Overview of completed research projects at IMCS


Experimental Characterization and Numerical Simulation of the Automated Fiber Placement (AFP) Process for Carbon-Fiber-Reinforced Plastics


Funding/Agency Deutsche Forschungsgemeinschaft (DFG), PO 1883/3-1
Funding Period 2017-2021


Institute for Carbon Composites, TU Munich (Prof. Drechsler)
Institute for Comutational Mechanics, TU Munich (Prof. Wall)
Project Abstract The efficient, high-quality and reproducible production of thermoplastic fiber-reinforced plastic components requires automated manufacturing processes. Due to its load-path oriented deposition of fibers to near-net-shape components, automated fiber placement (AFP) has particularly great potential. With proper temperature control during thermoplastic AFP (TP-AFP) in-situ consolidation is possible, i.e. a consolidation in place of the process without downstream thermosetting. However, the understanding of the process is still far from reaching the level of maturity necessary for a broad industrial application of TP-AFP. For example, it is still difficult today to define suitable process windows for the most important key parameters such as laser power, velocity and compaction pressure so that a consistently high quality of components is assured. In particular, the prediction of residual stresses and distortion is only solved insufficiently and process calibration is often based on a trial-and-error method. The reasons for this discrepancy between low prediction accuracy and high industrial demands can likewise be ascribed to possibilities of experimental characterization and modeling and simulation that are not yet maxed out. Therefore, the aim of this project is to improve process understanding in the area of TP-AFP fundamentally through novel experimental studies and methods of numerical simulation.
Contact at IMCS Prof. Dr.-Ing. Alexander Popp


Bottom-Up Modeling of Stents and Stent Grafts for Endovascular Aortic Repair (EVAR) of Abdominal Aortic Aneurysms


Funding/Agency Daimler and Benz Foundation
Funding Period 2016-2018
Partners Institute of Industrial Science, The University of Tokyo, Japan (Prof. Oshima)
Project Abstract Arterial stent placement has become a very important and successful intervention in vascular surgery. One of the most common scenarios includes so-called self-expandable stent grafts composed of a special fabric graft and a metal stent mesh. Stent grafts are used in endovascular aortic repair (EVAR) to support weak localized bulges (aneurysms) in an artery being at risk of rupture, most commonly for abdominal aortic aneurysms (AAA). Over the last decade, an enormous thrust of research regarding the computational analysis of biomedical engineering problems in general, and regarding vascular mechanics and AAA in particular has taken place. While significant progress has been made, the computational analysis of AAA stent grafts using finite element methods (FEM) is still not predictive enough to give specific advice to vascular surgeons on how to optimally place the device during EVAR. Possible risks, which are still far from being fully understood, include a movement of stents away from the desired location (migration), leaking of blood around stent grafts (endoleakage) and damage of the arterial wall caused by the stent itself. The main objective of this project is the development, implementation and validation of new innovative FEM simulation tools for AAA stent grafts based on a bottom-up modeling approach. All relevant micro-geometrical and mechanical features of the complex stent graft designs will be included into the new models, thus allowing for a significantly increased accuracy of stent expansion and placement simulations.
Contact at IMCS Prof. Dr.-Ing. Alexander Popp


A Novel Smooth Discretization Approach for Elasto-Plastic Contact of Solid Bodies and Thin-Walled Structures


Funding/Agency Deutsche Forschungsgemeinschaft (DFG), PO 1883/1-1
in the framework of the Priority Programme SPP 1748
Funding Period 2014-2017
Partners Institute of Numerical Mathematics, TU Munich (Prof. Wohlmuth)
Project Abstract This project aimed at introducing a new discretization method for contact of bulky and thin-walled structures exhibiting pronounced geometrical and material nonlinearities. The resulting smooth contact approach goes beyond traditional smoothing procedures with regard to a sound mathematical basis, but at the same time retains the simplicity of low-order finite element discretizations in the bulk of the computational domain. Volume and contact surface discretizations are strictly separated, but interconnected via variationally consistent coupling operators based on generic biorthogonal Lagrange multiplier bases. This new approach promises to offer maximal flexibility with regard to a smooth surface discretization (e.g. using higher-order FEM, Hermite interpolation, splines or NURBS) and a completely independent volume discretization (e.g. using low-order non-conforming FEM, EAS or F-Bar techniques). In addition, an integrated treatment of contact and friction as well as finite strain plasticity based on so-called nonlinear complementarity functions and semi-smooth Newton methods has been developed, which offers a superior robustness as compared with traditional radial return mapping schemes.
Contact at IMCS Prof. Dr.-Ing. Alexander Popp


Robust Simulation Methods for Contact, Friction, Wear and Fatigue in Blade-to-Disc Joints in Aircraft Engines


Funding/Agency Rolls-Royce Deutschland Ltd & Co KG
in the framework of the German Aviation Research Program (BMWi)
Funding Period 2007-2017
Partners Rolls-Royce plc (U.K.)
Project Abstract Long-term industry collaboration (over 10 years) with several sub-projects that were concerned with robust discretization schemes and solution algorithms for contact problems in turbine blade-to-disc joints. New computational methods for domain decomposition, frictional contact, fretting wear and fretting fatigue have been developed, validated and integrated into the industrial partner's in-house finite element code. Consulting on high-performance computing (HPC).
Contact at IMCS Prof. Dr.-Ing. Alexander Popp