Experimental study of the confined behaviour of PMMA under quasi-static and dynamic loadings

This study has investigated the confined behaviour of PMMA under quasi-static loading and at high strain-rates as well. To this goal, quasi-oedometric compression tests have been performed. A cylindrical specimen, tightly enclosed inside a thick confinement vessel which material is either brass or high strength aluminium alloy, is axially compressed. The constitutive law allowing the description of the ring metal being known, a processing method is proposed to deduce the confining pressure accounting for the plastic behaviour of the vessel as well as to calculate the s7hortening of the specimen. Next, the hydrostatic pressure and the Huber-Mises stress may be deduced. Both vessels permit us to explore the behaviour of PMMA under lateral pressure levels rising up to 500 MPa. Based on the proposed method quasi-static and dynamic tests performed in a range of strain-rates from 1E-3/s to 1E3/s are processed and the obtained results are compared to those corresponding to unconfined compression tests. It was found that the compressive strength of PMMA is weakly influenced by the level of pressure and is much more sensitive to strain-rate. Finally, an elastic brittle behaviour is observed at high strain-rates for unconfined as well as confined conditions, whereas an elasto-plastic behaviour followed by a mode II fracturing of the specimen is noticed for quasi-static confined loading.