Numerical Simulation Of Crack Damage At Interfacial Debonding In Honeycomb Sandwich Plate Under Pure Bending Load

Due to its nice quality of high strength and high modulus to density ratio the sandwich structure has been frequently applied into the engineering field. Nevertheless, in the process of its manufacturing and constant usage the damage of debonding would arise inevitably which will cause a drastic degradation in the structural strength, leading to an early global instability and failure of the structure. Of the various structural shapes made from the same amount of materials, only the honeycomb can achieve a large volume and a good stiffness. Therefore in recent years the honeycomb sandwich structure has been at a premium in the engineering world and the investigation on its damage of debonding is of great significance.This paper uses the finite element method to simulate the influence of the shape and the physical dimension of debonded area between the skin and the core layer of the honeycomb sandwich plate on the further propagation of its debonding under the pure bending load applied on the two side surfaces vertical to the direction of the length of the plate, summarizing the debonding rules and looking further into the effect of the physical and mechanical properties of different parts of the honeycomb sandwich plate on the critical load for debonding propagation. In order to make the finite element simulation accord with the actual situation as much as it can, this paper simulates a glue layer of certain thickness by creating a layer of solid element and takes advantage of the contact pairs established by TARGE and CONTA element to simulate the state of cohesion between the glue layer, the skin and the core layer and build it as a cohesive zone material model. Traction and Separation Law is used as failure criteria for glue layer.The conclusions are as follows: For those honeycomb sandwich plates that have the initial debonded area of a circle, they will experience local buckling which takes the form of snap-through buckling when the radius of the debonded area is no less than 13mm. The propagation of debonding is only discovered on the direction of the width of the plate while on the length direction some trend of closure of the debonded area is found instead of further propagation. The critical load for debonding propagation of the sandwich plate decreases as the radius of the initial debonded area increases. For those honeycomb sandwich plates that have the initial debonded area of an ellipse, when the major axis is parallel with the width direction of the plate, if the ratio of the length of minor axis to the length of major axis is relatively small, the propagation of debonding is discovered on both the direction of the length and the width and the propagation preferentially starts on the length direction. As that ratio increases, the propagation of debonding will firstly start on the width direction instead of the length. When the major axis is parallel with the length direction, within certain range of the ratio, the plate will experience the snap-through buckling and the debonding will firstly reveal itself on the width direction of the plate. In the case of a small ratio, the high order buckling can appear easily on the plate which will directly lead to the instability and the failure of the structure. The material properties of the skin, the core and the glue layer could exert certain effect on the structural strength and the debonding propagation load. The skin property is most influential factor while the density of the core comes the second and the modulus of the glue layer comes the last. Besides, the thickness of the skin, the core and the glue layer and the fracture elongation of the glue material will also have great impact on the strength of the structures.