Research On Optime Of Nature Frequence And Impact With Low Speed Of Advanced Grid Stiffened Structure

Advanced composite grid structure is a new kind of structural materials which is light andhigh-strengthen and has broad application prospects in aerospace engineering. After more than tenyears of development, many scholars have made deep researches on structural configurations，staticsmechanics properties, fabrication methods, damage properties and so on. Now, it has already beenused in real aeronautic and astronautic structures. But investigations on dynamics of composite gridstructures should be carried on deeply.In this paper, characteristics of natural frequency, bearing capacity, impact behaviors with lowspeed of AGS are researched through both theoretical and simulation analysis. The main researchworks are as follows：First of all, dynamic models of composite laminate with the boundary conditions of simplesupports of all four edges were established. At the same time, dynamics simulations of the samelaminate were finished in FEA software, MSC.Nastran/Patran. It shows that simulation results wereconsistent with theoretical results quite well. Then, natural frequencies optimization researches of thecomposite laminate were carried out based on the extended development of FEA software,MSC.Nastran, by the changing of every ply angles. The changes of composite laminate structure’sstrength were researched through the comparison of failure factor between un-optimized andoptimized structures. Thirdly, the relationships among isosceles triangle cell’s base angle and elasticconstants of the equivalent stiffness model of AGS were also established and confirmed withsimulation. Three kinds of AGS with different cells were designed and the best one was used toreplace a composite aerofoil box of pilotless aircraft under the conditions with same weight. Themechanics properties of the two structures were also compared and after that, the first naturalfrequency of AGS was improved by the above optimization method. Finally,3D Hashion strain failurecriterion and stiffness reduction project ware adopted to investigate the low-speed impaction damageof composite laminate with the extended development of FEA software, Abqus. Furtherly, the damagecharacteristics of AGS with low speed impaction were also founded with the same method.