EFFECT OF INTERLAYER THICKNESS ON THE MODE I FRACTURE ENERGY RELEASE RATE OF SANDWICH STRUCTURE

As a load transfer and connection element, the sandwich structure is widely used in aerospace, material characterization, flexible electronics and other fields. Understanding its fracture behavior and characteristics can provide theoretical guidance for designing the load capacity of the sandwich structure connector. In this paper, based on the improved elastic foundation theoretical model, we proposed a new theoretical model to calculate the energy release rate of the sandwich structure. The theoretical model considered the effect of the interlayer thickness on the energy release rate of the mode I fracture energy of the sandwich structure. Results showed that the influence of the middle layer on the energy release rate of mode I fracture has two parts: the influence of the shear force of the middle layer and the effect of the middle layer on the increase of structural stiffness. When the dimensionless interlayer thickness takes the maximum value of 2, the energy release rate from the traditional model may have a deviation greater than 70%, compared with the finite element calculation; our model can greatly improve the accuracy, and the error can be reduced to 5%. Compared with the improved elastic foundation theory, which is only applicable to the case where the thickness of the middle layer is small, the theoretical model has a wider range of applications. In addition, by using the present model, two geometric parameters (intermediate layer thickness and initial crack length) and one material parameter (modulus ratio) were selected for the study. The sensitivity of shear effect to structural geometry and material parameters was discussed. Based on the constant load, the influence of geometric and material parameters on the energy release rate was discussed; and on the assumption that the fracture toughness of the structure remains unchanged, the influence law of geometric and material parameters on the critical load of the sandwich structure was obtained.