Creep Simulation and Validation for a Finite Element Analysis of Expanded Polystyrene-Based Cushioning Systems

The creep strain resistance of expanded polystyrene (EPS) is important; thus, time-dependent creep properties of EPS have been of significant interest. This study is a part of the computer-aided engineering (CAE) prediction-technology development for the inclination of unitized loads of packaged appliances applied to EPS-based cushioning systems. Creep properties are validated to ensure finite element analysis (FEA) reliability regarding the creep behavior of EPS-based cushioning systems. The elastic modulus and Poisson’s ratio (EPS elastic properties) as well as creep properties (plastic properties) were measured. The EPS density range was 16–30 kg/m3, and the temperature range was 0–60 °C. Because the measured mechanical properties were not temperature-dependent, only their density dependence was analyzed. The EPS behavior, measured over 12 h, exhibited a significant creep amount and rate, depending on the applied stress level. FEA was performed on 7-day-long EPS creep, using the measured EPS elastic and plastic properties. The FEA and experimental results were strongly concordant. These EPS creep validation results are expected to improve the reliability of FEA for creep behavior studies of EPS-based cushioning systems.