COMP-DAMAGE - Damage Assessment of Fibre Reinforced Composite Materials Exposed to Cryogenic Environments

Cryogenic media storage and transportation systems for cryogenic fluids as used for the Ariane 5 upper/lower stage are made of stainless steel and aluminum components respectively. Composite components bear a potential for mass and weight savings among other advantages especially when exposed to extreme environmental conditions. They are used for tank vessels/systems, lines, ducts, and mechanical interfaces.

On material level for cryogenic storage vessels design drivers are

• Pressure of the cryogenic fluid
• Vacuum between the inner and the outer vessel (thermal insulation)
• Temperature load due to the cryogenic liquid and the surrounding thermal environment (LHe)
• External mechanical loads

The residual stresses due to manufacturing and the superimposed thermal stresses in the matrix have to be considered, as they can result in micro-cracking of the matrix. These micro-cracks can lead to a deterioration of the vacuum by diffusion of the evaporated cryogenic gases and subsequently a deterioration of the thermal insulation.

The assessment performed in the frame of this work put focus on:

• Selection of proper materials/lay-up for the intended use
• Failure characterisation for temperatures down to LHe (4,2K/- 269°C)
  - Shear
  - Tension/compression
  - Thermo-mechanical properties (thermal conductivity)
• Provision of a sound material database for assessing stress analysis as part of the development process
• Preparing the foundation for quality assurance related processes

For this purpose, several samples were tested under cryogenic conditions until damage of the specimen was observed. These values were used to assess the results of a finite element (FE) or analytical analysis in terms of the actual margin of safety (MOS). Furthermore, non-destructive inspection techniques were assessed, highlighting their basic feasibility for the applications defined.

The following tasks were performed by our partner, the Austrian Institute of Technology:

• Manufacturing of the samples
• Material characterisation by means of several tests at room temperature and cryogenic temperatures concerning tension, compression, in-plane shear, coefficient of thermal expansion, thermal conductivity

Coordinator

Magna Steyr Fahrzeugtechnik AG & Co KG, Division: Space Technology - Kurt Irnberger

Partners

Austrian Institute of Technology GmbH (formerly: Austrian Research Centre Seibersdorf) - Michael Scheerer

Magna Steyr Fahrzeugtechnik AG & Co KG, Division: Space Technology
Kurt Irnberger
Liebenauer Hauptstraße 317
A-8041 Graz
E-mail: kurt.irnberger@magnasteyr.com
Web: www.magnasteyr.com