Rigid polymer foams are used as sandwich core materials in a variety of structural applications including marine, automotive and wind energy. Foam cores can be light and uniform in properties, while delivering sufficient stiffness and strength. Optimum design of sandwich structures is important for materials and cost savings. Therefore, correct understanding of the mechanical properties of the sandwich components is necessary. In this project, compression and shear properties of an extruded polyethylene terephthalate (PET) foam is investigated. This grade is a new state-of-the-art core materials in wind blade manufacturing. Due to the especial foam extrusion process, an induced honeycomb pattern was obserevd in the foam morphology, resulting in anisotropic compression response. Optical strain analysis was performed using 3D Digital Image Correlation (DIC). In doing this, local and average surface strains were measured during foam compression in the three principle directions. The acquired information was then used to make structure-properties correlations. DIC compression stress-strain curves were then compared to the global curves measured by the testing machine. It is shown that the compression moduli of the foams in both out-of-plane and in-plane directions are significantly higher than the values measured by machine transverse. Poisson’s ratios of the foam was also calculated, which converged to values near zero at large compression strains. In-situ foam shear measurements where carried out using a four-point bending test coupled with optical strain analysis. The results were then verified by direct foam shear test.