The use of composite materials in aeronautics industry has increased constantly over the last 35 years, due mainly to their high specific strength and stiffness combined with the possibility of designing complex geometry components that are more aerodynamically efficient than metals. But due to the organic nature of the polymeric matrix component, composite materials are electrically and thermally bad conductors and they tend to burn easily, emitting toxic gases and smoke. For that reason, they require affordable, effective and certifiable protection systems against atmospheric hazards such as icing, as well as fire and burning in case of accidents.
Moreover, improved in-the-field inspection techniques are required with the increased use of composite materials. Current technologies address those issues separately. Ice protection is usually afforded by means of a metal mesh or foil incorporated into the outer ply of fabric on the skin of the structure. Fire protection is afforded with thermal barrier coatings on the structures and life monitoring is provided with embedded sensors. All of these measures add high weight and complexity during manufacturing and posterior maintenance, they may even go against the structural integrity of the component in some cases.
Based on needs to provide an efficient safety and security system for aircraft composite structures, the main objective of LAYSA project was to establish the scientific and technological basis for the development of a new multifunctional layer with ice/fire protection and health monitoring capacity to be integrated into composite structures.
- To design and manufacture novel layer concept with multi-functionality based on nano-materials, combining next properties:
- electrical/thermal conductivity capable of distribute the necessary heat on composite surface to prevent ice formation on its surface in rough fly conditions or remove the already existing one. With respect to current electro-thermal system it can be estimated that a weight reduction of 99% and a power consumption reduction of 50% can be achieved;
- fire resistance. Reduced flammability (50% of reduction in Heat Release Rate HRR with respect to base composite material);
- sensing of temperature and stress by electrical conductivity variation measures.
The project was broken down into several Work Packages (WP's). These were:
- WP0 (Project Management) focussed on the co-ordination, monitoring and reporting of the project progress through the whole duration of the project;
- WP1 (Definition of requirements and materials selection) was the starting point of the project. Specifications of aircraft composite structures in terms of materials and manufacturing processes and an analysis of commercial nano-materials and their properties has been carried out, in order to decide the base materials to be used during the project. Specifications of structural and functional requirements of ice/fire protection and sensoring systems of aircraft composite structures have also been defined in WP1. Several nano-materials have been considered: different carbon nano-tubes CNTs (single wall SWCNT or multi wall MWCNT), carbon nano-fibres CNFs, layered silicates (MMT) or also another less studied materials like metal nano-tubes and metallic nano-particles supported on micro-fibrous silicates. Moreover, the possibility of combining different types of nano-materials have been considered;
- WP2 (Synthesis of multifunctional nano-composite layer, LEVEL 1) was the core of the project, the scientific part. Development of nano-composite with triple functionality (electrical /thermal conductivity, fire resistance and sensing capability) have been carried out. First, three functionalities have been studied separately and in all the cases the work has focussed on pre-treatment, dispersion, adhesion and orientation (randomly or aligned) of nano-materials into resin for obtaining the required functionality. The work has been supported by modelling analysis and specific tests to evaluate the properties. Once the three functionalities were optimised, they have been integrated. For that, the best way to combine materials and processes defined for individual functionality has been studied. In this Work Package, modelling had an important role. The main task within this part was to derive a model that showed how each of the possible nano-fillers will interact with each other and with the available epoxy matrix in order to produce nano-composites of predictable electrical, thermal, sensing properties and fire protection;
- WP3 (Incorporation of functionality in novel composites, LEVEL 2) is the technological part, where the already developed nano-composite has been integrated in the traditional composite manufacturing process.
In January 2013 we have received information from the consortium that all project deliverables are considered confidential. The project website is not accessible, as per Autumn 2012.
The major project aim was establishing a scientific and technological basis for the development of a new multifunctional layer, based on nano-reinforcements with ice protection, fire protection and health monitoring capability to be integrated into composite structures.
The direct benefits of this application include: (1) improvement of aircraft safety and security, and (2) structural weight reduction and simplification of manufacturing processes and maintenance operations, due to elimination of current metal mesh or foils, by replacement with multifunctional layer integrated in composite structure.
Development of a new multifunctional layer based on nano-materials, to have among others the following characteristics: electrical/thermal conductivity (to distribute heat to prevent ice forming on its surface), significant weight reduction, higher fire resistant and reduced flammability.
Innovating for the future (technology and behaviour): A European Transport Research and Innovation Policy