Ply drop-off effects in CFRP/honeycomb sandwich panels - Theory

This paper introduces a simple method for engineering analysis of ply drop-off induced local bending effects in CFRP/honeycomb sandwich panels. The model constituent parts are the base-line face laminate of a CFRP/sandwich panel, a dropped sub-laminate, a supporting honeycomb core material, and an adhesive/resin layer interfacing the laminates. The interaction between the core material and the face. laminates is modelled using a two-parameter elastic foundation model. Two examples are evaluated, and it is shown that the elastic response is strongly influenced by the presence of a supporting core material. The results of a brief parametric study are presented, and it is demonstrated that the ply drop-off problem is influenced significantly by the out-of-plane stiffness of the honeycomb core, by the bending stiffness of the base-line face laminate and finally by the bending stiffness of the dropped sub-laminate. The paper is concluded by a discussion of design aspects. (C) 1996 Elsevier Science Limited