The objective of this academic proposal is to initiate a technological breakthrough by developing a new class of locally-resonant passive acoustic materials for stealth and discretion in underwater acoustics. These metamaterials are synthesized from polymer engineering and involve strong resonant multiple-scattering phenomena within the medium. The main focus of this project is the engineering of sound/noise control in marine environment for the military and civilian areas. The potentialities of these new materials are: increasing sound absorption levels; the possible reduction of thickness of anechoic or masking coatings; a good compatibility with the industrial constraints of manufacture and use. This proposal is a strongly multidisciplinary project between three CNRS laboratories from the Bordeaux campus (experts in wave-physics, soft-matter and microfluidics techniques) and a major industrial group specialized in naval defence. The academic partners have more than 7 years of joint research on the topic of metamaterials (design and manufacturing) and DCNS has recently had a CIFRE/DGA action with one of them. This long collaboration coupled with a geographical proximity and a complementarity of skills up to the industrial level, is a key point to meet the materials and acoustics challenges of the project. The materials challenge. These inclusion-type materials will incorporate sub-millimetric porous micro-resonators (made by emulsions or microfluidics) dispersed in an elastomer matrix adapted to the marine environment. Using "dense" and "resonant" inclusions must make it possible to address two major challenges for better performance of the boat-hull coverings: resistance to hydrostatic pressures during immersion; higher absorption properties due to the resonant multiple scattering. The wave physics challenge concerns the modeling and the experimental proof of the functions and characteristics sought for the synthesized subwavelength materials/structures. An important phase for ultrasonic characterization under mechanical loading of the laboratory samples will indicate the performance of the latter, in particular in terms of absorption. Contextualized experiments will be conducted to predict the anechoic/masking power of the laboratory materials, as well as acoustic measurements on metric panels placed in a pressurized tank. The industrial challenge seeks to take into account at the project outset, a number of manufacturing and use constraints that cannot be avoided by the industrial over the medium to long terms. This is why the soft-matter techniques that are easily-to-be-industrialized techniques, and the account for the hydrostatic pressure are two key elements at the heart of this exploratory-research project for naval engineering. The synoptic operational overview of PANAMA is as follows. 1. Definition of the resonant inclusion media (acoustic design) according to the targeted specifications (absorption level, frequency range, static/dynamic impedance, static loading). 2. Chemistry and synthesis of porous micro-resonators according to certain criteria: size, shape, calibration, controlled polydispersity, mass production. Incorporation of the objects in an elastomer matrix. 3. Acoustic experiments/tests (in laboratory: under loading in open air; in a conventional acoustic water-tank at atmospheric pressure; in a specialized laboratory: in a pressurized tank).

The NIDASTIC project (Functionalized honeycombs for Sciences, Information and Communication Technologies) is set up by a consortium of three partners: DCNS, University of Rennes 1 (IETR), and SERIBASE. Its main purpose concerns the development of multifunctional composite panels based on smart honeycombs. This proposal is directly derived from a CIFRE Défense PhD thesis (N ° 007/2013 - K. Rubrice) which has demonstrated the full potential of this innovative concept (Technology Readiness Level TRL 3-4), especially for applications in the microwave field: tunable radome panels, honeycomb sandwich, control vector, or antennas and antenna arrays made from the core of the sandwich panels. The basic idea of the proposed project concerns the use of conductive patterns (screen printing, inkjet printing, etc.), micropatch antennas, electronic components, etc. on the walls of the honeycomb cells, or to build honeycombs integrating the same components into each cell wall (by additive manufacturing for example). First of all, NIDASTIC project proposes to carry out technological developments on the materials themselves and the related processes, on inks and conductive fillers, on the integration of passive or active components (SMD surface mounted device type) and printed microcircuits. Secondly, functionalization of the structural composite panels will be demonstrated through scale model to address various challenges, in particular with a large frequency spectrum and targeted applications, and then by the design, the fabrication and the characterization of vehicles corresponding to each of the 3 targeted functions mentioned above: tunable radome panels, antenna panels, and control vector panels of surface mounted antennas (TRL> 5). The restricted and very complementary partnership finds origin in the two partners of the PhD thesis (DCNS and IETR) and SERIBASE, a SME specialist in printed electronics. The strong relationship between the partners, their high technological levels and their motivation offer a very rich prospect of dissemination, transfer and use of the results, an increasing maturity level as well as numerous applications in military field, such as civil area. It is all the NIDASTIC challenge to evolve laboratory test pieces or numerical models to functionalized structural composite panels manufactured under an industrial setting. The commitment made by several expert SMEs in high technology niches (nanoparticle-based inks), not part of the consortium, to support the development of the research demonstrates the willingness of the partners to implement the NIDASTIC results at the end of the project. The targeted applications of NIDASTIC mainly concern the microwave field (convergence point of the 3 partners) with the tunable radome panels, the devices embedded into the panel core to control surface mounted antennas or antenna arrays operating from the VUHF band (TETRA network) to the Ka band (collision avoidance radar), involving also geolocation devices, navigation devices, etc. Many of these applications are dual in nature: civil and military. Even they are less in the project to restrict the dispersion risks, the benefits of NIDASTIC out of the microwave field are also numerous and could constitute as many ways to diversify the potential markets for the industrial partners and in particular for the SERIBASE SME.

The NAIAD project is placed in the context of mastering the underwater domain and addresses a key issue for the telecommunications (underwater optical cable) and energy (renewable energy, oil and gas and even mining resources) sectors. The NAIAD project aims to find solutions to the technological challenges related to autonomous robotic operations in an underwater environment where underwater communication has inherent limitations due to the nature of the underwater environment. Precise localisation of drones may be impossible due to the need for stealth or the absence of signals or landmarks. However, a fleet of collaborative robotic agents needs to locate itself in relation to its objectives and to exchange information in order to carry out its mission. We therefore propose to solve the problem of deploying a fleet of underwater drones (without access to a positioning system) in a littoral zone, without immediate access for a support vessel, which remains in the open sea. The main problem in carrying out this operation is the ability for each drone to reach the area of interest and to be able to position itself accurately. To meet the need for accurate positioning, it is envisaged that an external positionable device will be used - in this case positioning beacons or daymarks dropped from an aerial or marine drone deployed from a carrier vessel sailing offshore (20km). The purpose of these synthetic landmarks will be to mark out a navigation plan in an optimal manner, taking into account the constraints of the environment and the means deployed. The dropping of these daymarks generates localization inaccuracies whose uncertainties are not perfectly known. The aim here is to overcome the limitations caused by uncertain localisation by using automatic planning techniques in artificial intelligence that will produce robust plans, allowing to rally the daymarks even under uncertainty, while maintaining the ability to guarantee a certain degree of coordination within the fleet. Traditionally, the generation of optimised trajectories with respect to the navigation and localisation capacity of UAVs has been placed in second place with respect to technological solutions capable of ensuring better localisation; NAIAD, on the other hand, relies on trajectories aligned with strategically placed daymarks in order to favour upstream better localisation of the fleet, while aiming at the optimisation of resources (autonomy, time). The autonomy of the navigation is ensured by the execution of the plans generated by the artificial intelligence software allowing to rally the daymarks along the route. Firstly, a planner in the uncertainty will produce plans for the release of the daymarks allowing a localisation based on the daymarks and possible geographical landmarks available. The automatic synthesis of mission plans taking into account the uncertainty on the position of the UUVs will be declined according to the Temporal Hierarchical Task Network (HTN) planning paradigm, in order to split the mission into elementary tasks, which allows a rational use of resources, and to coordinate the fleet on meeting points or on the chaining of collaborative tasks. Finally, a performance monitor that evaluates the difference between the estimated position and the measured position (despite the imprecision due to signals) will act as a supervisor capable of triggering replanning episodes, in order to adapt autonomous navigation to the hazards of the environment and to be able to re-align along a navigation plan in the event of the loss of a bittern. The implementation of these planning methodologies and their integration on robotic platforms will be carried out during sea trials from the second year of the project.

Acoustic discretion and stealth are major problems in underwater acoustics defense for next-generation ships, but the more general problematic of noise control also concerns the air domain, for example for planes, railway cars or engineering structures such as metallic bridges. The CLEOPATRE project is following the ANR ASTRID RAMSES project (Acoustic radiation engineered by resonant systems) in which the stiffeners inside the shell are geometrically modified and their distribution is optimized with the aim of jaming the acoustic response both in discretion and in stealth at low and very low frequencies. However, in conjunction with naval architects, the modifications tolerated for the stiffeners are too small to expect significant modifications in the acoustic responses. Therefore, the CLEOPATRE project aims to capitalize on previous developments to go further with more realistic geometries and propose solutions that do not impact naval architecture by focusing on the treatment of surfaces. Clearly, discretion and stealth are conventionally treated by coating the structure with layers of specific acoustic materials. Unfortunately, these two functions are not fulfilled by the same materials, which induces an additional complexity: generally the surfaces of the targets have specific treatments in specific regions according to the desired function. The CLEOPATRE project offers a solution under the form of a pavement of different materials, or even metamaterials, the distribution of which being optimized using the tools that will be developed for this purpose. Thus, we can see this approach as the use of a metamaterial of metamaterials, or metamaterial at two scales (the tile and the arrangement of the tiles) in order to optimize noise reduction whether radiated or diffracted. The analytical and numerical models developed will be used to design and optimize plates presenting controlled acoustic responses corresponding to realistic configurations and faithful to defense concerns. Six plates equipped with stiffeners and specific scale tiles will be manufactured and tested, in connection with targeted functions. The project will also propose to adapt the proposed solutions to periodically stiffened cylindrical shells as well as to the use of tiles made from metamaterials to extend the range of possibilities.