Study On Preparation And Properties Of Foam Filled Folded Core Sandwich Structure

The folded core sandwich structure is a new type of three-dimensional deployablecomposite sandwich structure with good mechanical properties such as high specific strength,it has good application in the lightweight of industrial equipment.However,the space between the panel and the folded core form hollow structure which become its deficiency in bending resistance.Therefore,it is very important to explore a method to improve the stiffness and energy absorption characteristics of folded core sandwich structure.This paper explores the preparation method of folded core sandwich structure filled with polyurethane foam and folded core was prepared at the same time.The static compression and three point bending of folded sandwich structures before and after foam filling were studied by means of mechanical test and numerical simulation.Firstly,the relationship between the three-dimensional structural parameters and the plane parameters of the folded structure is discussed and get the conversion formula between them which Lay the foundation for the design and preparation of folded core.At the same time,C-03P-200 carbon fiber and Kevlar-49 were used as raw materials to prepare the folded core by hot pressing process,the optimum process scheme based on three technological parameters of time,pressure and temperature is obtained.The folded core sandwich structure was bonded through two 3240 epoxy plates and a folded core.The polyurethane AB material were used as raw material to filled the folded core sandwich structure by the bottom-up free foaming method.The results show that the polyurethane foam can be filled with its own expansion and deformation evenly in the space between the panel and the folded core with a good filling effect.Secondly,the compression tests and three point bending tests were carried out on the folded core sandwich structure before and after foam filling,the load-displacement curves of them were obtained by compression test,and the performance parameters such as ultimate strength,specific strength were compared.The results show that the foam-filled folded core sandwich structure has a significant improvement in ultimate strength and compression modulus.Comparing the damage and failure modes of them,the mainly failure modes of foam-filled folded core sandwich structure were Panel fracture ? foam collapse and core buckling deformation,which has a more stable damage process.The reason is that the foamwas filled in the upper and lower space between the core and the plates,which not only played the role of supporting the core so that the folded core will not suddenly appear large deformation,but also to absorb the energy of external mutation load and achieve “offset”effect.The load-deflection curve obtained by the three-point bending test also shows that the foam-filled folded core sandwich structure has higher bending strength?bending modulus and bending stiffness.Finally,the finite element simulation model was established by ABAQUS,the finite simulation of the process of compression test and three-point bending test was carried.The purpose of the simulation is to establish an effective prediction model for folded core sandwich structures,the mechanical properties of the folded structures with different structural parameters can be predicted,which is of great importance to the optimization design of folded structures.The numerical simulation results were compared with the experimental results,the results show that the simulation results are in good agreement with the experimental results,which indicates that the simulation model has certain reference value,based on this,the folded structure is optimized.