experimental study on double-walled copper and carbon/epoxy composite tubes under the axial loading

this paper investigates axial compression process of multi-layered tubes with circular cross-section under the axial loading in the quasi-static condition using experimental method. some specimens are prepared in seven different groups, namely; empty carbon/epoxy composite tubes, solid carbon/epoxy composite rods, empty copper tubes, composite tubes with silicon sealant filler, concentrically solid carbon/epoxy composite rod and copper tube with silicon sealant-filler between them, double-walled copper and carbon/epoxy composite tubes with silicon sealant-filler between them, and double-walled copper and carbon/epoxy composite tubes with silicon sealant-filler between them and into the inner tube. for each test, diagrams of axial load-displacement and absorbed energy-displacement are sketched and also, specific absorbed energy by each specimen is measured. the experiments show that filling the copper tube with the composite tubes and also, filling the carbon/epoxy composite tubes with the silicon sealant increase instantaneous axial load and consequently, increase energy absorption capability of the structure. then, comparing the experimental measurements in viewpoint of energy absorption capacity and specific absorbed energy, an optimum sample is introduced. furthermore, the effects of geometrical characteristics of composite and copper tubes such as tube diameter and different filling conditions are investigated, based on the axial compression tests. the experiments show that absorbed energy of the circular copper tubes that are filled with the carbon/epoxy composite tubes is higher than sole copper tubes. also, it is found that copper tubes have less absorbed energy per unit of mass, compared to the empty carbon/epoxy composite tubes and also, the filled composite tubes by the silicon sealant.