Stiffness Design And Optimization Of Asymmetric Sandwich Structure

At present,honeycomb sandwich structures are widely used in aerospace,marine,automotive and construction industries.Honeycomb sandwich structures are increasingly valued by engineers for their light weight and high strength.As the engineering application environment becomes more and more complex,engineers put forward higher requirements for the carrying capacity and functionality of the honeycomb sandwich structure.Under the premise of not increasing the weight of the structure,it is particularly important to improve the bearing capacity of the honeycomb sandwich structure.This paper introduces the grid structure to improve the bending stiffness of the honeycomb sandwich structure,and uses the theoretical derivation and finite element simulation method to the honeycomb sandwich structure.The bending stiffness and strength improvement effect are measured by experiments,and the failure mode of the honeycomb sandwich structure is observed.Firstly,an analytical model of the grid sandwich structure is established.Based on the basic assumptions of the composite laminate,the thickness of the upper and lower panels and the total height of the structure are used as independent variables.The bending stiffness of the honeycomb sandwich structure is used as the dependent variable to derive the bending stiffness.The relationship between the thickness of the upper and lower panels and the total height shows that as the asymmetry of the upper and lower panels increases,the optimization of the bending stiffness of the structure increases continuously.As the total height decreases,the optimization of the bending stiffness of the structure increases.Finally,the geometry of the honeycomb core structure with the best optimization value was determined,and the finite element simulation and three-point bending test of the honeycomb sandwich structure were carried out according to the obtained geometrical dimensions.In the finite element simulation process,the ANSYS APDL(ANSYS Parametric Design Language)parameterized language is used to establish the geometric model of the honeycomb sandwich structure.In order to simplify the calculation,the honeycomb sandwich structure is equivalent to the sandwich model,and this paper analyzed six typical calculations.For example,the displacement cloud map is obtained,and the finite element results are compared with the grid-enhanced analytical solution.It is verified that under the premise that the thickness of the honeycomb sandwich structure remains unchanged,the degree of optimization of the bending stiffness increases with the increasing of asymmetry of the upper and lower panels.Finally,the strength test and three-point bending test of the honeycomb sandwich structure and the grid-reinforced honeycomb sandwich structure were carried out.Through the strength test,the traditional honeycomb sandwich structure undergoes two failures.When the load reaches 915N,the honeycomb core tears and the load drops momentarily.When the load reaches 669N,the honeycomb core is debonded from the lower panel,and the honeycomb sandwich structure loses the capacity of carry.The grid-enhanced honeycomb sandwich structure is in the linear elastic phase of the test machine,and the test is completed when the load reaches 1799N.In the three-point bending measurement,the bending stiffness of the sandwich structure is measured by the positive pressure test and the back pressure test.The final honeycomb sandwich beam positive pressure test measured the bending stiffness as 1.58×10~7N·mm~2,and the back pressure test measured the bending stiffness as 1.45×10~7N·mm~2.The bending stiffness measured by the grid-reinforced honeycomb sandwich beam positive pressure test was2.28×10~7N·mm~2,and the bending stiffness measured by the back pressure test is2.21×10~7N·mm~2.From the experimental phenomena and calculation results,it can be concluded that the introduction of the grid structure greatly improves the bending stiffness and ultimate load of the honeycomb sandwich structure.