A　circular–triangular　nested　tube　(CTNT)　was　proposed　for　dissipating　impact　or　blast　energy.　Experimental　studies　on　CTNT　energy　absorbers　under　a　lateral　quasi-static　crushing　load　were　first　conducted　to　reveal　their　deformation　modes,　force–displacement　responses,　and　energy　absorption　performances.　In　addition,　the　influences　of　the　circular-tube　thickness　and　triangular-tube　shape　on　the　energy　absorption　performances　of　CTNTs　were　also　discussed.　A　new　energy　absorption　parameter,　average　curvature　change　(ACC),　was　proposed　for　evaluating　the　influence　of　geometry　on　the　performance　of　an　energy　absorber　that　dissipates　energy　through　changes　in　its　curvature;　further,　the　optimum　geometric　performance　of　the　proposed　CTNT　energy　absorbers　was　demonstrated　based　on　a　comparison　with　other　nested　energy　absorbers　reported　in　extant　literature.　The　blast　responses　of　the　CTNT　energy　absorbers　used　as　sacrificial　claddings　were　numerically　studied.　The　numerical　results　clearly　presented　the　deformation　modes,　blast　load　mitigation,　and　energy　absorption　performances　of　the　sacrificial　claddings.　The　deformation　mode　of　a　CTNT　energy　absorber　used　as　sacrificial　cladding　under　blast　loading　was　significantly　different　from　that　under　quasi-static　loading　because　the　inertial　effect　and　energy　absorption　capacity　of　the　CTNT　energy　absorber　increased　as　the　weight　of　the　trinitrotoluene　(TNT)　charge　was　increased.　Moreover,　the　transmitted　force　was　found　to　be　reduced　by　50.1%–74.3%　on　employing　the　CTNT　energy　absorber　as　sacrificial　cladding,　and　the　reduction　magnitude　decreased　as　the　TNT　charge　weight　was　increased.　©　2020　Elsevier　Ltd