msp AN AXISYMMETRIC PARACHUTE MODEL WITH WRINKLING

We are honored to dedicate this paper to Charles Steele and to the memory of Marie-Louise Steele. Charles was my admired teacher at Stanford, and has opened my eyes to the wonderful world of shells. Marie-Louise was a friend who always had a few warm words for a PhD student undergoing stressful times. I will always remember her very fondly. – Dan Givoli The deformation and stresses in a parachute canopy are analyzed, using an axisymmetric model. The canopy is modeled as an ideal or nearly ideal elastic membrane shell. Steady state is assumed. No restriction is imposed on the size of the deformation, and thus the problem is strongly nonlinear. Wrinkles which form over parts of the surface are taken into consideration approximately via the use of wrinkle fields (tension fields). The solution is obtained by a double-iteration numerical procedure, based on a shooting technique and incremental loading. First a basic parachute model is considered in which the material is assumed isotropic and Hookean, the pressure distribution is assumed uniform (but with unknown magnitude), and the canopy is assumed to have a small central hole. Later all these assumptions are relaxed. Numerical examples are presented for some representative cases. 1