OPTIMIZATION OF HONEYCOMB CORE SANDWICH PANEL TO MITIGATE THE EFFECTS OF AIR BLAST LOADING

Open Access
Author:
Nayak, Sumanta Kumar
Graduate Program:
Mechanical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
None
Committee Members:
  • Ashok D Belegundu, Thesis Advisor
Keywords:
  • Blast load
  • Honeycomb core sandwich
  • Optimization
Abstract:
Optimization of the honeycomb core sandwich panel to minimize the effects of air blast loading is analyzed and presented in this thesis. The sandwich panel consists of three layers in which honeycomb core is embedded in between two face plates. The honeycomb core has a great potential to absorb the impact energy of the blast by undergoing cyclic plastic buckling deformation. This energy absorption is not only influenced by the cell sizes but also by the face plate size and geometry which are essential in maximizing the energy absorption of the core by providing external supports. The core also stiffens the sandwich by maintaining larger gap between the face plates. So the main purposes of the core are to reduce the transmitted acceleration to the back plate and also to reduce the back face plate deformation. The optimization study investigates the size and shape of the face plates, and depth and cell size of the core. Mass of the sandwich and the maximum plastic strain of the face plates are constrained. The optimization is carried out in two different ways (I) response surface optimization and (II) direct optimization using Differential Evolution. In the response surface method Design Expert software is used to create response equations from the response values determined from sampled points based on central composite face centered design method. The response equations are used in FMINCON, a gradient based optimizer in MATLAB optimization toolbox, for optimization. Function evaluations are done using LS-DYNA. Honeycomb core is modeled as a continuum solid structure with equivalent mechanical properties. The equivalent mechanical properties are determined by virtual testing method and parameterized in terms of the important honeycomb cell parameters. The results obtained shows that stiffer front face plate minimizes the back face plate deformation and acceleration by effectively transferring the blast load to a larger area of the core. Low dense core is found to be suitable for minimizing the back face acceleration whereas relatively high dense and high depth core is found to be useful for minimizing the back face plate deformation. The results are compared with solid flat plate and with shape optimized solid plate of equal mass. Honeycomb core sandwich structure proves to be much more effective over a shape optimized solid plate of equal mass in reducing the transmitted acceleration.