Optimising and adding value to composite materials
- Composite
Optimisation and recovery of materials through mechanical recycling of thermoplastic matrix composites and carbon reinforcements
Keywords : Mechanical shredding, Thermoplastic composite, Recycling, Optimisation, IA, Discontinuous fibres
This thesis is currently being carried out by Fabien Simonneau, Composites R&D Engineer.
Thermoplastic carbon fibre composites are high-performance materials used in fields of excellence such as aeronautics and space. Recycling these materials is still a new field for industry, and needs to be improved if it is to be viable. The mechanical recycling studied in this thesis can be broken down into several stages:
- Recovery of end-of-life materials (scrap, test parts, end-of-life parts, etc.), which today are generally landfilled or incinerated.
Shredding of parts to obtain smaller, homogeneous pieces. This part is at the heart of the thesis subject because of its difficulty and the lack of data in industry.
- Reprocessing of the shredded material using press processes (thermocompression or thermo-stamping). The parts manufactured will be either characterisation parts to gather more information on the grind and its performance, or parts with more complex geometries to improve the grind reprocessing processes.
The challenge of this thesis
The main aim of this thesis is to develop and optimise ways of recycling thermoplastic composite materials, the end-of-life of which currently has a very negative environmental impact (landfill or incineration). What's more, in addition to the important ecological issue, there is also a certain economic interest in reusing these high-performance materials, which are very expensive to manufacture.
The technical difficulties of this subject lie mainly in the use of composite materials in the form of coarse grindings. Conventional composite manufacturing processes are adapted to the use of very long fibres (from a few dozen centimetres to several metres). Mechanical recycling processes also exist, but they aim to reduce the recycled material to a powder and reincorporate it into new materials (these techniques are interesting, but give lesser performance to the final material). Here, the aim of the project is to reuse the material in the form of semi-long fibres (a few centimetres). On the one hand, this would reduce the costs (economic and ecological) of the shredding stage, and on the other hand, it would provide interesting mechanical performances (thanks to the length of the fibres used). However, the transformation processes for these semi-long fibres are fairly new and need to be optimised.
The thesis will also stand out for its multidisciplinary approach, combining experimental methods with advanced modelling techniques (such as the implementation of a neural model). This approach will make it possible to accurately predict the relationship between process parameters and the characteristics of the shredded material and parts obtained.
In this way, the knowledge and tools developed will make it possible to optimise the design of secondary parts manufactured from recycled shredded material. This ambitious project will then take us a step further: the industrialisation of parts produced using the innovative recycling process we have developed.