Numerical Investigation Of Buckling And Damage Propagation In Honeycomb Sandwich Structures With Face/Core Debond

Honeycomb sandwich structures consist of a low density honeycomb coreintercalated between two high stiffness and high strength face sheets, due to itsadvantage of lightweight, high strength and high modulus to density ratio, thesandwich structure has been frequently applied into the engineering field. A lot offace-core debonds emerge in the process of manufacturing, transport, fitting andrepair. When a sandwich structure is loaded in compression, the debond decreases thestrength and load carrying capacity of the structure. Debond propagation leads topremature failure of the structure and affects its mechanical property seriously.In this paper, the finite element method (FEM) was applied to predict the localbuckling behavior and the debond propagation in honeycomb sandwich panels withface-core debond under in-plane compressive load. The finite element model of thesandwich panel was built, the cohesive element was used to model the adhesivebetween faces and core, using the cohesive element can predict both onset andpropagation of debond without previous knowledge of the crack location andpropagation direction.First of all, the influence of the interface properties, the face’s stacking sequence,the thickness of face and core, the honeycomb dimensions on the critical bucklingload, residual compressive strength and debond growth of the honeycomb panels wasinvestigated. The results show that the face’s stacking sequence and face’s thicknesshave significant effect on the residual compressive strength of panels with face-coredebond, and the direction of debond growth is closely related to the face’s stackingsequence. Then, the influence of the debond shape and size on the failure mode,critical buckling load and residual compressive strength of the sandwich panels wasinvestigated, the rule of the damage propagation was summarized. The compressionstrength of the sandwich panels with through-width face/core debond decreases withincreasing debond length. For the panels with central circular debond, when thediameter is less than15mm, the panels will failure by global buckling and the debondwill not grow. When the diameter is greater than15mm, local buckling of thedebonded face sheet occurs firstly and then debond rapidly propagate perpendicular to the applied load and the structure failure completely. Besides, critical buckling load,maximum carrying load and strength retention strongly decrease with increasingdebond diameter. Furthermore, elliptical debond which tends to appear in engineeringwas examined, the influence of the debond size and ellipse’s direction on thestructural compression properties and debond growth was investigated. It is found thatthe residual compressive strength decreases with increasing major axis’ length whenthe minor axis’length of ellipse keeps constant. But the decrement is very differentwhen the direction of ellipse is not the same. For the elliptic debond with the samesize, the load carrying capacity is lower when the major axis is perpendicular to theload direction than the major axis is parallel with the load direction. In addition,ellipse’s direction makes no difference on the direction of debond growth. Finally,failure and debond propagation of the sandwich panels with different length wereinvestigated. Failure mode of the sandwich panels was summarized. The conclusionobtained in this paper can provide some reference for the design and repair of thehoneycomb sandwich structures.