Representative structural element approach for assessing the mechanical properties of automated fibre placement-induced defects

•Structural assessment of automated fibre placement-induced defects.•3D finite element mesoscale modelling approach to derive stress-strain response.•Evaluation of non-symmetric defects by processing computer tomography data.•Change in stiffness due to impact of gap, overlap and fuzzball. In this paper, a 3D finite element modelling approach is presented to assess the effects of manufacturing defects within composite structures. The mesoscale modelling approach derives the stress-strain response of a composite structure from a representative structural element. A set of tensile and bending loads is used to compute its ABD-Matrix. The boundary conditions of the model are described in detail as is the extraction of the strain and curvature response. The derived stiffness from the presented modelling approach is compared to the classical lamination theory and the models' shortcomings are discussed. Finally, the influence of a gap, an overlap and two different-sized fuzzballs on the macroscopic mechanical properties of a composite structure are evaluated using the presented multiscale modelling approach, thereby providing stiffness matrices influenced by the defects for the use in global models of composite parts.