Stochastic stress analysis and failure onset of variable angle tow laminates affected by spatial fibre variations

The usage of printed composites in the aerospace industry has been steadily increasing over the last years. Especially, 3D printers and automatic fibre placement machines have allowed the introduction of Variable Angle Tow (VAT) composites, which theoretically offer greater tailoring capabilities than classic composite laminates. Nevertheless, the steering of brittle fibres is not flaw-exempt and, in fact, is greatly affected by the printer signature. This manuscript aims to examine the influence of fibre misalignments on the stress and failure index distribution in laminated VAT composites. For doing so, the Carrera Unified Formulation (CUF) is employed to develop layerwise models with unprecedented accuracy. Flaws are introduced at the layer scale by means of stochastic fields and uncertainty analysis is carried out through a Monte Carlo analysis. The random variation (defects) is propagated through the scales and correlated with the stress and failure index distribution. The results show that misalignments greatly affect the in-plane normal stresses, which lately influence fibre tension and compression failure mechanisms.