CELPACT Project : Celular concept structure in aircraft
This event was organized in the frame of the final meeting of CELPACT, a 3-year EC FP6 aeronautics research project which generated very interesting results. CELPACT … is an upstream research project coordinated by the German Aerospace Center (DLR) on the development of breakthrough technologies and design tools for future airframe structures with high efficiency and safety. The European aircraft industry has strong interest in novel structural concepts for future aircraft fuselage and wing structures with lower fabrication costs and high performance. An important class of these next generation aerospace materials will employ advanced manufacturing techniques for sandwich structures with cellular core materials giving high strength/weight and improved impact resistance under critical aircraft load cases such as foreign object impact from birds, tyre rubber and runway debris. The main objective of the project was development and design of cellular materials and twin skinned sandwich structures made from hybrid composites and metals. CELPACT is progressing fabrication technology for cellular metals based on selective laser melting and developing new fabrication concepts for hybrid composite sandwich structures with folded cellular composite cores. Computational methods have been developed based on micromechanics cell models with multiscale modelling techniques for understanding progressive damage and collapse mechanisms and used for structural analysis. Impact performance is critical for sandwich aircraft structures and the simulation tools are being used to design efficient impact resistant aircraft structures. Structural integrity of these advanced cellular structures was assessed by testing generic cellular beam and shell structures under high velocity impact conditions relevant to aircraft structures. The research in CELPACT included next generation manufacturing techniques for both composite hybrid and metal cellular materials and structures : Cellular Hybrid Composites (CHC) with folded composite core structures, Cellular Metal (CM) with closed cell cores and selected laser melted lattice cores. Alastair Johnson, who coordinated the project for DLR during an interview highlighted some elements of the project. - Can you explain the “historic” context of CELPACT ? After the end of a very successful European project (CRAHVI), we had discussions between the partners involved on how to continue working together on another crash and impact dedicated project. There was already interest from Airbus and EADS IW in the idea of investigating more particularly aircraft sandwich structures, and we also had contact to universities with new technologies for lightweight sandwich core materials. It did not start from zero, it really started from a group and as coordinator, I invited other partners to join with specific expertise we required. - What is for you the main achievement within this project? First, we successfully manufactured and tested 2 generic types of new light weight structural core materials, metals with a regular microstruts and folded composite cores (foldcore). The 2nd main achievement was to use computational methods for the design of the core materials. Predicting the performances with modelling is crucial because changing the geometry of the core really modifies its properties. It is of course not possible to test the million of combinations of core materials and core microgeometry… Getting the design software validated to improve the design of the structure by predicting the performances has therefore a real value. - What are the main difficulties you have encountered? Main difficulties were linked to the project logistics. All activities were interconnected and done by 12 different technical partners: materials needed to be manufactured then tested, finite element (FE) modelling techniques had to be developed, and then test results had to be compared to modelling predictions for validation…. To get all this done within the 36-month project frame was a real challenge! - Can you list the keys to Celpact success ? First, a well balanced research team with specialists in each domain. Second, the proposal was very well detailed and defined, therefore very few changes had to be made during the project implementation. Finally, having ALMA on board for the management aspects. A management partner who is not involved in the technical work and only focused on the project organization is a real asset for having everything done on time. - Are you confident in the fact that the results of the project will be used ? For aeronautic applications, Celpact materials were ranked at level 3 on the Airbus Technology Readiness Level (TRL) scale. They showed some good potential, although a lot of further work with respect to an optimisation of manufacturing methods (quality, repeatability) or the treatment of topics like load introduction, reparability etc. has to be conducted. The next step would be to manufacture a real component of the plane with the new material and move to a higher TRL, which would rely on a strategic decision from the industry… So it is not clear yet if these materials will become important in future aeronautic structures, but they will certainly be used in other structural applications. CELPACT was a materials driven project and its results are valuable for automotive and railway structures for instance since some of the CELPACT sandwich structures have low weight and good energy absorption properties. - Will there be a CELPACT 2? I would say that there will certainly be included in future EU projects… Most likely projects centered on CELPACT metallic materials and other ones centered on composites foldcore with focused applications. And some ideas are also being discussed at national levels. - The groups from LMT and BRNO were not used to working on EC aeronautic projects before… What did LMT bring in this project? What did Brno bring? LMT Cachan is one of the European specialists for composite materials. They brought scientific know-how on the foldcore material and in particular, new ideas to test the core material at microscale level. This helped in the development of exact computational methods. In the case of the University of Brno, they were specialists in aeronautics with a dedicated aeronautics department. This department had designed and manufactured light aircraft in the past, so they were able to transfer this design experience to the project. -Current aircraft sandwich structures are not designed for high impact energy absorption – cores act as a spacer to the skins and have low energy absorption -New core concepts required for vulnerable areas with higher structural functionality and energy absorption properties. -Foldcore with aramid paper core has a high potential to become a structural energy absorbing core in aircraft structures – replacing polymer foams and Nomex honeycomb. -New cellular metallic cores with SLM fabrication and brazed truss cores have high potential for EA cores. -Cellular cores with improved impact behaviour have higher densities – niche applications in critical regions. -Gas gun tests with hard and deformable projectiles give valuable information on role of skin and core in absorbing energy. -FE simulation methods developed and validated to predict foldcore, SLM and sandwich properties. -Optimisation studies are now being applied to design aircraft SW structures with required mechanical properties and costs. CELPACT … 12 partners from 5 European countries 3 Mi€ budget More details : www.easn.net/supported-projects/celpact/consortium.htm Project coordinator: DLR Dr. Alastair Johnson - alastair.johnson@dlr.de Project management: ALMA CG Stéphanie Ousaci, sousaci@almacg.com Exploitation management: LTSM – University of Patras
Countries
Austria, Belgium, Bulgaria, Cyprus, Czechia, Germany, Denmark, Estonia, Spain, Finland, France, Hungary, Ireland, Italy, Lithuania, Luxembourg, Latvia, Malta, Netherlands, Poland, Portugal, Romania, Sweden, Slovenia, United Kingdom