APPLICABILITY OF OPTICAL FIBER BRAGG GRATING SENSORS IN THE STRUCTURAL HEALTH MONITORING OF COMPOSITE OVERWRAPPED PRESSURE VESSELS

Composite overwrapped pressure vessels (COPY) have been increasingly pointed to as the most effective solution for high pressure storage of liquid and gaseous fluids. Reasonably high stiffness-to-weight ratios make them suitable for both static and mobile applications. However, higher operating pressures are sought continuously, to get higher energy densities in such storage systems, and safety aspects become critical. Thus, reliable design and test procedures are required to reduce the risks of undesired and unpredicted failures. An in-service health monitoring system may contribute to a better product development, design and optimization, as well as to minimize the risks and improve the public acceptance. Within the scope of developing different COPV models for a wide range of operating pressures and applications, optical fiber Bragg grating (FBG) sensors were embedded in the liner-composite and composite-composite interfaces during their manufacture in order to allow the online strain monitoring during preliminary testing and service-life. The ability of these measuring systems to effectively assess the strain fields was to be investigated. Simultaneously, a finite element analysis (PEA) was made using the ABAQUS (R) platform. In this numerical analysis, accurate and realistic simulation of the different materials, geometry and loading conditions was approached. Particularly, the anisotropic nature of the wound laminate and the varying orientation of the fibers were attained. However, the cohesive zones were not attributed independent properties. Comparison between experimental and numerical data was addressed. In general, although the experimental-numerical data agreement was not as good as desired, a preliminary insight to both the structural health monitoring (SHM) system and the numerical modeling approaches was actually achieved. Full characterization and validation shall be further addressed in the continuation of the present work. The first set of results and difficulties on the development and implementation of this SHM system to COPV are presented and discussed in this paper.