Highly Tunable Mechanical Performance Of Newly Multistable Structures

Variant aircraft based on smart structures is one of the important directions for the development of future aircraft.The multi-stable variant structure has the ability to maintain a variety of stable states,so that it can be adaptive deformation according to the mission requirements.Besides,it can keep stables state without extra energy input,which is an ideal smart structure to ensure the characteristics of lightweight and low energy consumption for the future variant aircraft.But the research status at home and abroad reflects that there are still many difficulties and problems to be solved in the bearing capacity and stability of the multi-stable variant structure.In order to solve these problems,a new type of multi-steady variant structure based on the internal pressure expansion effect of thin-walled cylindrical shell is proposed.The research work as follows:(1)Research on the bistable mechanical properties of the unit structure.By deriving the theoretical analytical formula of the critical bearing capacity when the unit structure undergoes a steady state transition under the action of axial force,the force-displacement curve of the unit structure during the mutual transition between two stable states is clarified.With Finite element simulation and experiment,the response curve of the force-displacement in the steady-state transformation process of the unit structure is verified.What’s more,based on size of the element structure,carry out the parametric research on the bistable mechanical properties,analyze the influence of each size parameter on the bearing strength of the unit structure and the steady-state transformation process.The results show that: the theoretical analysis model proposed in this paper can be used to preliminaryly design the multi-stable variant structure;and when the total mass of the unit structure is almost unchanged,the bearing strength of the unit structure can be changed in a large range by changing the value of size,which achieves the excellent designability and tunability of the bistable unit structure.(2)Research on the mechanism of bearing properties of multi-stable variant structures.The three-dimensional multi-stable variant structure is constructed through the serial and parallel connection of the unit structures,and theoretical analysis is used to clarify the bearing capacity of the structure in any stable state.Furthermore,the paper research the influence of the change of the mechanical properties of any unit on the bearing capacity and stability of the multi-stable whole structure.Based on the results,carry out finite element simulation and experiment for the multi-stable bearing capacity of the variant structure by using the the displacement control method.The results show that the multi-stable variant structure based on unit bistable structure can achieve the required multi-stable performance under the displacement control,and by adjusting the mechanical properties of unit structure,the bearing performance of the multi-stable variant structure is highly tunable.(3)Research on the energy absorption characteristics of multi-stable variant structures.The force-displacement response of the bistable structure in cyclic loading process is clarified,and explore the energy absorption level of the unit under the cycle period.Through calculating the area enclosed by force-displacement curve,the influence of the structural size parameters and friction coefficient on the energy absorption of the bistable structure is studied.The results show that energy absorption strength of the bistable structure can be tunable by changing the structural parameters.On this basis,further research the influence of each size parameter of the unit structure on the energy absorption characteristics of the multi-stable variant structure,then form energy-absorbing multi-stable variant structure design methods for different environmental requirements.