Abstract: The honeycomb panel structure is composed of two upper and lower panels and a honeycomb core in the middle. It has the characteristics of light weight, high strength and high rigidity, and is widely used in the fields of aerospace, ships, automobiles and buildings. At present, the structure of honeycomb core is usually connected by cementing agent. The change of cementing agent has a great influence on its mechanical properties and its aging performance is not clear. The honeycomb panel is often used on the outer surface of the building, which is affected by the external environment for a long time, which puts a great test on its durability. The targeted index of structural durability evaluation usually needs to be set according to different use requirements. The honeycomb structure pays different attention to the objects according to different working conditions, among which the mechanical properties are an important evaluation index. This article focuses on the flat compressive strength of honeycomb panels.
This paper mainly conducts high temperature accelerated aging test on the structure of Titanium-Zinc honeycomb core, evaluate its durability by changing its flat compressive strength and predicts its service life. The life expectancy is set to 0, 25, 30 years, and the reaction rate change formula based on the Arrhenius equation to derive the temperature change is used to derive the high-temperature accelerated aging time. Select the standard test pieces of honeycomb core provided by four typical manufacturers, whose size is 60 mm×60 mm×20 mm, group them according to the expected life of 0, 25, and 30 years and perform accelerated aging at high temperature. One sample is reserved for each group, only accelerated aging without quasi-static compression, and the remaining groups are tested for quasi-static compression. Test the quasi-static compressive force of the sample piece by piece, record the load characteristic curve, read the crushing load, and record the crushing form. The flat compression strength and peak strength of the sample after aging are analyzed and compared with the corresponding values of the samples of the same batch before aging. Deviation is used for durability analysis, and the performance index of the sample before and after aging is set to not exceed ±15%.
The test results show that the deformation of the honeycomb core layer during the flattening process passes through three stages of elastic deformation, plastic deformation and instability. Elastic deformation stage I: The load-displacement curve is an oblique straight line, and the honeycomb core shows elastic deformation. Plastic deformation stage Ⅱ: Degumming and brittle cracking occurs between the honeycomb core wall panels, plastic buckling deformation occurs, and the flat compression strength decreases rapidly. Instability phase Ⅲ: As the loading continues, the constraints between the wall panels fail, and the honeycomb core is gradually pressed. And the surrounding honeycomb structure is gradually destroyed. When the structure is pressed, the flat compressive strength is maintained on a relatively low platform. The analysis results show that the strength changes of the test specimen within 30 years of aging time did not exceed the deviation of the index of 15% of the quality standards. And as the aging time increases, the flat compressive strength decreases. When the honeycomb cores are arranged denser and in real time, the improvement of flat compression strength is more obvious, and the overall test piece performs better after flat compression, and can basically maintain a square shape. As the aging time increases, the flat compressive strength of the honeycomb panel generally shows a downward trend. Within 25 years of aging, the strength of each series decreased slightly, and some series even increased in strength. Therefore, the design life is limited to 25 years is more reasonable. However, due to the differences in the manufacturing methods, the mechanical properties of the products vary greatly which demonstrate the necessity and feasibility of the life prediction of the honeycomb core structure.