Simulation of lightweight CMC sandwich structures

Job description

In the department of ceramic composites and structures at DLR (German Aerospace Center), Institute of Structures and Design, ceramic matrix composites (CMC) have been developed since the late 1980s.
So called C/C-SiC materials are manufactured via liquid silicon infiltration (LSI), a robust process based on three characteristic steps:
1. Manufacture of a CFRP preform
2. Pyrolysis, resulting in a porous C/C preform
3. Siliconization by capillary infiltration of Si in the C/C preform and chemical reaction of Si with C, building up a SiC matrix.
Currently, C/C-SiC materials, originally developed for thermal protection systems of reusable spacecraft, are opening new applications for highly stiff and thermally stable satellite structures. C/C-SiC sandwich parts offer a high potential for the use in lightweight optical benches with excellent specific stiffness. For those sandwich structures filigree core structures and top layers with high mechanical load capacity are needed. The aim of this work is the development of methods for designing C/C-SiC sandwich structures by using finite element analysis (FEA). Thereby different core structures, like folded cores, grid and honeycomb type cores have to be considered. In order to obtain lightweight structures, specific stiffness and strength has to be optimized by varying the wall thickness of skin plates and core structure as well as by the core density (cell size) and height. Therefore convenient tools based on parameterized structural models have to be developed. For evaluation, characteristic samples will be manufactured and tested in bending, shear and compression mode.

• Experience in using CAD and FEA software packages
• Knowledge in composite mechanics
• Interest in material science, structural mechanics and light weight structures

Starting date:immediate
Duration of contract:6 months