A significant research effort in aviation is currently focused on the integration of electric or hybrid-electric power-trains on board aircraft in an effort to improve efficiency and environmental friendliness. New designs incorporating these novel propulsion systems face the issue of penalizing battery characteristics, especially in terms of limited energy and power density performance, in turn imposing a toll on the inert weight of the machine. A possible solution to this issue is that of structural batteries. These are similar in structure to carbon fiber composites, where the matrix features dielectric characteristics, making the structure capable of storing electric energy while retaining the capability to withstand mechanical loads. The adoption of this technology, currently under advanced development, shall enable significant weight savings, yet it raises relevant issues concerning aircraft sizing procedures, that need to be conceived taking into account the specific characteristics of such multi-functional materials. This paper faces the new problem of aircraft initial design in presence of structural batteries. First, it presents a method for aircraft preliminary weight sizing, where the double effect of structural batteries on both structural mass and energy storage mass is considered. Subsequently, a procedure to size an airframe structure with the adoption of structural batteries in key components is shown, based on a weight-optimal approach. The complete sizing procedure is illustrated through an award-winning test case in the General Aviation category.
Particle dampers’ dissipative characteristics can be difficult to predict because of their highly non-linear behavior. The application of such devices in deformable vibrating systems can require extensive experimental and numerical analyses; therefore, improving the efficiency when simulating particle dampers would help in this regard. Two techniques often proposed to speed up the simulation, namely the adoption of a simplified frictional moment and the reduction of the contact stiffness, are considered; their effect on the simulation run-time, on the ability of the particle bed to sustain shear deformation, and on the prediction of the dissipation performance is investigated for different numerical case studies. The reduction in contact stiffness is studied in relation to the maximum overlap between particles, as well as the contacts’ duration. These numerical simulations are carried out over a wide range of motion regimes, frequencies, and amplitude levels. Experimental results are considered as well. All the simulations are performed using a GPU-based discrete element simulation tool coupled with the multi-body code MBDyn; the results and execution time are compared with those of other solvers.
A particle damper (PD) is an enclosure partially filled with small particles that can help to dampen the vibration of a structure. Despite its simplicity, the reliable prediction of the behavior of such a device in arbitrary operative conditions appears to be very difficult due to the complex non-linear interactions between the particles and the system. An experimental methodology is defined with the aim of minimizing the bias due to the PD non-linear response. The effect of the mutual orientation of motion, gravity, and enclosure and of different disturbance inputs on the performance of a PD is investigated in order to make available a set of reference experimental results for correlation purposes with prediction tools. An open-access database, gathering all the test results, is made available. Graphical abstract
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