A study was conducted on the effect of interleaving on laminated composites. An ethylene-based ionomer of various compositions and a silane-modified ethylene-vinyl-acetate were selected as the interleaving materials. The glass transition temperatures (Tg) of the ethylene-based polymers ranged from-24 to 50'C. The fracture toughness (GIc), impact performance, and damping properties of the composites were evaluated. G1c of interleaved composites was about 3-5 times higher than that of non-interleaved. However, G1c was sensitive to the composition of the interleaf. The silane-modified ethylenevinyl-acetate had the highest fracture toughness. The impact properties of the interleaved materials were superior to those of non-interleaved, as evident from CAI testing where delamination occurred at an early stage in non-interleaved samples. The damping ratio of interleaved materials was found to be more than 100 times higher than in the original material.