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Leveraging an end-to-end solution for composite wind turbine blades

News International-French

16 Mar 2011

As they are getting increasingly longer, wind turbine blades need to be stiffer and lighter to avoid cracks from fatigue loading and to help lower foundation construction costs. Current development processes are mainly 2D-based and rely on heterogeneous suites of tools that are not compatible with the quality and stiffness requirements of designing larger blades. Moreover, these tools do not allow to take last-minute engineering changes into account for manufacturing instructions.. In this context, wind turbine manufacturers are looking for innovative development solutions – particularly for blade architecture, design, simulation and manufacturing – that will help them meet these requirements while achieving longer life spans without defects.

Christian Lair - Dassault SystèmesBy

Christian Lair

Composites Business Development, Dassault Systèmes

 

(Published on April 2011 – JEC Magazine #64)

 

As they are getting increasingly longer, wind turbine blades need to be stiffer and lighter to avoid cracks from fatigue loading and to help lower foundation construction costs. Current development processes are mainly 2D-based and rely on heterogeneous suites of tools that are not compatible with the quality and stiffness requirements of designing larger blades. Moreover, these tools do not allow to take last-minute engineering changes into account for manufacturing instructions.. In this context, wind turbine manufacturers are looking for innovative development solutions – particularly for blade architecture, design, simulation and manufacturing – that will help them meet these requirements while achieving longer life spans without defects.

 

 

Optimizing composite blade design

Defining the aerodynamic properties of blades is critical in delivering outer shapes avoiding significant cracks in the aerodynamic structure. Advanced capabilities are needed to generate very high shape quality, i.e. a powerful and complete set of modelling capabilities, free-form and section-based modelling capabilities, realistic and fast quality analysis tools, and shape optimization capabilities.

The surface design is then provided to mechanical engineers, who define the detailed design and basic ply guidelines for the blade. Various methods, including zone, grid and solid slicing, are available for the automatic creation of plies, with full associativity between surface and composite parameters. A rotor blade is generally composed of structural elements such as spar webs and a shell, which are designed as sandwich composites. It is important for the designer to tightly control the properties of composite blades over their lifespan through appropriate optimization of ply orientation, thickness and lay-up.

 

 

Designing the composite lay-up in line with the complete blade assembly makes it possible to streamline the design process, ensuring a higher level of accuracy and reducing the number of physical prototypes needed to finalize the design. Powerful design optimization tools also

include the ability to swap ply edges, optimize drop-offs, shape plies and reroute sets of plies along a preferred path.

Integrating advanced specialized applications into the composite design environment makes it possible to simulate ply behaviour at an early stage and to evaluate fibre deformation. Engineers can visualize the ply stacking and tweak the laminate structure to eliminate wrinkles and other issues like fibre defects, fibre misalignments, broken fibres or missing fibres before the design is sent to manufacturing.

It also becomes possible to generate conceptual solids to quickly integrate the composite part in the mock-up, enable concurrent engineering with mating parts, and even provide preliminary inputs for tooling to start working on the mould.

 

Integration with tooling solutions means the tooling designer can create the mould based on the precise output surface. Rotor blade moulds can consist of several complex systems such as an integrated heating system, a hydraulic closing device and a built-in vacuum system that can be designed within the same environment. The lay-up of the composite plies onto the mould tool is simulated to identify areas where the part geometry will cause fabric distortion. The engineer can then add darts or splices, or make other changes to the ply and receive immediate feedback on whether the changes have corrected the design problem.

 

Improved composite blade reliability and durability
To test the blade durability and reliability, the analysis department applies many different loading conditions that simulate various wind conditions. Based on the results, the analyst goes back to the designer and recommends changes to the plies. This is typically a repetitive process involving numerous iterations between the analyst and the designer to reach the adequate level of performance.