Research On Low Speed Impact Response Of 3D Braided Composites Sandwich Panels With Aluminum Honeycomb Cores

As an efficient light-weight and high-strength structure,advanced composite laminated sandwich panels are conducive to reducing the weight of aircraft structure and improving the design quality of structure.However,in the course of service and maintenance,it is inevitable that the aircraft will be subjected to various low-energy impacts,which may easily lead to delamination and other damage of laminated panels,thereby decreasing the compression strength of the structure and reducing the service life.3D seven-directional braided composite is a novel structural form in the field of 3D textile composites,which has the advantage of high specific modulus and specific strength.For its unique spatial mesh polydirectional fabric reinforcement,the out-of-surface transverse mechanical properties of the material are enhanced significantly.Replacing the traditional laminated composite with the new composite as panel is expected to improve the impact resistance of honeycomb sandwich panel structure.As a result,there are important academic significances and engineering application values for developing the optimization design analysis methods of textile composites sandwich panels to study the basic mechanical properties of 3D seven-directional braided composite panels in depth,explore the low speed impact response characteristics of 3D seven-directional braided composites sandwich panels with aluminum honeycomb cores and reveal the impact damage mechanism and the influence law.In this paper,the low-speed impact response of 3D braided composite sandwich panels with aluminum honeycomb cores was studied by using a cross-scale research method.First,on the mesoscopic scale,based on the 3D seven-directional braided composite mesoscopic cell model,combined with the periodic boundary conditions and the small deformation assumptions,the finite element method was used to propose the macroscopic equivalent elastic properties analysis model of the material,and the prediction of the sandwich panel’s equivalent properties was realized.Subsequently,embedding the failure criterion and performance reduction scheme of cell component materials,using nonlinear finite element method,the gradual damage analysis model of the cell material under typical loads was established to predict the nonlinear stress-strain response and fracture strength of the material under working conditions of typical loads.And based on the analysis of the cell,the influence law of the stiffness and basic strength of seven-directional braided composite panels caused by the change of weaving process parameters was discussed systematically.Then,on the macroscopic scale,considering the constitutive relationship of the surface panel,the core material and the rubber layer of the sandwich panels,the macro low-speed impact model of the 3D braided composite sandwich panels with aluminum honeycomb cores was established embedding the failure criteria and the performance degradation scheme of the corresponding components of the structure.By the contrast and analysis of the low-speed impact response of the traditional laminated composite sandwich panels with aluminum honeycomb cores,the low-speed impact resistance of the new material structure was evaluated systematically.The influence law of the low-speed impact damage morphology of the structure caused by the changes of main weaving processing parameters of sandwich panels and the impact energy was discussed in detail,which obtains some important conclusions with reference value.The study shows that 3D braided composites can significantly enhance the low-speed impact resistant qualities of sandwich panels structure with honeycomb cores.The work in this paper not only contributes to the optimization design and analysis of 3D seven-directional braided composite sandwich panels structure,but also is expected to promote the wide application of this new material of sandwich panels in aerospace structure.