Fatigue Behavior of Smart Composites with Distributed Fiber Optic Sensors for Offshore Applications

Abstract

Continuous inspection of critical zones is essential to monitor the state of strain within offshore wind blades, thus, enabling appropriate actions to be taken when needed to avoid heavy maintenance. Wind-turbine blades contain various substructures made of composites, sandwich panel, and bond-joined parts that need reliable Structural Health Monitoring (SHM) techniques. Embedded, distributed Fiber-Optic Sensors (FOS) are one of the most promising techniques that are commonly used for large-scale smart composite structures. They are chosen as monitoring systems for their small size, being noise-free, and low electrical risk characteristics. In recent works, we have shown that embedded FOSs can be positioned linearly and/or in whatever position with the scope of providing pieces of information about actual strain in specific locations. However, linear positioning of distributed FOS fails to provide all strain parameters, whereas sinusoidal sensor positioning has been shown to overcome this issue. This method can provide multiparameter strains over the whole area when the sensor is embedded. Nevertheless, and beyond what a sensor can offer as valuable information, the fact remains that it is a “flaw” from the perspective of mechanics and materials. In this article and through some mechanical tests on smart composites, evidence was given that the presence of embedded FOS influences the mechanical behavior of smart composites, whether for quasi-static or fatigue tests, under 3-point bending. Some issues directly related to the fiber-architecture have to be solved.

Experimental and Numerical Analysis of the Deformation Behavior of Adaptive Fiber-Rubber Composites with Integrated Shape Memory Alloys

“…Furthermore, as was investigated by Drissi-Habti et al [34,35], an SMA actuator in tegrated into a composite can be understood as a "defect" to the structure and must, there fore, be integrated in such a way that the harm done to the composite is minimized, e.g by miniaturization, optimizing physical operating conditions, and reducing the overa invasiveness of the actuator. Thus, finite element analysis is required to capture the rele vant components with their properties as well as their interactions, estimating their influ ences on the structural deformation behavior and optimizing the composite topology to ward an optimal actuator integration while minimizing the harm inflicted upon the ove all structure.…”

Embedded measurement of process monitoring in melt-cast explosive based on distributed optical fiber sensing and numerical verification

“…The embedment of fiber optic sensors into offshore wind turbine blades made of composite carbon fiber panels allows for structural health monitoring and multi-directional strain sensing of the equipment [27]. Although it is an artificially created 'defect' from a mechanical and material point of view, no adverse effect has been proved to exist on the mechanical properties of smart composites provided that DOFS is arranged using a suitable method [28]. Therefore, fiber optics, as an embedded device, can serve the function of complete data acquisition without deteriorating the original performance of the device.…”