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High performance thermoplastic composites: physical study of interfacial phenomena during the proces

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General information

Reference : UMR8006-ILIILI-002
Workplace : PARIS 13
Date of publication : Wednesday, July 24, 2019
Scientific Responsible name : Guillaume Miquelard-Garnier, Gilles Régnier
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2019
Proportion of work : Full time
Remuneration : 2135,00 € gross monthly

Description of the thesis topic

The reduction of energy consumption in transport, especially in aeronautics, requires the reduction of the weight of the structures. The primary structure of modern civil aircrafts consist of more than 50% of polymer/carbon fiber composite, which allows a weight reduction of about 20%. The composites used today are essentially thermosets (chemically cross-linked polymer matrix), which implies long and expensive production processes and limits recyclability. For the new generations of aircrafts the solution consists in the use of thermoplastic composites based on high performance polymer matrices (very high melting point and resistance to aggressive environments), with potentially the huge advantage of being able to weld parts between them. The processing of such thermoplastic composites involves several steps: preparation of tapes consisting of thin unidirectional webs of carbon fibers pre-impregnated with thermoplastic matrix, automated tape placement, consolidation of parts, part-part welding.

The physical and physicochemical phenomena that play a key role during these steps are similar: melting/crystallization of the matrix, wetting of the fibers by the molten polymer, interdiffusion of the polymer chains at the interfaces, flow and rheology of the composite beyond the melting point of the matrix. The aim of the thesis will be to study these physical mechanisms in relation to the architecture of the tapes (volume fraction and distribution of carbon fibers) and to determine their impact on the consolidation and the properties of the composite parts.

The ideal candidate must have a strong background in physics and/or physical-chemistry of polymers and composite materials. Knowledge of the mechanics of materials will be much appreciated. He/she must like the development of new experimental setups, interdisciplinarity, teamwork and be fluent in oral and written communication with industrial and academic partners.

Work Context

The thesis is part of the collaborative project HAICoPAS (Highly Automated Integrated Composites for Performing Adaptable Structures) lead by Hexcel and Arkema and which has received financial support from the program investments for the future (https://www.hexcel.com/News/News-Releases/2804/new-consortium-haicopas-targets-innovative-solutions-for-carbon-thermoplastic-com).
The HAICoPAS project aims at optimizing unidirectional (UD) tape design and its manufacturing process in view of its use in highly productive, cost competitive, composite part production. The HAICoPAS project also targets the development of a highly productive UD tape placement technology and a new system providing the ability to assemble final parts by welding with in line quality control.
The HAiCoPAS project brings together a consortium of complementary, high-level competencies from Hexcel (carbon fiber), Arkema (high-performance polymers) and a number of highly skilled small and medium enterprises (Institut de Soudure, Ingecal, Coriolis Composites, PEI) - all widely recognized for their expertise in composites production equipment and processes. Scientific support is provided by two CNRS Research Units: PIMM (Arts et Métiers ParisTech / le Cnam / CNRS) and LTEN (University of Nantes / CNRS), which will develop the basic understanding for the optimization of the materials, their processing and long-term behavior in service conditions.

The thesis proposed here fits into this context and will run in parallel with two other theses of the project. The PhD student will be member of the Polymers & Composites team of PIMM Laboratory and will work in close collaboration with the other project partners. He/she will spend time for experiments in the R & D centers of the industrial partners and at the LTEN Laboratory, and will regularly present his/her results during the technical meetings of the project. He/she will benefit of an exceptional environment by having a broad vision in the field of high performance thermoplastic composites and on the complete value chain from materials to processes.

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