18 TH INTERNATIONAL CONFERENCE ON COMPOSITE MATERIALS APPLICATION OF FULL THERMOPLASTIC COMPOSITE FOR TYPE IV 70MPA HIGH PRESSURE VESSELS S. Villalonga 1 *, C. Thomas 1 , F. Nony 1 , F. Thiebaud 2 , M. Geli 3 , A. Lucas 4 , K. Kremer- Knobloch 5 , C. Maugy 5 1 CEA, DAM, Le Ripault, F-37260 Monts, France, 2 MaHyTec, F-39100 Dole, France 3 TORAY-SOFICAR, F-64150 Abidos, France, 4 PARIS TECH, ENSAM, F-75013 Paris, France 5 PSA Peugeot Citroën, F-78307 Carrières sous Poissy, France. Keywords : Thermoplastic Composite, Type IV High Pressure Vessel, Hydrogen Storage, Fuel Cell Vehicles, Hydrogen Energy, New Energy Technologies 1 General Introduction 2 Material The fossil resources shortage and climate change Considering gravimetric and volumetric densities, as both encourage an evolution of our energy supplying well as safety requirements, type-IV vessels are the system. For more than a decade, hydrogen as an most promising solutions for on-board hydrogen alternative to traditional energy sources has been storage. They display no fatigue issues, the H 2 focus of research and development efforts. leakage is far below standards, and they show decent Hydrogen, combined with efficient converters such weight performances. CEA PA6 liner technology as fuel cells, represents a very promising way to [3][4] has demonstrated abilities to withstand 15,000 realize a more sustainable energy system. cycles from 20 to 875 bar, as required by European Nowadays, for automotive applications, even if or ISO standards for a nominal operating pressure of several interesting prototypes have been displayed, 700 bar. Moreover, the CEA is involved in the no storage system meets every international development of innovative materials such as standards and car manufacturers’ requirements. materials for composite filament winding However, developments on 700 bar type IV vessels (thermoplastic and thermoset matrices) and materials with Thermoplastic PA6 liner [1][2] have for different types of liner (based either on demonstrated very encouraging results (cycling thermoplastics and thermosets). In the scope of resistance, burst pressure, H 2 tightness, gravimetric Hype project, the composite shell material, Carbostamp TM ‘Fig.1’ , is a polyamide matrix and volumetric storage capacities, H 2 barrier properties). Over the last decade, the CEA (French (polyamide 6) reinforced with T700 Carbon Fibers. Atomic Energy and Alternative Energies Its fiber volume fraction is about 50 %. The material Commission) has developed, with several industrial used for the liner is a PA6 thermoplastic material and academic partners, valuable knowledge and made by reactive rotomolding process so that the competences focused on reactive rotational molding vessel is a PA6 monopolymer vessel with a very of high performances polymeric liners. The CEA has good consolidation between the liner wall and the improved design, calculation, manufacturing and composite shell. Thermoplastic matrix composites testing of structural composite vessel shells too. This can be considered as relevant solutions since they paper reviews the most recent technical and present many advantages. They show numerous scientific achievements in comparison with the state- potential interests in term of storage, shell fiber of-the-art of CGH2 storage systems, especially volume fraction quality, impact resistance, durability results from the French collaborative research Hype and recyclability. Indeed, recyclability of CF/PA6 project. Vessel composite shells are manufactured composite is easier than CF/Epoxy composite, which by filament winding using Carbosatmp TM (Toray is very attractive for automotive industry. CF and T700 fiber, PA6 thermoplastic matrix). This paper PA6 can be separated by considering PA6 fusion presents the material used, its properties, composite temperature and re-used to make short carbon fibers and vessel design and calculation, manufacturing for example. Moreover, CF/PA6 process could be aspects, testing and automotive application. less expensive and faster. Compared to epoxy prepreg which has to be stored at -20°C and used
before 6 months, there is no special constraint to properties. Transverse cracking and delamination store CF/PA6 before the filament winding. have been studied ‘Fig. 2’. The results are described Compared to wet filament winding, there is no in the following reference: [6]. constraint of impregnation during the winding, no 4 Composite and Vessel Design and Calculation time and cost wasted to prepare resin, no pot-life time, no impregnation process parameters which The design of a composite vessel is extremely need to be adjusted, no volumic fiber rate variation specific as it should take into account boss, liner and of the composite in the ply or in the laminate of the composite materials, liner manufacturing process vessel, no time and cost wasted to clean the filament specifications as well as constraints for the filament winding machine, no safety constraint (equipments winding process. The composite architecture has to and workers) as using volatile resin, no time and be optimized in order to approach the predefined cost wasted due to the need of thermal curing after target as closely as possible. Moreover, the design the filament winding process. The main difficulty of should take into account the service and test the CF/PA6 process (impregnation / consolidation / pressures, the external stresses, which are specific to curing) is the consolidation step. the use (and dependent on, for instance, impact, aggressive media, temperature etc…). For the 3 Material Properties specific case of type-IV vessels, the main composite The design of reinforced laminated composites for design test is the burst pressure. type IV high pressure vessels application takes into account the initial mechanical properties of the Design of the dome shape region is one of the main material including safety coefficients [5]. difficulties for a high pressure vessel. The shape dome has to be compatible with the filament Carbostamp TM PA 6 is a polyamide matrix winding process. During the 18 th century, the French (polyamide 6) reinforced with T 700 Carbon Fibres mathematician Alexis Claude Clairaut (1713-1765) from Toray SOFICAR. The fibre volume fraction, ‘Fig. 3.’ studied the geodesic shape on the earth determined by pyrolysis at 500°C, is about 50 %. surface [7] and developed a theorie. Today, this The matrix is semi crystalline and presents a melting theorie is used to design and manufacture high point at 215°C. The density, measured according to pressure vessel by filament winding ‘Fig. 4.”. Archimede’s principle by weighing the samples in air and a liquid of known density (water), is about The best estimate calculation code for design 1.47 kg/m3 for Carbostamp TM PA6. evaluation has to be enough qualified to minimize result uncertainties and optimized High Pressure The first characterizations are dedicated to the Vessels. In each case, HPV should be optimized to mechanical behavior of the material. Tensile tests hold a maximum of fluid with a limited volume at have been conducted on unidirectional specimen the best manufacturing costs, load bearing capability with three different orientations 0°, 90° and 45° and lifespan. This previous step is vital before (orientations of fibres compared to the tensile load enlarging design parameters and finally answering direction) and cross-plied laminates [±45]s. The test industrial and economic stakes. samples are manufactured by hot compression moulding. The materials and the mould are heated to Current finite element calculation limitations are reach a temperature above the melting temperature related to different models and behavior of the matrix. Then a pressure is applied. Finally the uncertainties. We can quote for instance the mould is cooled still under pressure to a temperature following aspects: below the glass transition temperature before that the - The lay-up design about the winding consolidated specimen is extracted. evolution strategies on end-closures revolution areas (thickness evolutions, angles evolutions with The next mechanical experiments deal with different geodesic winding trajectories or with non-geodesic damages occurring in carbon fibers / polyamide winding techniques, laminate superposition, slippage matrix composite structures in the aim of parameters) understanding their influence on the mechanical
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