Static Modeling of Plywood–Polyurethane Structural Insulated Panels in Bending

Abstract

Structural insulated panels (SIPs) are thermally efficient, prefabricated structural elements that expedite on-site construction with a minimal number of skilled workers. This research aimed to model the time-independent mechanical response of transversely loaded SIPs with plywood skins and a closed-cell rigid polyurethane foam core. The foam core was characterized in both shear and compression through experimental testing, and a trilinear strain-based constitutive model was found suitable for the shear, while a linear response was adequate for compression. Two models, one analytical the other numerical, were produced using the component behavior and validated by comparison to the results of full-scale SIPs experimentally tested in quarter-point bending at two spans, 2.40 and 3.65 m. The analytical model is based on thin-faced, antiplane-core sandwich beam theory, while the numerical model is a two-dimensional plane-strain finite-element model (FEM). Good agreement was found between the analytical model and full-scale bending tests. However, it was found that the experimentally observed polyurethane shear moduli had to be reduced to 77% of their original values to provide good agreement of the FEM with the full-scale bending tests. While both models accurately predicted the bending deflection of the panels, neither was able to satisfactorily predict ultimate strength.