Multiphysical and Multi Scale Modelling of Composite Materials for Aircraft De-Icing

Abstract

Multifunctional composite materials provide structural integrity and at least one or more functions which can be applied beneficially in vehicle systems. One example of a multifunctional material is the structural battery. The energy storage function of this material is given by the carbon fibre that reinforces the plastic matrix and provides a lithium ion intercalation function. A tailored polymer electrolyte coating on the fibre’s surface is electrically insulating, ion conducting and significantly load bearing simultaneously so that the energy storage function is supported. The multifunctional use for structural integrity and energy storage enables a significant weight saving potential when monofunctional components and their assemblies are replaced. During operation, the Joule heat effect provides a significant temperature rise of the multifunctional composite material. An industry patent suggested the use of the polymer electrolyte coated carbon fibres for the De-Icing of aircraft structures. Traditional systems provide a significant additional mass to the primary structure due to a low level of optimisation and their monofunctional concept. A significant weight reduction could contribute to the reduction of fossil fuel burn in a next generation aircraft. It is expected that the existing monofunctional primary structure can be replaced by a multifunctional structure, so that no additional mass is needed to provide the De-Icing function. In addition, it is expected that the structure can be optimised for an ideal functional performance which can lead to a reduced energy consumption for De-Icing. The influence of the polymer electrolyte coating on the characteristics of the composite material as well as the effects resulting from physical couplings during operation are not sufficiently analysed. In addition, possible constraints of the multifunctional application need to be quantified, in order to take them into account for future system development. In order to face these challenges, this thesis builds on the basic principle of a model based, optimised application of multifunctional composite materials that comprise polymer electrolyte coated carbon fibres and a polymer matrix. Therefore, the electro-thermal and mechanical properties of the coated carbon fibres are examined experimentally to conclude suitable model assumptions in a first approach. Furthermore, an electro-thermomechanically coupled multi scale model is introduced which covers the multifunctional material behaviour under operational conditions for the first time. The model is successfully validated by measurements in a De-Icing test bed with a flat plate type specimen structure. Significant physical couplings like a temperature induced stiffness change and an optimisation of heat transfer towards a minimum energy supply are important results of this thesis. In addition, conclusions from thermal heat transfer within the multifunctional composite material as well as the convective heat dissipation are discussed with respect to model based innovation. Finally, a new benchmark compares the optimised multifunctional material performance for De-Icing with traditional De-Icing systems like the bleed-air system or the heater mat system. Based on the optimisation results, a complete removal of the De-Icing system’s mass is expected and a significant increase of energy efficiency can be enabled. Future research can build on the derived conclusions towards a refinement of the coupled multiphysics model and towards further application scenarios like the structural battery.