Methods and tools for structural analysis and testing, with applications

Research focus

The Peer review has evaluated this group as Good

Buckling and post-buckling of stiffened composite panels. The use of high performance composites in aerospace structures did not achieve the expected results in terms of weight reduction, mostly because composite panels were not allowed to work in the post-buckling range. The research, originated at DIA and then extended to a larger European partnership, through the improvement of the knowledge on analytical and experimental aspects of buckling and post-buckling, has the objective to ascertain the capability of stiffened composite panels to work safely in the post-buckling range, thus improving their potential efficiency. The first phase of the research was focused on unstiffened flat and curved panel in compression and shear. Great attention has been given to the development and evaluation of experimental and analytical/numerical methods. New analytical approaches are currently in use and Finite Element non linear analysis has been widely checked and validated with experimental results, exploiting a powerful and versatile experimental equipment developed at DIA. In particular, explicit Finite Element approaches were found as the more effective to predict the real post-buckling behavior of stiffened panels, including the possible onset of local damage. A second phase of the research considered stiffened panel loaded in compression and shear. The results showed that the analytical procedures allow the optimization of the panel design with the aim of maximizing the worth of the results obtainable from the experiment. On the other hand the experimental results showed that well designed composite stiffened panels can withstand repeated buckling without damage at least as well as equivalent metal structures. Multilevel optimization procedures for preliminary design. Research on optimization techniques suitable to improve the performance of aircraft primary structures, with special emphasis on the wing-box, has been active for several years. The attention is now focused on two topics. First, a multilevel approach to the multidisciplinary preliminary wing-box design of large and unconventional aircraft configurations. Classical analysis methods (beam models for the global behaviour and monocoque theory for the nonlinear analysis of thin-walled cross sections) have been fully exploited by the integration with optimization algorithms. Two main results were obtained: a good estimate of the primary structure weight, accounting for aeroelastic requirements, and of the torsional stiffness, suitable in a pre-design stage. The second, and more recent topic is related to the design of adaptive wings implementing different morphing concepts by means of optimization procedures. Modeling, analysis and testing of anisotropic and active structures. A semi-analytical method suitable for the characterization of composite laminates has been developed, based on the knowledge gathered in the modeling of smart structures for dynamic purposes. The characterization is complete and capable of describing a large variety of composite laminates, possibly including piezoelectric patches. A parallel research area is focused on shape memory alloys, studied both theoretically and experimentally, to control the buckling of thin panels. Continuum modeling in computational solid and shell mechanics. This focus area goes back to the theoretical foundations of the continuum modeling in deformable solid mechanics, with the aim at increasing the accuracy of approximate numerical solutions in nonlinear structural analyses. The basic idea of observing the micropolar orientation of the infinitesimal particles leads, through sound variational formulations, to finite element implementations that consistently satisfy also the local rotational equilibrium in a weak manner. The enhanced concept of helicoidal modeling is also a significant highlight of this research, and it represents the extension to multi-coordinate domains of the parameterization of motion exploited by the Research Topic 2.2.2.1 in the field of multibody dynamics. The natural coupling of positions and orientations inherent in such modeling view, makes this approach suitable for developing curved finite elements capable of representing arbitrarily large displacements and rotations. This modeling is presently being applied to a shell theory that reduces the 3D problem across the thickness to a 2D element, consistently including the drilling rotation field. Fatigue of materials and structures. Fatigue is one of the major technical areas of interest for aircraft engineers. Efforts at DIA in this field have been focused in the recent past on the development of procedures for producing reliable load conditions for the design of aircraft structures with fatigue considerations. Another field of interest is related to the development of a highly flexible digital controller for managing multi-load tests on aircraft structures/components as well as multi tests on small components. Research topic 4.1 - Methods and tools for structural analysis and testing, with applications 2-46 Computer aided design. These techniques have been introduced in course programs, and then readily applied to different fields such as biomedical applications and the rebuilding of historical aircrafts, where reverse engineering techniques have been successfully used.

Dipartimento di afferenza

Dipartimento di Ingegneria Aerospaziale

Docenti afferenti

Gian Luca Ghiringhelli (Full Professor)
Vittorio Giavotto (Full Professor)
Paolo Mantegazza (Full Professor)
Teodoro Merlini (Full Professor)
Giuseppe Sala (Full Professor)
Chiara Bisagni (Associate Professor)
Sergio Ricci (Associate Professor)
Giampiero Bindolino (Assistant Professor)
Lorenzo Dozio (Assistant Professor)
Pierangelo Masarati (Assistant Professor)