Experimental Analysis of Decohesive Phenomenon in Expanded Polystyrene under Bending and Tensile Loading Conditions

In this paper, the decohesive phenomenon of expanded polystyrene (EPS) is analysed using bending and tensile tests. Globally, the typical stress-strain curve is characterised by a wide linear or nonlinear elastic part, the plastic phase being almost neglected. The mechanical properties, such as the elastic modulus E* and the stress threshold σth*, increase with the EPS apparent density ρ*. The empirical equations have been proposed from experimental data fitting curve. The failure strain called εf, corresponding to the point where the final breakage occurs, decreases when the density value increases. Globally, these observations indicate a brittle behaviour of the EPS material under bending and tensile loading. On the other the hand, scanning electron microscopy (SEM) has been used in order to analyse the EPS fracture surfaces. The trans-beads (TB) fracture mode, where the crack grows through the beads, has sometimes been observed for the high diameters beads. But, according to all observations, the inter-beads (IB) mode generally seems to be the major mode of fracture. Therefore, this indicates that the EPS mechanical strength under bending and tensile loading essentially depends on the beads fusion quality.