Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - C3HARME (NEXT GENERATION CERAMIC COMPOSITES FOR COMBUSTION HARSH ENVIRONMENTS AND SPACE)

Teaser

As the aerospace industry advances towards hypersonic flight, the quest for new, ground-breaking aircraft technologies has begun: high-speed aviation needs advanced materials that can survive extreme conditions. During space flights, materials in the spacecraft are exposed to...

Summary

As the aerospace industry advances towards hypersonic flight, the quest for new, ground-breaking aircraft technologies has begun: high-speed aviation needs advanced materials that can survive extreme conditions. During space flights, materials in the spacecraft are exposed to extremely harsh conditions: temperatures can suddenly rise above 2000 °C while corrosive gases and winds strongly hit the surface. Only ceramics can withstand such high temperatures, and among them, only ceramic matrix composites (CMCs), which consist of fibers embedded in a matrix, can survive thermal shocks and critical mechanical stresses. However, the harsh environment and the high temperature experienced by a spacecraft can still cause the erosion of CMCs, making expensive vehicles unable to resist several launches and re-entries. C3HARME addresses this technological gap, investigating on new innovative materials, to supply the aerospace industry.
We will tackle this challenge by combining the best features of CMCs with the high-temperature resistance of another promising material: the Ultra-High Temperature Ceramics (UHTCs). C3HARME will design, develop, manufacture and test a composite material that joins the physical and chemical properties of CMCs and UHTCs, creating a new class of Ultra-High Temperature Ceramic Matrix Composites (UHTCMCs) able to self- repair damage without any external intervention (self-healing).
The proof of concept of C3HARME’s technology will be tested on two spacecraft\'s components:
• Nozzles of rocket motors that must survive temperatures above 2700 °C and the corrosive environment produced during the combustion of propellants;
• Tiles forming the Thermal Protection System (TPS) of hypersonic vehicles that should resist the thermal shocks and stresses during the launch and the re-entry into Earth’s atmosphere.

C3HARME objectives include the design and characterization of the UHTCMCs supported by lab-scale testing, the manufacturing and up-scale of realistic prototypes and finally, their validation in relevant ground simulated environment. Our project represents a well-balanced mix of innovative and consolidated technologies.

Work performed

Halfway to the project, C3HARME has reached several achievements:

1) Materials were produced following different processing routes (SPS / RMI / RF-CVI / PIP), spanning from spark plasma sintering that allows ultrafast consolidation of the new UHTCMCs, to radio frequency chemical vapour infiltration, which allows a much faster infiltration compared to conventional CVI due to quick and uniform heating from inside-out, or reactive metal infiltration, a reliable zero shrinkage technology which enables complete elimination of pores in the matrix. Also, the partners investigated cross-processing routes that combine their technologies to create innovative routes.

2) Partners prepared around 50 compositions of the new materials and analysed them to investigate the impact of different types of fibres, self-healing agents and manufacturing approaches. To guarantee homogeneity and reproducibility, multiple samples were produced and their microstructure was carefully checked.


3) Partners investigated different techniques to incorporate self-healing phases; efforts were also devoted to set-up methodologies to test the self-healing capability. The technique should create a known damage, possibly in a well-defined position and affecting a key property like strengths, and then measure its recovery rate. So far, three methods to inflict a damage were tested and evaluated.

4) About 500 samples have been tested at the lab scale (TRL 4) and fully characterized from the thermo-mechanical point of view. An extensive experimental campaign was carried out in the Aerospace Propulsion Laboratory and in an environment typical of atmospheric re-entry, the SPES arc-jet wind tunnel. Numerical models were also employed to predict of the flow field around test articles and the thermal behavior of the samples. The extensive campaign carried out allowed to screen compositions. For several processes, tests were successful and TRL4 was fully achieved in both applications.

5) Partners identified 6 technologies for the realization of final TPS prototypes and 3 technologies for the final nozzle prototype. Processes for the TPS application include three based on sintering (one is hybrid), three on non-sintering technologies. Concerning compositions, 6 compositions are being studied. For nozzles, 3 processes and 3 compositions were selected, with degree of maturity of 4. All processes selected for nozzles are based on sintering technologies.

6) In order to assess the possibility to scale–up the processing routes, the samples were produced with an increasing size. In the meantime, partners are setting up the ground systems in all the foreseen testing facilities. The aim is to manufacture prototypes for ground tests and produce specimens for the qualification tests aimed at propulsion and TPS applications.

7) Partners developed a multi-scale modelling approach to predict the material behavior, first at coupon level and then scaling it up at component level. The aim is to model the microstructure of UHTCMCs with consideration of geometrical parameters like fiber diameter distribution and processing parameters such as sintering temperature. In order to understand the impact of the chemical environment in real-life rocket combustion situations, partners also investigated through modelling the material’s chemical reactivity with the most common chemical agents. The final goal is to develop a descriptor for chemical reactivity, which can help to efficiently predict the aging effects in chemical-erosion conditions.

Final results

With respect to the state of the art, C3HARME brings three main advancements:
1. C3HARME utilizes both the experience on UHTCs and CMCs to design a new hybrid outperforming material, benefiting from these different classes of brittle and non-brittle, hard and soft, heavy and light materials, with the potential to successfully tailor the nano-, micro- and macro-structure.
2. The self-healing capability: in UHTCMCs, it will arise from the addition of nanosized substances that under thermal stress (during launch or re-entry) trigger the formation of an external solid protective layer and an internal liquid phase that heals the flaws. This will improve the reliability of the structural ceramic components and make our material reusable, dramatically reducing costs of space missions.
3. The processing routes: C3HARME will identify the best processing routes, amongst well established and new, hybrid processes, created from the unusual combination of different technologies. Not only performance but also timing and costs will be considered for screening the technologies.

The entire aerospace industry will benefit from such innovation: the availability of a new family of materials, capable of providing structural integrity, thermal protection and near-zero erosions rates will foster the implementation of new propellants for boost and thrust applications, while the development of reusable components will reduce cost and waste. This solution will potentially be a ground-breaking innovation also for many other fields with similar severe conditions, such as combustion and nuclear environments (Generation IV fission and fusion reactors) or the concentrating solar power system, thus paving the way for enormous exploitation opportunities.

Website & more info

More info: http://c3harme.eu/.