Expanded polystyrene foam design with emphasis on nonimpact cushioning applications

Studies into the design of expanded polystyrene (EPS) foam packaging were conducted. The studies were directed toward the development of design parameters and criteria for vibration type loadings applied to foam packaging. The mechanics of EPS foam pertaining to packaging design were examined. Design guidelines based on vibration load input and mechanical properties of EPS foam that are applicable to cushioning applications were explored.; A number of combinations of specimen size were tested to characterize the size effect on mechanical properties of EPS foam. Suites of specimens of varying thicknesses and cross sections were examined. It was observed that the modulus of elasticity and the yield strength exhibited a high degree of dependency on thickness.; Loading rate dependency tests were conducted on specimens having a single lateral dimension but varying thicknesses. Loading rates ranging from 8.47 x 10-3 mm/s (0.02 in./min) to 8.47 mm/s (20 in./min) were used. All mechanical properties examined in this study exhibited an increasing trend with an increase in loading rate. However, the rate of change in these properties varies with the foam thickness.; Quasi-static cyclic loading studies were conducted to investigate the energy dissipation capability inherent to EPS foams. Foam specimens were subjected to cyclic loadings varying in magnitude from 50% of the apparent yield strain up to the load that causes an initial deformation of 10%. The results provide clear evidence of hysteresis energy losses even at cyclic loads below the yield point of the material. Photographic examination of the samples subsequent to loading also showed evidence of permanent deformation occurring even for small load magnitudes.; Vibration studies showed that the amount of protection afforded by EPS foam from vibration loadings is generally small. It is possible to design a foam cushioning to operate as a vibration isolator only in the higher range of frequencies that are important in the shipping environment. EPS foam is not well suited for vibration protection in packaging applications. With this in mind, a guideline for adjusting an impact cushioning design to minimize the vibration impact on a packaging design is offered.