Coarse Mesh RIFF Method to Identify the Homogenized Flexural and Shear Complex Moduli of Composite Beams

This paper aims at identifying the flexural and shear complex moduli of a sandwich beam by simply measuring the displacement field and applying an inverse resolution of the Timoshenko beam problem. A first development [1] employed the RIFF technique (from the french "Resolution Inverse Filtrée Fenêtrée") [2]. This article presents an improvement, using the RIC method ("Résolution Inverse Corrigée" in french) that involves a correction of the finite difference scheme as originally suggested in [3]. By applying this method specifically to the Timoshenko beam problem [4], one can asses the viscoelastic parameters of composite beams, based on a coarse mesh measurement of the displacement field using a simple accelerometer and an instrumented hammer. An experimental validation conducted on a sandwich honeycomb beam with fibreglass faces allows satisfactory identifications despite a low spatial resolution (down to 2.1 samples per wavelength).