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New Enhanced Acoustic Damping Composite Materials

Periodic Reporting for period 2 - NEODAMP (New Enhanced Acoustic Damping Composite Materials)

Reporting period: 2017-07-01 to 2018-12-31

The idea is to design future multifunctional composite fuselages so that the structure itself is capable of efficiently minimizing noise and vibration propagation without the relevant weight and cost penalty of current add-on parts used as acoustic-dampers. The use of layered composites in aircraft fuselage structural components offers the opportunity to embed interleaved layers of different materials in the skin laminates so that additional performances may be added while maintaining the structural efficiency. In this sense, the presence of layers of damping materials inside the composite laminate normally results in an important reduction of mechanical properties. The goal, therefore, is to design composite laminates with integrated acoustic insulation without compromising the mechanical performance of the composite structure, maintaining in turn the automatic process-ability.

The main objective of NEODAMP project is to develop a structural composite material with an additional functionality: acoustic damping. The drivers for this development are the cost decrease and a high production rate. Specifically, most important targets that the composite material is expected to reach are:
• Acoustic-vibration damping: in the concerned frequency range to be covered (to be agreed with the TM).
• Structural performance: maintaining the same level as current fuselage materials.
• Automatic process-ability: suitable for automatic fuselage production by means of AFP.

The combination of these two functionalities in the composite material (structural and acoustic), together with the capability to be automatically produced, will lead to weight savings in aeronautic structures that are directly translated into a reduction of fuel consumption and therefore, contributing to reduce CO2 and NOx emissions.
The first period of NEODAMP project is developed between M1 and M18. During this period, the requirements were fixed, and the test plan for the characterization/validation of the vibration damping composite material was defined. One of the most important and challenging task was successfully accomplished: the acoustic material modification. The preliminary characterization tests of the new damping material were also performed. However, there was reported a delay in the manufacturing of the coupons for the tests, since the concerned material was not ready at the time planned. The reason behind this delay is that there were many challenges for Hexcel to obtain the desired new damping material due to the complexity inherent to the re-formulation/manufacturing process, although these were overtaken.

The second (and last) period of NEODAMP project (M19-M36) have been successfully completed. During this period, the modified hybrid material was used to manufacture coupons for the final test plan. The tests were conducted and analysed, although their results were reported to be unsatisfactory from the structural point of view. Due to this fact, an assessment on alternative laminate configuration, architecture, and elastomer formulation was conducted at this stage. After that, a new material architecture was determined as a compromise solution between acoustic and structural performance. Finally a demonstrator was produced by means of automated tape laying (ATL) considering the selected architecture; the demonstrator is comprised by a flat plate with two omega stiffeners.

The final conclusions of NEODAMP project are positive; a multifunctional material that enhances the acoustic performance of a standard CFRP, without detrimental effect to its structural properties, has been developed. The performance still needs to be improved in order to be suitable for the fuselage application, since the last architecture does not fulfil the acoustic performance at the 20% of the defined temperature range. However, the material is suitable for many other applications, and implies an important reduction of cost, weight and enhanced automation with respect to the current State of the Art.

With regard to the dissemination of the NEODAMP activities and results, in the first place the demonstrator has been exhibited at the JEC World event in Paris. Secondly, the technical details of the project have presented at the EMuS 2019 (European Conference on Multifunctional Structures) in Barcelona, a technical paper can be found at the conference proceedings.
The exploitable product foreseen from NEODAMP is the development of a structural composite material with the added functionality of acoustic / vibrational damping. The main advantages compared with respect to the current SoA solution will be the weight saving, cost decreasing and high-production rate.

The consortium of NEODAMP is constituted by two partners, FIDAMC and HEXCEL, the exploitation market of each partner is as follows:
• On the one hand, HEXCEL is willing to promote such technology to fill a gap in the market for multifunctional advanced composite materials, thus meeting with strategic objectives of existing customers, and also to offer the product to potential customers.
• On the other hand, FIDAMC will exploit project results by implementation in other end-users. This will become tangible through trainings for AIRBUS first-tier suppliers, consolidation of collaborations with train manufacturers in the railway sector, launching of manufacturing process patents and giving technical advice related to the use of industrial machines to other suppliers, among others.

In regard of the potential customers, the aeronautics industry is one of the targeted sectors. The weight saving shall enhance the performance of the aircrafts in regard of the emissions of CO2 and NOx, and operative costs, due to the reduction in fuel consumption. Besides, the production rate shall be highly improved since the current process is quite manual. However, the exploitable results shall be targeted to other industries as well, not only the aeronautics, for instance the automotive and the railway sectors may be interested in the product.