Essais & Simulations n°140

DOSSIERSPÉCIAL JEC

DOSSIERSPÉCIAL JEC WORLDCompression testsIs it possible to develop a transversalexpertise in polymer matrix compositematerials? Scientific issues revolvingaround the fire behaviour of aeronauticalmaterials, with little national andinternational attention, this collaborationhas quickly proven to be fruitful and hasled to the exploration of new avenues.WHAT HAVE YOU FOUND ANDWHAT ARE THE RESULTS OF YOURRESEARCH?The instrumented platform responds to atechnological lock by offering the possibilityof evaluating the in-situ evolutionof thermal (temperature mapping)and mechanical (force, displacement,deformation fields) responses duringa combined test. It therefore allows tounderstand neither the mechanisms ofthermal degradation, nor the physicalphenomena that operate in critical fireconditions. It is thus possible to accessknowledge of the fire behaviour of aeronauticalmaterials. Finally, this means ofcharacterization has a strong potential forindustrial deployment.WHAT IS THE AEROFIRE PLATFORMBASED ON AND WHAT DOES ITCONSIST OF?The demand of aeronautics industrialistsfor adapted and relevant experimentalcharacterization means istherefore strong. They have identifieda technological lock in the fire resistanceof materials. Therefore, it is essential toenable aeronautics manufacturers tounderstand/predict the thermo-mechanicalresponse of their materials indifferent configurations and, ultimately,of their parts and assemblies.This is the interest and ambition of theAerofire platform developed withinthe framework of the Carnot Decolleproject.CAN YOU TELL US MORE ABOUTTHE CHARACTERISTICS OF THEDECOLLE TEST PLATFORM ?The application of mechanical stressduring exposure to fire correspondsto the most critical situation of use inservice. In order to reproduce thesecritical conditions on a laboratory scale,this test platform has been developedto combine mechanical loading andthermal aggression (via a calorimetercone). The relevance and originality ofthis test bench is based on the controland very good reproducibility of thestresses (thermal and mechanical). Themulti-physical investigation capabilities,in terms of the study of thermal-mechanical-physicochemicalcouplings, offeredby this bench are transferable to anindustrial scale.HOW WILL THESE PLATFORMS BEINTEGRATED INTO THE INDUSTRIALACTIVITY? DO YOU ALREADY HAVEINDUSTRIAL APPLICATIONS ANDWITH WHICH PARTNERS?Despite the convenience of use andcontrol, the use of a radiant source toreproduce the effects of a fire exposuredoes not make it possible to accountfor the full physical reality of a fire.Aggression by a flame induces otherphysico-chemical transformations anda more critical degradation of the material,strongly impacting its mechanicalresistance. In order to reproduce asfaithfully as possible the critical conditionsin service according to the standardsin force (116kW/m² flux andsurface temperature of 1150°C), thebench developed is currently evolvingby integrating a kerosene burner inorder to gain a finer understanding ofthe fire resistance of composite materials.A Cifre thesis in partnership with SafranNacelles has begun on the problemof fire resistance of composite/metalassemblies. Since the end of 2019, aproject with the company Daher hasbeen studying the thermo-mechanicalcoupling in thermoplastic compositessubjected to a kerosene flame. Thesecollaborations with major players in theaeronautics industry confirm the relevanceof the means developed and allowto acquire a rare expertise. ●Interviewed by Olivier Guillon48 IESSAIS & SIMULATIONS • N°140 • février - mars 2020

DOSSIERCASE STUDYInspiring young engineersto design for the future at EPFLEPFLoop, one of the top three teams invited to the SpaceX Hyperloop Pod Competition, usedmultiphysics simulation to hit the ground running with a unique design advantage.Over the course of theannual SpaceX HyperloopPod Competition,engineering teams workto design and build hyperloop pods.The ultimate goal of the hyperloopconcept is to achieve a mode oftransportation that is high speed,intercontinental, and self-propelled.Such a system would both revolutionizethe experience of transportationand offer a greener alternativeto other modes of travel.The Hyperloop Pod Competition,which started in 2015 as thebrainchild of Elon Musk, culminateswith a weeklong competition eachsummer in Hawthorne, California,located in southwestern Los Angeles.Over the course of the competitionweek, participants get to testtheir hyperloop pod designs on amile-long track (Figure 1) at speedsof approximately 500 km per hour.WORKING ALONGSIDE THEWORLD'S TOP ENGINEERSEach year, the top 20 teams worldwideare invited to the Californiatesting facility, and the top threeteams can run on the track undervacuum at the final event. As a firsttimecompetitor, EPFLoop exceededall expectations by makinga presence in the finale as one ofthe three teams to run in vacuumthat year. Even more impressivewas the fact that they classified firstat the end of the testing week andwere told that their pod showed thehighest design reliability. Overall,the EPFLoop team ended up placingthird in the high-speed run on thefinal day of the competition due tothe unexpected presence of dust onthe test track, which affected theirpod's performance. Their experienceat SpaceX proved to be invaluable formany reasons.Made up of engineering studentsand technical advisors, the EPFLoopcompetition team formed at theSwiss Federal Institute of TechnologyLausanne (EPFL). Dr. Mario Paolone,principal advisor of the EPFLoopteam, says that the Hyperloop PodCompetition is a "chance for studentsand young engineers to participatein a state-of-the-art challenge, withsome of the world's top engineers."Besides the chance to use high-techFigure 1: An inside view of the hyperloop test track.testing equipment and rub elbowswith professional engineers, theexperience is a great opportunity forstudents to learn the importance ofresearching energy-efficient modes oftransportation. It also gets studentsexcited about research and inspiresthem to pursue careers in engineering.SIMULATING THE HYPERLOOPPODAside from the opportunity to visitSpaceX and experience an advancedtesting facility, the students whoparticipate in EPFLoop havesomething more to gain: valuableexperience using multiphysics simulation.Each aspect of EPFLoop'shyperloop pod design (Figure 2)involves modeling and simulation.In fact, Paolone calls simulation the"core" of their project. One obviousreason: The team’s 60-meter test trackis nowhere close to the mile-long testESSAIS & SIMULATIONS • N°140 • Février - Mars 2020 I49