Keynote Lectures
The keynote speakers of the conference are listed below (continuous updates)
Holm Altenbach
Otto-von-Guericke-Universität Magdeburg
Since 2011 Prof. Altenbach is a full professor in Engineering Mechanics of the Institute of Mechanics of the Faculty of Mechanical Engineering at the Otto-von-Guericke-Universität Magdeburg. He is an author/co-author of 23 textbooks and monographs, about 300 peer-reviewed journal papers a co-editor of 47 books. His research focus is on various branches of Continuum Mechanics (one-, two- and three-dimensional structures, creep and damage behavior, failure criteria, etc.).
He was educated in the former Soviet Union (diploma in 1980, PhD in 1983, and habilitation in 1987 at the Leningrad Polytechnic Institute, now Peter the Great St. Petersburg State Polytechnic University). He worked in Magdeburg at the department of engines and later materials science. In 1996, he was appointed as a professor of Engineering Mechanics at the Martin-Luther-Universität Halle-Wittenberg.
Recent Honors include: Krupp-Award (Alexander von Humboldt-Foundation, 1992), Best paper of the year Journal of Strain Analysis for Engineering Design (2000), Gold Medal of the Faculty of Mechanical Engineering, Politechnika Lubelska, Lublin, Poland (2003), Semko-Medal of the National Technical University Kharkov, Ukraine (2004), Doctor honoris causa, National Technical University Kharkov, Ukraine (2007), Fellow of the Japanese Society for the Promotion of Science (2011), Doctor honoris causa, University Constanta, Romania (2014), Doctor honoris causa, Vekua-Institute, Tbilisi, Georgia (2016), and Alexander von Humboldt Award (Poland, 2018). Since 2019, he is a foreign member of the Russian Academy of Sciences.
Layered Structures – Advantages and Disadvantages of Various Modeling Approaches
Layered Structures are used in many applications because of the possibility to design materials with prescribed properties. At the same time, they are often thin and one gets a lightweight structure. During the last 100 years, many suggestions were made to improve the Euler-Bernoulli beam theory or the Kirchhoff plate theory. The idea was to have simple one- or two-dimensional theories, but better predictions of the mechanical behavior of such structures which is necessary for high inhomogeneous in the thickness direction structures. The mechanical behavior is influenced by both the mechanical properties’ ratios and the thickness size of the different layers.
There are four main directions in development beam or plate theories:
- Assuming hypotheses with respect to the stress, strain, etc. states one can deduce the full set of governing equations including the constitutive relations.
- Introducing a deformable surface a set of two-dimensional continuum mechanics equations can be established. The problem is the identification of the constitutive parameters from the three-dimensional images.
- Assuming a small parameter, mathematical techniques can be used to formulate the two-dimensional equations. Such techniques are series expansions or asymptotic integration.
- Consistent formulation are based on power series expansions and on consistent truncation of the series the strains, etc.
It is obvious that each approach has advantages and disadvantages. Anyway, on gets only an approximation of the structures, which are three-dimensional even if the thickness is small. The last one is also the reason for inaccuracies of Finite Element based simulations. On different aspects will be reported in the lecture.
Gennady Kulikov
Tambov State Technical University, Russia
Professor Kulikov received his first doctoral degree in Solid Mechanics in 1981 at the Moscow State University and his second degree of the doctor of Physics and Mathematics in Solid Mechanics in 1991 at the Kazan State University. From 1991 to 2015 he was a head of the Department of Applied Mathematics and Mechanics at the Tambov State Technical University. Since 2015 he is a head of Lab of Intelligent Materials and Structures. Professor Kulikov is a prize-winner of the Russian Ministry of Education and Science for his outstanding contribution to sciences (2003). He was visiting professor at the Institute of Mechanics, Technische Universität Berlin (1995, 1999 and 2002) and the Department of Aeronautics and Aerospace Engineering, Politecnico di Torino (2007, 2016, 2017). His fields of research are finite element method, sampling surfaces method, nonlinear structural analysis, composite shell structures, adaptive structures and smart systems, contact interactions, and tire mechanics.
Nonlinear solid-shell elements for 3D stress analysis of composite and smart structures
The effective nonlinear exact geometry or geometrically exact (GeX) four-node laminated composite and piezoelectric solid-shell elements using the method of sampling surfaces (SaS) are presented. The term GeX reflects the fact that the parametrization of the middle surface is known and, therefore, the coefficients of the first and second fundamental forms and Christoffel symbols are taken exactly at element nodes. The SaS formulation is based on the choice inside the layers of an arbitrarily number of SaS parallel to the middle surface and located at Chebyshev polynomial nodes to introduce the displacements and electric potentials of these surfaces as basic shell unknowns. The outer surfaces and interfaces are also included into a set of SaS. The SaS shell formulation uses the objective Green-Lagrange strain tensor that exactly represents large rigid-body motions of the shell in a curvilinear coordinate system. The developed solid-shell elements are based on the hybrid-mixed method through the Hu-Washizu variational formulation. The tangent stiffness matrices are evaluated by efficient 3D analytical integration proposed by the author. As a result, both GeX solid-shell elements exhibit a superior performance in the case of course meshes and allow the use of load increments, which are much larger than possible with existing displacement-based finite elements. They can be utilized for the analysis of the second Piola-Kirchhoff stresses and electric displacements in thick and thin laminated composite and piezoelectric doubly-curved shells because the SaS solutions asymptotically approach the exact solutions of elasticity and piezoelectricity as a number of SaS tends to infinity.
Michele D'Ottavio
University of Paris Nanterre, France
After earning the degree in Aerospace Engineering at the Politecnico di Torino, Michele has spent several years as Research Fellow at the University of Stuttgart, where he obtained his PhD under the guidance of Professor B.H. Kröplin at the Institute of Statics and Dynamics of Aerospace Structures. Since 2008 he is Associate Professor of the University of Paris Nanterre and he is a member of the Laboratoire Energétique Mécanique Electromagnétisme (LEME). His main research topics are modeling of composite laminated and sandwich plates/shells, including multiphysics coupling such as thermomechanics and piezoelectricity, as well as the development of appropriate numerical simulation tools, in particular based on the finite element method.
Sublaminate variable kinematics approach for the numerical analysis of composite structures
The complexity of composite structures (laminates, sandwich panels) calls for structural models that go beyond the limitations of classical theories such as CLT, based on Kirchhoff-Love’s hypotheses, and FSDT, based on Reissner-Mindlin’s hypotheses. A huge number of models have been thus developed in the past decades to include refined descriptions of the kinematics as well as the stress response, as well as towards meeting the so-called C0z-Requirements that should be met for taking into account the mesoscale heterogeneity of a composite stack. The large variety of models that have been proposed, ranging from Equivalent Single Layer (ESL) to Layer-Wise (LW) and Zig-Zag models, can be explained by the fact that their accuracy is strongly application-dependent.
Variable kinematics approaches offer a generic framework for the mechanics of structures, which can be exploited for assessing the accuracy of such axiomatically formulated models and, eventually, for identifying the ``best’’ model in terms of the ratio between accuracy and computational cost. The Sublaminate Generalized Unified Formulation (SGUF) is the formal extension of the well established Carrera’s Unified Formulation (CUF) to formulate arbitrary models for groups of plies (the sublaminates): in SGUF, different axiomatic models (ESL, ZigZag, LW) are introduced in each sublaminate by referring to Demasi’s Generalized Unified Formulation (GUF), and the model of the whole composite stack is obtained as a LW assembly of sublaminates.
Displacement based plate models expressed in SGUF have been implemented within a highly efficient Ritz-type solution as well as within a dedicated, locking-free FEM. The talk provides an overview of this approach along with numerical applications highlighting its current capabilities. Linear elastic problems are addressed to highlight the robust FEM implementation, which is also available as Abaqus User Element. The Ritz-type solution is used to discuss the extension of the SGUF approach to geometrically nonlinear bending problems. Applications to heterogeneous composites are also considered, in particular by addressing the modal and harmonic response of composite panels hosting piezoelectric plies and frequency-dependent viscoelastic materials.
Kian K. Sepahvand
Technical University of Munich, Germany
Kian K. Sepahvand is an adj. Prof. at the department of mechanical engineering, Technical University of Munich (TUM), Germany. His fields of research are computational mechanics, structural dynamics, vibroacoustics, optimization and composite structures. In particular, he investigated the impact of uncertainty in parameters, e.g. fiber orientations, on the dynamic behavior of fiber-reinforced composites, numerically and as well as experimentally. He focuses also on the application of Machine learning based method in composite structures.
Machine learning based modeling in composite materials
Developing of conventional continuum-based numerical models in composite materials has been grown continuously over the past decades. Diversity of these models, however, prevents them from the practical applications. Machine Learning (ML) based methods, in contrast, have a great potential to construct generalized surrogate models to realize the behavior of composite materials from the available data under various conditions and loading terms. This yields particularly to reliable results for any nonlinearity between input and outputs. Assuming the availability of limited data on the response of composite materials, ML methods employ the deep learning algorithms constructed based on the multi-layer artificial neural networks (ANN) to build the input-output relationships. The data can be extracted from the numerical simulations or experimental data. In this contribution, various aspects of the ML based modeling for composite materials including training and testing methods are investigated. Particularly, the proper orthogonal decomposition (POD) and the dynamic mode decomposition (DMD) in combination with the ANN is introduced to simulate the dynamical behavior of composite materials under material uncertainties in load terms and modeling parameters. The method leads to a drastically reduction in the rank of system matrices to improve the computational time. Application of the method is presented for the dynamic analysis of fiber reinforced composite plates under material uncertainties.
Antony Waas
University of Michigan, USA
Anthony M. Waas is the Richard A Auhll Department Chair of Aerospace Engineering at the University of Michigan, Ann Arbor where he holds the Felix Pawlowski Collegiate Chair. Prior to that he was the Boeing Egtvedt Endowed Chair Professor and Department Chair in the William E. Boeing Department of Aeronautics and Astronautics at the University of Washington (UW), Seattle. His current research interests are: computational modeling of lightweight composite structures, robotically manufactured aerospace structures, 3D printed structures, damage tolerance of structures, mechanics of textile composites, and data science applications in structural mechanics. Professor Waas was the Felix Pawlowski Collegiate Chair Professor of Aerospace Engineering and Director, Composite Structures Laboratory at the University of Michigan, from 1988 to 2014, prior to joining UW in January 2015. He assumed is current position in Fall 2018. Professor Waas is a Fellow of the American Institute of Aeronautics and Astronautics (AIAA), the American Society of Mechanical Engineering (ASME), the American Society for Composites (ASC), the American Academy of Mechanics (AAM) and the Royal Aeronautical Society, UK. He is a recipient of several best paper awards, the 2016 AIAA/ASME SDM award, the AAM Jr. Research Award, the ASC Outstanding Researcher Award, and several distinguished awards from the University of Michigan, including the Stephen S. Attwood award for Excellence in Engineering, one of the highest honors for an Engineering faculty member at the University of Michigan. He received the AIAA-ASC James H. Starnes, jr. Award, 2017, for seminal contributions to composite structures and materials, and for mentoring students and other young professionals. In 2017, Professor Waas was elected to the Washington State Academy of Sciences, and in 2018 to the European Academy of Sciences and Arts. He is also the recipient of the AIAA ICME Prize, 2020, and the ASME Warner T. Koiter Medal, 2020.
Steered Fiber Paths and Effects of Manufacturing Constraints on Future Advanced Aerospace Structures
Automated Fiber Placement (AFP) technology has revolutionized composites manufacturing and is quickly replacing traditional manual production. Among others, the notable advantage of AFP is that the designer is no more restricted to the use straight fibers, which means it is possible to have steered fiber paths designed for optimizing structural performance. The scope of this work is to identify the manufacturing parameters and associated constraints imposed by these parameters on the mathematical design space and introduce this in an optimization framework to design future aerospace structures (wings, fuselages etc.) for superior mechanical performance. In this talk, the design of a structural panel with a cutout to minizime stress concentration and the design of a skin to maximize buckling loads will be addressed. Furthermore, the effects of manufacturing induced unintended defects on the strength (tensile and compressive) of these strucures will also be addressed through experimentally validated computational models that account for the material microstructure.