Session: 09-04-02 Wind Energy: Turbine blades

Submission Number: 157377

Study of Moisture Diffusion in Wind Turbine Blades and its Role in Accelerating Cumulative Damage 

Wind turbine blades (WTB) are subjected to harsh environmental conditions, leading to significant challenges in maintaining their structural integrity. Moisture ingress into the multilayered blade structure, governed by Fick's law of diffusion. It induces hygroscopic expansion and generates internal stresses within the coating, putty, and composite laminate layers. This process not only deteriorates material properties but also accelerates interfacial damage and coating debonding. Despite the critical role of moisture-induced stresses in the performance of WTB, this study is not widely reported in the literature. The present study aims to address this gap by developing a comprehensive numerical model to quantify hygroscopic stresses and their impact on the structural integrity of WTBs. A coupled diffusion-stress model is developed in ABAQUS to simulate the effects of moisture ingress and the determination of resulting hygroscopic stresses. Fick's first and second laws govern the diffusion process, while the resulting strains are incorporated using material-specific hygroscopic expansion coefficients. Boundary conditions replicate real-world moisture exposure scenarios. Interfacial debonding is predicted employing cohesive zone model.

The results reveal that hygroscopic stresses are of significant magnitude and substantially contribute to the failures in the layered configuration of WTBs during operation by interacting with the inherent state of stress. In high-humidity regions within India, these stresses accelerate material degradation and compromise the structural performance of the blades. The model accurately predicts moisture concentration profiles and the resulting hygroscopic strains, enabling the identification of damage-prone regions. This information supports targeted maintenance and material selection to mitigate moisture-induced degradation. Furthermore, moisture ingress exacerbates operational damage mechanisms by reducing material strength and weakening of the interfacial adhesion. These effects, combined with aerodynamic, gravitational, and centrifugal loads, lead to accelerating fatigue debonding, crack propagation, and structural weakening, significantly reducing blade lifespan. In case of random rain scenario, drop impacts induce repetitive stresses that contribute significantly.

This study underscores the critical interplay between moisture diffusion and mechanical stresses, offering valuable insights to guide the development of durable materials and effective maintenance strategies for wind turbines operating in harsh environmental conditions.

Presenting Author: Suhail Ahmed Indian institute of technology Delhi

Presenting Author Biography: Prof Suhail is an emeritus professor at IIT Delhi, New Delhi, India