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Coarse Mesh RIFF Method to Identify the Homogenized Flexural and Shear Complex Moduli of Composite Beams
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on September 30, 2020 by SAE International in United States
Event: 11th International Styrian Noise, Vibration & Harshness Congress: The European Automotive Noise Conference
Facing the increasing use of composite materials regarding their stiffness to mass ratio, industries need to design complex structures. Hence specific methods must developed to predict the vibratory behavior of such materials but also to check their performances in-situ, analyse the presence of flaws or quantify degradation of properties throughout time. This paper describes a method to estimate the flexural and shear complex moduli of composite beams, based on a simple measurement of the transverse displacement on a coarse mesh using a hammer and an accelerometer. The herein depicted approach consists in an adaptation of the corrected finite difference scheme (Leclere et al. 2012) applied to an inverse vibratory method developed by the authors in previous works (Wassereau et al. 2017). The Timoshenko’s equation of motion and the corrected finite difference scheme are the two major key points of the method. The first allows estimation of Young and shear complex moduli simultaneously (sometimes crucial to describe composite beams) but also simplifies the representation of the composite structure by considering it as an homogeneous material, which is a lot easier for implementation into commercial simulation softwares. The second consists in a correction term introduced into the discretized equation of motion. By doing so the measurement mesh then acts like a built-in low pass filter and simplifies the regularization in the presence of measurement noise. The paper depicts the theoretical principle, the optimization steps and an experimental validation performed on a multilayer beam presenting a honeycomb core sandwiched in between two faces made of glass fibers impregnated in an epoxy resine. This experimental proof of concept allows satisfactory results on a wide frequency range despite a low measurement resolution.