Parametric investigation of cantilevered IsoTruss beams subjected to axial compression

摘要

A parametric study of 6- and 8-node composite IsoTruss grid structures subjected to axial compression was conducted. A geometrically nonlinear finite element analysis was employed to quantify the influence of overall length, overall grid diameter, individual member diameter, and elastic modulus on the axial capacity of single and double configurations of IsoTruss grid structures. Four 13 cm (5 in.) diameter by 1.8 m (71 in.) long specimens were manufactured and tested to verify the numerical predictions. The specimens were tested in axial compression to failure. The first two specimens were tested with clamped-pinned end conditions. The first specimen was made of prepreg carbon fibers, while the second specimen was wet wound carbon/epoxy. The third and fourth specimens were also wet wound and tested with clamped-pinned end conditions. A significant design simplification comes from the observation that IsoTruss grid structures with large length-to-diameter ratios obey Euler's column buckling formula. The analysis predicts that double grid configurations perform better than single grid configurations when global buckling controls, due to the inherently larger moment of inertia in the double grid configuration. Likewise, the global buckling behavior of 8-node trusses is better than that of 6-node configurations because of their higher overall flexural stiffness.