ESI Group Partnership in ITOOL

14 April 2008

ESI Group has said that it is a partner in ITOOL, a project to simulate preform manufacturing, draping and impregnation, followed by the external loading of the finished component.

Textile preforming of composites can offer the potential of significant cost savings, but to enable engineers to make use of dry fibre textiles, reliable simulation tools and design principles are needed. In contrast to conventional, unidirectional reinforced composites, textile reinforcement results in 3d fibre architectures so that standard analysis procedures like 2d rules of mixture and laminate theory are no longer valid. It is also important to consider the manufacturing process since it has a strong influence on the textile properties.

The technical approach of ITOOL is a simulation along the process line with a virtual manufacturing chain incorporating the preform manufacturing, draping and impregnation process followed by the external loading of the finished component. The scientific objective of ITOOL is to close the gap between missing knowledge and proved advantages of dry fibre textiles by development of an adequate integrated simulation tool for textile preforming technologies including braiding, advanced engineering textiles, weaving and stitching. Reliable simulation tools and design methods provide the enabling prerequisites for an increased use of these materials in Aerospace (and other) industries. By achieving the above-mentioned objectives, ITOOL provides the basis of a standard for the design, analysis and testing of textile preformed composites in Europe.

As there are already stand-alone solutions for several parts of the simulation in use, the approach of ITOOL is mainly the linking and integration of these tools to ensure a fluid interaction and data interchange. This approach enables a flexible and adaptable solution, which may be extended by the user to include alternative technologies. The materials used in the project, especially the ones that will be used for a set of validation examples, are characterized. The relevant data is stored in a database structure allowing the user to access the properties they need. The mechanical behaviour is analyzed on three different approximation levels called 3M (micro / meso / macro) mechanics:

• on the microscale the different constituents are always modelled separately,
• on the mesoscale fiber and matrix properties are homogenized locally,
• on macro level the micro or mesoscale models are homogenized in a coarser way to lower the computational effort.

The processes used in production and handling of textile preforms are evaluated and appropriate models are developed to predict their influence on the properties of the preform materials. The draping and infiltration behaviour of textile preforms is the focus of this subtask.

Static stress and failure models are developed to predict macroscopic structural deformation, stress and failure of textile-reinforced structures. Global analysis methods, which compute structural behavior under external loads, are provided. The developed tools regard static stress, quasi-static failure, crash and dynamic impact computations.

The proof for this integration concept is performed for different application fields of textile-preformed composites in Aerospace: typical stiffened skin sections, integral joining technologies and braided stiffeners. The evaluation also includes the interface and the related flow of data as the quality of results in comparison with tests.

In parallel to the development of the integrated simulation tool the second aspect of the project is to build up physical understanding of textile preformed composites behaviour to increase their usage. Therefore design rules for the use of dry fibre textiles are extracted and made easily available for the design engineer in a guideline.

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