Experimental-numerical characterization of the nonlinear microstructural behavior of fibre-reinforced polymer structures

Abstract The mechanical properties and especially the damage behavior of discontinuous fibre-reinforced composites greatly depend on their constituents and also on their microstructural characteristics, namely the extent and distribution of fibre agglomerations, the fibre orientation distribution, and the fibre-matrix interfaces. Although individual characteristics can be analyzed well, the overall behavior of the composite is dominated by the interdependencies of the individual characteristics. Aspects such as the initiation of fracture in a given microstructure are almost impossible to predict. To shed light on such processes, the microscopic fracture behavior of a glass fibre-reinforced sheet molding compound is investigated in situ by means of a micro-tensile test. In situ observation gives access to the position and orientation of each fibre. A detailed microstructural finite element model is built for each tested specimen and the fibre-matrix interface characteristics are extracted with a reverse-engineering approach. The tests show a microstructure-specific fracture behavior, which can be reproduced reasonably well with the numerical simulations, making the obtained parameters suitable for further simulations of the investigated structure on a larger scale.