Leibniz Universität Hannover Faculty Faculty of Civil Engineering and Geodetic Science
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Institute of Structural Analysis
 
Research
Composites Department

Main research topics in the Composites Department

© FBG / C. Bierwagen
© FBG / C. Bierwagen
© FBG / C. Bierwagen

The sustainability and reliability of structures is of central importance for mobility and regenerative energy from a technical and economic point of view. Accordingly, understanding the structural and material behavior under different environmental influences (temperature, humidity, etc.) and the ability to predict damage play a key role in the development of lightweight components, reliable systems and the achievement of low electricity generation costs. Physically motivated numerical simulation models are an essential part of the development process of sustainable structures. In order to increase the efficiency of the simulation models and thus expand the area of ​​application, reduction methods and machine learning are used. The Composites department combines the concepts of sustainability, service life and method efficiency. The scientific work is divided into the following main research areas:

Composite Materials

New and detailed simulation models are developed in the Composite Materials group. Material laws and failure models of fiber composites are developed here on different scales from the nano to the meso scale. At the nano-level, atomistic simulation methods are used to model the atomic components by using the molecular dynamics, while at the micro- and meso-level physically motivated constitutive material models are developed and integrated in a finite element framework. The material models take into account  non-linear viscoelasticities, viscoplasticities, damage and various environmental influences. For this purpose, both monotonic and cyclic loads are taken into account during material modeling.

Composite Structures

This team is concerned with the stability analysis and dynamic analysis  of slender  and thin-walled structures.  A second theme is the fatigue analysis  of composite structures. Important aspects in this team are probabilistic analysis and reduced order modeling.  

RECENT RESEARCH PROJECTS

Material Modeling

  • Virtual Materials and their Validation: German-French School of Computational Engineering (ViVaCE)
    Compressive failure mechanism of unidirectional fibre composites has been studied extensively over the past decades. Stochastic fibre misalignments were identified as an essential factor in the prediction of compressive strength. There is a need to characterize the effects of distribution of misalignment on the strength values in compressive regime. Hence, the scope of this project is to further the development in this regard and extend the definition of failure surfaces under compressively dominated loads by statistical information. A probabilistic definition of failure surface based on imperfections at micro level, and a subsequent experimental validation are the goals of the project. This would lead to subsequent better representation of material properties at the macro scale.
    Led by: Prof. Dr-Ing. habil. Raimund Rolfes
    Team: Nabeel Safdar, M.Sc., Benedikt Daum, Dipl.-Ing. Dr.
    Year: 2016
    Funding: Deutsche Forschungsgemeinschaft – DFG (International Research and Training Group IRTG1627)
    Duration: 01.12.2016 – 30.09.2019
  • Development and validation of a virtual process chain for composite structural components considering imperfections with application to a rotor blade component (Prosim R)
    Within the scope of this research project, the essential parts of the process chain in the production of a rotor blade are to be numerically simulated and fundamentally investigated. The primary goal is the reduction of defects in the production of fiber composite materials with the help of simulating the full process chain (manufacturing simulation and structural analysis). In order to obtain a statement on material behaviour and progressive failure, the ISD will extend the sequential multi-scale analysis by including imperfections at the ISD. The results of the draping and infusion simulation are thereby the input information.
    Led by: Prof. Dr-Ing. habil. Raimund Rolfes
    Team: Gerrit Gottlieb, M.Sc., Benedikt Daum, Dipl.-Ing. Dr.
    Year: 2017
    Funding: German Research Foundation (DFG) - Project number 329147126
    Duration: 01.08.2017 – 31.07.2020
  • Modeling and simulation of the fatigue damage behavior of fiber composites under variable block loading conditions
    The goal of this research project is the extension and application of a progressive fatigue damage model for unidirectional multi-layered fiber composites for damage analysis under variable cyclic block loading patterns. The focus is on the development of damage evolution laws to accurately predict the degradation of strength and stiffness properties based on the load direction and the stress level. In addition to the influence of load sequence effects, particular attention will be paid to the effects of passive damage occurring under combined cyclic tension and compression loading. Finally, the extended fatigue damage model is to be applied to a fuselage structure segment of a future passenger aircraft for fatigue analysis.
    Led by: Prof. Dr.-Ing. habil. Raimund Rolfes
    Team: M.Sc. Marting Brod
    Year: 2020
    Funding: Internes Projekt
    Duration: seit 2020

Structures

  • Development of a safety cockpit for gliders (CraCpit)
    The aim is to develop a crash retrofit solution made of composite materials for gliders. Particularly challenging is the rapid loading, which requires a non-linear viscoelastic damage model. The high complexity of the model, resulting from the high level of geometric detail. The energy dissipation and the separation of subcomponents is a particular challenge during the explicit calculation. The developed and simulated retrofit solution is validated in a large-scale test on a glider.
    Led by: Prof. Dr-Ing habil. Raimund Rolfes
    Team: Oliver Dorn, M.Sc., Dr.-Ing. Sven Scheffler
    Year: 2017
    Funding: Federal Ministry for Economic Affairs and Energy – 20E1703D
    Duration: 2018-2021
  • Improved structural performance through the use of random field analysis
    The research performed within this project uses the effect of random variations in structure’s geometry and/or material to get information on local sensitivity of structures to deviations from their baseline value. This information cannot only be useful in quality assurance, by finding areas most sensitive to deviations, but can also be used to improve the design. This approach can load to an increase in structural parameters such as buckling load, fatigue life and others.
    Led by: Prof. Dr-Ing habil. Raimund Rolfes
    Team: Muzzamil Tariq, M.Sc.
    Year: 2019
    Funding: SE²A excellence, Cluster of DFG
    Duration: 2019-2022
  • Multistable Morphing Structures using Variable Stiffness Composites
    The research project aims at developing multistable structures with morphing capabilities. A variable stiffness composite is used which allows stiffness tailoring with much larger design space. The developed semi analytical method is validated well within a Finite element framework. In this work, the concept of static, smart and dynamic actuations are exploited on bistable laminates to reduce the snap-through requirements.
    Led by: Prof. Dr-Ing habil. Raimund Rolfes
    Team: Anilkumar P M Nair, M.Tech.
    Year: 2019
    Funding: Deutscher Akademischer Austauschdienst (DAAD)
    Duration: 2019-2021
  • FANFOLD – Fast nonlinear machine learned analysis for rotor blades
    Constructions made of fiber-plastic composites are primarily light and thin-walled. Different semi-finished products (materials, weaving etc.) give the designer a wide range of possibilities. Thus, a component can be dimensioned and manufactured according to the requirements and stresses. But exactly this dimensioning requires a complex determination of the material parameters of the unidirectional single layer. If the strengths and stiffnesses are too low, the structure becomes too heavy, if they are too high, the structure may fail. In a novel approach, the structural properties of the laminate will be predicted by machine learning. By means of an orthotropic damage model a fast nonlinear calculation shall be realized. The goal is to shorten the calculation and development time.
    Led by: Prof. Dr-Ing. habil. Raimund Rolfes
    Team: Oliver Dorn, M.Sc., Dr.-Ing. Sven Scheffler
    Year: 2020
    Funding: Federal Ministry for Economic Affairs and Energy – FKZ 03EE3028A
    Duration: 2020 –2023

Nanocomposites

  • Acting Principles of Nano-Scaled Matrix Additives for Composite Structures (FOR 2021)
    The research project aims at gaining a comprehensive understanding of the acting mechanism of nano-scaled additives to polymer matrices of continuous fibre reinforced polymer composites with respect to improved matrix dominated properties. Particularly, a sequential multi-scale simulation scheme for the prediction of mechanical properties is developed, ranging from particle-matrix interactions on nano scale up to fibre reinforced materials on micro/meso scale. It combines Finite Element and atomistic simulations based on the Molecular Dynamic Finite Element Method (MDFEM).
    Led by: Prof. Dr-Ing. habil. Raimund Rolfes
    Team: Atiyeh Mousavi, M.Sc., Johannes Fankhänel, Dipl.-Ing.
    Year: 2017
    Funding: Deutsche Forschungsgemeinschaft (DFG)
    Duration: 01.07.2017 – 31.10.2020
  • Challenges of industrial application of nanomodified and hybrid material systems in lightweight rotor blade design (HANNAH)
    The HANNAH research project is the follow-up to the LENAH research project. In LENAH, material systems from the fields of nanomodified materials and hybrid laminates were developed, tested and numerically simulated. This allowed the high potential of these material systems for the application in rotor blade design to be demonstrated under laboratory conditions. The investigated material systems are far superior to currently established materials, especially with regard to fatigue resistance. In the follow-up project HANNAH the (further) development of production and simulation methods for these material systems for industrial standards is now in the foreground. On the one hand, the aim is to guarantee the excellent properties of the developed material systems in large-scale production and to be able to simulate the mechanical behaviour to answer industry-related issues. In this context, the ISD develops material-specific simulation models in order increase time and cost efficiency for processes of material development and component design for nanomodified materials and hybrid laminates.
    Led by: Prof. Dr-Ing. habil. Raimund Rolfes
    Team: Christian Gerendt, M. Sc.; Betim Bahtiri, M. Sc.; Behrouz Arash, Dr. Ing.;
    Year: 2019
    Funding: Bundesministerium für Wirtschaft und Energie (BMWI) - FKZ 0324345A
    Duration: 01.03.2019 – 28.02.2022

Fatigue

  • Challenges of industrial application of nanomodified and hybrid material systems in lightweight rotor blade design (HANNAH)
    The HANNAH research project is the follow-up to the LENAH research project. In LENAH, material systems from the fields of nanomodified materials and hybrid laminates were developed, tested and numerically simulated. This allowed the high potential of these material systems for the application in rotor blade design to be demonstrated under laboratory conditions. The investigated material systems are far superior to currently established materials, especially with regard to fatigue resistance. In the follow-up project HANNAH the (further) development of production and simulation methods for these material systems for industrial standards is now in the foreground. On the one hand, the aim is to guarantee the excellent properties of the developed material systems in large-scale production and to be able to simulate the mechanical behaviour to answer industry-related issues. In this context, the ISD develops material-specific simulation models in order increase time and cost efficiency for processes of material development and component design for nanomodified materials and hybrid laminates.
    Led by: Prof. Dr-Ing. habil. Raimund Rolfes
    Team: Christian Gerendt, M. Sc.; Betim Bahtiri, M. Sc.; Behrouz Arash, Dr. Ing.;
    Year: 2019
    Funding: Bundesministerium für Wirtschaft und Energie (BMWI) - FKZ 0324345A
    Duration: 01.03.2019 – 28.02.2022
  • New methods for failure and fatigue analysis of suction panels for laminar flow control
    Although the suction panel concept holds a high potential to increase the sustainability of future aircrafts, it comes with some structural mechanical challenges that need to be carefully examined. With the panel’s underlying backbone structure adopting the load-carrying function of the outer airfoil in the suction area (see Fig. 1), the stress flux in the airfoil is considerably disturbed, resulting in multiple, potentially critical stress concentrations. To ensure a sufficient robustness of the suction panel concept in terms of static strength and fatigue resistance, the backbone structure is to be analyzed numerically by means of finite element simulations. With deep knowledge in the field of continuum damage mechanics and progressive fatigue analysis, ISD will perform high fidelity strength and fatigue analyses of the backbone structure to identify sufficiently robust designs of the backbone structure. To calibrate the numerical methods, experimental coupon tests of the backbone structure’s base material are scheduled to identify respective static and fatigue-related material properties. Beside the identification of mechanically robust designs of the suction panel, the numerical simulations are also to address topics like scalability of the suction concept and the benefits of thin ply laminates, which are well known to feature a superior fatigue resistance.
    Led by: Prof. Dr-Ing habil Raimund Rolfes
    Team: Muzzamil Tariq, Christian Gerendt, Dr-Ing. Sven Scheffler
    Year: 2019
    Funding: DFG, German Research Foundation
    Duration: 01.04.2019-31.12.2022
  • Global-local thermomechanical analysis of fracture in polycrystalline silicon shells using a phase-field approach.
    Abstract: The existing works in the literature addressing damage events in PV-Modules have different drawbacks and needs for improvements. On the one hand, the lack of a computationally efficient multiscale-based framework to model progressive failure in PSWs is observed. Furthermore, a coupled thermomechanical phase-field modeling framework for shells based on the geometrically nonlinear theory which takes into account the anisotropy effects as well as the presence of residual stresses is not yet available. Thus, the present proposal aims at covering these shortcomings in a unified way and at modeling progressive failure at both the micro- and macroscale by developing a theoretically robust and computationally efficient framework. This project is carried out in a close collaboration with the Institute of Applied Mechanics of the Technische Universität Braunschweig.
    Led by: Prof. Dr-Ing. habil. Raimund Rolfes
    Team: Muzzamil Tariq, M.Sc.
    Year: 2020
    Funding: DFG, German Research Foundation
    Duration: Muzzamil Tariq, M.Sc.
  • Modeling and simulation of the fatigue damage behavior of fiber composites under variable block loading conditions
    The goal of this research project is the extension and application of a progressive fatigue damage model for unidirectional multi-layered fiber composites for damage analysis under variable cyclic block loading patterns. The focus is on the development of damage evolution laws to accurately predict the degradation of strength and stiffness properties based on the load direction and the stress level. In addition to the influence of load sequence effects, particular attention will be paid to the effects of passive damage occurring under combined cyclic tension and compression loading. Finally, the extended fatigue damage model is to be applied to a fuselage structure segment of a future passenger aircraft for fatigue analysis.
    Led by: Prof. Dr.-Ing. habil. Raimund Rolfes
    Team: M.Sc. Marting Brod
    Year: 2020
    Funding: Internes Projekt
    Duration: seit 2020
  • Experimental analysis and numerical modelling of microcrack induced delaminations under cyclic loading with load reversals
    The aim of this joint research project (ISD - Leibniz Universität Hannover, ILK - TU Dresden) is to develop a profound understanding of the damage process during delamination growth in fibre-reinforced polymer laminates (FRP) based on existing inter fibre failures during cyclic loading with load reversals. By analysing and quantifying the relevant damage processes during loading, the influence of the level and direction of the applied load on delamination growth in FRP laminates is clarified. Based on the experimental work, detailed numerical simulations on a macro- and mesoscopic level are developed which allow a purposeful analysis of the delamination process in DCB- and ENF- as well as in laminate experiments. Thus, the delamination length-dependent analysis of the fracture modes, which cannot be implemented experimentally, is made possible. Consequently, it is analysed whether characteristic values determined by standardised crack propagation investigations (DCB, ENF etc.) can be transferred to embedded layers. In addition, the investigations provide extensive experimental results on the delamination process in FRP laminates under in-plane loading and thus create a basis for the development of suitable analytical and numerical models. It is investigated to what extent existing numerical damage models (e.g. cohesive zone approaches) allow reliable and efficient modelling of cyclic delamination growth and how the mesoscopic simulation results can be used for macroscopic simulations in terms of continuum mechanics.
    Led by: Prof. Dr.-Ing. habil. Raimund Rolfes
    Team: Gereon Hacker, M.Sc., Martin Brod, M.Sc., Dr.-Ing Sven Scheffler
    Year: 2021
    Funding: German Research Foundation (DFG) - Project number 457043708
    Duration: 01.09.2021-31.08.2023

Last Change: 08.09.22 Print

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