17th International Conference on Composite Structures
ICCS 17
A. J. M. Ferreira (Editor)
 FEUP, Porto, 2013
ESTIMATING DESIGN PARAMETER VARIABILITY OF
THERMOPLASTIC HONEYCOMB SANDWICH PANELS THROUGH
STOCHASTIC ANALYSIS OF THEIR DYNAMIC BEHAVIOUR
Stijn Debruyne†, Dirk Vandepitte†, Eric Debrabandere*
† Department of Mechanical Engineering
Katholieke Universiteit Leuven (KUL)
Celestijnenlaan 300b, 3001 Heverlee, Belgium
e-mail: stijn.debruyne@khbo.be, dirk.vandepitte@mech.kuleuven.be
*
Department of Industrial Science
Katholieke Hogeschool Brugge Oostende
Zeedijk 101, Oostende, Belgium
e-mail: eric.debrabandere@khbo.be
Key words: Thermoplastic honeycomb panels, stochastic model updating, design parameter
variability, correlation length
Summary. This paper deals with design parameter variability of thermoplastic honeycomb
sandwich panels and how this can be estimated from the dynamic behaviour of rectangular
panels with free boundary conditions.
ABSTRACT
In this paper it is described how the variability of some design parameter of honeycomb
sandwich panels is estimated from their experimentally determined vibration behaviour.
Honeycomb panels are sandwich structures that combine a high specific strength and
stiffness with a low areal mass. They have a complex but regular geometry.
A first part of the paper describes the physics of a set of seven thermoplastic honeycomb
sandwich test panels. Special attention is given to the observed variability on some of the
parameters that govern the dynamic behaviour of a panel.
A second part in the article discusses the full process of experimental modal analysis.
Focus is laid on the estimation of the modal parameters and their variability due to
measurement and parameter estimation uncertainty.
In the third part of the paper a suitable FE – model is proposed in order to calculate
resonance frequencies and mode shapes of honeycomb panels with free boundary conditions.
Stijn Debruyne, Dirk Vandepitte and Eric Debrabandere.
It is outlined how the (elastic) parameters of the homogenized FE – model (using orthotropic
material properties for both skin faces and honeycomb core) are obtained from the real
physical parameters of skin faces and honeycomb core. These are the Young’s moduli of both
skin faces in length and width direction and the two relevant out-of-plane shear moduli of the
homogenized honeycomb core. It is extensively discussed how stochastic model updating is
applied to deal with the specific problem of underdetermined model updating.
The fourth part of the article describes how the dynamic behaviour of a honeycomb panel
can be regarded as a stochastic process that is governed by a set of stochastic variables.
Taking into account the whole set of test samples, each of the considered elastic model
parameters is treated as a stochastic random field. Both epistemic and aleatory uncertainty are
estimated and discussed. The implementation of the random field method is also validated.
Furthermore, the correlation length of each parameter is estimated from the estimated
covariance matrices.
Finally, the relation between model parameter variability and physical parameter
variability is discussed and general conclusions are made.
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