Abstract: For restraining skin wrinkling and improve interfacial properties, a novel foam core sandwich structure was proposed by inserting glass fibre-reinforced plastic(GFRP) stiffeners attached to the sandwich skins. A vacuum-assisted resin infusion method was used to manufacture the sandwich panels. In-plane compression tests and double cantilever beam tests were conducted to compare their load-displacement curves and failure modes of stiffened specimens and non-stiffened specimens. The results of in-plane compression tests indicate that upon the insertion of stiffeners, the failure mode of the foam core sandwich composite structures change from inefficient skin wrinkling to efficient compressive microbuckling or global buckling. Compared to non-stiffened specimens, with the same dosage of glass fibre-reinforced plastic, the average failure load increases by 40.87% for length of 130 mm and 35.63% for length of 190 mm, respectively. The results of double cantilever beam tests indicate that the bridging fiber between skin and stiffener can effectively prevent the development of crack. Comparing with to non-stiffened specimens, the energy release rate increases by 57.35%.