Glass　fibre　polymer　composites　under　loading　usually　exhibit　a　linear　stress–strain　behavior　until　a　sudden　failure　without　yielding　as　a　pre-failure　warning.　This　study　introduced　a　non-linear　elastoplastic　adhesive　layer　in　a　sandwich　beam　configuration　with　glass　fibre　polymer　facesheets　and　timber　cores,　where　nonlinear　and　ductile　flexural　behavior　resulted　from　load-dependent　composite　action　was　achieved.　Experimental　investigation,　finite　element　(FE)　modelling　and　classic　beam　theory　were　used　to　understand　the　effects　of　adhesive　properties,　timber　types　and　span-to-depth　ratios　on　the　flexural　behavior　of　such　sandwich　beams.　Comparative　analyses　were　conducted　among　specimens　with　elastoplastic　acrylic　or　elastic　epoxy　adhesives,　as　well　as　softwood　or　hardwood　timber　cores.　It　can　be　found　that　the　acrylic　adhesive　and　softwood　cores　effectively　offered　ductility　and　pre-failure　deflection.　For　the　specimens　with　hardwood　cores,　the　epoxy　adhesive　provided　a　composite　action　and　linear　load–deflection　behavior　in　most　of　the　loading　process;　while　due　to　a　load-dependent　stress–strain　behavior　under　shearing,　the　acrylic　adhesive　provided　a　partial　composite　action　and　bilinear　load–deflection　behavior,　showing　increased　mid-span　deflection　and　ductility.　Finite　element　modelling　well　described　the　flexural　behaviors　of　the　specimens,　including　deflection　development　with　loads,　bending　stiffness　and　composite　action.　©　2025　Elsevier　Ltd