Collocated interfacial stress intensity factors for finite bi-material plates

This paper deals with elastic stress intensity factors associated with stress fields near partially debonded interfaces in finite, bi-material plates. Bi-materiai stress intensity factors K₁ and K₂ are not associated, respectively, with symmetric and skew-symmetric loading and are functions of an arbitrary length parameter. Any fracture condition involving bi-material stress intensity factors must be independent of the arbitrary length parameter and must be consistent with experiment. We define a new parameter K_i called the interfacial stress intensity factor which satisfies the former condition. A truncated Williams power series stress function for stresses in a cracked bi-material plate, as modified by Sih and Rice, is used with a modified boundary collocation procedure to generate interfacial stress intensity factors for finite bi-material plates. This modified collocation technique eliminates the need for tuning the boundary points. The method is exemplified by application to a centrally cracked bi-material plate and to a partially debonded composite laminate.