Strength prediction methods for composite structures: Ensuring aeronautical design office requirements

We have seen an increase in the use of uni-directional carbon fibre-reinforced polymer composites in the design of primary structures, such as the centre wing box, over the past few years. However, composite structures can be weakened by the introduction of geometrical singularities, such as holes or notches. The semi-empirical aspect of the current open-hole failure requires the allowables to be systematically fitted against specific test results. This points out a strong limitation for optimal design. Different strength analysis methods for perforated plates, ensuring the requirements of precision and computational time of design offices, are presented. We compare predictions of the proposed approaches using a large experimental data basis, with different configurations of perforations, different stacking sequences and different carbon/epoxy materials. Finally, we propose a discussion of the use of these strength analysis methods in aeronautical design offices and the necessity to take advantage of the complementarity between advanced and fast computational methods.