Mechanical-morphology relationship of PS foams

The relationship between the morphology and the mechanical behavior of commercial PS foams has been investigated. The foams studied bad a closed cell morphology with densities between 25 and 74kg/m(3) and number-average cell sizes between 75 and 230 mum, and a normal cell size distribution (d(v)/d(n) approximate to 1.20). Mechanical results showed that the compressive strength and modulus could be expressed as a function of the foam morphology, using a unique morphological parameter taking into account the cell size and foam density. Flat sheet impact tests showed that three stages, i.e. damage initiation, damage propagation and damage coalescence leading to foam collapse, could be identified in the impact behavior of the foams. The maximum stress and the energy absorbed during impact could also be related to the morphological parameter proposed. A transition from a brittle to a ductile behavior could be rationalized using the proposed parameter.