A DYNAMIC-MODEL FOR LAMINATED PLATES WITH DELAMINATIONS

A generalized theory for laminated plates, including delamination, is developed. The laminate model is based on a generalized displacement f ormulation implemented at the layer level, The equations of motion for a layer, which are explicitly coupled with both the interfacial tract ion continuity and the interfacial displacement jump conditions betwee n layers, are used to develop the governing equations for a laminated composite plate. The delamination behavior can be modeled using any ge neral constitutive fracture law. The interfacial displacement jumps ar e expressed in an internally consistent fashion in terms of the fundam ental unknown interfacial tractions. The current theory imposes no res trictions on the size, location, distribution, or direction of growth bf the delaminations. Therefore, the theory can predict the initiation and growth of delaminations at any location as well as interactive ef fects between delaminations at different locations within the laminate . The proposed theory is used to consider the dynamic response of lami nated plates in cylindrical bending. First it is shown that the dynami c implementation agrees well with the exact predictions of a plate und er static loading conditions. Static, cylindrical bending is considere d to validate the numerical implementation. Next, different dynamic lo ading cases are considered. First, the required level of discretizatio n through the thickness of the laminate necessary to accurately captur e the wave propagation characteristics for monotonic tensile loading t ransverse to the plate is determined. Next, the influence of the delam ination on the free vibration behavior of a plate is considered. It is shown that the presence of delaminations can result in significant de viations from the perfectly bonded free vibration behavior. Finally, t he plate is subjected to dynamic loading conditions that demonstrate t he influence of internal wave interactions on the overall behavior of the plate. (C) 1997 Elsevier Science Ltd.