The Influence of Foam Density on the Flexural Properties of Structural Insulated Panels

The effect of foam core density on the strength of structural insulated panels (SIPs) was investigated herein as part of a larger study to determine the creep performance of SIPs. Two depths (16.5 cm and 31.1 cm [6.5 in. and 12.25 in.]) of SIPs were tested in 1/3rd-point flexure according to the American Society of Testing and Materials standard ASTM D6815. Parent SIP panels, each approximately 122 cm (48 in.) wide, were manufactured by a SIPA member in accordance with ESR 4698 and sawn into beam, type elements, each approximately 29.8 cm (11.8 in.) wide, for mechanical testing. All specimens had discontinuities in the foam core in a location that was subject to high shear stress, i.e., between the reaction support and the load head, during the bending tests. The foam density in half of the specimens was approximately 0.016 g/cm³ (1.0 lb/ft³) and in the other half of the specimens, it was approximately 0.019 g/cm³ (1.2 lb/ft³). The flexural properties of these specimens based on the maximum load, P_max and deflection at failure Dy_max (two different depths and two different foam densities) were statistically compared by 2-tailed t test. The results showed that foam density affects the bending performance of SIPs. In both depths, beams with heavier foam cores were stronger for the specific test conditions used in this study. It is noted that results may not be applicable to other design situations such as SIPs subjected to uniform loading with randomly placed foam core joints.