-layers

The problem of residual stress-driven axisymmetric delamination in successively deposited isotropic multi-layers is addressed in this study. A circular-shaped multi-layer is modeled with a delamination crack extending uniformly from the free edge. Applications for this work include the modeling of residual stress-driver, delamination of multi-layered coatings and films. The application of specific interest is residual stress-driven debonding in parts created by layered manufacturing methods; where molten metal layers are successively deposited to form three-dimensional shapes. Results for energy release rates as a function of delamination crack length are presented from fracture mechanics models of various axisymmetric multi-layer geometries. Results are compared to those from planar delamination problems. Methods are outlined for determining a conservative upper bound for the maximum energy release rate for an axisymmetrically extending delamination crack. These methods are based on potent:al energy calculations from a residual stress model for an uncracked multi-layer and do not require fracture mechanics modeling. The easily calculated bound for the maximum energy release rate can be used to guide the design of delamination-resistant multi-layers. (C) 1997 Elsevier Science Ltd.