The strengthening effect of polystyrene foam filling in aluminum thin-walled cylindrical tubes

The strengthening effect of foam filling in thin-walled circular tubes, deforming in diamond and concertina modes, was investigated in polystyrene foam filled aluminum tubes. Empty tubes of two different diameters (16 and 25 mm) deformed in diamond mode, while foam filling changed the deformation mode into concertina in 25 mm tube due to thickening effect of foam filling. The strengthening coefficient in concertina mode was found around unity, while in diamond mode it was greater than unity. In concertina mode, foam and tube were observed to deform independently. However, in diamond mode, foam was compressed in between the folds, leading to a higher strengthening coefficient. The effects of deformation rate and the use adhesive on the average crushing loads of the filled tubes were also determined.