The unique characteristics and properties offered by the sandwich structures system provide a huge potential in various fields. Such uniqueness can be comprised in the relatively low weight to stiffness ratio compared with different kind of structures. Such superiority have increased its application within several industries including aerospace and naval industries, however, its application is still limited within the context of structural engineering. This paper aims to explore the performance of polyethylene terephthalate (PET) foam core sandwich panels and assess its applicability within the structural applications as structural beams and slabs. This paper experimentally and numerically investigate the performance of PET sandwich panels and propose a failure map for the PET sandwich panels to be used later to predict the failure mode of a given PET sandwich panel. The presented research lays the foundation for further implementation of PET sandwich panels in the field of structural applications such as cladding panels.