Title: A two scale analysis of the failure of a joint between two steel plates

			    Dominique Leguillon
           Laboratoire de Modélisation en Mécanique  CNRS UMR7607
	             Université P.et M. Curie (Paris 6)
		4 place Jussieu, 75252 PARIS Cedex 05  France

Abstract: 
An Irwin-like criterion, initially developed to predict crack initiation in 
monolithic v-notched specimens, is used to examine the failure of two plates 
bonded together by an adhesive joint. It is based on an estimate of the 
critical value of the generalized stress intensity factor (GSIF) of the 
elastic singular fields appearing in some regions of the structure, due to 
the geometry and to the elastic mismatch of the components. 
 The analysis is carried out at two scales: a macroscopic one ignoring the 
thin adhesive layer and considering the two plates as perfectly bonded along 
an idealized interface and a microscopic one taking into account the elastic 
fields within the joint. It is shown that these two approaches are equivalent 
and that a macroscopic failure criterion can be derived from microscopic 
parameters such as the strength and the toughness characterizing either the 
adhesive itself (cohesive failure) or the adhesion between the joint and the 
plates (adhesive failure). Clearly, the same procedure can be carried out to 
study delamination mechanisms (initiation and growth) in composites, it allows
taking into account some micro-characteristics of the interfacial zone.