State of the art in fatigue modelling of composite wind turbine blades

Abstract

This paper provides a literature review of the most notable models relevant to the evaluation of the fatigue response of composite wind turbine blades. As wind turbines spread worldwide, ongoing research to maximize their lifetime -and particularly that of wind turbine blades -has increasingly popularized the use of composite materials, which boast attractive mechanical properties. The review first presents the wind turbine blade environment, before distributing fatigue models broadly between three categories: life-based failure criterion models, which are based on S-N curve formulations and constant-life diagrams to introduce failure criteria; residual property calculation models, which evaluate the gradual degradation of material properties; and progressive damage models, which model fatigue via the cycle-by-cycle growth of one or more damage parameters. These are then linked to current testing standards, databases, and experimental campaigns. Among the fatigue modeling approaches covered, progressive damage models appear to be the most promising tool, as they both quantify and qualify physical damage growth to a reasonable extent during fatigue. The lack of consensus and shortcomings of literature are also discussed, with abundant referencing.This review aims to provide an overview of the current methods, in comparison to the other ones and most prominent theories, through a critical viewpoint, so as to be constructive and conclusive. Despite the fact that the fatigue behaviour of metals are already well-developed and validated, their "conventional" fatigue models may not be applied to composites due to their high anisotropic and heterogeneous behaviour.The underlying aim is to identify new paths for future improvements and shed light on the most ambiguous 40 aspects of composite fatigue research, particularly in the evolving case of wind turbine applications. 70 account for such effects, as we shall see.As wind turbines increase in size, the edgewise fatigue loading becomes increasingly relevant for life prediction, as shown by Kensche [7]. In addition, the torsional eigenfrequency drops, with a risk that it may couple with lower bending modes, with disastrous consequences. Toward the trailing and leading edge of the blade structure, gravity increasingly dominates the stress and strains applied to the load-bearing structure in the 75 rotor plane. An alternating, cyclic stress emerges as a result, with mean stress almost null. Furthermore,

A practical nonlinear damage accumulation method to predict the life and crack propagation of blade subjected to multilevel cyclic fatigue loads

“…To solve the MCF problem, several models have been proposed in previous studies and were widely used in practical engineering. The Goodman diagram was a widely used method to design a blade, 7 which uses a stress fatigue limit to control the stress below the Goodman curve, but it could not predict the blade life. The nominal stress method based on S-N curves was also used for life prediction, 8 but the nominal stress is relatively empirical.…”

“…[9][10][11] However, Miner's rule did not take the loading sequence into consideration, and the MCF life of a blade obtained using Miner's rule usually deviates from experiment results. 7 Marco-Starkey model and Manson-Halford model took into consideration the multilevel sequential loading, but those models have limitations: the power coefficient of Marco-Starkey model has to be determined for every different load, which limits its engineering application 12 ; Manson-Halford model usually predicts lower lifespan under the high-low condition and higher lifespan under the lowhigh condition. 9 Chaboche proposed a continuum damage model, 13 and this model took into account both the multilevel sequential loading and multiaxial stress state.…”

Comparative Fatigue Life Assessment of Wind Turbine Blades Operating with Different Regulation Schemes

“…Given that fatigue loading is a major concern in wind turbines, a large body of literature exists on the subject, with an emphasis on utility-scale turbines. While much of the knowledge on fatigue damage in wind turbine blades has been generated by testing, both of the composite materials commonly used [15,16] and of components and systems, design procedures based on a combination of simulations and standards are becoming more common. This is particularly important in the field of small wind turbines where extensive testing is not cost effective for manufacturers.…”

High-cycle fatigue constitutive model and a load-advance strategy for the analysis of unidirectional fiber reinforced composites subjected to longitudinal loads

“…However, cohesive zone models do not take into account different specific behaviors for each component of the composite and do not take into account the load history which is an important factor in considering damage evolution. A comprehensive review on the topic and on different linear and nonlinear damage models for composite materials can be found in Rubiella et al [47].…”