On the specimen for interfacial fracture toughness evaluation of foam-core sandwich structures

Foam-core sandwich specimens for interfacial fracture toughness measurement are designed based on the prediction method of steady-state crack location in foam-core sandwich beams using the crack deflection model developed previously. This paper derives the necessary condition that the face sheet debonding grows along the interface between the face sheet and the core during the fracture toughness tests. The recommended specimen thickness ratios for several testing methods are presented. Finally, the physical meaning of the derived condition is explained, and the effect of residual thermal stresses on the condition is discussed.