Hybrid materials or Bi-materials are increasingly used in engineering applications, and better understanding of interface behavior is crucial to integrity and applicability of such materials and structures. Interface debonding or delamination is one of common failure modes in hybrid layered structures. In this study, two newly developed bi-layer beam theories (Wang and Qiao 2004; Qiao and Wang 2004) are introduced, and their application to fracture analysis of laminated structures is illustrated. Three joint deformation models (i.e., the rigid, semi-rigid and flexible joint models) describing the different degrees of crack tip deformation are obtained based on three corresponding bi-layer beam theories (i.e., the conventional composite beam, shear deformable bi-layer beam, and interface deformable bi-layer beam). Due to different considerations of the interface displacement compatibility in each bi-layer beam theory, these joint models, among which the semi-rigid and flexible joint ones are newly developed, demonstrate three distinct levels of accuracy in predicting the crack tip deformation. By using these two novel joint models, the new terms, which are “missing” in the rigid joint model, are recovered for the compliances and energy release rates (ERRs) of several common delamination specimens. It is significant that shear deformable (Wang and Qiao 2004) and interface deformable (Qiao and Wang 2004) bi-layer beam theories are developed, and their resulting novel semi-rigid and flexible joint deformation models provide explicit closed-form solutions of fracture parameters which can be easily adopted in practice.


References:

Wang, JL and Qiao PZ (2004). “Interface Crack between Two Shear Deformable Elastic Layers,” Journal of the Mechanics and Physics of Solids, 52(4): 891-905.

Qiao, PZ and Wang, JL, (2004). “Mechanics and Fracture of Crack-tip Deformable Bimaterial Interface,” International Journal of Solids and Structures, 41(26): 7423-7444.