The Design,Manufacturing And Mechanical Properties For Fold-core Cylinder Structures

Sandwich panels have been used widely in the aerospace industry,due to their high specific bending resistance performance.Honeycomb and foam sandwich panels were used in some secondary structures,such as fairings and wings,while the condensation of water imposes restrictions to their application.The fold-core structure proposed by a Japanese scholar named Miura attracts attention from people.It could be folded from a 2-D sheet and solve the problem of water condensation,which brings it the possibility to be used in fuselages.Additionally,folded cores are negative poisson's ratio structures and the advantage in energy absorption could help decrease noise within the cabin.In this paper,geometric parameters for the fold-core sandwich cylinder were designed,and the structure was manufactured.Mechanical properties and energy absorption characteristics analysis under compressive loading was also conductedAt first,the fold-core sandwich cylinder was molded by numerical method.Vertex coordinates figured out by MATLAB programs were used into ANSYS to establish facets of cores.Then import the geometrical model into ABAQUS,setting directions and mechanical properties for carbon-fibre reinforced(CFR)composite.Geometric parameters study was done to find out influence law between variables and configuration of the structure.Programs was written to make sure integral period in the peripheral direction.Secondly,the manufacturing technology for the fold-core sandwich cylinder was put forward.The core was divided by four parts and two parts for the wall.Cores and walls were all manufactured by vacuum hot-press method and then spliced together.At last,the curing process was needed.As for these two processes,hot-press molds and curing molds which could provide inside and outside constraints were designed and produced.In addition,the predictions for equivalent compressive modulus and limit stresses were derived through work equivalence principle.Three ply-up thickness structures with CFR composite material was analyzed with finite element method(FEM)and verified the reasonability for analytical formulas.The sandwich cylinder folded by aluminum foil was tested and the whole experimental process was recorded.Make comparisons between force-displacement curves from tests and FEM,ensuring the reasonability for numerical modeling,which was also used to study energy absorption for sandwich cylinder with folded cores and axial-direction corrugated cores.Finally,buckling limit loads for the fold-core sandwich cylinder suffering compressive loads were studied.Analytical results for various failure modes were derived,and the figure of failure mechanism was plotted.The fold-core sandwich cylinder with CFR composite was tested under compressive loads.The failure mode and limit load were analyzed.Strain analysis was also done on typical locations.The study and exploration based on the fold-core sandwich cylinder in this paper provides instructive reference for the practical engineering application.