Rüdiger Schmidt

Bio: Rüdiger Schmidt is an academic researcher from RWTH Aachen University. The author has contributed to research in topics: Finite element method & Shell (structure). The author has an hindex of 21, co-authored 82 publications receiving 1060 citations.

Modeling and simulation of macro-fiber composite layered smart structures

Abstract: Piezo fiber composite material, macro-fiber composite (MFC), is increasingly applied in engineering, due to its high flexibility and strong actuation forces. This paper develops a linear electro-mechanically coupled finite element (FE) model for composite laminated thin-walled smart structures bonded with orthotropic MFCs having arbitrary piezo fiber orientation. Two types of MFCs are considered, namely, MFC-d31 in which the d 31 effect dominates the actuation forces, and MFC-d33 which mainly uses the d 33 effect. The FE model is developed based on the Reissner–Mindlin hypothesis using linear piezoelectric constitutive equations. The present results are compared with ANSYS and experimental results reported in the literature (Bowen et al., 2011). Afterwards, isotropic or composite structures with cross-ply laminates, integrated with MFC-d31 or -d33 patches having different fiber orientation, are simulated under a certain electric voltage on the MFC patches.

A general linear theory of laminated composite shells featuring interlaminar bonding imperfections

Abstract: This paper is devoted to the foundation of a general linear theory of laminated composite anisotropic shells of arbitrary shape and curvature, in which the effect of the interfacial damage induced by the imperfect bonding between the constituent laminae is incorporated. In this context, the imperfect interface conditions are described in terms of linear relations between the interface tractions in the normal and tangential directions, and the respective displacement jumps. In addition to the effects of imperfectly bonded interfaces, the theory incorporates the effects of transverse shear and transverse normal strain, the dynamic effects, as well as the anisotropy of constituent material layers. Due to its general character, this theory can contribute to a more reliable prediction in the linear range of the load carrying capacitiy and failure of laminated composite shell structures featuring imperfectly bonded interfaces.

Active vibration control of piezoelectric bonded smart structures using PID algorithm

Abstract: Thin-walled structures are sensitive to vibrate under even very small disturbances. In order to design a suitable controller for vibration suppression of thin-walled smart structures, an electro-mechanically coupled finite element (FE) model of smart structures is developed based on first-order shear deformation (FOSD) hypothesis. Considering the vibrations generated by various disturbances, which include free and forced vibrations, a PID control is implemented to damp both the free and forced vibrations. Additionally, an LQR optimal control is applied for comparison. The implemented control strategies are validated by a piezoelectric layered smart plate under various excitations.

Large rotations in first-order shear deformation FE analysis of laminated shells

Abstract: The paper deals with the geometrically non-linear analysis of laminated composite beams, plates and shells in the framework of the first-order transverse shear deformation (FOSD) theory. A central point of the present paper is the discussion of the relevance of five- and six-parameter variants, respectively, of the FOSD hypothesis for large rotation plate and shell problems. In particular, it is shown that the assumption of constant through-thickness distribution of the transverse normal displacements is acceptable only for small and moderate rotation problems. Implications inherent in this assumption that are incompatible with large rotations are discussed from the point of view of the transverse normal strain–displacement relations as well as in the light of an enhanced, accurate large rotation formulation based on the use of Euler angles. The latter one is implemented as an updating process within a Total Lagrangian formulation of the six-parameter FOSD large rotation plate and shell theory. Numerical solutions are obtained by using isoparametric eight-node Serendipity-type shell finite elements with reduced integration. The Riks–Wempner–Ramm arc-length control method is used to trace primary and secondary equilibrium paths in the pre- and post-buckling range of deformation. A number of sample problems of non-linear, large rotation response of composite laminated plate and shell structures are presented including symmetric and asymmetric snap-through and snap-back problems.

Hybrid lightweight composite pyramidal truss sandwich panels with high damping and stiffness efficiency

Abstract: Hybrid composite pyramidal truss sandwich panels combined with multiple damping configurations are fabricated in this work. Modal and quasi-static compressive tests are carried out to investigate the damping and stiffness efficiency of the candidate structures. Experimental results show that such structures combined with damping materials would significantly improve the damping loss efficiency but decrease simultaneously the stiffness efficiency in varying degrees compared with the bare hybrid sandwich panels. In order to evaluate the compatible effect of total damping and stiffness efficiency of the present sandwich structures, a synthetic evaluation criterion is developed, which shows that bare sandwich panels filled with hard polyurethane foam (B-II-HPF) and soft polyurethane foam (B-II-SPF) can yield the best performance up to 2–4 times higher than the base hybrid sandwich panels. It is also shown that multiple patch damping treatments based on the finite element-modal strain energy (FE-MSE) approach are suitable and effective to further improve the total damping efficiency.

Pulsed laser deposition of thin films

Abstract: The pulsed laser deposition is a new technique for the growth of thin films,which has been attended generally by people recently The physical principle, unique characteristics and the proceeding of the study were introduced briefly In addation, the result of the PtSi nanometer thin film based on silicon prepared by the pulsed laser deposition was describedPULS

Recent research advances on the dynamic analysis of composite shells: 2000-2009

Abstract: Laminated composite shells are frequently used in various engineering applications in the aerospace, mechanical, marine, and automotive industries. This article follows a previous book and review articles published by the leading author (Qatu, 2004, 2002, 1989, 1992, 1999 [1–5]). It reviews most of the research done in recent years (2000–2009) on the dynamic behavior (including vibration) of composite shells. This review is conducted with emphasis on the type of testing or analysis performed (free vibration, impact, transient, shock, etc.), complicating effects in material (damping, piezoelectric, etc.) and structure (stiffened shells, etc.), and the various shell geometries that are subjected to dynamic research (cylindrical, conical, spherical and others). A general discussion of the various theories (classical, shear deformation, 3D, non-linear etc.) is also given. The main aim of this review article is to collate the research performed in the area of dynamic analyses of composite shells during the last 10 years, thereby giving a broad perspective of the state of art in this field. This review article contains close to 200 references.

Nuclear instruments and methods in physics research section B : beam interactions with materials and atoms

Abstract: The impact-induced deposition of Al13 clusters with icosahedral structure on Ni(0 0 1) surface was studied by molecular dynamics (MD) simulation using Finnis–Sinclair potentials. The incident kinetic energy (Ein) ranged from 0.01 to 30 eV per atom. The structural and dynamical properties of Al clusters on Ni surfaces were found to be strongly dependent on the impact energy. At much lower energy, the Al cluster deposited on the surface as a bulk molecule. However, the original icosahedral structure was transformed to the fcc-like one due to the interaction and the structure mismatch between the Al cluster and Ni surface. With increasing the impinging energy, the cluster was deformed severely when it contacted the substrate, and then broken up due to dense collision cascade. The cluster atoms spread on the surface at last. When the impact energy was higher than 11 eV, the defects, such as Al substitutions and Ni ejections, were observed. The simulation indicated that there exists an optimum energy range, which is suitable for Al epitaxial growth in layer by layer. In addition, at higher impinging energy, the atomic exchange between Al and Ni atoms will be favourable to surface alloying.