1. Design and analysis of conformal composite LH2 fuel tanks for hypersonic aircrafts Background The need for more detailed investigations on liquid hydrogen tanks in future airliners is urgent in hypersonic aviation. The propellant tank technologies are critical for the vehicle operations, cost and safety. New materials and design concepts are required, such as fibre composites, in order to reduce the tank weight and to increase the structural performance. This is particularly important if the tank has load carrying functions. CHATT Project The main focus is to reduce tank weight and increase structural performance of cryogenic tanks. New materials (Carbon Fiber Reinforced plastic-CFRP) and design concepts need to be explored [1]. To minimize the weight, ‘iso-tensoid’ structures provide the lightest solutions. Fibre reinforced materials are structurally the most efficient material for pressure vessels due to their high specific strength, stiffness and because there is the possibility to direct the right amount of fibers according to the orientation and the magnitude of the principal stresses. Cryogenic environment Long duration flights Tank geometry and size Fuel permeation Tank wall & Liner material selection Hydrogen embrittlement Aim of my research The aim of the research would be the design, prototyping and testing of composite tanks -that deviate from classic shape- for cryogenic fuel containment. The challenge in my research is to preserve structural optimality, select suitable materials, design the tank within the limitations posed by manufacturing, maintenance and operation, manufacture proof-of-concept tanks and employ various testing methods. Research methodology A) Design Procedures Flight duration time affects significantly tank architecture. Design challenges: Integration or no-integration at aircraft Volume efficiency Tank weight minimization Optimum distribution of thermo-mechanical loads D) Testing Procedures Permeability tests for various polymer liners – Helium at a) room and b) cryogenic temperatures Thermo-mechanical tests (TMA) for various polymer liners and composite materials for linear thermal expansion coefficient (CTE) calculation Micro-cracking tests on representative of reinforced candidate materials (LCP & toughened epoxy) at a) room temperature and at b) –55 o C Run comparative tests on load concentration between experimental and FE Model Progress A small deal of progress was obtained to my own judgment, since I’ve started working on CHATT project only recently (2 months). Results can be seen below: Definition of liner materials demands and selection Liner requirements: (H 2 permeation resistance, thermal expansion compatibility with composite, low density & good resistance to thermo-mechanical loads) Definition of permeability testing apparatus setup requirements Publications -M. Sippel, A. Kopp, K. Sinkó, D. Mattsson, (2012) “ Advanced Hypersonic Cryo-Tanks Research in CHATT’’, 18th AIAA International Space Planes and Hypersonic Systems and Technologies Conference -S. Choi, B.V. Sankar, (2008) “Gas permeability of various graphite/epoxy composite laminates for cryogenic storage systems ’’, Composites Part B: Engineering 39, pp 782–791 - ASTM D1434-82, (2009) “ Standard test method for determining gas permeability characteristics of plastic film and sheeting’’ SpaceLiner hypersonic passenger transport with a non- integral cryogenic tank with cryogenic propellant Cryogenic LH 2 Tanks Key Challenges (a) Permeability tests for various polymer liners – Helium (b) Thermo-mechanical tests (TMA) for various polymer liners and composite materials Several design concepts will be considered for a proof-of- concept demonstrator cryogenic tank. Classical shaped Multi-bubble shaped (quadri-spherical) Conical shaped B) Cryogenic Tank Structure Modeling Built-up of parametric pressure vessel generator (FE analysis) Thin-walled and thick-walled pressure vessel analysis Definition of load environment Classical Lamination Theory (CLT) for laminate analysis Progressive Failure Analysis (PFA) for definition of material degradation Failure criteria application to tank structure components Evaluation methods for structural analysis (FE analysis) C) Manufacturing Methods Composite Pressure Vessel Evaluate the use of different pressure vessel manufacturing methods for the multi-bubble, conical concept (filament winding, fiber placement) Liner Evaluate the use of different liner manufacturing methods for the multi-bubble, conical concept (rotational/ injection/ blow moulding). Aerodynamic drag coefficient for a sphere PhD Candidate: Ilias Tapeinos Department: ASM Section: Structural Integrity & Composites Supervisor: S. Koussios Promoter: R. Benedictus Start date: 01-2-2013 Funding: TU Delft Cooperations: DLR-SICOMP-FOI-ULB-ECM-ELTE-CENAERO- GDL-ORB Aerospace Engineering Structural Configurations Internal pressure in spherical and cylindrical pressure vessels in thin-walled analysis Multi-bubble concept of cryogenic tanks for LH 2 storage Filament Winding Permeability experimental set-up for volumetric determination method [3] [2] Correlation of tensile strength and thermal conductivity for various polymer liner material candidates