Session: 08 - 01 NDE for Civil Infrastructure

Paper Number: 120426

120426 - SMART COMPOSITES FOR THE NON DESTRUCTIVE TESTING (NDT) AND STRUCTURAL HEALTH MONITORING (SHM) OF OFFSHORE INFRASTRUCTURES 

Carbon neutrality passes, among others, through the development of reliable renewable energy sources, among which is offshore wind energy. At the European level, offshore wind-production is expected to range from 230 to 450 GW, by 2050, to target climate neutrality. This ambition is corroborated by the International Energy Agency (IEA), who expect offshore wind energy to be ranked as the number one source of electric power in Europe within less than twenty years. Scaling up from 20 GW today to 450 GW by 2050 will require a revolutionary approach, which imposes upgrading of infrastructures, especially large-dimension wind blades and high-voltage electrical transport cables, whose maintenance is a major concern. Appropriate Structural Health Monitoring (SHM) of these offshore structures have been assessed through embedded fiber-optic sensors that are placed in various areas with new concepts that were applied within EVEREST and FLOW-CAM Projects.

                SHM techniques can prevent heavy maintenance by monitoring structures under harsh environments, remotely. For smart composite materials are accepted for structural applications, several points regarding the intrinsic and extrinsic mechanical behavior to the parent material should be finely characterized and modeled. By intrinsic problems we mean the potential areas of excess stress in the parent composite material; while by extrinsic problems, we aim those linked to the presence of embedded sensors. Numerical simulation was implemented to predict the stress distribution over a wind turbine blade and composite High-Voltage cables. The scope was to highlight areas with high stress concentration. Finite Element Analysis (FEA) was used to find optimal material and bonding techniques to construct the structures. Appropriate SHM sensors were designed, numerically modeled and experimentally-validated to ensure the best use. Fiber optic sensors (FOSs) are a reliable choice for SHM of composites. Embedding FOS into a structure is an important challenge, since the

interface between FOS and surrounding material has to allow accurate measurements. FOS is an origin entity to the host structure and while embedding it in-between the composite plies, a flaw called resin-eye rich pocket forms around the FOS and its consequences on fatigue behavior have been experimentally estimated. The placement of sensors within composites and bond joints has been also modeled and two main solutions have been suggested, namely straight placement FOS parallel to bonded joints and a sinusoid-placement of FOS, so covering the largest part of bond joint surfaces and/or plies. Sinusoid and double-sinusoid placement strategies of a single FOS along with a well-mastered periodicity showed promising result.

                Shipping, handling, and embedding high-voltage cables in bed seas can result in an upfront performance loss, and thus to a fear of premature shutdown, which can result in geo-politics consequences. Offshore cables are prone to failures which account for 80% of total financial losses and insurance claims. In the past 7 years, about 90 offshore cable failures have been reported, with over €350 million in insurance claims. The repair costs of an offshore cable can be between €0.7 million and €1.5 million. The loss of performance of cables is mainly due to the plastic deformation of copper, which occurs with very small loads and directly impacts other physical properties. Embedded FOS were placed within wires, to monitor live and very precisely what is happening inside high-voltage cables for offshore farms. Various embedding FOS options in-between copper wires or within the insulator XLPE (cross-linked polyethylene) are suggested, modeled and discussed. The placement strategy is targeting finer tension and bending monitoring of phases. The options are numerically discussed, which will provide help to engineers to target the right cost-effective solutions, hopefully.

Presenting Author: Monssef DRISSI HABTI Université Gustave Eiffel

Presenting Author Biography: Monssef DRISSI-HABTI (linkedin.com/in/monssef-drissi-habti-85100a66) is Research Professor at The French Institute for Transports (IFSTTAR). Monssef DRISSI-HABTI holds a PhD thesis (1994) and the title of Research Professor (HdR) since 1999, both of them on ceramic composite materials for aerospace. In Japan, He has been working from 1995 to 1998 as visiting researcher in NIRI Nagoya and then from 1998 to 1999 as Professor at the University of Tokyo, while being a member of Science and Technology Club of the French Embassy in Japan. He then switched to USA where he has been working until 2003 at Brown University of Engineering, RI, USA. The experience of Monssef includes ceramic matrix composites for thermal protection of space shuttles, in both space programs, HERMES (European Space Program) and NIPPON HOPE (Japan Space Program). His experience also includes smart composite materials for transport, smart cities and renewable energies. In The USA, he worked on super-alloys and thermal protection materials for nuclear applications, in collaboration with the Research Centre Norton - St Gobain (Northboroo, MA, USA). His current research is mainly focusing on smart structures and infrastructures that are based on smart composite materials in renewable energies, transports, smart cities and security of critical infrastructures. Monssef DRISSI-HABTI is PI of some research programs on smart composites both in France and in Europe, as well. Author of about 70 articles in peer-review journals and 75 articles in conference proceedings, he published two special issues, one in 1998 on Advanced Materials in Japanese aerospace program, the other in 2001 on advanced materials for aeronautical and aerospace applications in Japan, too.