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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The total deformation plot is depicted in Fig. 6. As expected the total deformation is maximum at the trailing edge of honeycomb bracket. Because of relatively lower stiffness of bracket assembly, higher deformation of 1.8mm is observed in plate. Since the bracket design is mainly governed by strength rather than stiffness based, the deformations experienced is acceptable for the application.

3.2.2. Stress plot:

Fig. 6: Total displacement plot of bracket assembly

Since the bracket construction involves only ductile metals viz. aluminium alloy, the design is based on equivalent stress i.e Von-Mises stress calculation. The Von-Mises stress plot of the complete assembly (packages mounted on bracket) is depicted in Fig. 7. The maximum stress of 346 MPa is observed on bracket through all the layers of bracket.

Fig. 7: Von-Mises plot of hybrid bracket assembly

The layer wise stress plots are depicted in Fig. 8(a) and 8(b). Because of very low stiffness of honeycomb material, the maximum Von-Mises stress experienced by honeycomb core is only 2.7 MPa. Strength limits and corresponding stresses observed in honeycomb plate in different directions are tabulated below:

Table 1. Strength limits and stresses observed in honeycomb core. Stress direction Strength limits (MPa)

Stress observed (MPa)

Tensile Z direction

5.31 -5.31 1.21 2.24

0.86 -1.84 0.84

Compressive Z direction

Shear YZ direction Shear XZ direction

1.45 Note: Strength in other directions is negligible and stresses observed in those directions are also negligible.

Since face sheet is isotropic material, the Von-Mises stresses are to be compared with strength limits of the materials. The stress plot for face sheet is depicted in Fig. 8(b). Maximum Von-Mises stress of 346.2 MPa is