Investigation of the Dynamics Performance of Rheinforced Cork Composites

Vibration is a common occurrence in both industrial and domestic environments. It can cause fatigue and potential failure in structures and machines due to cyclic stress. Transmitting vibrations to humans can also lead to discomfort and decreased efficiency in engineering systems. Most conventional damping devices commercially used in industrial machinery consist of pads or sheets of flexible materials that are not eco-friendly and present several limitations. This experimental work focuses on developing a tuneable nonlinear energy-dissipating device, specifically a vibration attenuator constructed with environmentally friendly composite materials (Rheinforced Cork Composites). This innovative design merges the mechanical resilience of cork with an eco-friendly formulation of shear thickening fluid, consisting of a dense suspension of precipitated calcium carbonate in glycerol. To that end, three different samples were prepared: one composite containing the shear-thickening fluid embedded within the cork lamina following a simple microfluidic pattern, another composite with an identical pattern engraved in the agglomerated cork layer without the fluid and a third composite with a cork layer core without channels. The experimental study followed an Experimental Modal Analysis procedure. Dynamic loading was applied to the specimens using an electrodynamic shaker, and their velocity response was measured and analysed. The stiffness and damping were evaluated using modal identification techniques on the acquired Frequency Response Functions (Mobility). Results showed that the composite filled with STF exhibited a higher natural frequency despite having a greater mass due to the stiffness increase resulting from the presence of STF.