Axial Compression of a Helically Wound,Laminated Paper Tube

Abstract

When one end of a helically wound, laminated tube is free to rotate, axial loading alone will induce a torsional twist about the tube axis. This paper concerns an experimental investigation of this compressive deforma tion behavior of such tubes. Helically wound, laminated paper tubes serve to model the structure. The special apparatus used to accurately measure the free end rotation of the specimen is described. It is found that the total angle of twist reaches a critical value at roughly the same time that the axial compressive force achieves a maximum value at which the cylinder walls buckle by folding inward along the helical fiber lines of the tube. At the onset of buckling, the previously nonlinear and monotonically in creasing twisting rate changes rather abruptly to a constant value; thus, this effect further identifies collapse of the tube. Although the critical angle of twist increases with the tube length, for the short tubes studied here, there seems to be no apparent dependence of the critical load on the length. Empirical equations that relate the critical angle of twist and the subse quent uniform, post buckling twisting rate to the tube length are pre sented.