Configuration Analysis And Dynamics Research Of Bistable Composite Laminates

Advanced composite materials are widely applied in aerospace structures, due to their high specific strength, high specific stiffness, corrosion resistance and fatigue resistance. In general, laminated composite are designed to be symmetric to decrease the curing deformation. However, as the application range of composite materials is expanding, in the future it is possible to take advantage of the curing deformation of laminated composites in certain circumstance.Bistable composite laminates are laminated composite structures have two stable configurations, and are able to transform between stable configurations under external load, while no energy is needed to maintain the stable configuration. The bistability and nonlinear characteristics make bistable laminates be potential in application on morphing structures, energy harvesting and nonlinear vibration isolation. In this thesis a systematic study on the bistable laminates is conducted. The research contents including the configuration prediction and bifurcation analysis of bistable laminates, new hybrid bistable laminates, the heating actuation method, the dynamic characteristics of bistable laminates, the broadband vibration energy harvesting system based on bistable laminates and multistable structures based on bistable laminates.Using Rayleigh-Ritz method, the sixth-order theoretical shape prediction model is established. The influence of bending-stretching coupling on the mid-plane strains is considered in the theoretical model. For laminates with relative large sizes, saturated curvature model is established. Using theoretical model and finite element method, systematic parametric analyses are conducted to investigate the influences of aspect ratio, ply thickness and laminate size, on the bifurcation phenomenon of bistable laminates. Critical bistable dimensions and critical central load are predicted. The parametric analyses show the design space of bistable laminates.Novel hybrid bistable laminates are put forward and analyzed. By adding mental ply on the surface of cross-ply laminates, the two stable configurations of the [0/90/Al] bistable laminate curls to the same side. Using sixth-order theoretical model with 25 unknown parameters, the influence of dimensions, the slippery between mental ply and composite ply, and the moisture effect on [0/90/Al] laminates are investigated. By adding mental ply in the symmetric laminates, the novel hybrid symmetric bistable laminates(HSBL) are put forward. The two stable configurations of a HSBL curls in the same direction, and have identical curvatures with opposite signs. Theoretical shape prediction model with 9 unknown parameters is established. The design space of HSBL is investigated using the 9-parameter model and finite element method. The nonlinearity of HSBL under different boundary conditions is investigated by finite element method.A multi-stable lattice structure and a multi-stable wavy skin based on bistable laminates are developed. The multi-stable lattice structure consists of tri-stable lattice cell, which is assembled by 4 pieces of bistable laminates. The stability of tri-stable lattice cell is experimentally and numerically investigated. The influence of cell arrangement on the stable configurations of the multi-stable lattice structure is investigated. The snap-through processes among multiple states are simulated using finite element method. The results show a good correlation and give an intuitive understanding of multiple snap-through behavior. The feature highlights its potential application in morphing structures.A novel heating actuation method is put forward and verified. The heating actuation method changes the stability and the stable configurations of bistable laminates, by elevating the temperature of local area on the laminates. Two heating strategies are developed for bistable laminates of different shapes and different thicknesses. The heating actuation method is verified in experiments, and its adaptability is verified by finite element method. By embedding the electro-thermal material into bistable laminates, the thermal-driven bistable laminates(TDBL) are put forward. Two TDBLs are manufactured and verified. The experimental morphing processes of two TDBLs are compared with the simulated process, and good agreement between experiments and predictions are found.Theoretical kinetic model of unsymmetric bistable laminates is established. Experimental and theoretical studies on dynamic responses of four unsymmetric bistable laminates around the first vibration mode are conducted. The dynamic responses of two hybrid symmetric bistable laminates around the first and the second vibration modes are investigated by experiment and FEA. Results show that bistable laminates show soften stiffness in oscillation, and have two fundamental oscillation patterns including the single-well oscillation and cross-well oscillation. A bistable broadband vibration energy harvesting system is developed and analyzed. A rectangular bistable laminate is employed as the support structure of PZT. By exploiting the nonlinear oscillations around the second vibration mode, the bistable energy harvesting system(BEHS) is able to achieve broadband vibration energy harvesting at relative higher frequencies. The broadband characteristics and the considerable energy conversion efficiency of the BEHS are demonstrated in experiments. The static nonlinearity and the dynamic responses of the BEHS are investigated by finite element method. The optimization method of the BEHS is discussed and verified by finite element method.