P11: Dynamic mechanical behaviour of chocolate for simulating handling and transportation

Costas Elezoglou, Maria Charalambides, and Sunil Rana

Imperial College London, UK

Chocolate is a highly complex, multi-phase composite. Its mechanical properties strongly depend on the applied strain-rate. The present research examines the mechanical properties of solid milk chocolate at varying strain rates including the high strain rate regimes. Therefore, this investigation can reveal insights about the appropriate handling and transportation of chocolate, during which, chocolate is imposed to dynamic loadings. Under these conditions, cracks in the chocolate may form in the product before it reaches the consumer.

An experimental methodology was developed of quasi-static uniaxial compression tests conducted using an Instron 5543 as well as high-speed tests using a VHS Instron together with a bespoke compression rig. Specimens were cylindrical with 20 mm length and 20 mm diameter. The tests were speed-controlled at constant speeds of 0.001 m/s, 0.01 m/s, 0.1 m/s and 1 m/s. All tests were conducted monotonically (continuous increase of the applied force with no unloading taking place). At the high-speed tests, dynamic effects were observed which caused oscillations in the Load-Displacement curves. An analysis to understand and eliminate these oscillations was performed and included: a) the alteration of the mass and damping of the testing system and b) the analytical calculation of the natural frequencies of the system. Results showed that the oscillations could be attributed to free vibrations of the testing system, and thus, a careful smoothing of the stress-strain curves could be performed.

Key dates

Registration deadline:

31 January 2022

Organised by the IOP Food Physics Group