Sandwich composites provide excellent structural integrity for a variety of applications. Typically the inner core can be composed of foam material, a honeycomb structure, or balsa wood and usually lacks the structural integrity of the outer reinforcement, particularly in the foam materials. In this study pristine and functionalized 30 nm Silicon Carbide nanoparticles are infused into a low density polyurethane foam. Basic mechanical testing reveals changes in the strength, stiffness, and elongation of the foam based on compressive, tensile, and flexural tests. A plane-strain fracture test is employed to evaluate the effect of the nanoparticle addition on the fracture toughness of the foam. Additionally, a TSD (Tilted Sandwich Debond) test characterizes the delamination fracture properties of core-skin interface for sandwich construction with the nanophased cores. Dynamic Mechanical Analysis (DMA) testing distinguishes any changes in the glass transition temperature (T_g) of the polymer and Thermo-Gravimetric Analysis (TGA) testing confirms the influence of nanoparticles restricting the thermal degradation of the polymer. FTIR spectral analysis reveals changes in molecular bonding due to pristine and functionalized nanoparticle infusion. The fracture resistance of the foam is improved at particular weight concentrations (e.g. 02 wt%). In addition the delamination strength of the sandwich construction with nanophased cores is dramatically improved. Tests have indicated that the G_IC value rose from 0.14 kJ/m² in the neat foam to 0.56 kJ/m² with just 0.1 wt% of SiC nanoparticle inclusion reflecting an enhancement of almost 300%.