Prediction of elastic behaviour and initial failure of textile composites
When a component is produced from textile reinforcement, it is well known that the reinforcement conforms to the shape of the tooling, predominantly by in-plane shear deformation. Current structural analysis techniques for composite components frequently neglect the effects of this deformation on subsequent mechanical properties. In this thesis the effects of shear deformation in the reinforcement on mechanical properties of the composite are shown to be significant, both for flat laminates with uniform reinforcement deformation, and for a component where deformation changes over the geometry. Methods are developed to predict the elastic behaviour and initial failure of components manufactured from textile reinforced composites, giving consideration to reinforcement deformation. One of the main objectives is to employ techniques which are purely predictive wherever possible, such that experimental test data are required principally for validation, rather than as input to the models. Implementation is performed in a modular fashion such that alternative models may be substituted at any stage in the procedure without affecting subsequent stages. Micromechanics models are employed to predict the properties of unidirectional composites from fibre and matrix properties and experimental validation is performed. A failure criterion is employed to determine lamina failure under biaxial loading. A simple model for woven fabric stiffness is implemented and extended to predict failure. Classical laminate theory is used to predict elastic and failure behaviour of angle-ply laminates; predictions are subsequently validated against experimental data. Material property and compaction models are incorporated into a draping simulation software tool which is used to create input files for structural analysis of components using layered shell finite elements, thought to be the most rigorous technique for textile composite components published to date. Results are shown to agree well with experimental data. To give full consideration of reinforcement geometry, initial studies of finite element modelling of the repeating unit cell are performed, whereupon the benefits and disadvantages of this technique are highlighted.