New　composite　sandwich　structures　filled　with　foam　concrete　were　proposed　to　improve　the　failure　mode　subjected　to　compression　and　enhance　the　energy　absorption　capacity.　The　composite　structures　were　made　by　filling　foam　concrete　of　different　densities　(409　kg/m3,　575　kg/m3,　848　kg/m3,　1　014　kg/m3)　into　negative　Poisson＇s　ratio　aluminum　structures.　The　failure　modes　and　energy　absorption　capacities　of　the　specimens　subjected　to　quasi-static　compression　were　compared　among　the　empty　auxetic　structures,　the　auxetic　structures　filled　with　foam　concrete　as　well　as　the　standalone　foam　concrete　control　specimens.　Based　on　the　load-displacement　relationship　and　failure　mode,　the　findings　can　be　reached:　With　foam　concrete　of　relatively　low　density　filled,　the　Poisson＇s　ratio　of　the　auxetic　composite　structures　is　limited　to　a　small　value,　leading　to　auxetic　deformation　of　the　cells　and　progressive　compression　mode　of　the　whole　structures.　With　foam　concrete　of　relatively　high　density　filled,　the　structures　exhibit　X-type　shear　failure,　in　which　the　cell　walls　around　plastic　hinges　and　shear　bands　fracture.　The　energy　absorption　increases,　and　the　densification　strain　of　the　composite　structures　decreases,　with　increasing　density　of　the　foam　concrete.　However,　with　filler　density　greater　than　a　certain　value,　the　enhancement　of　energy　absorption　of　the　composite　structures　becomes　less　remarkable,　and　the　specific　energy　absorption　decreases,　with　increasing　density　of　the　filled　foam　concrete.　©　2020,　Editorial　Office　of　Acta　Materiae　Compositae　Sinica.　All　right　reserved.