The space conditions are very hostile for both spacecrafts and human life. It's well known that UV radiation, vacuum, atomic oxygen and large temperature gradients, damage the aerospace components and in particular lead to a degradation of polymer-based materials that are the basic elements of different spacecraft subsystems, such as multy-layer-insulation (MLI) in satellites and propulsion systems in solar sails. Moreover, the international scientific community is focusing its attention on the design of new radiation monitors and more radiation resistant spacesuits and human habitat structures for exploration of Moon and Mars. For these reasons, the membrane general performance can be improved by nano-reinforced coating on such membranes.
This project will be focused on the development of nanocomposite films on flexible membranes which have unique properties. The realization of multifunctional films on a sufficiently large scale will be the target for a technological demonstrator to be tested in satellite applications. In particular, the nanoparticles geometry, functionalization and concentration in the polymer blend will be studied. An analytical model for the manufacturing process of spray coating of nanocomposites fluids will be developed. Conductive measurements, before and after bending at 180° and UV-C exposure, will be performed on all films by using electrical resistance tomography technique to estimate changes in the conductivity distribution on the surface of the films and the piezoresistive properties of the overall structure. The performance of multifunctional films will be tested in simulated space environments this will bring information on the expected behavior of the films in satellite applications and the Atomistic Finite Element Method (A-FEM) techniques will be used to transfer the mechanical and electric properties of carbon nanoparticles to the polymeric matrix in order to predict the overall properties of the nanostructured composite film.
The main expected result of the proposed research is the manufacturing of multifunctional nanocomposite films on Mylar substrate with controlled thermal, electrical and electromagnetic absorbing characteristics, while maintaining the flexional features of the membrane substrate. The realization of multifunctional films on a sufficiently large scale (at least 50 cm x 50 cm) will be the target for a technological demonstrator to be tested in satellite applications.
In particular, expected results from the research project can be summarized as follows:
1. Determination of the relationship among the different parameters affecting dispersion of carbon nanoparticles in aerospace-grade resins.
The dispersion of nanofillers in the polymer matrix is an important issue that greatly affects the outcome of the manufacturing process of nanocomposites. The role of nanoparticles geometry, functionalization and concentration in the polymer blend will be assessed. A dispersion coefficient based on the elaboration of optical microscopy images of nanocomposite blends before cure using a custom-made code (for example in Matlab) will be developed.
2. Definition of the mechanisms behind the multifunctional properties of the carbon-based films
The understanding of the physical-chemical interactions of the different material components, and of the phenomena at the base of their mechanical, thermal and electrical behavior, is crucial for tuning the performance of the multifunctional films. In addition, this objective aims at further increasing knowledge of the scientific community on the physical-chemical fundamentals of multifunctional materials.
3. Development of an analytical model for the spraying process of carbon-based nanocomposites fluids and optimization of the process parameters.
The process parameters are strongly affected by the nature of the blends. In the case of nanocomposite fluids (such as epoxy/carbon nanoparticles), the material properties that affect the outcome of the spraying process, in particular viscosity and wettability, vary in a nonlinear way. Therefore, the relation between process parameters and material properties will be determined.
4. Understanding the interconnected phenomena at the base of the multifunctional properties of the nanocomposite films.
This result is crucial for tuning and modeling the performance of the multifunctional films, in particular in terms of thermal, mechanical and electrical properties. Moreover, it will be checked if these nanocomposite coatings on membranes as sustrates will be able to increase the piezoresistive properties of the overall structure both before and after UV-C exposure, lead to growth of the knowledge in in structural health monitoring (SHM) of composites in the aerospace and astronautic fieldsand, and in the characterization of their micromechanical behavior. In addition, the performance of nanocomposite films in a simulated space environment will bring information on the expected behavior of the films in satellite applications.
5. Development of a numerical model based on A-FEM and modeling the UV-response.
An analysis based on Atomistic Finite Element Method will generate a model that connects the mechanical, electrical and thermal behavior of the nanocomposite films with measurable experimental data.
Results from the proposed project will be published in high impact international journals and presented at major international conferences in the fields of aerospace engineering and of composite structures.