PSI - Issue 14

G Vamsi Krishna et al. / Procedia Structural Integrity 14 (2019) 820–829 G. Vamsi Krishna / Structural Integrity Procedia 00 (2018) 000–000

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Fig. 3: Fastening details of package to the bracket

2.2. Material model

During configuration design of the bracket, it is ensured that stress levels in all the components involved in assembly is within yield limits. Hence all the materials involved are modelled as linear elastic materials until failure. Top face sheet, bottom face sheet and sleeves are of aluminium alloy material and honeycomb core is of aluminium alloy material. The properties of different materials are given below:

2.2.1. Aluminium alloy

All components made up of aluminium alloy are modelled as homogenous isotropic material with linear elastic behaviour till failure, with following properties: Young’s Modulus, E = 71 GPa, Poisson’s ratio, ν = 0.33.

2.2.2. Honeycomb

Honeycomb grid structure is made up of aluminium alloy material. Honeycomb is treated as continuum (homogenous), orthotropic material. Honeycomb material properties are a function of the grid material as well as the cell wall thickness and cell size. The tested properties of used configuration of honeycomb material, are as follows: Density, ρ = 105 / � , Elastic modulus E x = 1 MPa, E y = 1 MPa, and E z = 255 MPa; Poisson’s ratio ν xy = 0.49, ν yz = 0.001, and ν xz = 0.001; and Shear modulus G xy =1e-6 MPa, G yz = 365 MPa, and G xz = 100 MPa. (X, Y, Z are directions in orthogonal coordinate system. Z direction is along axis of honeycomb grid, X and Y are any transverse

direction perpendicular to Z direction.) 3. Numerical Modeling and Simulation

The FEM codes of ANSYS 18.0 [9] is used for carrying out static structural analysis. The interfacial bond between aluminium alloy face sheets and honeycomb core is modeled as bonded always using a bonded contact in the simulation. Honeycomb bracket experiences severe deceleration loads due to self-weight of packages mounted on it, during vehicle re-entry to the tune of 60g. Static analysis of the honeycomb bracket is carried out and results are presented here.

3.1. Boundary conditions and FE model

The two subsystems are modelled as flexible bodies with quadratic, 3D homogenous structural solid elements, SOLID186/ SOLID187 elements. The actual mass and stiffness of packages is considered for analysis, since the stiffness of packages can affect overall stiffness of assembly and hence modes of vibration and their corresponding