Multilevel Design of Sandwich Composite Armors for Blast Mitigation using Bayesian Optimization and Non-Uniform Rational B-Splines

Abstract

I n regions at war, the increasing use of improvised explosive devices (IEDs) is the main threat against military vehicles. Large cabin"s penetrations and high gross accelerations are primary threats against the occupants" survivability. The occupants" survivability under an IED event largely depends on the design of the vehicle armor. Under a blast load, a vehicle armor should maintain its structural integrity while providing low cabin penetrations and low gross accelerations. This investigation employs Bayesian global optimization (BGO) and non-uniform rational B-splines (NURBS) to design sandwich composite armors that simultaneously mitigate the cabin"s penetrations and the reaction force at the armor"s supports. The armors are made of four layers: steel, carbon fiber reinforced polymer (CFRP), aluminum honeycomb, and CFRP. BGO is a methodology to solve optimization problems that require the evaluation of expensive black-box functions such as the finite element (FE) simulations of the vehicle armor under a blast event. BGO has two main components: the surrogate model of the black-box function and the acquisition function that guides the optimization. In this study, the surrogate models are Gaussian processes and the acquisition function is the multi-objective expected improvement function. NURBS generate the armor"s shape. The numerical examples show three alternatives to optimize the armor at two levels: (1) thicknesses of the sandwich"s layers and (2) the armor"s shape. The three design alternatives differ in the number of optimized levels and the optimization approach (sequential or simultaneous). The results show that the simultaneous optimization of the thicknesses of the sandwich"s layers and the armor"s shape is the most effective approach to design vehicle armors for blast mitigation.