Optimization of fiber distribution in fiber reinforced composite by using NURBS functions

Abstract

This research deals with the optimization of short fibers distribution in continuum structures made of Fiber Reinforced Composite (FRC) by adopting an efficient gradient based optimization approach. Motivated by lack of non-heuristic and mesh independent optimization algorithm to obtain the optimum distribution of short fibers through a design domain, Non-Uniform Rational B-spline (NURBS) basis functions have been implemented to define continuous and smooth mesh independent fiber distribution function as well as domain discretization. Thanks to higher order (here quadratic) NURBS basis functions along with their compact support, a drastic reduction in computational time has been obtained by increasing mesh size while the accuracy of the model is maintained. Moreover combination of NURBS with sensitivity based optimization method allows a fast convergence to optimum fiber distribution layout. Minimization of elastic strain energy and maximization of fundamental frequency have been considered as objective functions for static and free vibration problems, respectively; to get the maximum fiber exploitation in the structural element. Nodal volume fraction of fiber was defined as the optimization design variable while a homogenization approach based on the random orientation of short fibers in the matrix has been adopted. Some numerical examples related to the structural response under static loading as well as the free vibration behavior are finally conducted to demonstrate the capability and reliability of the model.