Axial Force Effect on Honeycomb Nonlinear Elasticity

• Main Authors: WANG,LI-RAN, 王立然
• Other Authors: YU,CHAU-CHO
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/63997666071339459038

碩士 === 國立高雄大學 === 土木與環境工程學系碩士班 === 104 === Hexagonal honeycomb has been a popular construction material used in building light structure. Due to its uniform pattern, symmetry is often applied in analyses. That leaves no nodal rotation at the joints inside the material. It is found differently through the general numerical analysis that the buckling mode is more likely in Z-Shaped instead of uniformly leaning in one direction. The uniform deformation may over estimate the buckling strength. A Z-shaped buckling is proposed lately. Its buckling strength is approximately 60% of a Euler Column and its correlation with the boundary condition is not obvious. However, these are only the results of analytical and numerical approach. It is worth efforts to seek for lab test support. Such kind of material in current market is made of two thin metal plies attached to each other with the source sheet metal of the thickness up to tens of micro meters level. Small dimension and complexity in composite make the corresponding lab test pretty difficult. It is what there is this proposal is furnished up for. Through this project, the standard lab test procedure was set up, the two-dimensional hexagonal honeycomb structure was tested. Some possible difficulties in the tests were resolved. The lab test results were compared with those from analytical solution as well as the numerical solution. Most of the honeycomb related researches in the past assume that honeycomb is a two-dimensional thin-walled structure. The in-walled deformation is often neglected due to the fact that most of the deflection of a thin-walled structure is contributed by flexure. When the thickness-length ratio t/L is greater than 0.1, such thin-walled assumption is no longer appropriate because the deformation induced by the in-walled forces, called axial effect in this study, is not negligible, especially when the external load is approaching the critical load of any type of buckling. In the present study, theoretical expression of the axial effect on equivalent macro-elasticity of the honeycomb material is derived. Some numerical results are carried out through a trial-and-error method. The present study shows that macro elastic constant of a honeycomb decreases as the external load increases. Different thickness-length ratio will have different decay rate in elasticity. Basically, the relation between elasticity and external load is linear, if the thickness-length ratio is less than 0.1. Z-Shaped buckling is the dominating buckling mode, even if the lateral constraints are applied, but for most of the cases, Z-shaped buckling shows up within a relatively short period of time during the initiation of buckling.