Aluminum foam core density and geometry influences on the deformation mechanisms of foam filled braided tubular structures in tension

The mechanical responses of aluminum foam filled braided stainless steel tubes subjected to tensile loading are presented in this manuscript. Testing of these structures was completed using a custom built testing machine. The braided tubular specimens considered in this study were round AISI 301 stainless steel tubes with a wire diameter of 0.51 mm and external nominal diameter of 64.5 mm. Six different foam core configurations were tested, including circular and rectangular foam prisms with densities ranging from 162 kg/m3 to 490 kg/m3. Mechanical responses were determined when specimens were subjected to an approximate extension velocity of 9.3 mm/s. Deformation mechanisms of these structures were identified through use of a high speed camera and digital image tracking software. Force/displacement behaviour was strongly dependent upon foam density; however after tow lockup this dependency was reduced. Theoretical predictions were consistent with experimental findings for specimens having a low density foam core. Higher density cores, resulted in localized foam crush and fracture and tube necking. Correspondingly, the mechanical response of specimens with high density cores deviated from predictions. Energy dissipation was noted to vary from approximately 4.34 kJ to 10.81 kJ.