Mechanical assessment and deformation mechanisms of aluminum foam filled stainless steel braided tubes subjected to transverse loading

An experimental study investigating the mechanical response of both empty and aluminum foam filled braided stainless steel tubes subjected to transverse loading is presented in this manuscript. Tube specimens were loaded using a custom built testing machine which operated at a constant velocity of 18.8 mm/s. The braided tubular specimens utilized in this study were round AISI 301 stainless steel tubes with a nominal wire diameter of 0.51 mm, external nominal diameter of 64.5 mm, and length of 330 mm. Four different foam core configurations were tested, with densities ranging from 248 kg/m3 to 493 kg/m3. Additionally, two different core geometries were considered, namely cylindrical and rectangular prism configurations. Both core geometries were constructed from circular and rectangular flat panel sections of larger metallic foam panels. Structural adhesive was used to bond the smaller sections of the foam panels together to generate the cylindrical and rectangular prism cores. Deformation mechanisms of these structures were identified through use of a high speed, high resolution camera. The applied transverse load resulted in significant tensile loads within the braided tube and further resulted in braid diameter reduction as well as crushing and pulverization of the metallic foam core. Failure of the circular foam filled braided tubes was observed to be a combination of foam core separation, foam pulverization, as well as braid tow failure resulting from tensile forces and to a lesser extent bending. Failure of rectangular foam filled braided tubes was generally consistent with the mechanisms associated with the cylindrical cores, with the exception of the foam core separation. Force/displacement behavior was dependent on foam core density prior to tow lockup. Energy absorption levels ranged from 2.37 kJ to 9.13 kJ for the core densities and geometries are considered within this investigation.