Polyester foam core sandwich structures can be fabricated to have strength properties approaching those of plywood-based structures.The presence of glass fibers and their distribution and orientation has a significant effect on strength properties.Continuous fibers reinforce the core better than chopped fibers, although in some materials the laminar distribution of continuous filament creates planes resulting in shear failure.Comparative composites such as plywood-based materials which show flexural failure followed by shear had better strength properties with some inherent fracture toughness, although those materials which showed compression-wrinkling failure had a high flexural strength and modulus and high fracture toughness.