Research On Impact Resistance And Interface Performance Of Composite Structure Based On 3D Printing Method

Sandwich structures are composed of core layers and metal alloy face sheets.They have the characteristics of light weight and high strength due to a lot of pores in them.Compared with traditional laminate structures,the structure has the advantages such as energy absorption,vibration damping,weight reduction,low cost and so on.So they have been widely used in aerospace,vehicles,military industry and other important fields in recent years.In the application of engineering structure,the structure will inevitably be subjected to compression,impact and other loads,which will lead to the fracture and interface debonding induced damage of composite structures.Therefore,it is very important to study the skin-core interface and whole mechanical behavior of lightweight metal-polymer composite structures with various structural parameters of porous cores under different loading conditions.This can provide a reference for predicting the load-bearing and failure modes of the new type of composite structures.In this paper,based on the mathematical definition of Voronoi structure and various parameter determination methods,porous polylactic acid(PLA)polymer structures with different irregularities are firstly established.The accuracy of the proposed method is verified by determining statistical parameters of the distance between seed points in the Voronoi model.The finite element model is then established by means of extracting information from ANSYS APDL language,porous honeycomb structures with five kinds of irregularity and random missing 5% of microtrusses are established,and the influence of different structural parameters on their bearing capacity under compressive loading has been investigated.In addition,the sandwich interface microstructure is designed based on interface toughening mechanism for enhancing mechanical properties of the magnesium alloy skin/PLA porous core interface.The improved interface fracture toughness parameters have been obtained through experiments and used in the VUMAT subroutine for exponential interface cohesive model.The low speed impact mechanical behavior of two kinds of composite structures with 2 irregularity parameters and stable energy absorption characteristics is finally studied,and the effects of different impact energies and punch sizes on the impact resistance of sandwich structure are also studied.The results show that: among the porous honeycomb structure with different irregularity,the structure with higher relative density has better load-bearing and energy absorption characteristics.With the increased irregularity,the equivalent elastic modulus of the structure increases,but the energy absorption characteristics gradually decrease.When the irregularity is about 0.5,the mechanical properties are stable,while the influence of random missing microtruss on the compressive load-bearing is far greater than that of the irregularity.The bonding property of the designed rough interface between PLA and magnesium alloy can be greatly improved,which is more than 1.5 times higher than that of smooth interface.Under dynamic impact loading,3D Voronoi structure has stronger impact resistance than that of 2D structure.Punch size have a greater impact on the impact response of the sandwich structure,and the dynamic response of 2D Voronoi structure is more sensitive to punch size.By comparing simulation predictions and experimental results for typical 3D Voronoi porous honeycomb sandwich structure subjected to low velocity impact load,it is found that the results are in good agreement,indicating that the designed porous sandwich composite structure has good impact resistance and energy absorption characteristics.