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New tool for fatigue life prediction of woven fibres

News International-French

28 May 2013

Safe Technology Limited announces a new and unique capability for the fatigue analysis of woven fibres from Finite Element models.

The tool is included in the latest release of fe-safe/Composites, the add-on module to the Safe Technology’s advanced suite of fatigue analysis software for Finite Element models, fe-safe. This release extends the fatigue of composites module’s capabilities from unidirectional laminae, to include plain woven architectures.

This new capability was developed by a consortium of companies led by Safe Technology and Firehole Composites. The methodology was refined using materials and test data from three leading engineering companies: DSO National Laboratories, Singapore, Royal National Lifeboat Institute (RNLI), UK, and Daimler AG, Germany. These companies represent key industries for whom the new woven fibre fatigue life capability has particular relevance; namely the defence, aerospace, marine and automotive/ground vehicle sectors. Wind turbine blade manufacturers will be another obvious sector to benefit; the unidirectional materials capability has already been successfully tested and verified with turbine blade applications.

The latest release of fe-safe/Composites expands the current capabilities of the product to new microstructures and loading definitions, while retaining the functionality of the previous versions.
This latest version supports fatigue life predictions of plain woven microstructures using the same unique physics based solution as that already applied to unidirectional composites. Implementation of the physics based solution, the Kinetic Theory of Fracture, allows fatigue life predictions to be completed for multiaxial load states for which the material is not characterized, an extremely powerful tool for any engineer, from designer to analyst.

Additionally, it has expanded the applicable loading definitions within the fe-safe environment to allow for multiple repeats and block loadings. Block loadings and multiple repeats are very useful for defining complex duty cycles, and are utilized widely by wind turbine blade manufacturers and other industries subjected to design lives of anywhere from several months to many years.

The fatigue solution is based upon the Kinetic Theory of fracture and applied to the matrix constituent of the woven microstructure, which makes the solution load, time, temperature, and material dependent. Hysteresis heating is accounted for through the use of Newton’s law of cooling, and its effect is included in the fatigue life solution. Finally, the effects of material healing at low stress levels has been included to accommodate infinite life scenarios often encountered in analyses with low loads applied for long time histories. Initial tests revealed excellent correlation between the experimental and predicted lives of the woven lamina, which provides evidence of a physically realistic approach to modelling the fatigue behaviour of woven materials.

The fatigue solution is based upon the Kinetic Theory of fracture and applied to the matrix constituent of the woven microstructure, which makes the solution load, time, temperature, and material dependent. Hysteresis heating is accounted for through the use of Newton’s law of cooling, and its effect is included in the fatigue life solution. Finally, the effects of material healing at low stress levels has been included to accommodate infinite life scenarios often encountered in analyses with low loads applied for long time histories. Initial tests revealed excellent correlation between the experimental and predicted lives of the woven lamina, which provides evidence of a physically realistic approach to modelling the fatigue behaviour of woven materials.

More information:www.safetechnology.com