In　this　study,　a　sandwich　structure　composed　of　functionally　graded　graphene　platelet　(GPL)-reinforced　composite　(FG-GPLRC)　face-sheets　and　a　metal　foam　core　considering　GPL　agglomeration　is　proposed.　The　face-sheets　are　multilayered,　and　the　GPL　volume　fraction　is　constant　in　each　layer.　However,　this　volume　varies　according　to　a　layer-wise　rule　in　the　thickness　direction.　A　two-parameter　model　supported　by　the　Mori–Tanaka　approach　is　developed　to　provide　solutions　that　quantifiably　consider　the　negative　influence　of　GPL　agglomeration　on　the　elastic　properties　of　nanocomposites.　The　core　is　made　of　a　metal　foam　with　closed　cells　whose　effective　elastic　properties　are　determined　using　the　Gibson–Ashby　model.　Two　types　of　porosity　distributions,　uniform　and　non-uniform　variations　in　thickness,　are　considered.　The　nonlinear　bending　behaviors　of　this　sandwich　beam　are　investigated.　Within　the　framework　of　an　equivalent　single-layer　theory,　the　formulations　governing　the　nonlinear　bending　problems　are　derived　from　a　third-order　shear　deformation　theory　supported　by　the　von　Kármán　nonlinearity.　The　Chebyshev–Ritz　method,　a　numerically　stable　method,　is　applied　to　describe　the　beam　under　various　classical　boundary　conditions.　An　extensive　numerical　study　is　implemented　to　examine　the　effects　of　the　agglomerations　and　volume　fraction　of　GPLs　in　the　face-sheets,　internal　pores,　and　core-to-face　ratio　on　the　nonlinear　bending　response　of　sandwich　beams.　©　2022　Elsevier　Ltd