Future Design for Composite Airframe structures – The Projects POSICOSS and COCOMAT 4 th International Conference on New Aerospace Trends 1 of 10 Future Design for Composite Airframe structures – The Projects POSICOSS and COCOMAT Richard Degenhardt DLR, Institute of Composite Structural and Adaptive Systems, Braunschweig, Germany Summary: European aircraft industry demands for reduced development and operating costs, by 20% and 50% in the short and long term, respectively. Contributions to this aim are provided by the completed project POSICOSS and the running follow-up project COCOMAT, both supported by the European Commission. As an important contribution to cost reduction a decrease in structural weight can be reached by exploiting considerable reserves in primary fibre composite fuselage structures through an accurate and reliable simulation of postbuckling and collapse. The POSICOSS team developed fast procedures for postbuckling analysis of fibre composite stiffened panels, created comprehensive experimental data bases and derived design guidelines. COCOMAT builds up on the POSICOSS results and considers in addition the simulation of collapse by taking degradation into account. The results comprise an extended experimental data base, degradation models, improved certification and design tools as well as design guidelines. This paper presents an overview of major results from the POSICOSS project as well as the objectives and planned tasks of COCOMAT. In addition, DLR’s first findings of the COCOMAT project are given. Keywords: Collapse, Buckling, Postbuckling, Composites, Simulation tools, Experiments, Degradation, Skin stringer separation 1. Introduction European aircraft industry demands for reduced development and operating costs, by 20% and 50% in the short and long term, respectively. Supported by the European Commission the project POSICOSS, which lasted from January 2000 to September 2004 and the 4-year follow-up project COCOMAT, which started in January 2004 (cf. Fig. 1), contribute to this aim. POSICOSS stands for Improved PO stbuckling SI mulation for Design of Fibre CO mposite S tiffened Fuselage Structures and COCOMAT is the acronym of Improved MAT erial Exploitation at Safe Design of CO mposite Airframe Structures by Accurate Simulation of CO llapse. Both projects are co-ordinated by DLR, Institute of Composite Structural and Adaptive Systems. They allow for a structural weight reduction by exploiting considerable reserves in primary fibre composite fuselage structures through an accurate and reliable simulation of postbuckling and collapse. The POSICOSS team has developed improved, fast and reliable procedures for buckling and postbuckling analysis of fibre composite stiffened panels of future fuselage structures. For the purpose of validation comprehensive experimental data bases were created. Finally, design guidelines were derived. The COCOMAT project builds up on the POSICOSS results and goes beyond by a simulation of collapse. That requires knowing about degradation due to static as well as low cycle loading in the postbuckling range. COCOMAT will improve existing slow and fast simulation tools and will set up design guidelines for stiffened panels which take skin stringer separation and material degradation into account. Reliable fast tools allow for an economic design process, whereas very accurate but necessarily slow tools are required for the final certification. The results will comprise a substantially extended data base on material properties and on collapse of undamaged and pre-damaged statically and low cyclically loaded structures, degradation models, improved slow and fast computation tools as well as design guidelines.