Papers by Author: Mircea Calomfirescu

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Authors: Ch.R. Koenig, D.H. Mueller, J. Mueller, Mircea Calomfirescu
Abstract: Structural failure of fibre-reinforced polymers (FRP) caused by impact is an important factor in product development for the aircraft industry. Therefore it is necessary to obtain knowledge of the mechanisms and of the material loading during and shortly after an impact load. On account of this a Finite-Element-Model was developed with the goal to deduce design rules for impact tolerant composite materials. To verify and validate the Finite-Element-Model it is essential to have information of the state of stress on the surface of the FRP shortly after the impact. An impact test device was developed at the University of Bremen. The time variable, stress and strain conditions in composite plates are measured using photoelastic technique, strain gauges and holographic interferometry.
Authors: Mircea Calomfirescu, Axel S. Herrmann
Abstract: This paper presents a theoretical model for anisotropic wave attenuation in composites. The model has been implemented in a software called FIBREWAVE in order to predict dispersion and attenuation of A0 Lamb wave modes. The required input data are the complex stiffness matrix coefficients of the unidirectional plies of the composites, which have been measured by an immersion technique. Good agreement has been observed between predicted and experimental group velocities and wave attenuations.
Authors: Ch.R. Koenig, D.H. Mueller, O. Focke, Mircea Calomfirescu
Abstract: Fibre reinforced polymers (FRP) offer a high potential to reduce kinetic energy. As a consequence of this, fibre reinforced polymers often have a higher risk of being exposed to impact loads. The knowledge of the mechanisms and of the material loading during and shortly after an impact load is essential for an ‘impact-load-monitoring-system’ to predict possible structural failures. Especially a prognosis of structural failures caused by – often unrecognized - barely visible impacts is an important factor. Primary impact damages often leads to a sudden structural failure. These unheralded failures seems to be one of the most important problems in product development for the aircraft industry. By measuring the structural response at several discrete measurement points an impact can be detected, reconstructed and also rated.
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