Transient Analysis of Nylon 6/6 for a Thin Shell Structure by FEM

Abstract

In the design of Micro Aerial Vehicles, decreasing the size is one of the most common challenging aims and to approach this aim, the weight of the whole aircraft shall decrease and structure is the second part which has the most weight [13]. In this paper, the use of a shell structure made from Nylon 6/6 is studied. Nylon was chosen because of its good mechanical properties and low mass density which is of great importance. Also due to the low aspect ratio, the shell structure is used without any kind of ribs or spars to let the user put the instruments easily inside the structure which facilitates assembly and maintenance. Then the aerodynamic forces are calculated by CFD, Fluent, at Reynolds number 300000 at 5 AOA in a laminar flow. Afterwards the nodal results of Fluent after a nodal interpolation by MATLAB are imported in ANSYS for a full transient analysis. The model in ANSYS is a simple thin shell structure with low aspect ratio, AR=2, with 0.29 mm thickness and volume of 37.2 cubic centimeters, which is calculated in SOLIDWORKS. Finally Nylon 6/6 is modeled as a nonlinear visco-elastic material and the model is assumed to have large deformations, and the constitutive model is based on the Prony series, which consists of 5 Maxwell elements parallel to a spring. The dynamic bulk and shear modulus are then defined in ANSYS. Finally, the weight of structure is reduced to 42.40 grams, for the half of aircraft which is equal to about 16.74% of the whole aircraft’s weight. Simulation results are presented to prove the efficiency of this material for this structure.