Optimization of the microstructure of unidirectional hybrid composites under uniaxial tensile loads.

Typical composite structures are characterized by having brittle failure and thus higher safety factors. Alternatively, hybrid composites with pseudo-ductile behaviour can contribute to safer and more efficient designs. The objective of this work is to achieve a "pseudo-ductile" behaviour in the response of unidirectional hybrid composites when subjected to uniaxial traction. To understand under what circumstances such behaviour is obtained, optimization problems are formulated and solved here. A Spring Element Model is used to predict the hybrid composite failure with relatively low computational cost. This cost is an important issue since optimization requires several analyses of the composite response. Two different types of optimization problems are considered. Firstly, one finds out the optimal properties of fibres to hybridize and get the pseudo-ductile behaviour. Once an optimal hybridization is found, another optimization problem is solved in order to understand the influence of the fibre dispersion on the composite response. Both optimization problems are solved using a Genetic Algorithm. The optimal results obtained show hybrid composites having a considerable pseudo-ductile behaviour. It is also shown that the degree of spatial fibre dispersion at the composite microstructure level greatly affects the composite response. High fibre dispersion favours the pseudo-ductile behaviour. [ABSTRACT FROM AUTHOR]