Shear stress at the interface of coaxial composites determined by the resonance of low-amplitude vibrations

The aim of this work is to determine the viscoelastic behaviour of the interface in a coaxial composite material made of a tough shield and a ductile core. The elastic modulus and the amplitude-independent internal friction are measured using a longitudinal oscillating resonant system at 50 kHz. The contribution of the interface is modelled as a shear stress that modifies the elastic behaviour of the constituents. The value of this shear stress is determined for different interfaces (epoxy resin-brass, epoxy resin-Pyrex and paraffin-Pyrex). The model is autovalidated by the excellent agreement between the calculated and experimental values of the internal friction (damping) of the composites.