Fiber-reinforced composites are currently adopted as an alternative to conventional materials. Nevertheless, many parameters are needed to obtain an accurate dynamical model of a system made of fiber-reinforced composite material. In order to use such a model for design, diagnostics or other industrial tasks it is necessary to take into account of model uncertainties, such as unknown material properties, constraint and joint characteristics. In this paper, a technique to update the parameters of a finite element (FE) model for thin-walled structures made of composite material, by means of nondestructive testing is proposed. The updating procedure adopts experimental estimates of frequency response functions (FRFs) as input data. The FE model adopts B-spline basis functions for modeling both the geometry and the displacement field. The effect of damping is considered by adopting a real damping assumption (real eigen-modes), where mode damping ratios are assumed to vary with respect to frequency and modeled using non-parametric B-spline functions. The updating approach is based on the least squares minimization of an objective function dealing with residues, defined as the difference between the model based response and the experimental measured response, at the same frequency. The objective function is iteratively minimized by adopting a sensitivity approach, where a variable transformation is employed to constrain the updated parameters to lie in a compact domain without using additional variables. The parameters defining the material behavior and the damping model are taken into account in the updating process. Some examples are reported using measured data on a carbon-fiber reinforced tubolar structure. Results are shown and critically discussed.

Thin shell laminate B spline FE model updating by means of experimental FRFs

CATANIA, GIUSEPPE;CARMINELLI, ANTONIO
2011

Abstract

Fiber-reinforced composites are currently adopted as an alternative to conventional materials. Nevertheless, many parameters are needed to obtain an accurate dynamical model of a system made of fiber-reinforced composite material. In order to use such a model for design, diagnostics or other industrial tasks it is necessary to take into account of model uncertainties, such as unknown material properties, constraint and joint characteristics. In this paper, a technique to update the parameters of a finite element (FE) model for thin-walled structures made of composite material, by means of nondestructive testing is proposed. The updating procedure adopts experimental estimates of frequency response functions (FRFs) as input data. The FE model adopts B-spline basis functions for modeling both the geometry and the displacement field. The effect of damping is considered by adopting a real damping assumption (real eigen-modes), where mode damping ratios are assumed to vary with respect to frequency and modeled using non-parametric B-spline functions. The updating approach is based on the least squares minimization of an objective function dealing with residues, defined as the difference between the model based response and the experimental measured response, at the same frequency. The objective function is iteratively minimized by adopting a sensitivity approach, where a variable transformation is employed to constrain the updated parameters to lie in a compact domain without using additional variables. The parameters defining the material behavior and the damping model are taken into account in the updating process. Some examples are reported using measured data on a carbon-fiber reinforced tubolar structure. Results are shown and critically discussed.
Atti del XX Convegno di Meccanica Teorica e Applicata AIMETA
1
14
G. Catania; A. Carminelli
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/105619
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