High-Order Theory Approach for Debonded Sandwich Panels—Part II: Energy Release Rate and Mode Mixity

Abstract A novel re-formulation of the extended high-order sandwich panel theory (EHSAPT) for the case of a face/core debond was done in Part I of this two-part series of papers. This high-order theory is capable of including not only the transverse shear but also the transverse compressibility and axial rigidity of the core. In this Part II paper, a closed-form expression for the energy release rate is derived in terms of the equivalent resultant forces and displacements at the two edge sections. Together with the crack surface displacement method, the mode mixity is determined from the displacement field. Benefiting from the accurate displacement field given by the proposed theory, this paper presents a self-contained approach for the mode mixity that is free of parameters that need to be determined via additional numerical simulations (i.e., no extrapolation needed). Results are compared with the ones given by the classical theory in the literature and the ones given by the finite element method with a very fine mesh. The accuracy is proven for a wide range of core materials from the stiffer cores to the very compliant ones, and for a wide range of debond lengths.