Fictitious Elastic Stiffness Parameters of Zero-Thickness Finite Elements at Bi-Material Interfaces

Abstract

Zero-thickness interface elements can be used to simulate delamination processes or more in general to model discrete cracks or debonding effects in heterogeneous materials. These elements are inserted amongst the mesh lines in correspondence with the bi-material interface. The zero-thickness interfaces behave as non-linear elements that dissipate energy only after certain cracking conditions have been reached. To keep the interface closed while the cracking conditions are not yet satisfied, a fictitious elastic behaviour is imposed through penalty stiffness parameters. These are elastic stiffness parameters set as high as possible to guarantee that no penetration or separation take place while the cracking nucleation conditions are not satisfied, but not so high to avoid ill-posed problems. Based on a recent formulation, this paper investigates the use of optimal fictitious elastic parameters that guarantee the recovery of accurate pre-cracking inter-element forces and stresses at the bi-material interfaces.