Characterisation of nonlinear response of 3D layer-to-layer angle interlock woven composites under warp tension

3D woven composites, known for their exceptional structural integrity, are highly attractive for aeronautical applications, particularly in critical components such as aero-engine fan blades. Despite their promising potential, a comprehensive understanding of their mechanical behaviour remains essential for optimised design and application. Significant nonlinear behaviour well before the ultimate failure of 3D woven composites with a layer-to-layer angle interlock fibre architecture under warp tension has been observed in experiments. Although the same experimental observation for this type of material had been reported in the literature previously, the fundamental mechanisms of nonlinearity were not fully studied. In this work, the contributing factors that lead to this severe nonlinearity are investigated and their effects on modelling the response of 3D woven composites are characterised. An appropriately defined mesoscale single-layer unit cell is adopted for this purpose to simplify the finite element modelling, along with a justification performed. Fibre tow/matrix debonding, damage in neat matrix and nonlinear shear in fibre tows have been identified as the most significant sources of nonlinearity and their modelling strategies are discussed. In comparison with the experiments, the results demonstrate the specific effects of each identified factor on the nonlinear behaviour of the material. As modelling of 3D woven composites is computationally costly, this study would provide important insights into the choice of appropriate modelling strategies for 3D woven composites in a design process.