JEC COMPOSITES MAGAZINE - Issue #47 - March/April 2009 - 28

BUSINESS Trends …… / Composite challenges to meet growing wind-industry needs • development of raw materials by suppliers for cost-effective solutions, • quality control methods, • non-destructive analysis, • reliability tests, • advanced life-prediction tests and analyses for composites, • structural health monitoring systems. There are also logistic challenges to be solved, due to the larger size of wind turbines. Apart from product innovations, process innovations are key in manufacturing high-quality, high-volume components in a cost-effective manner. While wet lay-up was the main blade production method in the early days, firms like Vestas with the necessary know-how are now using enhanced methods such as prepregs. Such new-generation processes should allow improved defect control during blade manufacture in terms of voids, debonds, delamination, impact damage, density variation, resin variation, broken fibres, fibre misalignment, wrinkles, resin cracks, cure variations, inclusions and moisture. Today, Vestas wind turbines operate in a range of geographical locations and conditions that spans from hot desert with sand-storms to cold/frosting/snowy/ arctic climates. Wind turbines are now operating from land all the way out to sea, due to the better marine wind resources. The level of performance confidence involved for these regions and design requirements is high (as much as 95+% ), and the service life is 20 years. This raises the material challenge to a new dimension that exceeds even aviation requirements. multiaxial loading (aerodynamic loading, gravity, etc.). At present, fatigue design is based only on uniaxial tests, and knockdown factors are applied to take multiaxial effects into account. More sophisticated methods are needed to factor in the multidirectional nature of stress. However, different operating environments such as sub-zero conditions where ice and snow are common, desert conditions, offshore conditions, lightning-prone conditions and dirt-rich areas involve different sets of requirements that will lead to unique material challenges. Wind speeds in different regions also pose different levels of load and power delivery challenges, so that product differentiation becomes essential. Accordingly, companies develop unique product types to address the specific needs and demands of customers. Below a certain performance level, there is a wider choice of materials available for lines that are similar, but for longer blades, only advanced composites can meet the application requirements. More information Biography Narasimalu Srikanth is the technical director of the research and development department of Vestas Wind Turbine. He received his first masters from the Department of Mechanical Engineering of the Indian Institute of Technology, Bombay, India in the area of design engineering and his second masters from National University of Singapore (NUS) with a specialization in materials engineering and further pursued his doctoral degree from the department of mechanical engineering of NUS. Dr Narasimalu has published in more than 100 international journals and conferences, and his areas of technical interests are mechanics & design, simulation, materials engineering and technology roadmaps & management. He is a member of ASME, ASM, ASPE, IEEE and MRS(S). composite product and process innovations in wind turbine applications, such as nanomaterials, biodegradable materials, lightning-resistant materials, self-cleaning materials, and low-cost materials, in order to meet performance challenges and benefit from the booming market conditions. This can only be possible if key players such as material scientists, raw-material manufacturers and tooling manufacturers, among others, work together with wind-turbine market leaders such as Vestas. Contact: srnar@vestas.com References [1] Tony Burton, David Sharpe, Nick Jenkins, Wind Energy Handbook, Wiley, New York, 2001. [2] Alan Baker, Stuart Dutton, Donald Kelly, Composite Materials for Aircraft Structures, American Institute of Aeronautics and Astronautics, 2004. [3] Martin O. L. Hansen, Aerodynamics of Wind Turbines, Earthscan, Sterling, 2007. [4] Dick Veldkamp, Chances in Wind Energy, PhD Thesis, Denmark, 2005. Fig. 3: Performance versus productivity for various composite manufacturing processes. (source: Hexcel) The main application demands and the challenges posed by the wind industry include: • new advanced composites/materials, • high-performance fibres and matrix materials, • advanced coatings (wear-resistant, anticorrosion, minimum shrinkage, etc.), • new manufacturing processes to scale up production, • composite joining processes, • bulk composite materials, Conclusion Composite technology is a key enabling technology that will directly enhance future wind-turbine capabilities, in terms of lower energy costs for mass production due to reduced loads, increased power, reduced weight and increased reliability. This encourages the use of new 28 jec composites magazine / No47 March-April 2009

JEC COMPOSITES MAGAZINE - Issue #47 - March/April 2009

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #47 - March/April 2009