Experimental Study On Mechanical Behaviors Of Expanded Polystyrene(EPS)

Expanded polystyrene(EPS) is the lightest material used in packing. Due to high compressive strength, it is used in a series of civil engineering. Futhermore, it can also be used for insulation. EPS is a new-style material with great potential.By combining experimental study with theoretical analysis, the compressive mechanical properties and the viscoelastic properties of EPS are studied. The major contents are followed by these:The defining, classification, development, manufacturing techniques, characteristic and application of EPS are introduced briefly.The structure and morphology of polymer foam materials are introduced. Several parameters that are used to evaluate the structure of polymer foam materials are given, and effect of some parameters on the mechanical properties of polymer foam are also summarized. In addition, the essential mechanical properties of polymer foam are introduced briefly.A series of quasi-static state compressive tests on EPS are conducted. Based on the experimental results, effects of density and strain rate on the compressive mechanical properties of EPS are analyzed. It shows that density greatly affects the mechanics properties of EPS, and its compressive elastic modulus and yield strength increase with increasing of density; In the rang of this experiment, the same density EPS has about same linear elastic modulus under different strain rates but yield strength obviously increases with the increasing of strain rates. Their properties of absorption energy have been investigated by quasi-static compressive experiments. The experimental results show that absorption energy of EPS with same density increases with the increasing of strain and absorption energy of EPS with same strain decreases with the increasing of density. Based on energy- absorption curves, we can gain that the most value of absorption energy efficiency(E) of EPS is 38.1 percent and the most value of absorption energy ideality efficiency(I) of EPS is 85.0 percent. At the same time we do the work that the experience formulas of Gibson and Ashby were applied and validated in EPS. The volume fraction of polymer in struts and the theoretical elastic yield stress were gained.A series of creep and relaxation tests on EPS are carried out. Based on the creep experimental results, it shows that the creep values of same density EPS increase with the increasing of stress levels and the creep values of different density EPS decrease with the increasing of densities under same stress level. By analysing a series of stress-relaxation curves of EPS, we have built up a model of fitting relaxation curves including various densities and the model was validated by experiment.