Your application must include a recommendation letter from your Ph.D. supervisor, a detailed CV including university education and work experience, a list of publications, a 2-page description of the work undertaken during the course of your PhD.

For more Information, contact : adrian.garciamartinez@cnes.fr

Submit the complete application online (Apply) before March 13th, 2026 Midnight Paris time

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The use of composite materials in the field of launcher structures has a major impact not only on performance, weight, cost, and the environment but also on the ability to maintain their flight readiness over time. The early integration of revalidation constraints—such as damage detectability, repairability, post-event justification capability, or defect tolerance—has become a key factor in the design of launcher structures.

To equip ourselves with means of evaluating this comparison criterion in the context of preliminary design trade-off studies, it is necessary to work on the methodological aspect. Methods and tools must be developed to assess the criticality of damage that has been diagnosed (damage tolerance) and to assess the criticality of an accidental event that has occurred but whose consequences in terms of damage have not yet been diagnosed. These are two complementary methodological frameworks. In addition, regardless of whether we consider the perspective of loading or damage, the need may justify the trade-off between precision and agility. Methods and tools must be developed to meet these two needs.

Within the DTN/STS/STM department, and since 2019, we have been working on implementing means of evaluating the criticality of an accidental event of the impact type on launcher structures made of composite materials [1], [2], [3]. Our approach based on the need (precision vs. agility) is presented below:

- On the one hand, and in response to a need for precision, our solution consists of numerical modeling with Abaqus of a 3D model with cohesive elements to simulate progressive intra-, trans-, and inter-laminar damage [3]. The integration scheme we use is implicit, but we wish to switch to explicit. This requires the development of a user material law (VUMAT) for implementing the 3D intra-laminar initiation criterion (Hashin).

- On the other hand, and in response to a need for agility, our solution consists of a semi-analytical approach based on an experimental database. A prototype of a tool has been developed in-house to provide a qualitative and quantitative estimate of the consequences of an impact-type loading [1]. However, the implementation of the method remains incomplete to date. In addition, the validation of its steps has not been carried out. An experimental campaign has been conducted, and the data are available to serve as a validation source [4].

The objective of the proposed work is to contribute to the consolidation of the approaches presented, through the exploitation of test data, and to complement them while addressing the following challenges:

- Development of a VUMAT law (FORTRAN) to implement Hashin in explicit form;

- Design of a method for estimating the material parameters of the cohesive law;

- Correlation of the impact test in terms of force-displacement and delaminated area;

- Formalization of the database associated with the qualitative estimation tool;

- Completion of the prototype of the qualitative estimation tool with statistical methods;

- Completion of the prototype of the quantitative estimation tool with small finite element models.

References:

[1] DLA-RST-0000000-599-CNES

[2] DLA-RST-0000000-676-CNES

[3] DLA-RST-0000000-684-CNES

[4] DLA-NT-0000000-ZZ-2317-CRIT