Strain Rate Effect on the Compressive Behaviour of Reinforced Cork Agglomerates

The demand for bio-sourced materials is currently increasing. Cork material because of its unique properties (fire resistant, energy absorbing, …) is then an excellent candidate for a large set of applications. In order to widen its possible uses, cork agglomerates with reinforcements at a 0.48 density were studied to compare their mechanical performances with classical cork agglomerates. This paper investigates the effect of these foreign reinforcements on the properties of agglomerated cork under a compressive loading. The material behavior has been determined as a function of the average strain rate and the direction of solicitation. The microstructure was first observed through optical and scanning electronic microscopy, spotting charges between each cork bead. The characterisation of cork at different strain rates was then carried out. An electromechanical testing machine was used to apply an uniaxial compression at quasi-static strain rates. Reinforced agglomerated cork was found to be anisotropic and strain-rate dependant. Its micro-structure reveals at complex composite material influencing strongly mechanical properties. Both Young's modulus and absorbed energy density at 0.6 strain increase with the cross-head speed displacement. From 12.7 MPa and 0.77 J.mm-3 when compressed at 0.05 mm·min-1 to 19.9 MPa and 1.44 J·mm-3 at 500mm·min-1 in the Off-plane direction