Experimental and computational assessment of the bending behavior of inflatable drop-stitch fabric panels

Abstract

This paper details the experimental assessment and nonlinear finite-element analysis of the flexural behavior of inflated drop-stitch panels. Coupon-level fabric tests as well as panel inflation and panel torsion tests were performed to determine the effective orthotropic moduli of the panel fabric skin. Large displacement bending tests were conducted for a range of inflation pressures and two different span-to-depth ratios to assess the significance of these important parameters on panel stiffness and capacity. A novel, nonlinear beam finite-element modeling strategy for predicting the load–deflection behavior of inflatable drop-stitch panels subjected to bending loads is subsequently presented. The underlying Timoshenko beam element incorporates nonlinearity caused by fabric wrinkling, the work done by the internal pressure and its effect on panel stiffness and capacity, and the effect of the drop stitch yarns on panel bending response. Comparisons between model-predicted and measured panel load–displacement response demonstrate that the model is capable of predicting both pre- and post-wrinkling panel bending behavior over a wide range of deflections with reasonable accuracy. Additional model simulations demonstrate the significant impact of pressure–volume work, shear deformations, and drop yarns on panel bending response.