Development of a Mechaplastronic approach for optimizing hydrogen tank composites with in-situ Structural Health Monitoring (SHM)

Abstract

sustainable environments. Hydrogen, as a vector of energy, offers a high energy density and produces only water when used in fuel cells, making it an environmentally friendly alternative to fossil fuels. Hydrogen storage in gaseous form is typically achieved in type IV composite tanks. These tanks feature a thermosetting matrix, usually an epoxy reinforced with carbon fibers, which provides mechanical strength. Additionally, a polymer liner, onto which the composite is deposited via filament winding, ensures the hydrogen barrier function. A metal base is incorporated to facilitate the introduction of hydrogen into the tank. Type V hydrogen tanks are made from thermoplastic polymers and consist of a monolithic structure including an internal layer of unfilled polymer and a multilayer composite external layer made of the same thermoplastic matrix reinforced with continuous carbon fibres. The interface between the composite and the liner is thus assumed to be perfect. These tanks will be subjected to the different types of thermomechanical loads as type IV tanks: nominal pressure of 700 bars, burst pressure of 1750 bars, temperature ranging from -60°C to 85°C, fill-drain cycles, shocks, and impacts (figure 1). However, in terms of service life, the difficulty of damage detection and measurement and monitoring of physical quantities within composite structures still requires the development of specific and reliable technological tools and methods, such as the integration of sensors into the composite structure. The interest in integrating such a function lies in the potential for in-situ health monitoring of the structure from its implementation (Process Health Monitoring - PHM) to its service life (Structural Health Monitoring - SHM). Mastering this technology in all its aspects could significantly reduce maintenance costs and ensure better durability while optimizing the manufacturing process. The integration of sensors into hydrogen storage structures is essential to advancing the use of hydrogen as an energy carrier in transportation. Integrated sensors can provide an easy and effective means to monitor manufacturing quality and mechanical performance of the tanks during their service life. Indeed, these sensors contribute to several essential functions of so-called "smart tanks" currently in development. However, the integration of sensors is complex and poses several challenges such as type of sensors, the methodology of integration of the sensors. To overcome these challenges, the proposed methodology aims to establish a structured approach for selecting and/or optimizing the Process-Material-Sensor (PMS) trio to ensure the reliability of the mechanical and electronic functions integrated within hydrogen tanks. The proposed approach involves combining an experimental method with a numerical one. Additionally, it leverages cross-disciplinary skills, including: • The characterization and modeling of the Mechanical behavior of materials and the optimization of tank performance. • The processes involved in the manufacturing of hydrogen tanks (plastics engineering). • The integration and use of sensors, particularly the analysis of electronic signals to correlate with the assessment of the tank's degradation state. In this paper the development of a highly transversal global approach that called Mechaplastronic has been proposed. Indeed, it can be considered that optimizing the integration of sensors within a tank involves studying different types of intrusiveness: A) Intrusiveness of the Fabrication Process on Electronic Functions: Firstly, when sensors are integrated within the materials or at their interfaces, they must be compatible with the fabrication process of the structure (Automated Fiber Placement (AFP) / Filament Winding). Therefore, it is necessary to study the impact of the process on the operating mechanisms of the sensors and the reliability of its electrical and magnetic properties. This involves optimizing the process parameters and the choice of materials. B) Mutual Intrusiveness of Electronic and Mechanical Functions: The presence of sensors creates interfaces and stress concentrations that can weaken the structures. Therefore, it is important to study the effect of the presence of sensors on the mechanical properties of the structural materials (especially the composite). Conversely, the various thermomechanical stresses endured by the structure can affect the operation of the sensors. The proposed methodology, aiming to control the different potential intrusiveness and their interactions within a hydrogen tank, can be schematized as illustrated in figure 2. Thus, this study aims to enhance the understanding of the performance of critical areas in H2 tanks. The entirety of this study's results, along with the understanding of the phenomena involved, particularly damage, constitutes an important experimental and numerical foundation.