MODELING THE INITIATION AND GROWTH OF DELAMINATIONS IN COMPOSITE STRUCTURES

A method for modeling the initiation and growth of discrete delaminati ons in shell-like composite structures is presented. The laminate is d ivided into two or more sublaminates, with each sublaminate modeled wi th four-noded quadrilateral shell elements. A special, eight-noded hex constraint element connects opposing sublaminate shell elements, and makes the two opposing shell elements act as a single shell element un til a prescribed failure criterion is satisfied. Once the failure crit erion is met, the connection is broken, and a discrete delamination in itiates or grows. This approach has been implemented in a three-dimens ional finite element code. This code uses explicit time integration, a nd can analyze shell-like structures subjected to large deformations a nd complex contact conditions. Tensile, compressive, and shear laminat e failures are also modeled. This paper describes the eight-noded hex constraint element used to model the initiation and growth of a delami nation, and discusses associated implementation issues. In addition, c alculated results for double cantilever beam and end notched flexure s pecimens are presented and compared to measure data to assess the abil ity of the present approach to model a growing delamination. Results a re also presented for a diametrally compressed ring to demonstrate the capability for analyzing progressive failure in a highly deformed com posite structure.