Experimental and finite element analysis of creep behavior of extruded polystyrene rigid foam

Experimental and finite element analysis of creep behavior of extruded polystyrene rigid foam. Extruded polystyrene (XPS) rigid foams have recently attracted a great attention as a superior load-bearing thermal insulation material. This type of thermal insulation material is commonly used under raft foundations, where high levels of compression loads and sometimes shear loads take place. To apply these boards safely in such application areas, their creep behavior should be intensively evaluated and analyzed to avoid any hazardous potential settlement. The principle objective of the current research is to investigate the creep behavior of XPS load-bearing thermal insulation boards under pure shear and combined shear-compression stress states and to explore any potential effect the compression stresses could have on the shear creep strains under the combined loading state. Creep tests were performed on XPS rigid foam boards under shear and combined shear-compression stress states using a specially developed test set-up. Experimental results showed a slight increase in the creep shear strains due to the application of compression stresses in the combined loading conditions. Creep test results have been used to investigate the most accurate approach able to model and extrapolate the creep behavior under these types of stresses. An overview of simulating the creep behavior through finite element method using microstructure-based FE models was introduced. The microstructure was captured by the x-ray computer tomography imaging technique. The developed microstructure-based FE models were then used to carry out a parametric study aiming to optimize the creep response of XPS boards under shear and compression loads.