Research On The Numerical Simulation Of Press Forming For The Double Trapezoidal Sandwich Panel

Sandwich composite panels are widely used in aerospace,aviation,transportation,construction and other fields,because of its many advantages,including the specific strength,specific stiffness,and good shock resistance.In recent years,there has been a great demand for sandwich panels.At present,the sandwich panel surfaces is mainly prepared by vacuum bonding curing method,mechanical properties are limited by the adhesive,prone to degumming and aging,greatly limit its applications.From the existing literature,there is no research on the direct surface forming of sandwich panels.Therefore,it is of great practical significance to study the forming of sandwich panels.The double trapezoidal sandwich panel is a new type of composite plate,with two-way trapezoidal convex and concave corrugated aluminum alloy plate as sandwich,to overcome problem of the traditional discontinuous sandwich,making the sandwich plate get better resistance to different directions deformation.In this paper,the double trapezoidal sandwich panel is used to study the deformation characteristics,regularity and main defects of sandwich panel in the process of forming a curved surface by numerical simulation.The main contents are as follows:1.Numerical simulations are carried out for the forming process of the double trapezoidal sandwich composite panel.Stress and strain analysis of upper and lower panels and sandwich are analyzed,the results show that the stress and strain in the welding zone are smaller than those in the floating area,and the deformation of the cell is mainly concentrated in the transition surface area.The differences in the variation of the angle between the incline and the top surface of the trapezoidal table in the two different directions are analyzed and compared,and the anisotropy of the sandwich is explained.2.The main forming defects of the sandwich panel are analyzed.By changing the radius of curvature of the surface,the morphological features of the upper and lower panels and the sandwich are analyzed.It is found that the cylindrical forming process of the sandwich panel are mainly depression,straight plane and wrinkle,and the spherical forming defects of the sandwich panel are mainly wrinkled,the local face effect and sandwich sidewall buckling.3.The effect of changing the cross-section parameters on the cylindrical forming results was analyzed.The influence of the thickness of the upper panel and the height of the sandwich on the forming quality was analyzed.The influence of the thickness of the lower panel on the face effect of the floating zone is analyzed.The strain distribution of the cylindrical surface of the sandwich panel is analyzed,and the influence of the length of the welding zone in the bending direction on the wrinkling of the upper panel is studied.4.The cylindrical surface forming effect of sandwich plate forming is tested by forming experiment and the validity of predicting the forming defects via numerical simulation is verified.The measurement of the test piece by using the PRO CMM and the error analysis of the surface and the cross section shows that the sandwich plate has high forming precision.