Develpoment of advanced structural multifield models for the study of smart wing
In the field of aeronautics, shape morphing has been used to identify those aircraft that undergo certain geometrical changes to enhance or adapt to their mission profile. In spite of there is not a clear definition of shape morphing, it is a general agreement that the conventional hinged control surfaces or high lift device, such as flap or slat that provide discrete geometry changes cannot be considered as morphing. Otherwise from the conventional solution the shape morphing required: distributed high-power density actuation, structural mechanization, flexible skins, and control law development. In these scenario, models able to capture the insertion of new generation sensor and actuator, and able to minimize the computational cost become very interesting. Refined plate theories offer significant advantages in terms of accuracy of the solution and detection of non-classical effects. The drawback of these theories is that a higher computational cost is incurred because of the presence of a large number of variables. Such an increase could become prohibitive in the case of the application of computational methods such as the Finite Element Method. Moreover to control the behaviour of an distributed actuated wing are necessary model with low computational times. In fact the computational time must be lower than the characteristic time of the controlled phenomenon. In this contest it is very interesting try to identify a method able to build reduced model which didn't penalize the results fidelity. The question which require an answer to identify the reduced model is: for a given problem (geometry, loading, boundary conditions, lamination lay-out) what is the most accurate theory in terms of a fixed accuracy with the lowest computational time? A method able to find an answer has been developed in the first part of this work. The Carrera Unified Formulations (CUF) give the possibility to run various theories for an assigned problem (materials, geometry, lamination lay-out, boundary conditions) at the same time. Trough the use of the CUF it is possible to introduce the so-called mixed axiomatic/asymptotic method, which is able to recognize the effectiveness of each displacement variable of an arbitrary refined plate theory. The recognizing of the effectiveness of each terms can be done in different way, evaluating the influence of each terms of the model or trough a genetic optimization method. All the two methods bring to build the Best Plate Theory Diagram (BPTD). Trough the BPTD it is possible, for a given problem, to identify those models with the lowest computational time and the best results fidelity. One-dimensional (1D) structural models, commonly known as beams, are intensively exploited in many engineering applications. Beam theories are, in fact, used to analyse the structural behaviour of slender bodies, such as columns, arches, blades, aircraft wings and bridges. In a beam model, the 3D problem is reduced to a set of variables that only depends on the beam-axis coordinate. One-dimensional structural elements obtained are simpler and computationally more efficient than 2D (plate/shell) and 3D (solid) elements. These feature make beam theories still very attractive. Classical model (Euler-Bernulli and Timoshenko) have intrinsic limitation which preclude their applications for the analysis of a wide class of engineering problems. A multi-field formulations based on an higher order structural model has been developed in the second part of this work. The structural model is based on the Carrera Unified Formulation. CUF 1D models are extremely cost competitive with respect to plate/shell and solid models with no accuracy lost. In other words CUF 1D structural elements lead to shell- and solid-like solutions with a lesser computational cost. These capabilities allow to use the 1D CUF formulation to simulate the insertion of an distributed actuation and sensing, like piezo-materials, in a wing, using a model lighter than shell or solid. In the results sections are reported some comparison with bibliographic results in order to validate the model.
Settore ING-IND/04 - Costruzioni e Strutture Aerospaziali
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