Fracture mechanics and new techniques and criteria for the design of structural components for wind tu rbines

One of the issues to be solved to make of upscaling of wind turbines a reality is the design of improv ed structural components. Since finite element computations are a lready spread among the industry, the aim is now to find new simulation tools and improved failure criteria whic h could be used to design lighter but stiffer and s tronger components. The application of fracture mechanics i nto the analysis of composite materials is a quite new trend which provides solutions for the former topics. Among the proposed failure criteria, Puck’s one see ms to be nowadays the one which both world wide industry and science have accepted as the most accurate. However, some failure modes and mechanical degradation mechanisms are not still well understood and not included in t his criterion. Aerospace industry has already propo sed new criteria which try to improve the accuracy obtained when usi ng Puck’s by using fracture mechanics to analyze lo cal phenomena such as fibre kinking and in-situ effects . On the other hand, several commercial finite elemen t codes start to include fracture mechanics tools ( VCCT, cohesive elements) which offer the possibility to c onsider mechanical degradation caused by delamination and loss of adhesion in the analysis and design of the componen ts.