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Innovative Materials<img alt="" src="" style="BORDER:0px solid;" /> MaterialsInnovative Materials<h3>Goals</h3><p style="text-align:justify;">The main goals of this area are:</p><ul style="text-align:justify;"><li><p>Develop advanced models for the mechanical response of materials</p></li><li><p>Study physical properties of surfaces and develop methods for their control</p></li><li><p>Analysis of the thermal and mechanical properties of materials</p></li><li><p>Develop innovative materials and solutions for thermal protection systems</p></li><li><p>Develop advanced methods for the formulation and synthesis of nanoparticles</p></li></ul><h3><span lang="EN-GB">Research topics</span></h3><p style="text-align:justify;"><span lang="EN-GB"><strong>Mechanics of microstructured materials/multiscale mechanics</strong></span></p><p style="text-align:justify;">Cellular materials with random (foams) or periodic (lattice materials) microstructure make up a wide class of both natural and artificial materials with a remarkable potential for aerospace application because they combine remarkable lightness with high strength, together with large energy absorption capability. By careful selection of the topology of the microstructure, it is possible to obtain materials with very high specific stiffness, or to induce unusual behaviours such as null or negative Poisson's ratio along specific directions. Recent advances in additive layer manufacturing techniques allows manufacturing very complex and large parts featuring a well specified microstructure, both out of metal or polymers. Nevertheless, accurate modelling tools for such materials are not available yet. In fact, on one hand individual modelling of every single strut comprising the component leads to very large models, on the other hand excessively simplified linear homogenized models are not capable to capture the nonlinear behaviours of lattice materials, which represent their uniqueness. One solution is given by multiscale methods. </p><p style="text-align:justify;">Multiscale methods evaluate the constitutive relationships of a heterogeneous medium from the analysis of a small portion of it, the Representative Volume Element (RVE). The RVE consists in a limited region of the domain that contains the main microstructural features of the material and responds as the infinite medium. On one hand, we have the macroscopic finite element model of the component, whose boundary conditions are defined by the general problem, where the material is treated as a continuum. On the other hand, we have the microscopic model of the RVE, which numerically evaluates the stress strain relationship, whose boundary conditions are generated by the macroscopic model. The RVE model is interrogated at every integration point of the component model, a process that allows the assembly of the macroscopic internal force vector and of the tangent stiffness matrix, as it is done for a fully solid material. The key element in these approaches is the definition of suitable kinematic and equilibrium relations that allow exchanging information between the models at each scale. In the case of materials with a repetitive microstructure, the periodicity allows certain assumptions and linking directly the macroscopic deformation tensor to the microscopic counterpart, taking into account both geometric non linearity, arising from large displacements, and material non linearity due to finite strain. Following an approach developed by CIRA researchers the macroscopic constitutive model for lattice materials can be derived by applying to the RVE the following boundary conditions</p><ul style="text-align:justify;"><li><p>A kinematic boundary condition that links the deformation of the periodic vectors of the material to the macroscopic deformation gradient of the component;</p></li><li><p>Periodic equilibrium condition that ensures self-equilibrium of the material.</p></li></ul><p style="text-align:justify;">Such an approach is capable of capturing non-linear behaviours of lattice materials with arbitrary topology and is very promising for the solution of complex problems such as the dynamic response of cellular materials and the evolution of damage of fracture.</p><p style="text-align:justify;"><span lang="EN-GB"><strong>Surface engineering</strong></span></p><p style="text-align:justify;">Material surfaces have fundamental importance in any sector and application fields because they directly interact with the environment (many examples can be found in nature and in biology). With availability of nanomaterials and nanotechnologies, it is possible to modify the structure of matter up to and below the nano-scale. As the scale of the system reduces, the surface properties take greater and greater importance. As the dimensions decrease the surface to volume ratio increases, as consequence properties that are shadowed at larger scale become evident. CIRA has been working on nanomaterials (silicon, titanium, carbon nanotube, graphene) since many years. In particular, by properly selecting micro and nano charges, added to polymer resins, CIRA have developed high performing innovative coatings for aerospace applications that are at the global foremost edge.</p><p style="text-align:justify;">Surface engineering requires a deep knowledge of the properties and performances of materials, which change dramatically depending on the length scale at which they are observed or employed. When the properties of the base materials are related to the shape of the components we want to manufacture, and when the optimal processes for their production is taken into account, it is clear that surface engineering is a very complex science dealing with many different variables. Surface engineering affects many aspects of material science. From the development of innovative coatings, to the improvement of the structural adhesion among diverse materials (such as metal-composite systems), up to the functionalization of the fibres surface in composite materials, for the regulation and tuning of the adhesion between fibres and matrix and the global optimization of the laminate at the macroscopic scale. The main research themes in this sector are mainly the study and the development of innovative formulations for hydrophobic and super hydrophobic polymer coatings (self-cleaning, anti-fog, ice-phobic), but also hydrophilic and super-hydrophilic coatings (for instance self-lubricating coatings) are investigated. Applications can be found in both aeronautics and space. For instance, it is particularly interesting to investigate the capillarity of water in contact with surfaces functionalised with such extreme properties. Another research theme is the topological optimization of the surface of components 3D printed in Ti-Al alloys to obtain extreme properties. The same goal can be also obtained by surface electrochemical processes. In both cases, no coating deposition is necessary. With the advantage of avoiding de-bonding problems due to mismatch of thermomechanical properties on the interfaces. In addition, such surfaces will preserve their properties even if they are exposed to very rough environments.</p><p style="text-align:justify;"><span lang="EN-GB"><strong>Synthesis of nano-structured materials</strong></span></p><p style="text-align:justify;">Nano-charges or particles with nano-size have the capability of improving the properties of the hosting matrix, especially if they have been properly functionalised and are well dispersed into it. In this way, small quantities of nanotube or graphene added to an epoxy resin can make this conductive; silicon particles obtained in situ by means of sol-gel processes can improve the mechanical properties of the matrix in terms of Tg increment and elastic modulus after glass-transition. The addition of aluminosilicates, such as montmorillonites, can improve thermal properties of resins. The above cited are only a few examples of the wide range of properties modification of materials that can be obtained by the addition of nanoparticles. Within this context, the Innovative Materials Laboratory focuses on the characterization and synthesis of nanostructured materials including the synthesis of polymer matrices ad-hoc formulated for specific applications, the synthesis and functionalization of nano-charges, and the dispersion and mixing of nano-systems.</p><p style="text-align:justify;">The main research themes are the synthesis of purposely-functionalised nano-particles, the formulation of polymer matrices (elastomeric, epossidic, hydrogels etc) with the aim of guaranteeing ad-hoc properties for specific applications, the synthesis of hybrid organic/inorganic systems both using preformed particles (MWNT, SiO2, TiO2, Graphene, MMT, etc), and in-situ obtained particles by means of sol-gel processes, the synthesis of super-hydrophobic coatings for aeronautical applications, the formulation and the characterization nano-charged hybrid propellant for rocket engines </p>