Measuring the complex moduli of materials by using the double pendulum system

A interesting double pendulum system permits evaluating complex moduli (Young and shear) without independent excitation and transducers. This instrument was described at France in 1934 by Le Rolland and Sorin in Etude d'une méthode utilisant le couplage entre deux systèmes oscillants pour la détermination de la résistance mécanique des constructions et la mesure des modules d'élasticité, scientific and technical publications of the Air Force Ministry, no. 47, 1934. This device is revisited and improved in order to make it applicable to measurements of viscoelastic materials.